Merge branch 'dev' into phase1-validator

2020-06-03 10:43:42 -06:00 · 2020-06-03 10:43:42 -06:00 · d1647c28e0
parent f135eff021 8ad2e936dd
commit d1647c28e0
92 changed files with 4065 additions and 1235 deletions
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@ -79,16 +79,16 @@ jobs:
      # Restore git repo at point close to target branch/revision, to speed up checkout
      - restore_cache:
          keys:
-            - v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+            - v3-specs-repo-{{ .Branch }}-{{ .Revision }}
-            - v2-specs-repo-{{ .Branch }}-
+            - v3-specs-repo-{{ .Branch }}-
-            - v2-specs-repo-
+            - v3-specs-repo-
      - checkout
      - run:
          name: Clean up git repo to reduce cache size
          command: git gc
      # Save the git checkout as a cache, to make cloning next time faster.
      - save_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
          paths:
            - ~/specs-repo
  install_pyspec_test:
@ -97,7 +97,7 @@ jobs:
    working_directory: ~/specs-repo
    steps:
      - restore_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
      - restore_pyspec_cached_venv
      - run:
          name: Install pyspec requirements
@ -109,7 +109,7 @@ jobs:
    working_directory: ~/specs-repo
    steps:
      - restore_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
      - restore_pyspec_cached_venv
      - run:
          name: Run py-tests
@ -140,7 +140,7 @@ jobs:
    working_directory: ~/specs-repo
    steps:
      - restore_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
      - restore_pyspec_cached_venv
      - run:
          name: Run linter
@ -152,7 +152,7 @@ jobs:
    working_directory: ~/specs-repo
    steps:
      - restore_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
      - restore_deposit_contract_compiler_cached_venv
      - run:
          name: Install deposit contract compiler requirements
@ -164,7 +164,7 @@ jobs:
    working_directory: ~/specs-repo
    steps:
      - restore_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
      - restore_deposit_contract_tester_cached_venv
      - run:
          name: Install deposit contract tester requirements
@ -176,7 +176,7 @@ jobs:
    working_directory: ~/specs-repo
    steps:
      - restore_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
      - restore_deposit_contract_compiler_cached_venv
      - run:
          name: Run deposit contract compile test
@ -187,7 +187,7 @@ jobs:
    working_directory: ~/specs-repo
    steps:
      - restore_cache:
-          key: v2-specs-repo-{{ .Branch }}-{{ .Revision }}
+          key: v3-specs-repo-{{ .Branch }}-{{ .Revision }}
      - restore_deposit_contract_tester_cached_venv
      - run:
          name: Run deposit contract test
--- a/8
+++ b/8
@ -75,15 +75,15 @@ install_test:
 test: pyspec
 	. venv/bin/activate; cd $(PY_SPEC_DIR); \
-	python -m pytest -n 4 --cov=eth2spec.phase0.spec --cov=eth2spec.phase1.spec --cov-report="html:$(COV_HTML_OUT)" --cov-branch eth2spec
+	python -m pytest -n 4 --disable-bls --cov=eth2spec.phase0.spec --cov=eth2spec.phase1.spec --cov-report="html:$(COV_HTML_OUT)" --cov-branch eth2spec
 find_test: pyspec
 	. venv/bin/activate; cd $(PY_SPEC_DIR); \
-	python -m pytest -k=$(K) --cov=eth2spec.phase0.spec --cov=eth2spec.phase1.spec --cov-report="html:$(COV_HTML_OUT)" --cov-branch eth2spec
+	python -m pytest -k=$(K) --disable-bls --cov=eth2spec.phase0.spec --cov=eth2spec.phase1.spec --cov-report="html:$(COV_HTML_OUT)" --cov-branch eth2spec
 citest: pyspec
 	mkdir -p tests/core/pyspec/test-reports/eth2spec; . venv/bin/activate; cd $(PY_SPEC_DIR); \
-	python -m pytest -n 4 --junitxml=eth2spec/test_results.xml eth2spec
+	python -m pytest -n 4 --disable-bls --junitxml=eth2spec/test_results.xml eth2spec
 open_cov:
 	((open "$(COV_INDEX_FILE)" || xdg-open "$(COV_INDEX_FILE)") &> /dev/null) &
@ -117,7 +117,7 @@ install_deposit_contract_compiler:
 compile_deposit_contract:
 	cd $(DEPOSIT_CONTRACT_COMPILER_DIR); . venv/bin/activate; \
-	python3.7 deposit_contract/compile.py contracts/validator_registration.vy
+	python3.7 deposit_contract/compile.py ../contracts/validator_registration.vy
 test_compile_deposit_contract:
 	cd $(DEPOSIT_CONTRACT_COMPILER_DIR); . venv/bin/activate; \
--- a/README.md
+++ b/README.md
@ -9,11 +9,14 @@ This repository hosts the current Eth2 specifications. Discussions about design
 ## Specs
-Core specifications for Eth2 clients be found in [specs/](specs/). These are divided into phases. Each subsequent phase depends upon the prior. The current phases specified are:
+[![GitHub release](https://img.shields.io/github/v/release/ethereum/eth2.0-specs)](https://github.com/ethereum/eth2.0-specs/releases/) [![PyPI version](https://badge.fury.io/py/eth2spec.svg)](https://badge.fury.io/py/eth2spec)
 Core specifications for Eth2 clients be found in [specs](specs/). These are divided into phases. Each subsequent phase depends upon the prior. The current phases specified are:
 ### Phase 0
 * [The Beacon Chain](specs/phase0/beacon-chain.md)
-* [Fork Choice](specs/phase0/fork-choice.md)
+* [Beacon Chain Fork Choice](specs/phase0/fork-choice.md)
 * [Deposit Contract](specs/phase0/deposit-contract.md)
 * [Honest Validator](specs/phase0/validator.md)
 * [P2P Networking](specs/phase0/p2p-interface.md)
@ -22,8 +25,9 @@ Core specifications for Eth2 clients be found in [specs/](specs/). These are div
 * [From Phase 0 to Phase 1](specs/phase1/phase1-fork.md)
 * [The Beacon Chain for Shards](specs/phase1/beacon-chain.md)
 * [Custody Game](specs/phase1/custody-game.md)
-* [Shard Transition and Fraud Proofs](specs/phase1/fraud-proofs.md)
+* [Shard Transition and Fraud Proofs](specs/phase1/shard-transition.md)
 * [Light client syncing protocol](specs/phase1/light-client-sync.md)
 * [Beacon Chain Fork Choice for Shards](specs/phase1/fork-choice.md)
 ### Phase 2
--- a/configs/mainnet.yaml
+++ b/configs/mainnet.yaml
@ -76,8 +76,8 @@ BLS_WITHDRAWAL_PREFIX: 0x00
 # Time parameters
 # ---------------------------------------------------------------
-# 86400 seconds (1 day)
+# 172800 seconds (2 days)
-MIN_GENESIS_DELAY: 86400
+GENESIS_DELAY: 172800
 # 12 seconds
 SECONDS_PER_SLOT: 12
 # 2**0 (= 1) slots 12 seconds
@ -94,8 +94,8 @@ EPOCHS_PER_ETH1_VOTING_PERIOD: 32
 SLOTS_PER_HISTORICAL_ROOT: 8192
 # 2**8 (= 256) epochs ~27 hours
 MIN_VALIDATOR_WITHDRAWABILITY_DELAY: 256
-# 2**11 (= 2,048) epochs 9 days
+# 2**8 (= 256) epochs ~27 hours
-PERSISTENT_COMMITTEE_PERIOD: 2048
+SHARD_COMMITTEE_PERIOD: 256
 # 2**6 (= 64) epochs ~7 hours
 MAX_EPOCHS_PER_CROSSLINK: 64
 # 2**2 (= 4) epochs 25.6 minutes
@ -122,8 +122,8 @@ BASE_REWARD_FACTOR: 64
 WHISTLEBLOWER_REWARD_QUOTIENT: 512
 # 2**3 (= 8)
 PROPOSER_REWARD_QUOTIENT: 8
-# 2**25 (= 33,554,432)
+# 2**24 (= 16,777,216)
-INACTIVITY_PENALTY_QUOTIENT: 33554432
+INACTIVITY_PENALTY_QUOTIENT: 16777216
 # 2**5 (= 32)
 MIN_SLASHING_PENALTY_QUOTIENT: 32
@ -132,8 +132,8 @@ MIN_SLASHING_PENALTY_QUOTIENT: 32
 # ---------------------------------------------------------------
 # 2**4 (= 16)
 MAX_PROPOSER_SLASHINGS: 16
-# 2**0 (= 1)
+# 2**1 (= 2)
-MAX_ATTESTER_SLASHINGS: 1
+MAX_ATTESTER_SLASHINGS: 2
 # 2**7 (= 128)
 MAX_ATTESTATIONS: 128
 # 2**4 (= 16)
@ -161,6 +161,8 @@ DOMAIN_CUSTODY_BIT_SLASHING: 0x83000000
 # Phase 1: Upgrade from Phase 0
 # ---------------------------------------------------------------
 PHASE_1_FORK_VERSION: 0x01000000
 # [STUB]
 PHASE_1_GENESIS_SLOT: 32
 INITIAL_ACTIVE_SHARDS: 64
 # Phase 1: General
@ -173,8 +175,6 @@ ONLINE_PERIOD: 8
 LIGHT_CLIENT_COMMITTEE_SIZE: 128
 # 2**8 (= 256) | epochs | ~27 hours
 LIGHT_CLIENT_COMMITTEE_PERIOD: 256
 # 2**8 (= 256) | epochs | ~27 hours
 SHARD_COMMITTEE_PERIOD: 256
 # 2**18 (= 262,144)
 SHARD_BLOCK_CHUNK_SIZE: 262144
 # 2**2 (= 4)
--- a/configs/minimal.yaml
+++ b/configs/minimal.yaml
@ -77,7 +77,7 @@ BLS_WITHDRAWAL_PREFIX: 0x00
 # Time parameters
 # ---------------------------------------------------------------
 # [customized] Faster to spin up testnets, but does not give validator reasonable warning time for genesis
-MIN_GENESIS_DELAY: 300
+GENESIS_DELAY: 300
 # [customized] Faster for testing purposes
 SECONDS_PER_SLOT: 6
 # 2**0 (= 1) slots 6 seconds
@ -89,13 +89,13 @@ MIN_SEED_LOOKAHEAD: 1
 # 2**2 (= 4) epochs
 MAX_SEED_LOOKAHEAD: 4
 # [customized] higher frequency new deposits from eth1 for testing
-EPOCHS_PER_ETH1_VOTING_PERIOD: 2
+EPOCHS_PER_ETH1_VOTING_PERIOD: 4
 # [customized] smaller state
 SLOTS_PER_HISTORICAL_ROOT: 64
 # 2**8 (= 256) epochs
 MIN_VALIDATOR_WITHDRAWABILITY_DELAY: 256
 # [customized] higher frequency of committee turnover and faster time to acceptable voluntary exit
-PERSISTENT_COMMITTEE_PERIOD: 128
+SHARD_COMMITTEE_PERIOD: 64
 # [customized] fast catchup crosslinks
 MAX_EPOCHS_PER_CROSSLINK: 4
 # 2**2 (= 4) epochs
@ -122,8 +122,8 @@ BASE_REWARD_FACTOR: 64
 WHISTLEBLOWER_REWARD_QUOTIENT: 512
 # 2**3 (= 8)
 PROPOSER_REWARD_QUOTIENT: 8
-# 2**25 (= 33,554,432)
+# 2**24 (= 16,777,216)
-INACTIVITY_PENALTY_QUOTIENT: 33554432
+INACTIVITY_PENALTY_QUOTIENT: 16777216
 # 2**5 (= 32)
 MIN_SLASHING_PENALTY_QUOTIENT: 32
@ -132,8 +132,8 @@ MIN_SLASHING_PENALTY_QUOTIENT: 32
 # ---------------------------------------------------------------
 # 2**4 (= 16)
 MAX_PROPOSER_SLASHINGS: 16
-# 2**0 (= 1)
+# 2**1 (= 2)
-MAX_ATTESTER_SLASHINGS: 1
+MAX_ATTESTER_SLASHINGS: 2
 # 2**7 (= 128)
 MAX_ATTESTATIONS: 128
 # 2**4 (= 16)
@ -162,6 +162,8 @@ DOMAIN_CUSTODY_BIT_SLASHING: 0x83000000
 # ---------------------------------------------------------------
 # [customized] for testnet distinction
 PHASE_1_FORK_VERSION: 0x01000001
 # [customized] for testing
 PHASE_1_GENESIS_SLOT: 8
 # [customized] reduced for testing
 INITIAL_ACTIVE_SHARDS: 4
@ -176,8 +178,6 @@ ONLINE_PERIOD: 8
 LIGHT_CLIENT_COMMITTEE_SIZE: 128
 # 2**8 (= 256) | epochs
 LIGHT_CLIENT_COMMITTEE_PERIOD: 256
 # 2**8 (= 256) | epochs
 SHARD_COMMITTEE_PERIOD: 256
 # 2**18 (= 262,144)
 SHARD_BLOCK_CHUNK_SIZE: 262144
 # 2**2 (= 4)
--- a/setup.py
+++ b/setup.py
@ -108,7 +108,7 @@ SSZObject = TypeVar('SSZObject', bound=View)
 PHASE1_IMPORTS = '''from eth2spec.phase0 import spec as phase0
 from eth2spec.config.config_util import apply_constants_config
 from typing import (
-    Any, Dict, Set, Sequence, NewType, Tuple, Optional, TypeVar, Callable
+    Any, Dict, Set, Sequence, NewType, Tuple, TypeVar, Callable, Optional
 )
 from dataclasses import (
@ -146,8 +146,14 @@ _hash = hash
 hash_cache: Dict[bytes, Bytes32] = {}
-def get_eth1_data(distance: uint64) -> Bytes32:
+def get_eth1_data(block: Eth1Block) -> Eth1Data:
-    return hash(distance)
+    """
    A stub function return mocking Eth1Data.
    """
    return Eth1Data(
        deposit_root=block.deposit_root,
        deposit_count=block.deposit_count,
        block_hash=hash_tree_root(block))
 def hash(x: bytes) -> Bytes32:  # type: ignore
@ -376,7 +382,7 @@ class PySpecCommand(Command):
                    specs/phase0/validator.md
                    specs/phase1/custody-game.md
                    specs/phase1/beacon-chain.md
-                    specs/phase1/fraud-proofs.md
+                    specs/phase1/shard-transition.md
                    specs/phase1/fork-choice.md
                    specs/phase1/phase1-fork.md
                    specs/phase1/validator.md
@ -480,6 +486,7 @@ setup(
    url="https://github.com/ethereum/eth2.0-specs",
    include_package_data=False,
    package_data={'configs': ['*.yaml'],
                  'specs': ['**/*.md'],
                  'eth2spec': ['VERSION.txt']},
    package_dir={
@ -499,9 +506,10 @@ setup(
        "eth-utils>=1.3.0,<2",
        "eth-typing>=2.1.0,<3.0.0",
        "pycryptodome==3.9.4",
-        "py_ecc==2.0.0",
+        "py_ecc==4.0.0",
        "milagro_bls_binding==1.3.0",
        "dataclasses==0.6",
-        "remerkleable==0.1.12",
+        "remerkleable==0.1.16",
        "ruamel.yaml==0.16.5",
        "lru-dict==1.1.6"
    ]
--- a/specs/phase0/beacon-chain.md
+++ b/specs/phase0/beacon-chain.md
@ -35,7 +35,7 @@
    - [`DepositMessage`](#depositmessage)
    - [`DepositData`](#depositdata)
    - [`BeaconBlockHeader`](#beaconblockheader)
-    - [`SigningRoot`](#signingroot)
+    - [`SigningData`](#signingdata)
  - [Beacon operations](#beacon-operations)
    - [`ProposerSlashing`](#proposerslashing)
    - [`AttesterSlashing`](#attesterslashing)
@ -110,6 +110,10 @@
    - [Helper functions](#helper-functions-1)
    - [Justification and finalization](#justification-and-finalization)
    - [Rewards and penalties](#rewards-and-penalties-1)
      - [Helpers](#helpers)
      - [Components of attestation deltas](#components-of-attestation-deltas)
      - [`get_attestation_deltas`](#get_attestation_deltas)
      - [`process_rewards_and_penalties`](#process_rewards_and_penalties)
    - [Registry updates](#registry-updates)
    - [Slashings](#slashings)
    - [Final updates](#final-updates)
@ -179,6 +183,7 @@ The following values are (non-configurable) constants used throughout the specif
 | Name | Value |
 | - | - |
 | `ETH1_FOLLOW_DISTANCE` | `2**10` (= 1,024) |
 | `MAX_COMMITTEES_PER_SLOT` | `2**6` (= 64) |
 | `TARGET_COMMITTEE_SIZE` | `2**7` (= 128) |
 | `MAX_VALIDATORS_PER_COMMITTEE` | `2**11` (= 2,048) |
@ -191,7 +196,6 @@ The following values are (non-configurable) constants used throughout the specif
 | `HYSTERESIS_DOWNWARD_MULTIPLIER` | `1` |
 | `HYSTERESIS_UPWARD_MULTIPLIER` | `5` |
 - For the safety of committees, `TARGET_COMMITTEE_SIZE` exceeds [the recommended minimum committee size of 111](http://web.archive.org/web/20190504131341/https://vitalik.ca/files/Ithaca201807_Sharding.pdf); with sufficient active validators (at least `SLOTS_PER_EPOCH * TARGET_COMMITTEE_SIZE`), the shuffling algorithm ensures committee sizes of at least `TARGET_COMMITTEE_SIZE`. (Unbiasable randomness with a Verifiable Delay Function (VDF) will improve committee robustness and lower the safe minimum committee size.)
 ### Gwei values
@ -214,8 +218,9 @@ The following values are (non-configurable) constants used throughout the specif
 | Name | Value | Unit | Duration |
 | - | - | :-: | :-: |
-| `MIN_GENESIS_DELAY` | `86400` | seconds | 1 day |
+| `GENESIS_DELAY` | `172800` | seconds | 2 days |
 | `SECONDS_PER_SLOT` | `12` | seconds | 12 seconds |
 | `SECONDS_PER_ETH1_BLOCK` | `14` | seconds | 14 seconds |
 | `MIN_ATTESTATION_INCLUSION_DELAY` | `2**0` (= 1) | slots | 12 seconds |
 | `SLOTS_PER_EPOCH` | `2**5` (= 32) | slots | 6.4 minutes |
 | `MIN_SEED_LOOKAHEAD` | `2**0` (= 1) | epochs | 6.4 minutes |
@ -224,7 +229,7 @@ The following values are (non-configurable) constants used throughout the specif
 | `EPOCHS_PER_ETH1_VOTING_PERIOD` | `2**5` (= 32) | epochs | ~3.4 hours |
 | `SLOTS_PER_HISTORICAL_ROOT` | `2**13` (= 8,192) | slots | ~27 hours |
 | `MIN_VALIDATOR_WITHDRAWABILITY_DELAY` | `2**8` (= 256) | epochs | ~27 hours |
-| `PERSISTENT_COMMITTEE_PERIOD` | `2**11` (= 2,048) | epochs | 9 days |
+| `SHARD_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
 ### State list lengths
@ -242,17 +247,17 @@ The following values are (non-configurable) constants used throughout the specif
 | `BASE_REWARD_FACTOR` | `2**6` (= 64) |
 | `WHISTLEBLOWER_REWARD_QUOTIENT` | `2**9` (= 512) |
 | `PROPOSER_REWARD_QUOTIENT` | `2**3` (= 8) |
-| `INACTIVITY_PENALTY_QUOTIENT` | `2**25` (= 33,554,432) |
+| `INACTIVITY_PENALTY_QUOTIENT` | `2**24` (= 16,777,216) |
 | `MIN_SLASHING_PENALTY_QUOTIENT` | `2**5` (= 32) |
- The `INACTIVITY_PENALTY_QUOTIENT` equals `INVERSE_SQRT_E_DROP_TIME**2` where `INVERSE_SQRT_E_DROP_TIME := 2**12 epochs` (about 18 days) is the time it takes the inactivity penalty to reduce the balance of non-participating validators to about `1/sqrt(e) ~= 60.6%`. Indeed, the balance retained by offline validators after `n` epochs is about `(1 - 1/INACTIVITY_PENALTY_QUOTIENT)**(n**2/2)`; so after `INVERSE_SQRT_E_DROP_TIME` epochs, it is roughly `(1 - 1/INACTIVITY_PENALTY_QUOTIENT)**(INACTIVITY_PENALTY_QUOTIENT/2) ~= 1/sqrt(e)`.
+- The `INACTIVITY_PENALTY_QUOTIENT` equals `INVERSE_SQRT_E_DROP_TIME**2` where `INVERSE_SQRT_E_DROP_TIME := 2**12` epochs (about 18 days) is the time it takes the inactivity penalty to reduce the balance of non-participating validators to about `1/sqrt(e) ~= 60.6%`. Indeed, the balance retained by offline validators after `n` epochs is about `(1 - 1/INACTIVITY_PENALTY_QUOTIENT)**(n**2/2)`; so after `INVERSE_SQRT_E_DROP_TIME` epochs, it is roughly `(1 - 1/INACTIVITY_PENALTY_QUOTIENT)**(INACTIVITY_PENALTY_QUOTIENT/2) ~= 1/sqrt(e)`.
 ### Max operations per block
 | Name | Value |
 | - | - |
 | `MAX_PROPOSER_SLASHINGS` | `2**4` (= 16) |
-| `MAX_ATTESTER_SLASHINGS` | `2**0` (= 1) |
+| `MAX_ATTESTER_SLASHINGS` | `2**1` (= 2) |
 | `MAX_ATTESTATIONS` | `2**7` (= 128) |
 | `MAX_DEPOSITS` | `2**4` (= 16) |
 | `MAX_VOLUNTARY_EXITS` | `2**4` (= 16) |
@ -269,7 +274,6 @@ The following values are (non-configurable) constants used throughout the specif
 | `DOMAIN_SELECTION_PROOF`     | `DomainType('0x05000000')` |
 | `DOMAIN_AGGREGATE_AND_PROOF` | `DomainType('0x06000000')` |
 ## Containers
 The following types are [SimpleSerialize (SSZ)](../../ssz/simple-serialize.md) containers.
@ -399,10 +403,10 @@ class BeaconBlockHeader(Container):
    body_root: Root
 ```
-#### `SigningRoot`
+#### `SigningData`
 ```python
-class SigningRoot(Container):
+class SigningData(Container):
    object_root: Root
    domain: Domain
 ```
@ -604,16 +608,18 @@ def bytes_to_int(data: bytes) -> uint64:
 #### BLS Signatures
-Eth2 makes use of BLS signatures as specified in the [IETF draft BLS specification](https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-00). Specifically, eth2 uses the `BLS_SIG_BLS12381G2-SHA256-SSWU-RO-_POP_` ciphersuite which implements the following interfaces:
+Eth2 makes use of BLS signatures as specified in the [IETF draft BLS specification draft-irtf-cfrg-bls-signature-02](https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-02) but uses [Hashing to Elliptic Curves - draft-irtf-cfrg-hash-to-curve-07](https://tools.ietf.org/html/draft-irtf-cfrg-hash-to-curve-07) instead of draft-irtf-cfrg-hash-to-curve-06. Specifically, eth2 uses the `BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_` ciphersuite which implements the following interfaces:
 - `def Sign(SK: int, message: Bytes) -> BLSSignature`
 - `def Verify(PK: BLSPubkey, message: Bytes, signature: BLSSignature) -> bool`
 - `def Aggregate(signatures: Sequence[BLSSignature]) -> BLSSignature`
 - `def FastAggregateVerify(PKs: Sequence[BLSPubkey], message: Bytes, signature: BLSSignature) -> bool`
- `def AggregateVerify(pairs: Sequence[PK: BLSPubkey, message: Bytes], signature: BLSSignature) -> bool`
+- `def AggregateVerify(PKs: Sequence[BLSPubkey], messages: Sequence[Bytes], signature: BLSSignature) -> bool`
 Within these specifications, BLS signatures are treated as a module for notational clarity, thus to verify a signature `bls.Verify(...)` is used.
 *Note*: The non-standard configuration of the BLS and hash to curve specs is temporary and will be resolved once IETF releases BLS spec draft 3.
 ### Predicates
 #### `is_active_validator`
@ -684,15 +690,11 @@ def is_slashable_attestation_data(data_1: AttestationData, data_2: AttestationDa
 ```python
 def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: IndexedAttestation) -> bool:
    """
-    Check if ``indexed_attestation`` has valid indices and signature.
+    Check if ``indexed_attestation`` is not empty, has sorted and unique indices and has a valid aggregate signature.
    """
    indices = indexed_attestation.attesting_indices
    # Verify max number of indices
    if not len(indices) <= MAX_VALIDATORS_PER_COMMITTEE:
        return False
    # Verify indices are sorted and unique
-    if not indices == sorted(set(indices)):
+    indices = indexed_attestation.attesting_indices
    if len(indices) == 0 or not indices == sorted(set(indices)):
        return False
    # Verify aggregate signature
    pubkeys = [state.validators[i].pubkey for i in indices]
@ -722,9 +724,9 @@ def is_valid_merkle_branch(leaf: Bytes32, branch: Sequence[Bytes32], depth: uint
 #### `compute_shuffled_index`
 ```python
-def compute_shuffled_index(index: ValidatorIndex, index_count: uint64, seed: Bytes32) -> ValidatorIndex:
+def compute_shuffled_index(index: uint64, index_count: uint64, seed: Bytes32) -> uint64:
    """
-    Return the shuffled validator index corresponding to ``seed`` (and ``index_count``).
+    Return the shuffled index corresponding to ``seed`` (and ``index_count``).
    """
    assert index < index_count
@ -732,14 +734,14 @@ def compute_shuffled_index(index: ValidatorIndex, index_count: uint64, seed: Byt
    # See the 'generalized domain' algorithm on page 3
    for current_round in range(SHUFFLE_ROUND_COUNT):
        pivot = bytes_to_int(hash(seed + int_to_bytes(current_round, length=1))[0:8]) % index_count
-        flip = ValidatorIndex((pivot + index_count - index) % index_count)
+        flip = (pivot + index_count - index) % index_count
        position = max(index, flip)
        source = hash(seed + int_to_bytes(current_round, length=1) + int_to_bytes(position // 256, length=4))
        byte = source[(position % 256) // 8]
        bit = (byte >> (position % 8)) % 2
        index = flip if bit else index
-    return ValidatorIndex(index)
+    return index
 ```
 #### `compute_proposer_index`
@ -753,11 +755,11 @@ def compute_proposer_index(state: BeaconState, indices: Sequence[ValidatorIndex]
    MAX_RANDOM_BYTE = 2**8 - 1
    i = 0
    while True:
-        candidate_index = indices[compute_shuffled_index(ValidatorIndex(i % len(indices)), len(indices), seed)]
+        candidate_index = indices[compute_shuffled_index(i % len(indices), len(indices), seed)]
        random_byte = hash(seed + int_to_bytes(i // 32, length=8))[i % 32]
        effective_balance = state.validators[candidate_index].effective_balance
        if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte:
-            return ValidatorIndex(candidate_index)
+            return candidate_index
        i += 1
 ```
@ -773,7 +775,7 @@ def compute_committee(indices: Sequence[ValidatorIndex],
    """
    start = (len(indices) * index) // count
    end = (len(indices) * (index + 1)) // count
-    return [indices[compute_shuffled_index(ValidatorIndex(i), len(indices), seed)] for i in range(start, end)]
+    return [indices[compute_shuffled_index(i, len(indices), seed)] for i in range(start, end)]
 ```
 #### `compute_epoch_at_slot`
@ -852,13 +854,12 @@ def compute_domain(domain_type: DomainType, fork_version: Version=None, genesis_
 ```python
 def compute_signing_root(ssz_object: SSZObject, domain: Domain) -> Root:
    """
-    Return the signing root of an object by calculating the root of the object-domain tree.
+    Return the signing root for the corresponding signing data.
    """
-    domain_wrapped_object = SigningRoot(
+    return hash_tree_root(SigningData(
        object_root=hash_tree_root(ssz_object),
        domain=domain,
-    )
+    ))
    return hash_tree_root(domain_wrapped_object)
 ```
 ### Beacon state accessors
@ -1125,7 +1126,7 @@ def slash_validator(state: BeaconState,
    whistleblower_reward = Gwei(validator.effective_balance // WHISTLEBLOWER_REWARD_QUOTIENT)
    proposer_reward = Gwei(whistleblower_reward // PROPOSER_REWARD_QUOTIENT)
    increase_balance(state, proposer_index, proposer_reward)
-    increase_balance(state, whistleblower_index, whistleblower_reward - proposer_reward)
+    increase_balance(state, whistleblower_index, Gwei(whistleblower_reward - proposer_reward))
 ```
 ## Genesis
@ -1136,6 +1137,8 @@ Before the Ethereum 2.0 genesis has been triggered, and for every Ethereum 1.0 b
 - `eth1_timestamp` is the Unix timestamp corresponding to `eth1_block_hash`
 - `deposits` is the sequence of all deposits, ordered chronologically, up to (and including) the block with hash `eth1_block_hash`
 Eth1 blocks must only be considered once they are at least `SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE` seconds old (i.e. `eth1_timestamp + SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE <= current_unix_time`). Due to this constraint, if `GENESIS_DELAY < SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE`, then the `genesis_time` can happen before the time/state is first known. Values should be configured to avoid this case.
 ```python
 def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
                                      eth1_timestamp: uint64,
@ -1146,7 +1149,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
        epoch=GENESIS_EPOCH,
    )
    state = BeaconState(
-        genesis_time=eth1_timestamp - eth1_timestamp % MIN_GENESIS_DELAY + 2 * MIN_GENESIS_DELAY,
+        genesis_time=eth1_timestamp + GENESIS_DELAY,
        fork=fork,
        eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=len(deposits)),
        latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
@ -1174,6 +1177,8 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
    return state
 ```
 *Note*: The ETH1 block with `eth1_timestamp` meeting the minimum genesis active validator count criteria can also occur before `MIN_GENESIS_TIME`.
 ### Genesis state
 Let `genesis_state = candidate_state` whenever `is_valid_genesis_state(candidate_state) is True` for the first time.
@ -1195,7 +1200,7 @@ Let `genesis_block = BeaconBlock(state_root=hash_tree_root(genesis_state))`.
 ## Beacon chain state transition function
-The post-state corresponding to a pre-state `state` and a signed block `signed_block` is defined as `state_transition(state, signed_block)`. State transitions that trigger an unhandled exception (e.g. a failed `assert` or an out-of-range list access) are considered invalid.
+The post-state corresponding to a pre-state `state` and a signed block `signed_block` is defined as `state_transition(state, signed_block)`. State transitions that trigger an unhandled exception (e.g. a failed `assert` or an out-of-range list access) are considered invalid. State transitions that cause a `uint64` overflow or underflow are also considered invalid.
 ```python
 def state_transition(state: BeaconState, signed_block: SignedBeaconBlock, validate_result: bool=True) -> BeaconState:
@ -1223,13 +1228,13 @@ def verify_block_signature(state: BeaconState, signed_block: SignedBeaconBlock)
 ```python
 def process_slots(state: BeaconState, slot: Slot) -> None:
-    assert state.slot <= slot
+    assert state.slot < slot
    while state.slot < slot:
        process_slot(state)
        # Process epoch on the start slot of the next epoch
        if (state.slot + 1) % SLOTS_PER_EPOCH == 0:
            process_epoch(state)
-        state.slot += Slot(1)
+        state.slot = Slot(state.slot + 1)
 ```
 ```python
@ -1343,6 +1348,8 @@ def process_justification_and_finalization(state: BeaconState) -> None:
 #### Rewards and penalties
 ##### Helpers
 ```python
 def get_base_reward(state: BeaconState, index: ValidatorIndex) -> Gwei:
    total_balance = get_total_active_balance(state)
@ -1350,56 +1357,161 @@ def get_base_reward(state: BeaconState, index: ValidatorIndex) -> Gwei:
    return Gwei(effective_balance * BASE_REWARD_FACTOR // integer_squareroot(total_balance) // BASE_REWARDS_PER_EPOCH)
 ```
 ```python
-def get_attestation_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
+def get_proposer_reward(state: BeaconState, attesting_index: ValidatorIndex) -> Gwei:
    return Gwei(get_base_reward(state, attesting_index) // PROPOSER_REWARD_QUOTIENT)
 ```
 ```python
 def get_finality_delay(state: BeaconState) -> uint64:
    return get_previous_epoch(state) - state.finalized_checkpoint.epoch
 ```
 ```python
 def is_in_inactivity_leak(state: BeaconState) -> bool:
    return get_finality_delay(state) > MIN_EPOCHS_TO_INACTIVITY_PENALTY
 ```
 ```python
 def get_eligible_validator_indices(state: BeaconState) -> Sequence[ValidatorIndex]:
    previous_epoch = get_previous_epoch(state)
-    total_balance = get_total_active_balance(state)
+    return [
    rewards = [Gwei(0) for _ in range(len(state.validators))]
    penalties = [Gwei(0) for _ in range(len(state.validators))]
    eligible_validator_indices = [
        ValidatorIndex(index) for index, v in enumerate(state.validators)
        if is_active_validator(v, previous_epoch) or (v.slashed and previous_epoch + 1 < v.withdrawable_epoch)
    ]
 ```
-    # Micro-incentives for matching FFG source, FFG target, and head
+```python
-    matching_source_attestations = get_matching_source_attestations(state, previous_epoch)
+def get_attestation_component_deltas(state: BeaconState,
-    matching_target_attestations = get_matching_target_attestations(state, previous_epoch)
+                                     attestations: Sequence[PendingAttestation]
-    matching_head_attestations = get_matching_head_attestations(state, previous_epoch)
+                                     ) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
-    for attestations in (matching_source_attestations, matching_target_attestations, matching_head_attestations):
+    """
-        unslashed_attesting_indices = get_unslashed_attesting_indices(state, attestations)
+    Helper with shared logic for use by get source, target, and head deltas functions
-        attesting_balance = get_total_balance(state, unslashed_attesting_indices)
+    """
-        for index in eligible_validator_indices:
+    rewards = [Gwei(0)] * len(state.validators)
-            if index in unslashed_attesting_indices:
+    penalties = [Gwei(0)] * len(state.validators)
-                increment = EFFECTIVE_BALANCE_INCREMENT  # Factored out from balance totals to avoid uint64 overflow
+    total_balance = get_total_active_balance(state)
    unslashed_attesting_indices = get_unslashed_attesting_indices(state, attestations)
    attesting_balance = get_total_balance(state, unslashed_attesting_indices)
    for index in get_eligible_validator_indices(state):
        if index in unslashed_attesting_indices:
            increment = EFFECTIVE_BALANCE_INCREMENT  # Factored out from balance totals to avoid uint64 overflow
            if is_in_inactivity_leak(state):
                # Since full base reward will be canceled out by inactivity penalty deltas,
                # optimal participation receives full base reward compensation here.
                rewards[index] += get_base_reward(state, index)
            else:
                reward_numerator = get_base_reward(state, index) * (attesting_balance // increment)
                rewards[index] += reward_numerator // (total_balance // increment)
-            else:
+        else:
-                penalties[index] += get_base_reward(state, index)
+            penalties[index] += get_base_reward(state, index)
    return rewards, penalties
 ```
-    # Proposer and inclusion delay micro-rewards
+##### Components of attestation deltas
 ```python
 def get_source_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
    """
    Return attester micro-rewards/penalties for source-vote for each validator.
    """
    matching_source_attestations = get_matching_source_attestations(state, get_previous_epoch(state))
    return get_attestation_component_deltas(state, matching_source_attestations)
 ```
 ```python
 def get_target_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
    """
    Return attester micro-rewards/penalties for target-vote for each validator.
    """
    matching_target_attestations = get_matching_target_attestations(state, get_previous_epoch(state))
    return get_attestation_component_deltas(state, matching_target_attestations)
 ```
 ```python
 def get_head_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
    """
    Return attester micro-rewards/penalties for head-vote for each validator.
    """
    matching_head_attestations = get_matching_head_attestations(state, get_previous_epoch(state))
    return get_attestation_component_deltas(state, matching_head_attestations)
 ```
 ```python
 def get_inclusion_delay_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
    """
    Return proposer and inclusion delay micro-rewards/penalties for each validator.
    """
    rewards = [Gwei(0) for _ in range(len(state.validators))]
    matching_source_attestations = get_matching_source_attestations(state, get_previous_epoch(state))
    for index in get_unslashed_attesting_indices(state, matching_source_attestations):
        attestation = min([
            a for a in matching_source_attestations
            if index in get_attesting_indices(state, a.data, a.aggregation_bits)
        ], key=lambda a: a.inclusion_delay)
-        proposer_reward = Gwei(get_base_reward(state, index) // PROPOSER_REWARD_QUOTIENT)
+        rewards[attestation.proposer_index] += get_proposer_reward(state, index)
-        rewards[attestation.proposer_index] += proposer_reward
+        max_attester_reward = get_base_reward(state, index) - get_proposer_reward(state, index)
        max_attester_reward = get_base_reward(state, index) - proposer_reward
        rewards[index] += Gwei(max_attester_reward // attestation.inclusion_delay)
-    # Inactivity penalty
+    # No penalties associated with inclusion delay
-    finality_delay = previous_epoch - state.finalized_checkpoint.epoch
+    penalties = [Gwei(0) for _ in range(len(state.validators))]
-    if finality_delay > MIN_EPOCHS_TO_INACTIVITY_PENALTY:
+    return rewards, penalties
 ```
 ```python
 def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
    """
    Return inactivity reward/penalty deltas for each validator.
    """
    penalties = [Gwei(0) for _ in range(len(state.validators))]
    if is_in_inactivity_leak(state):
        matching_target_attestations = get_matching_target_attestations(state, get_previous_epoch(state))
        matching_target_attesting_indices = get_unslashed_attesting_indices(state, matching_target_attestations)
-        for index in eligible_validator_indices:
+        for index in get_eligible_validator_indices(state):
-            penalties[index] += Gwei(BASE_REWARDS_PER_EPOCH * get_base_reward(state, index))
+            # If validator is performing optimally this cancels all rewards for a neutral balance
            base_reward = get_base_reward(state, index)
            penalties[index] += Gwei(BASE_REWARDS_PER_EPOCH * base_reward - get_proposer_reward(state, index))
            if index not in matching_target_attesting_indices:
                effective_balance = state.validators[index].effective_balance
-                penalties[index] += Gwei(effective_balance * finality_delay // INACTIVITY_PENALTY_QUOTIENT)
+                penalties[index] += Gwei(effective_balance * get_finality_delay(state) // INACTIVITY_PENALTY_QUOTIENT)
    # No rewards associated with inactivity penalties
    rewards = [Gwei(0) for _ in range(len(state.validators))]
    return rewards, penalties
 ```
 ##### `get_attestation_deltas`
 ```python
 def get_attestation_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
    """
    Return attestation reward/penalty deltas for each validator.
    """
    source_rewards, source_penalties = get_source_deltas(state)
    target_rewards, target_penalties = get_target_deltas(state)
    head_rewards, head_penalties = get_head_deltas(state)
    inclusion_delay_rewards, _ = get_inclusion_delay_deltas(state)
    _, inactivity_penalties = get_inactivity_penalty_deltas(state)
    rewards = [
        source_rewards[i] + target_rewards[i] + head_rewards[i] + inclusion_delay_rewards[i]
        for i in range(len(state.validators))
    ]
    penalties = [
        source_penalties[i] + target_penalties[i] + head_penalties[i] + inactivity_penalties[i]
        for i in range(len(state.validators))
    ]
    return rewards, penalties
 ```
 ##### `process_rewards_and_penalties`
 ```python
 def process_rewards_and_penalties(state: BeaconState) -> None:
    if get_current_epoch(state) == GENESIS_EPOCH:
@ -1498,6 +1610,8 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
 def process_block_header(state: BeaconState, block: BeaconBlock) -> None:
    # Verify that the slots match
    assert block.slot == state.slot
    # Verify that the block is newer than latest block header
    assert block.slot > state.latest_block_header.slot
    # Verify that proposer index is the correct index
    assert block.proposer_index == get_beacon_proposer_index(state)
    # Verify that the parent matches
@ -1693,7 +1807,7 @@ def process_voluntary_exit(state: BeaconState, signed_voluntary_exit: SignedVolu
    # Exits must specify an epoch when they become valid; they are not valid before then
    assert get_current_epoch(state) >= voluntary_exit.epoch
    # Verify the validator has been active long enough
-    assert get_current_epoch(state) >= validator.activation_epoch + PERSISTENT_COMMITTEE_PERIOD
+    assert get_current_epoch(state) >= validator.activation_epoch + SHARD_COMMITTEE_PERIOD
    # Verify signature
    domain = get_domain(state, DOMAIN_VOLUNTARY_EXIT, voluntary_exit.epoch)
    signing_root = compute_signing_root(voluntary_exit, domain)
--- a/specs/phase0/fork-choice.md
+++ b/specs/phase0/fork-choice.md
@ -150,7 +150,7 @@ def get_ancestor(store: Store, root: Root, slot: Slot) -> Root:
    elif block.slot == slot:
        return root
    else:
-        # root is older than queried slot, thus a skip slot. Return earliest root prior to slot
+        # root is older than queried slot, thus a skip slot. Return most recent root prior to slot
        return root
 ```
@ -273,19 +273,22 @@ def validate_on_attestation(store: Store, attestation: Attestation) -> None:
    current_epoch = compute_epoch_at_slot(get_current_slot(store))
    # Use GENESIS_EPOCH for previous when genesis to avoid underflow
    previous_epoch = current_epoch - 1 if current_epoch > GENESIS_EPOCH else GENESIS_EPOCH
    # If attestation target is from a future epoch, delay consideration until the epoch arrives
    assert target.epoch in [current_epoch, previous_epoch]
    assert target.epoch == compute_epoch_at_slot(attestation.data.slot)
    # Attestations target be for a known block. If target block is unknown, delay consideration until the block is found
    assert target.root in store.blocks
    # Attestations cannot be from future epochs. If they are, delay consideration until the epoch arrives
    assert get_current_slot(store) >= compute_start_slot_at_epoch(target.epoch)
    # Attestations must be for a known block. If block is unknown, delay consideration until the block is found
    assert attestation.data.beacon_block_root in store.blocks
    # Attestations must not be for blocks in the future. If not, the attestation should not be considered
    assert store.blocks[attestation.data.beacon_block_root].slot <= attestation.data.slot
    # LMD vote must be consistent with FFG vote target
    target_slot = compute_start_slot_at_epoch(target.epoch)
    assert target.root == get_ancestor(store, attestation.data.beacon_block_root, target_slot)
    # Attestations can only affect the fork choice of subsequent slots.
    # Delay consideration in the fork choice until their slot is in the past.
    assert get_current_slot(store) >= attestation.data.slot + 1
--- a/specs/phase0/p2p-interface.md
+++ b/specs/phase0/p2p-interface.md
@ -4,7 +4,7 @@ This document contains the networking specification for Ethereum 2.0 clients.
 It consists of four main sections:
-1. A specification of the network fundamentals detailing the two network configurations: interoperability test network and mainnet launch.
+1. A specification of the network fundamentals.
 2. A specification of the three network interaction *domains* of Eth2: (a) the gossip domain, (b) the discovery domain, and (c) the Req/Resp domain.
 3. The rationale and further explanation for the design choices made in the previous two sections.
 4. An analysis of the maturity/state of the libp2p features required by this spec across the languages in which Eth2 clients are being developed.
@ -17,14 +17,8 @@ It consists of four main sections:
 - [Network fundamentals](#network-fundamentals)
  - [Transport](#transport)
      - [Interop](#interop)
      - [Mainnet](#mainnet)
  - [Encryption and identification](#encryption-and-identification)
      - [Interop](#interop-1)
      - [Mainnet](#mainnet-1)
  - [Protocol Negotiation](#protocol-negotiation)
      - [Interop](#interop-2)
      - [Mainnet](#mainnet-2)
  - [Multiplexing](#multiplexing)
 - [Eth2 network interaction domains](#eth2-network-interaction-domains)
  - [Configuration](#configuration)
@ -33,11 +27,8 @@ It consists of four main sections:
    - [Topics and messages](#topics-and-messages)
      - [Global topics](#global-topics)
      - [Attestation subnets](#attestation-subnets)
-      - [Interop](#interop-3)
+      - [Attestations and Aggregation](#attestations-and-aggregation)
      - [Mainnet](#mainnet-3)
    - [Encodings](#encodings)
      - [Interop](#interop-4)
      - [Mainnet](#mainnet-4)
  - [The Req/Resp domain](#the-reqresp-domain)
    - [Protocol identification](#protocol-identification)
    - [Req/Resp interaction](#reqresp-interaction)
@ -56,29 +47,25 @@ It consists of four main sections:
    - [Integration into libp2p stacks](#integration-into-libp2p-stacks)
    - [ENR structure](#enr-structure)
      - [Attestation subnet bitfield](#attestation-subnet-bitfield)
-      - [Interop](#interop-5)
+      - [`eth2` field](#eth2-field)
-      - [Mainnet](#mainnet-5)
+      - [General capabilities](#general-capabilities)
        - [`eth2` field](#eth2-field)
        - [General capabilities](#general-capabilities)
    - [Topic advertisement](#topic-advertisement)
      - [Mainnet](#mainnet-6)
 - [Design decision rationale](#design-decision-rationale)
  - [Transport](#transport-1)
    - [Why are we defining specific transports?](#why-are-we-defining-specific-transports)
    - [Can clients support other transports/handshakes than the ones mandated by the spec?](#can-clients-support-other-transportshandshakes-than-the-ones-mandated-by-the-spec)
    - [What are the advantages of using TCP/QUIC/Websockets?](#what-are-the-advantages-of-using-tcpquicwebsockets)
    - [Why do we not just support a single transport?](#why-do-we-not-just-support-a-single-transport)
-    - [Why are we not using QUIC for mainnet from the start?](#why-are-we-not-using-quic-for-mainnet-from-the-start)
+    - [Why are we not using QUIC from the start?](#why-are-we-not-using-quic-from-the-start)
  - [Multiplexing](#multiplexing-1)
    - [Why are we using mplex/yamux?](#why-are-we-using-mplexyamux)
  - [Protocol Negotiation](#protocol-negotiation-1)
-    - [When is multiselect 2.0 due and why are we using it for mainnet?](#when-is-multiselect-20-due-and-why-are-we-using-it-for-mainnet)
+    - [When is multiselect 2.0 due and why do we plan to migrate to it?](#when-is-multiselect-20-due-and-why-do-we-plan-to-migrate-to-it)
    - [What is the difference between connection-level and stream-level protocol negotiation?](#what-is-the-difference-between-connection-level-and-stream-level-protocol-negotiation)
  - [Encryption](#encryption)
-    - [Why are we using SecIO for interop? Why not for mainnet?](#why-are-we-using-secio-for-interop-why-not-for-mainnet)
+    - [Why are we not supporting SecIO?](#why-are-we-not-supporting-secio)
-    - [Why are we using Noise/TLS 1.3 for mainnet?](#why-are-we-using-noisetls-13-for-mainnet)
+    - [Why are we using Noise/TLS 1.3?](#why-are-we-using-noisetls-13)
    - [Why are we using encryption at all?](#why-are-we-using-encryption-at-all)
    - [Will mainnnet networking be untested when it launches?](#will-mainnnet-networking-be-untested-when-it-launches)
  - [Gossipsub](#gossipsub)
    - [Why are we using a pub/sub algorithm for block and attestation propagation?](#why-are-we-using-a-pubsub-algorithm-for-block-and-attestation-propagation)
    - [Why are we using topics to segregate encodings, yet only support one encoding?](#why-are-we-using-topics-to-segregate-encodings-yet-only-support-one-encoding)
@ -105,11 +92,13 @@ It consists of four main sections:
  - [Discovery](#discovery)
    - [Why are we using discv5 and not libp2p Kademlia DHT?](#why-are-we-using-discv5-and-not-libp2p-kademlia-dht)
    - [What is the difference between an ENR and a multiaddr, and why are we using ENRs?](#what-is-the-difference-between-an-enr-and-a-multiaddr-and-why-are-we-using-enrs)
    - [Why do we not form ENRs and find peers until genesis block/state is known?](#why-do-we-not-form-enrs-and-find-peers-until-genesis-blockstate-is-known)
  - [Compression/Encoding](#compressionencoding)
    - [Why are we using SSZ for encoding?](#why-are-we-using-ssz-for-encoding)
    - [Why are we compressing, and at which layers?](#why-are-we-compressing-and-at-which-layers)
    - [Why are using Snappy for compression?](#why-are-using-snappy-for-compression)
    - [Can I get access to unencrypted bytes on the wire for debugging purposes?](#can-i-get-access-to-unencrypted-bytes-on-the-wire-for-debugging-purposes)
    - [What are SSZ type size bounds?](#what-are-ssz-type-size-bounds)
 - [libp2p implementations matrix](#libp2p-implementations-matrix)
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
@ -119,46 +108,22 @@ It consists of four main sections:
 This section outlines the specification for the networking stack in Ethereum 2.0 clients.
 Sections that have differing parameters for mainnet launch and interoperability testing are split into subsections. Sections that are not split have the same parameters for interoperability testing as mainnet launch.
 ## Transport
 Even though libp2p is a multi-transport stack (designed to listen on multiple simultaneous transports and endpoints transparently), we hereby define a profile for basic interoperability.
 #### Interop
 All implementations MUST support the TCP libp2p transport, and it MUST be enabled for both dialing and listening (i.e. outbound and inbound connections). The libp2p TCP transport supports listening on IPv4 and IPv6 addresses (and on multiple simultaneously).
-To facilitate connectivity and avert possible IPv6 routability/support issues, clients participating in the interoperability testnet MUST expose at least ONE IPv4 endpoint.
+Clients must support listening on at least one of IPv4 or IPv6. Clients that do _not_ have support for listening on IPv4 SHOULD be cognizant of the potential disadvantages in terms of Internet-wide routability/support. Clients MAY choose to listen only on IPv6, but MUST be capable of dialing both IPv4 and IPv6 addresses.
-All listening endpoints must be publicly dialable, and thus not rely on libp2p circuit relay, AutoNAT, or AutoRelay facilities.
+All listening endpoints must be publicly dialable, and thus not rely on libp2p circuit relay, AutoNAT, or AutoRelay facilities. (Usage of circuit relay, AutoNAT, or AutoRelay will be specifically re-examined soon.)
 Nodes operating behind a NAT, or otherwise undialable by default (e.g. container runtime, firewall, etc.), MUST have their infrastructure configured to enable inbound traffic on the announced public listening endpoint.
 #### Mainnet
 All requirements from the interoperability testnet apply, except for the IPv4 addressing scheme requirement.
 At this stage, clients are licensed to drop IPv4 support if they wish to do so, cognizant of the potential disadvantages in terms of Internet-wide routability/support. Clients MAY choose to listen only on IPv6, but MUST retain capability to dial both IPv4 and IPv6 addresses.
 Usage of circuit relay, AutoNAT, or AutoRelay will be specifically re-examined closer to the time.
 ## Encryption and identification
 #### Interop
 [SecIO](https://github.com/libp2p/specs/tree/master/secio) with `secp256k1` identities will be used for initial interoperability testing.
 The following SecIO parameters MUST be supported by all stacks:
 -  Key agreement: ECDH-P256.
 -  Cipher: AES-128.
 -  Digest: SHA-256.
 #### Mainnet
 The [Libp2p-noise](https://github.com/libp2p/specs/tree/master/noise) secure
-channel handshake with `secp256k1` identities will be used for mainnet.
+channel handshake with `secp256k1` identities will be used for encryption.
 As specified in the libp2p specification, clients MUST support the `XX` handshake pattern.
@ -166,13 +131,7 @@ As specified in the libp2p specification, clients MUST support the `XX` handshak
 Clients MUST use exact equality when negotiating protocol versions to use and MAY use the version to give priority to higher version numbers.
-#### Interop
+Clients MUST support [multistream-select 1.0](https://github.com/multiformats/multistream-select/) and MAY support [multiselect 2.0](https://github.com/libp2p/specs/pull/95) when the spec solidifies. Once all clients have implementations for multiselect 2.0, multistream-select 1.0 MAY be phased out.
 Connection-level and stream-level (see the [Rationale](#design-decision-rationale) section below for explanations) protocol negotiation MUST be conducted using [multistream-select v1.0](https://github.com/multiformats/multistream-select/). Its protocol ID is: `/multistream/1.0.0`.
 #### Mainnet
 Clients MUST support [multistream-select 1.0](https://github.com/multiformats/multistream-select/) and MAY support [multiselect 2.0](https://github.com/libp2p/specs/pull/95). Depending on the number of clients that have implementations for multiselect 2.0 by mainnet, [multistream-select 1.0](https://github.com/multiformats/multistream-select/) may be phased out.
 ## Multiplexing
@ -180,7 +139,7 @@ During connection bootstrapping, libp2p dynamically negotiates a mutually suppor
 Two multiplexers are commonplace in libp2p implementations: [mplex](https://github.com/libp2p/specs/tree/master/mplex) and [yamux](https://github.com/hashicorp/yamux/blob/master/spec.md). Their protocol IDs are, respectively: `/mplex/6.7.0` and `/yamux/1.0.0`.
-Clients MUST support [mplex](https://github.com/libp2p/specs/tree/master/mplex) and MAY support [yamux](https://github.com/hashicorp/yamux/blob/master/spec.md). If both are supported by the client, yamux must take precedence during negotiation. See the [Rationale](#design-decision-rationale) section below for tradeoffs.
+Clients MUST support [mplex](https://github.com/libp2p/specs/tree/master/mplex) and MAY support [yamux](https://github.com/hashicorp/yamux/blob/master/spec.md). If both are supported by the client, yamux MUST take precedence during negotiation. See the [Rationale](#design-decision-rationale) section below for tradeoffs.
 # Eth2 network interaction domains
@ -191,8 +150,8 @@ This section outlines constants that are used in this spec.
 | Name | Value | Description |
 |---|---|---|
 | `GOSSIP_MAX_SIZE` | `2**20` (= 1048576, 1 MiB) | The maximum allowed size of uncompressed gossip messages. |
 | `MAX_REQUEST_BLOCKS` | `2**10` (= 1024) | Maximum number of blocks in a single request |
 | `MAX_CHUNK_SIZE` | `2**20` (1048576, 1 MiB) | The maximum allowed size of uncompressed req/resp chunked responses. |
 | `ATTESTATION_SUBNET_COUNT` | `64` | The number of attestation subnets used in the gossipsub protocol. |
 | `TTFB_TIMEOUT` | `5s` | The maximum time to wait for first byte of request response (time-to-first-byte). |
 | `RESP_TIMEOUT` | `10s` | The maximum time for complete response transfer. |
 | `ATTESTATION_PROPAGATION_SLOT_RANGE` | `32` | The maximum number of slots during which an attestation can be propagated. |
@ -218,9 +177,9 @@ Where
 ## The gossip domain: gossipsub
-Clients MUST support the [gossipsub](https://github.com/libp2p/specs/tree/master/pubsub/gossipsub) libp2p protocol.
+Clients MUST support the [gossipsub v1](https://github.com/libp2p/specs/tree/master/pubsub/gossipsub) libp2p protocol including the [gossipsub v1.1](https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/gossipsub-v1.1.md) extension.
-**Protocol ID:** `/meshsub/1.0.0`
+**Protocol ID:** `/meshsub/1.1.0`
 **Gossipsub Parameters**
@ -245,7 +204,9 @@ Topics are plain UTF-8 strings and are encoded on the wire as determined by prot
    - `current_fork_version` is the fork version of the epoch of the message to be sent on the topic
    - `genesis_validators_root` is the static `Root` found in `state.genesis_validators_root`
 - `Name` - see table below
- `Encoding` - the encoding strategy describes a specific representation of bytes that will be transmitted over the wire. See the [Encodings](#Encoding-strategies) section for further details.
+- `Encoding` - the encoding strategy describes a specific representation of bytes that will be transmitted over the wire. See the [Encodings](#Encodings) section for further details.
 *Note*: `ForkDigestValue` is composed of values that are not known until the genesis block/state are available. Due to this, clients SHOULD NOT subscribe to gossipsub topics until these genesis values are known.
 Each gossipsub [message](https://github.com/libp2p/go-libp2p-pubsub/blob/master/pb/rpc.proto#L17-L24) has a maximum size of `GOSSIP_MAX_SIZE`. Clients MUST reject (fail validation) messages that are over this size limit. Likewise, clients MUST NOT emit or propagate messages larger than this limit.
@ -258,77 +219,74 @@ where `base64` is the [URL-safe base64 alphabet](https://tools.ietf.org/html/rfc
 The payload is carried in the `data` field of a gossipsub message, and varies depending on the topic:
-| Name                                           | Message Type            |
+| Name                             | Message Type              |
-|------------------------------------------------|-------------------------|
+|----------------------------------|---------------------------|
-| beacon_block                                   | SignedBeaconBlock       |
+| `beacon_block`                   | `SignedBeaconBlock`       |
-| beacon_aggregate_and_proof                     | SignedAggregateAndProof |
+| `beacon_aggregate_and_proof`     | `SignedAggregateAndProof` |
-| beacon_attestation\*                           | Attestation             |
+| `beacon_attestation_{subnet_id}` | `Attestation`             |
-| committee_index{subnet_id}\_beacon_attestation | Attestation             |
+| `voluntary_exit`                 | `SignedVoluntaryExit`     |
-| voluntary_exit                                 | SignedVoluntaryExit     |
+| `proposer_slashing`              | `ProposerSlashing`        |
-| proposer_slashing                              | ProposerSlashing        |
+| `attester_slashing`              | `AttesterSlashing`        |
 | attester_slashing                              | AttesterSlashing        |
 Clients MUST reject (fail validation) messages containing an incorrect type, or invalid payload.
 When processing incoming gossip, clients MAY descore or disconnect peers who fail to observe these constraints.
-\* The `beacon_attestation` topic is only for interop and will be removed prior to mainnet.
+Gossipsub v1.1 introduces [Extended Validators](https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/gossipsub-v1.1.md#extended-validators) for the application to aid in the gossipsub peer-scoring scheme.
 We utilize `ACCEPT`, `REJECT`, and `IGNORE`. For each gossipsub topic, there are application specific validations. If all validations pass, return `ACCEPT`. If one or more validations fail while processing the items in order, return either `REJECT` or `IGNORE` as specified in the prefix of the particular condition.
 #### Global topics
 There are two primary global topics used to propagate beacon blocks and aggregate attestations to all nodes on the network. Their `Name`s are:
 - `beacon_block` - This topic is used solely for propagating new signed beacon blocks to all nodes on the networks. Signed blocks are sent in their entirety. The following validations MUST pass before forwarding the `signed_beacon_block` on the network
-    - The block is not from a future slot (with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance) -- i.e. validate that `signed_beacon_block.message.slot <= current_slot` (a client MAY queue future blocks for processing at the appropriate slot).
+    - _[IGNORE]_ The block is not from a future slot (with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance) -- i.e. validate that `signed_beacon_block.message.slot <= current_slot` (a client MAY queue future blocks for processing at the appropriate slot).
-    - The block is from a slot greater than the latest finalized slot -- i.e. validate that `signed_beacon_block.message.slot > compute_start_slot_at_epoch(state.finalized_checkpoint.epoch)` (a client MAY choose to validate and store such blocks for additional purposes -- e.g. slashing detection, archive nodes, etc).
+    - _[IGNORE]_ The block is from a slot greater than the latest finalized slot -- i.e. validate that `signed_beacon_block.message.slot > compute_start_slot_at_epoch(state.finalized_checkpoint.epoch)` (a client MAY choose to validate and store such blocks for additional purposes -- e.g. slashing detection, archive nodes, etc).
-    - The block is the first block with valid signature received for the proposer for the slot, `signed_beacon_block.message.slot`.
+    - _[IGNORE]_ The block is the first block with valid signature received for the proposer for the slot, `signed_beacon_block.message.slot`.
-    - The proposer signature, `signed_beacon_block.signature`, is valid with respect to the `proposer_index` pubkey.
+    - _[REJECT]_ The proposer signature, `signed_beacon_block.signature`, is valid with respect to the `proposer_index` pubkey.
-    - The block is proposed by the expected `proposer_index` for the block's slot in the context of the current shuffling (defined by `parent_root`/`slot`). If the `proposer_index` cannot immediately be verified against the expected shuffling, the block MAY be queued for later processing while proposers for the block's branch are calculated.
+    - _[REJECT]_ The block is proposed by the expected `proposer_index` for the block's slot in the context of the current shuffling (defined by `parent_root`/`slot`). If the `proposer_index` cannot immediately be verified against the expected shuffling, the block MAY be queued for later processing while proposers for the block's branch are calculated -- in such a case _do not_ `REJECT`, instead `IGNORE` this message.
 - `beacon_aggregate_and_proof` - This topic is used to propagate aggregated attestations (as `SignedAggregateAndProof`s) to subscribing nodes (typically validators) to be included in future blocks. The following validations MUST pass before forwarding the `signed_aggregate_and_proof` on the network. (We define the following for convenience -- `aggregate_and_proof = signed_aggregate_and_proof.message` and `aggregate = aggregate_and_proof.aggregate`)
-    - `aggregate.data.slot` is within the last `ATTESTATION_PROPAGATION_SLOT_RANGE` slots (with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance) -- i.e. `aggregate.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= aggregate.data.slot` (a client MAY queue future aggregates for processing at the appropriate slot).
+    - _[IGNORE]_ `aggregate.data.slot` is within the last `ATTESTATION_PROPAGATION_SLOT_RANGE` slots (with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance) -- i.e. `aggregate.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= aggregate.data.slot` (a client MAY queue future aggregates for processing at the appropriate slot).
-    - The aggregate attestation defined by `hash_tree_root(aggregate)` has _not_ already been seen (via aggregate gossip, within a block, or through the creation of an equivalent aggregate locally).
+    - _[IGNORE]_ The valid aggregate attestation defined by `hash_tree_root(aggregate)` has _not_ already been seen (via aggregate gossip, within a verified block, or through the creation of an equivalent aggregate locally).
-    - The `aggregate` is the first valid aggregate received for the aggregator with index `aggregate_and_proof.aggregator_index` for the slot `aggregate.data.slot`.
+    - _[IGNORE]_ The `aggregate` is the first valid aggregate received for the aggregator with index `aggregate_and_proof.aggregator_index` for the epoch `aggregate.data.target.epoch`.
-    - The block being voted for (`aggregate.data.beacon_block_root`) passes validation.
+    - _[REJECT]_ The block being voted for (`aggregate.data.beacon_block_root`) passes validation.
-    - `aggregate_and_proof.selection_proof` selects the validator as an aggregator for the slot -- i.e. `is_aggregator(state, aggregate.data.slot, aggregate.data.index, aggregate_and_proof.selection_proof)` returns `True`.
+    - _[REJECT]_ The attestation has participants -- that is, `len(get_attesting_indices(state, aggregate.data, aggregate.aggregation_bits)) >= 1`.
-    - The aggregator's validator index is within the aggregate's committee -- i.e. `aggregate_and_proof.aggregator_index in get_attesting_indices(state, aggregate.data, aggregate.aggregation_bits)`.
+    - _[REJECT]_ `aggregate_and_proof.selection_proof` selects the validator as an aggregator for the slot -- i.e. `is_aggregator(state, aggregate.data.slot, aggregate.data.index, aggregate_and_proof.selection_proof)` returns `True`.
-    - The `aggregate_and_proof.selection_proof` is a valid signature of the `aggregate.data.slot` by the validator with index `aggregate_and_proof.aggregator_index`.
+    - _[REJECT]_ The aggregator's validator index is within the committee -- i.e. `aggregate_and_proof.aggregator_index in get_beacon_committee(state, aggregate.data.slot, aggregate.data.index)`.
-    - The aggregator signature, `signed_aggregate_and_proof.signature`, is valid.
+    - _[REJECT]_ The `aggregate_and_proof.selection_proof` is a valid signature of the `aggregate.data.slot` by the validator with index `aggregate_and_proof.aggregator_index`.
-    - The signature of `aggregate` is valid.
+    - _[REJECT]_ The aggregator signature, `signed_aggregate_and_proof.signature`, is valid.
    - _[REJECT]_ The signature of `aggregate` is valid.
 Additional global topics are used to propagate lower frequency validator messages. Their `Name`s are:
 - `voluntary_exit` - This topic is used solely for propagating signed voluntary validator exits to proposers on the network. Signed voluntary exits are sent in their entirety. The following validations MUST pass before forwarding the `signed_voluntary_exit` on to the network
-    - The voluntary exit is the first valid voluntary exit received for the validator with index `signed_voluntary_exit.message.validator_index`.
+    - _[IGNORE]_ The voluntary exit is the first valid voluntary exit received for the validator with index `signed_voluntary_exit.message.validator_index`.
-    - All of the conditions within `process_voluntary_exit` pass validation.
+    - _[REJECT]_ All of the conditions within `process_voluntary_exit` pass validation.
 - `proposer_slashing` - This topic is used solely for propagating proposer slashings to proposers on the network. Proposer slashings are sent in their entirety. The following validations MUST pass before forwarding the `proposer_slashing` on to the network
-    - The proposer slashing is the first valid proposer slashing received for the proposer with index `proposer_slashing.index`.
+    - _[IGNORE]_ The proposer slashing is the first valid proposer slashing received for the proposer with index `proposer_slashing.index`.
-    - All of the conditions within `process_proposer_slashing` pass validation.
+    - _[REJECT]_ All of the conditions within `process_proposer_slashing` pass validation.
 - `attester_slashing` - This topic is used solely for propagating attester slashings to proposers on the network. Attester slashings are sent in their entirety. Clients who receive an attester slashing on this topic MUST validate the conditions within `process_attester_slashing` before forwarding it across the network.
-    - At least one index in the intersection of the attesting indices of each attestation has not yet been seen in any prior `attester_slashing` (i.e. `attester_slashed_indices = set(attestation_1.attesting_indices).intersection(attestation_2.attesting_indices)`, verify if `any(attester_slashed_indices.difference(prior_seen_attester_slashed_indices))`).
+    - _[IGNORE]_ At least one index in the intersection of the attesting indices of each attestation has not yet been seen in any prior `attester_slashing` (i.e. `attester_slashed_indices = set(attestation_1.attesting_indices).intersection(attestation_2.attesting_indices)`, verify if `any(attester_slashed_indices.difference(prior_seen_attester_slashed_indices))`).
-    - All of the conditions within `process_attester_slashing` pass validation.
+    - _[REJECT]_ All of the conditions within `process_attester_slashing` pass validation.
 #### Attestation subnets
 Attestation subnets are used to propagate unaggregated attestations to subsections of the network. Their `Name`s are:
- `committee_index{subnet_id}_beacon_attestation` - These topics are used to propagate unaggregated attestations to the subnet `subnet_id` (typically beacon and persistent committees) to be aggregated before being gossiped to `beacon_aggregate_and_proof`. The following validations MUST pass before forwarding the `attestation` on the subnet.
+- `beacon_attestation_{subnet_id}` - These topics are used to propagate unaggregated attestations to the subnet `subnet_id` (typically beacon and persistent committees) to be aggregated before being gossiped to `beacon_aggregate_and_proof`. The following validations MUST pass before forwarding the `attestation` on the subnet.
-    - The attestation's committee index (`attestation.data.index`) is for the correct subnet.
+    - _[REJECT]_ The attestation is for the correct subnet (i.e. `compute_subnet_for_attestation(state, attestation) == subnet_id`).
-    - `attestation.data.slot` is within the last `ATTESTATION_PROPAGATION_SLOT_RANGE` slots (within a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance) -- i.e. `attestation.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= attestation.data.slot` (a client MAY queue future attestations for processing at the appropriate slot).
+    - _[IGNORE]_ `attestation.data.slot` is within the last `ATTESTATION_PROPAGATION_SLOT_RANGE` slots (within a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance) -- i.e. `attestation.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= attestation.data.slot` (a client MAY queue future attestations for processing at the appropriate slot).
-    - The attestation is unaggregated -- that is, it has exactly one participating validator (`len([bit for bit in attestation.aggregation_bits if bit == 0b1]) == 1`).
+    - _[REJECT]_ The attestation is unaggregated -- that is, it has exactly one participating validator (`len(get_attesting_indices(state, attestation.data, attestation.aggregation_bits)) == 1`).
-    - The attestation is the first valid attestation received for the participating validator for the slot, `attestation.data.slot`.
+    - _[IGNORE]_ There has been no other valid attestation seen on an attestation subnet that has an identical `attestation.data.target.epoch` and participating validator index.
-    - The block being voted for (`attestation.data.beacon_block_root`) passes validation.
+    - _[REJECT]_ The block being voted for (`attestation.data.beacon_block_root`) passes validation.
-    - The signature of `attestation` is valid.
+    - _[REJECT]_ The signature of `attestation` is valid.
-#### Interop
+#### Attestations and Aggregation
-Unaggregated and aggregated attestations from all shards are sent as `Attestation`s to the `beacon_attestation` topic. Clients are not required to publish aggregate attestations but must be able to process them. All validating clients SHOULD try to perform local attestation aggregation to prepare for block proposing.
+Attestation broadcasting is grouped into subnets defined by a topic. The number of subnets is defined via `ATTESTATION_SUBNET_COUNT`. The correct subnet for an attestation can be calculated with `compute_subnet_for_attestation`. `beacon_attestation_{subnet_id}` topics, are rotated through throughout the epoch in a similar fashion to rotating through shards in committees in Phase 1.
-#### Mainnet
+Unaggregated attestations are sent to the subnet topic, `beacon_attestation_{compute_subnet_for_attestation(state, attestation)}` as `Attestation`s.
 Attestation broadcasting is grouped into subnets defined by a topic. The number of subnets is defined via `ATTESTATION_SUBNET_COUNT`. For the `committee_index{subnet_id}_beacon_attestation` topics, `subnet_id` is set to `index % ATTESTATION_SUBNET_COUNT`, where `index` is the `CommitteeIndex` of the given committee.
 Unaggregated attestations are sent to the subnet topic, `committee_index{attestation.data.index % ATTESTATION_SUBNET_COUNT}_beacon_attestation` as `Attestation`s.
 Aggregated attestations are sent to the `beacon_aggregate_and_proof` topic as `AggregateAndProof`s.
@ -336,15 +294,11 @@ Aggregated attestations are sent to the `beacon_aggregate_and_proof` topic as `A
 Topics are post-fixed with an encoding. Encodings define how the payload of a gossipsub message is encoded.
-#### Interop
+- `ssz_snappy` - All objects are SSZ-encoded and then compressed with [Snappy](https://github.com/google/snappy) block compression. Example: The beacon aggregate attestation topic string is `/eth2/446a7232/beacon_aggregate_and_proof/ssz_snappy`, the fork digest is `446a7232` and the data field of a gossipsub message is an `AggregateAndProof` that has been SSZ-encoded and then compressed with Snappy.
- `ssz` - All objects are [SSZ-encoded](#ssz-encoding). Example: The beacon block topic string is `/eth2/beacon_block/ssz`, and the data field of a gossipsub message is an ssz-encoded `SignedBeaconBlock`.
+Snappy has two formats: "block" and "frames" (streaming). Gossip messages remain relatively small (100s of bytes to 100s of kilobytes) so [basic snappy block compression](https://github.com/google/snappy/blob/master/format_description.txt) is used to avoid the additional overhead associated with snappy frames.
-#### Mainnet
+Implementations MUST use a single encoding for gossip. Changing an encoding will require coordination between participating implementations.
 - `ssz_snappy` - All objects are SSZ-encoded and then compressed with [Snappy](https://github.com/google/snappy). Example: The beacon aggregate attestation topic string is `/eth2/beacon_aggregate_and_proof/ssz_snappy`, and the data field of a gossipsub message is an `AggregateAndProof` that has been SSZ-encoded and then compressed with Snappy.
 Implementations MUST use a single encoding. Changing an encoding will require coordination between participating implementations.
 ## The Req/Resp domain
@ -380,9 +334,12 @@ result    ::= “0” | “1” | “2” | [“128” ... ”255”]
 The encoding-dependent header may carry metadata or assertions such as the encoded payload length, for integrity and attack proofing purposes. Because req/resp streams are single-use and stream closures implicitly delimit the boundaries, it is not strictly necessary to length-prefix payloads; however, certain encodings like SSZ do, for added security.
-A `response` is formed by zero or more `response_chunk`s. Responses that consist of a single SSZ-list (such as `BlocksByRange` and `BlocksByRoot`) send each list item as a `response_chunk`. All other response types (non-Lists) send a single `response_chunk`. The encoded-payload of a `response_chunk` has a maximum uncompressed byte size of `MAX_CHUNK_SIZE`.
+A `response` is formed by zero or more `response_chunk`s. Responses that consist of a single SSZ-list (such as `BlocksByRange` and `BlocksByRoot`) send each list item as a `response_chunk`. All other response types (non-Lists) send a single `response_chunk`.
-Clients MUST ensure the each encoded payload of a `response_chunk` is less than or equal to `MAX_CHUNK_SIZE`; if not, they SHOULD reset the stream immediately. Clients tracking peer reputation MAY decrement the score of the misbehaving peer under this circumstance.
+For both `request`s and `response`s, the `encoding-dependent-header` MUST be valid, and the `encoded-payload` must be valid within the constraints of the `encoding-dependent-header`.
 This includes type-specific bounds on payload size for some encoding strategies. Regardless of these type specific bounds, a global maximum uncompressed byte size of `MAX_CHUNK_SIZE` MUST be applied to all method response chunks.
 Clients MUST ensure that lengths are within these bounds; if not, they SHOULD reset the stream immediately. Clients tracking peer reputation MAY decrement the score of the misbehaving peer under this circumstance.
 #### Requesting side
@ -390,13 +347,22 @@ Once a new stream with the protocol ID for the request type has been negotiated,
 The requester MUST close the write side of the stream once it finishes writing the request message. At this point, the stream will be half-closed.
-The requester MUST wait a maximum of `TTFB_TIMEOUT` for the first response byte to arrive (time to first byte—or TTFB—timeout). On that happening, the requester allows a further `RESP_TIMEOUT` for each subsequent `response_chunk` received. For responses consisting of potentially many `response_chunk`s (an SSZ-list) the requester SHOULD read from the stream until either; a) An error result is received in one of the chunks, b) The responder closes the stream,  c) More than `MAX_CHUNK_SIZE` bytes have been read for a single `response_chunk` payload or d) More than the maximum number of requested chunks are read. For requests consisting of a single `response_chunk` and a length-prefix, the requester should read the exact number of bytes defined by the length-prefix before closing the stream.
+The requester MUST wait a maximum of `TTFB_TIMEOUT` for the first response byte to arrive (time to first byte—or TTFB—timeout). On that happening, the requester allows a further `RESP_TIMEOUT` for each subsequent `response_chunk` received.
 If any of these timeouts fire, the requester SHOULD reset the stream and deem the req/resp operation to have failed.
 A requester SHOULD read from the stream until either:
 1. An error result is received in one of the chunks (the error payload MAY be read before stopping).
 2. The responder closes the stream.
 3. Any part of the `response_chunk` fails validation.
 4. The maximum number of requested chunks are read.
 For requests consisting of a single valid `response_chunk`, the requester SHOULD read the chunk fully, as defined by the `encoding-dependent-header`, before closing the stream.
 #### Responding side
-Once a new stream with the protocol ID for the request type has been negotiated, the responder must process the incoming request message according to the encoding strategy, until EOF (denoting stream half-closure by the requester).
+Once a new stream with the protocol ID for the request type has been negotiated, the responder SHOULD process the incoming request and MUST validate it before processing it.
 Request processing and validation MUST be done according to the encoding strategy, until EOF (denoting stream half-closure by the requester).
 The responder MUST:
@ -426,26 +392,18 @@ The `ErrorMessage` schema is:
 ```
 (
-  error_message: String
+  error_message: List[byte, 256]
 )
 ```
-*Note*: The String type is encoded as UTF-8 bytes without NULL terminator when SSZ-encoded. As the `ErrorMessage` is not an SSZ-container, only the UTF-8 bytes will be sent when SSZ-encoded.
+*Note*: By convention, the `error_message` is a sequence of bytes that MAY be interpreted as a UTF-8 string (for debugging purposes). Clients MUST treat as valid any byte sequences.
 A response therefore has the form of one or more `response_chunk`s, each structured as follows:
 ```
  +--------+--------+--------+--------+--------+--------+
  | result |   header (opt)  |     encoded_response     |
  +--------+--------+--------+--------+--------+--------+
 ```
 Here, `result` represents the 1-byte response code.
 ### Encoding strategies
 The token of the negotiated protocol ID specifies the type of encoding to be used for the req/resp interaction. Two values are possible at this time:
 -  `ssz`: the contents are [SSZ-encoded](../../ssz/simple-serialize.md). This encoding type MUST be supported by all clients. For objects containing a single field, only the field is SSZ-encoded not a container with a single field. For example, the `BeaconBlocksByRoot` request is an SSZ-encoded list of `Root`'s.
-  `ssz_snappy`: The contents are SSZ-encoded and then compressed with [Snappy](https://github.com/google/snappy). MAY be supported in the interoperability testnet; MUST be supported in mainnet.
+-  `ssz_snappy`: The contents are SSZ-encoded and then compressed with [Snappy](https://github.com/google/snappy) frames compression. This encoding type MUST be supported by all clients.
 #### SSZ-encoding strategy (with or without Snappy)
@ -466,26 +424,29 @@ If Snappy is applied, it can be passed through a buffered Snappy writer to compr
 *Reading*: After reading the expected SSZ byte length, the SSZ decoder can directly read the contents from the stream.
 If snappy is applied, it can be passed through a buffered Snappy reader to decompress frame by frame.
-A reader SHOULD NOT read more than `max_encoded_len(n)` bytes after reading the SSZ length prefix `n` from the header.
+Before reading the payload, the header MUST be validated:
 - The unsigned protobuf varint used for the length-prefix MUST not be longer than 10 bytes, which is sufficient for any `uint64`.
 - The length-prefix is within the expected [size bounds derived from the payload SSZ type](#what-are-ssz-type-size-bounds).
 After reading a valid header, the payload MAY be read, while maintaining the size constraints from the header.
 A reader SHOULD NOT read more than `max_encoded_len(n)` bytes after reading the SSZ length-prefix `n` from the header.
 - For `ssz` this is: `n`
 - For `ssz_snappy` this is: `32 + n + n // 6`. This is considered the [worst-case compression result](https://github.com/google/snappy/blob/537f4ad6240e586970fe554614542e9717df7902/snappy.cc#L98) by Snappy.
 A reader SHOULD consider the following cases as invalid input:
- A SSZ length prefix that, compared against the SSZ type information (vector lengths, list limits, integer sizes, etc.), is:
+- Any remaining bytes, after having read the `n` SSZ bytes. An EOF is expected if more bytes are read than required.
-    - Smaller than the expected minimum serialized length.
+- An early EOF, before fully reading the declared length-prefix worth of SSZ bytes.
    - Bigger than the expected maximum serialized length.
 - Any remaining bytes, after having read the `n` SSZ bytes. An EOF is expected.
 - An early EOF, before fully reading the declared length prefix worth of SSZ bytes.
-In case of an invalid input, a reader MUST:
+In case of an invalid input (header or payload), a reader MUST:
 - From requests: send back an error message, response code `InvalidRequest`. The request itself is ignored.
 - From responses: ignore the response, the response MUST be considered bad server behavior.
 All messages that contain only a single field MUST be encoded directly as the type of that field and MUST NOT be encoded as an SSZ container.
-Responses that are SSZ-lists (for example `[]SignedBeaconBlock`) send their
+Responses that are SSZ-lists (for example `List[SignedBeaconBlock, ...]`) send their
 constituents individually as `response_chunk`s. For example, the
-`[]SignedBeaconBlock` response type sends zero or more `response_chunk`s. Each _successful_ `response_chunk` contains a single `SignedBeaconBlock` payload.
+`List[SignedBeaconBlock, ...]` response type sends zero or more `response_chunk`s. Each _successful_ `response_chunk` contains a single `SignedBeaconBlock` payload.
 ### Messages
@ -508,9 +469,9 @@ The fields are, as seen by the client at the time of sending the message:
 - `fork_digest`: The node's `ForkDigest` (`compute_fork_digest(current_fork_version, genesis_validators_root)`) where
    - `current_fork_version` is the fork version at the node's current epoch defined by the wall-clock time (not necessarily the epoch to which the node is sync)
    - `genesis_validators_root` is the static `Root` found in `state.genesis_validators_root`
- `finalized_root`: `state.finalized_checkpoint.root` for the state corresponding to the head block.
+- `finalized_root`: `state.finalized_checkpoint.root` for the state corresponding to the head block (Note this defaults to `Root(b'\x00' * 32)` for the genesis finalized checkpoint).
 - `finalized_epoch`: `state.finalized_checkpoint.epoch` for the state corresponding to the head block.
- `head_root`: The hash_tree_root root of the current head block.
+- `head_root`: The `hash_tree_root` root of the current head block (`BeaconBlock`).
 - `head_slot`: The slot of the block corresponding to the `head_root`.
 The dialing client MUST send a `Status` request upon connection.
@ -568,11 +529,14 @@ Request Content:
 Response Content:
 ```
 (
-  []SignedBeaconBlock
+  List[SignedBeaconBlock, MAX_REQUEST_BLOCKS]
 )
 ```
-Requests count beacon blocks from the peer starting from `start_slot`, leading up to the current head block as selected by fork choice. `step` defines the slot increment between blocks. For example, requesting blocks starting at `start_slot` 2 with a step value of 2 would return the blocks at slots [2, 4, 6, …]. In cases where a slot is empty for a given slot number, no block is returned. For example, if slot 4 were empty in the previous example, the returned array would contain [2, 6, …]. A step value of 1 returns all blocks on the range `[start_slot, start_slot + count)`.
+Requests beacon blocks in the slot range `[start_slot, start_slot + count * step)`, leading up to the current head block as selected by fork choice.
 `step` defines the slot increment between blocks. For example, requesting blocks starting at `start_slot` 2 with a step value of 2 would return the blocks at slots [2, 4, 6, …].
 In cases where a slot is empty for a given slot number, no block is returned. For example, if slot 4 were empty in the previous example, the returned array would contain [2, 6, …].
 A request MUST NOT have a 0 slot increment, i.e. `step >= 1`.
 `BeaconBlocksByRange` is primarily used to sync historical blocks.
@ -582,13 +546,20 @@ The response MUST consist of zero or more `response_chunk`. Each _successful_ `r
 Clients MUST keep a record of signed blocks seen since the since the start of the weak subjectivity period and MUST support serving requests of blocks up to their own `head_block_root`.
-Clients MUST respond with at least one block, if they have it and it exists in the range. Clients MAY limit the number of blocks in the response.
+Clients MUST respond with at least the first block that exists in the range, if they have it, and no more than `MAX_REQUEST_BLOCKS` blocks.
 The following blocks, where they exist, MUST be send in consecutive order.
 Clients MAY limit the number of blocks in the response.
 The response MUST contain no more than `count` blocks.
-Clients MUST order blocks by increasing slot number.
+Clients MUST respond with blocks from their view of the current fork choice -- that is, blocks from the single chain defined by the current head. Of note, blocks from slots before the finalization MUST lead to the finalized block reported in the `Status` handshake.
-Clients MUST respond with blocks from their view of the current fork choice. In particular, blocks from slots before the finalization MUST lead to the finalized block reported in the `Status` handshake.
+Clients MUST respond with blocks that are consistent from a single chain within the context of the request.
 This applies to any `step` value. In particular when `step == 1`, each `parent_root` MUST match the `hash_tree_root` of the preceding block.
 After the initial block, clients MAY stop in the process of responding if their fork choice changes the view of the chain in the context of the request.
 #### BeaconBlocksByRoot
@ -598,7 +569,7 @@ Request Content:
 ```
 (
-  []Root
+  List[Root, MAX_REQUEST_BLOCKS]
 )
 ```
@ -606,12 +577,14 @@ Response Content:
 ```
 (
-  []SignedBeaconBlock
+  List[SignedBeaconBlock, MAX_REQUEST_BLOCKS]
 )
 ```
 Requests blocks by block root (= `hash_tree_root(SignedBeaconBlock.message)`). The response is a list of `SignedBeaconBlock` whose length is less than or equal to the number of requested blocks. It may be less in the case that the responding peer is missing blocks.
 No more than `MAX_REQUEST_BLOCKS` may be requested at a time.
 `BeaconBlocksByRoot` is primarily used to recover recent blocks (e.g. when receiving a block or attestation whose parent is unknown).
 The request MUST be encoded as an SSZ-field.
@ -678,7 +651,7 @@ The response MUST consist of a single `response_chunk`.
 ## The discovery domain: discv5
-Discovery Version 5 ([discv5](https://github.com/ethereum/devp2p/blob/master/discv5/discv5.md)) is used for peer discovery, both in the interoperability testnet and mainnet.
+Discovery Version 5 ([discv5](https://github.com/ethereum/devp2p/blob/master/discv5/discv5.md)) is used for peer discovery.
 `discv5` is a standalone protocol, running on UDP on a dedicated port, meant for peer discovery only. `discv5` supports self-certified, flexible peer records (ENRs) and topic-based advertisement, both of which are (or will be) requirements in this context.
@ -718,15 +691,7 @@ If a node's `MetaData.attnets` has any non-zero bit, the ENR MUST include the `a
 If a node's `MetaData.attnets` is composed of all zeros, the ENR MAY optionally include the `attnets` entry or leave it out entirely.
-#### Interop
+#### `eth2` field
 In the interoperability testnet, all peers will support all capabilities defined in this document (gossip, full Req/Resp suite, discovery protocol), therefore the ENR record does not need to carry Eth2 capability information, as it would be superfluous.
 Nonetheless, ENRs MUST carry a generic `eth2` key with nil value, denoting that the peer is indeed an Eth2 peer, in order to eschew connecting to Eth 1.0 peers.
 #### Mainnet
 ##### `eth2` field
 ENRs MUST carry a generic `eth2` key with an 16-byte value of the node's current fork digest, next fork version, and next fork epoch to ensure connections are made with peers on the intended eth2 network.
@ -752,18 +717,18 @@ where the fields of `ENRForkID` are defined as
 * `next_fork_version` is the fork version corresponding to the next planned hard fork at a future epoch. If no future fork is planned, set `next_fork_version = current_fork_version` to signal this fact
 * `next_fork_epoch` is the epoch at which the next fork is planned and the `current_fork_version` will be updated. If no future fork is planned, set `next_fork_epoch = FAR_FUTURE_EPOCH` to signal this fact
 *Note*: `fork_digest` is composed of values that are not not known until the genesis block/state are available. Due to this, clients SHOULD NOT form ENRs and begin peer discovery until genesis values are known. One notable exception to this rule is the distribution of bootnode ENRs prior to genesis. In this case, bootnode ENRs SHOULD be initially distributed with `eth2` field set as `ENRForkID(fork_digest=compute_fork_digest(GENESIS_FORK_VERSION, b'\x00'*32), next_fork_version=GENESIS_FORK_VERSION, next_fork_epoch=FAR_FUTURE_EPOCH)`. After genesis values are known, the bootnodes SHOULD update ENRs to participate in normal discovery operations.
 Clients SHOULD connect to peers with `fork_digest`, `next_fork_version`, and `next_fork_epoch` that match local values.
 Clients MAY connect to peers with the same `fork_digest` but a different `next_fork_version`/`next_fork_epoch`. Unless `ENRForkID` is manually updated to matching prior to the earlier `next_fork_epoch` of the two clients, these connecting clients will be unable to successfully interact starting at the earlier `next_fork_epoch`.
-##### General capabilities
+#### General capabilities
-On mainnet, ENRs MUST include a structure enumerating the capabilities offered by the peer in an efficient manner. The concrete solution is currently undefined. Proposals include using namespaced bloom filters mapping capabilities to specific protocol IDs supported under that capability.
+ENRs MUST include a structure enumerating the capabilities offered by the peer in an efficient manner. The concrete solution is currently undefined. Proposals include using namespaced bloom filters mapping capabilities to specific protocol IDs supported under that capability.
 ### Topic advertisement
 #### Mainnet
 discv5's topic advertisement feature is not expected to be ready for mainnet launch of Phase 0.
 Once this feature is built out and stable, we expect to use topic advertisement as a rendezvous facility for peers on shards. Until then, the ENR [attestation subnet bitfield](#attestation-subnet-bitfield) will be used for discovery of peers on particular subnets.
@ -809,7 +774,7 @@ Modeling for upgradeability and dynamic transport selection from the get-go lays
 Clients can adopt new transports without breaking old ones, and the multi-transport ability enables constrained and sandboxed environments (e.g. browsers, embedded devices) to interact with the network as first-class citizens via suitable/native transports (e.g. WSS), without the need for proxying or trust delegation to servers.
-### Why are we not using QUIC for mainnet from the start?
+### Why are we not using QUIC from the start?
 The QUIC standard is still not finalized (at working draft 22 at the time of writing), and not all mainstream runtimes/languages have mature, standard, and/or fully-interoperable [QUIC support](https://github.com/quicwg/base-drafts/wiki/Implementations). One remarkable example is node.js, where the QUIC implementation is [in early development](https://github.com/nodejs/quic).
@ -825,13 +790,13 @@ Overlay multiplexers are not necessary with QUIC since the protocol provides nat
 ## Protocol Negotiation
-### When is multiselect 2.0 due and why are we using it for mainnet?
+### When is multiselect 2.0 due and why do we plan to migrate to it?
 multiselect 2.0 is currently being conceptualized. The debate started [on this issue](https://github.com/libp2p/specs/pull/95), but it got overloaded—as it tends to happen with large conceptual OSS discussions that touch the heart and core of a system.
-In the following weeks (August 2019), there will be a renewed initiative to first define the requirements, constraints, assumptions, and features, in order to lock in basic consensus upfront and subsequently build on that consensus by submitting a specification for implementation.
+At some point in 2020, we expect a renewed initiative to first define the requirements, constraints, assumptions, and features, in order to lock in basic consensus upfront and subsequently build on that consensus by submitting a specification for implementation.
-We plan to use multiselect 2.0 for mainnet because it will:
+We plan to eventually migrate to multiselect 2.0 because it will:
 1. Reduce round trips during connection bootstrapping and stream protocol negotiation.
 2. Enable efficient one-stream-per-request interaction patterns.
@ -853,17 +818,15 @@ At present, multistream-select 1.0 is used for both types of negotiation, but mu
 ## Encryption
-### Why are we using SecIO for interop? Why not for mainnet?
+### Why are we not supporting SecIO?
 SecIO has been the default encryption layer for libp2p for years. It is used in IPFS and Filecoin. And although it will be superseded shortly, it is proven to work at scale.
-SecIO is the common denominator across the various language libraries at this stage. It is widely implemented. That’s why we have chosen to use it for initial interop to minimize overhead in getting to a basic interoperability testnet.
+Although SecIO has wide language support, we won’t be using it for mainnet because, amongst other things, it requires several round trips to be sound, and doesn’t support early data (0-RTT data), a mechanism that multiselect 2.0 will leverage to reduce round trips during connection bootstrapping.
 We won’t be using it for mainnet because, amongst other things, it requires several round trips to be sound, and doesn’t support early data (0-RTT data), a mechanism that multiselect 2.0 will leverage to reduce round trips during connection bootstrapping.
 SecIO is not considered secure for the purposes of this spec.
-### Why are we using Noise/TLS 1.3 for mainnet?
+### Why are we using Noise/TLS 1.3?
 Copied from the Noise Protocol Framework [website](http://www.noiseprotocol.org):
@ -889,10 +852,6 @@ Transport level encryption secures message exchange and provides properties that
 Note that transport-level encryption is not exclusive of application-level encryption or cryptography. Transport-level encryption secures the communication itself, while application-level cryptography is necessary for the application’s use cases (e.g. signatures, randomness, etc.).
 ### Will mainnnet networking be untested when it launches?
 Before launching mainnet, the testnet will be switched over to mainnet networking parameters, including Noise handshakes, and other new protocols. This gives us an opportunity to drill coordinated network upgrades and verifying that there are no significant upgradeability gaps.
 ## Gossipsub
 ### Why are we using a pub/sub algorithm for block and attestation propagation?
@ -1001,7 +960,7 @@ Requests are segregated by protocol ID to:
  2. Affording this level of granularity with a top-level protocol would imply creating as many variants (e.g. /protocol/43-{a,b,c,d,...}) as the cartesian product of RFCs inflight, O(n^2).
 7. Allow us to simplify the payload of requests. Request-id’s and method-ids no longer need to be sent. The encoding/request type and version can all be handled by the framework.
-**Caveat**: The protocol negotiation component in the current version of libp2p is called multistream-select 1.0. It is somewhat naïve and introduces overhead on every request when negotiating streams, although implementation-specific optimizations are possible to save this cost. Multiselect 2.0 will remove this overhead by memoizing previously selected protocols, and modeling shared protocol tables. Fortunately, this req/resp protocol is not the expected network bottleneck in the protocol so the additional overhead is not expected to hinder interop testing. More info is to be released from the libp2p community in the coming weeks.
+**Caveat**: The protocol negotiation component in the current version of libp2p is called multistream-select 1.0. It is somewhat naïve and introduces overhead on every request when negotiating streams, although implementation-specific optimizations are possible to save this cost. Multiselect 2.0 will eventually remove this overhead by memoizing previously selected protocols, and modeling shared protocol tables. Fortunately, this req/resp protocol is not the expected network bottleneck in the protocol so the additional overhead is not expected to significantly hinder this domain.
 ### Why are messages length-prefixed with a protobuf varint in the SSZ-encoding?
@ -1092,6 +1051,12 @@ discv5 uses ENRs and we will presumably need to:
 1. Add `multiaddr` to the dictionary, so that nodes can advertise their multiaddr under a reserved namespace in ENRs. – and/or –
 2. Define a bi-directional conversion function between multiaddrs and the corresponding denormalized fields in an ENR (ip, ip6, tcp, tcp6, etc.), for compatibility with nodes that do not support multiaddr natively (e.g. Eth 1.0 nodes).
 ### Why do we not form ENRs and find peers until genesis block/state is known?
 Although client software might very well be running locally prior to the solidification of the eth2 genesis state and block, clients cannot form valid ENRs prior to this point. ENRs contain `fork_digest` which utilizes the `genesis_validators_root` for a cleaner separation between chains so prior to knowing genesis, we cannot use `fork_digest` to cleanly find peers on our intended chain. Once genesis data is known, we can then form ENRs and safely find peers.
 When using an eth1 deposit contract for deposits, `fork_digest` will be known `GENESIS_DELAY` (48hours in mainnet configuration) before `genesis_time`, providing ample time to find peers and form initial connections and gossip subnets prior to genesis.
 ## Compression/Encoding
 ### Why are we using SSZ for encoding?
@ -1114,7 +1079,7 @@ For all these reasons, generically negotiating compression algorithms may be tre
 At this stage, the wisest choice is to consider libp2p a messenger of bytes, and to make application layer participate in compressing those bytes. This looks different depending on the interaction layer:
-  Gossip domain: since gossipsub has a framing protocol and exposes an API, we compress the payload (when dictated by the encoding token in the topic name) prior to publishing the message via the API. No length prefixing is necessary because protobuf takes care of bounding the field in the serialized form.
+-  Gossip domain: since gossipsub has a framing protocol and exposes an API, we compress the payload (when dictated by the encoding token in the topic name) prior to publishing the message via the API. No length-prefixing is necessary because protobuf takes care of bounding the field in the serialized form.
 -  Req/Resp domain: since we define custom protocols that operate on byte streams, implementers are encouraged to encapsulate the encoding and compression logic behind MessageReader and MessageWriter components/strategies that can be layered on top of the raw byte streams.
 ### Why are using Snappy for compression?
@ -1129,6 +1094,14 @@ If your libp2p library relies on frameworks/runtimes such as Netty (jvm) or Node
 For specific ad-hoc testing scenarios, you can use the [plaintext/2.0.0 secure channel](https://github.com/libp2p/specs/blob/master/plaintext/README.md) (which is essentially no-op encryption or message authentication), in combination with tcpdump or Wireshark to inspect the wire.
 ### What are SSZ type size bounds?
 The SSZ encoding outputs of each type have size bounds: each dynamic type, such as a list, has a "limit", which can be used to compute the maximum valid output size.
 Note that for some more complex dynamic-length objects, element offsets (4 bytes each) may need to be included.
 Other types are static, they have a fixed size: no dynamic-length content is involved, and the minimum and maximum bounds are the same.
 For reference, the type bounds can be computed ahead of time, [as per this example](https://gist.github.com/protolambda/db75c7faa1e94f2464787a480e5d613e). It is advisable to derive these lengths from the SSZ type definitions in use, to ensure that version changes do not cause out-of-sync type bounds.
 # libp2p implementations matrix
 This section will soon contain a matrix showing the maturity/state of the libp2p features required by this spec across the languages in which Eth2 clients are being developed.
--- a/specs/phase0/validator.md
+++ b/specs/phase0/validator.md
@ -85,11 +85,10 @@ All terminology, constants, functions, and protocol mechanics defined in the [Ph
 | Name | Value | Unit | Duration |
 | - | - | :-: | :-: |
 | `ETH1_FOLLOW_DISTANCE` | `2**10` (= 1,024) | blocks | ~4 hours |
 | `TARGET_AGGREGATORS_PER_COMMITTEE` | `2**4` (= 16) | validators | |
 | `RANDOM_SUBNETS_PER_VALIDATOR` | `2**0` (= 1) | subnets | |
 | `EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION` | `2**8` (= 256) | epochs | ~27 hours |
-| `SECONDS_PER_ETH1_BLOCK` | `14` | seconds | |
+| `ATTESTATION_SUBNET_COUNT` | `64` | The number of attestation subnets used in the gossipsub protocol. |
 ## Becoming a validator
@ -253,11 +252,13 @@ The `block.body.eth1_data` field is for block proposers to vote on recent Eth1 d
 ###### `Eth1Block`
-Let `Eth1Block` be an abstract object representing Eth1 blocks with the `timestamp` field available.
+Let `Eth1Block` be an abstract object representing Eth1 blocks with the `timestamp` and depost contract data available.
 ```python
 class Eth1Block(Container):
    timestamp: uint64
    deposit_root: Root
    deposit_count: uint64
    # All other eth1 block fields
 ```
@ -281,8 +282,8 @@ def voting_period_start_time(state: BeaconState) -> uint64:
 ```python
 def is_candidate_block(block: Eth1Block, period_start: uint64) -> bool:
    return (
-        block.timestamp <= period_start - SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE
+        block.timestamp + SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE <= period_start
-        and block.timestamp >= period_start - SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE * 2
+        and block.timestamp + SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE * 2 >= period_start
    )
 ```
@ -290,8 +291,14 @@ def is_candidate_block(block: Eth1Block, period_start: uint64) -> bool:
 def get_eth1_vote(state: BeaconState, eth1_chain: Sequence[Eth1Block]) -> Eth1Data:
    period_start = voting_period_start_time(state)
    # `eth1_chain` abstractly represents all blocks in the eth1 chain sorted by ascending block height
-    votes_to_consider = [get_eth1_data(block) for block in eth1_chain if
+    votes_to_consider = [
-                         is_candidate_block(block, period_start)]
+        get_eth1_data(block) for block in eth1_chain
        if (
            is_candidate_block(block, period_start)
            # Ensure cannot move back to earlier deposit contract states
            and get_eth1_data(block).deposit_count >= state.eth1_data.deposit_count
        )
    ]
    # Valid votes already cast during this period
    valid_votes = [vote for vote in state.eth1_data_votes if vote in votes_to_consider]
@ -340,9 +347,10 @@ It is useful to be able to run a state transition function (working on a copy of
 ```python
 def compute_new_state_root(state: BeaconState, block: BeaconBlock) -> Root:
-    process_slots(state, block.slot)
+    temp_state: BeaconState = state.copy()
-    process_block(state, block)
+    signed_block = SignedBeaconBlock(message=block)
-    return hash_tree_root(state)
+    temp_state = state_transition(temp_state, signed_block, validate_result=False)
    return hash_tree_root(temp_state)
 ```
 ##### Signature
@ -350,9 +358,9 @@ def compute_new_state_root(state: BeaconState, block: BeaconBlock) -> Root:
 `signed_block = SignedBeaconBlock(message=block, signature=block_signature)`, where `block_signature` is obtained from:
 ```python
-def get_block_signature(state: BeaconState, header: BeaconBlockHeader, privkey: int) -> BLSSignature:
+def get_block_signature(state: BeaconState, block: BeaconBlock, privkey: int) -> BLSSignature:
-    domain = get_domain(state, DOMAIN_BEACON_PROPOSER, compute_epoch_at_slot(header.slot))
+    domain = get_domain(state, DOMAIN_BEACON_PROPOSER, compute_epoch_at_slot(block.slot))
-    signing_root = compute_signing_root(header, domain)
+    signing_root = compute_signing_root(block, domain)
    return bls.Sign(privkey, signing_root)
 ```
@ -417,7 +425,19 @@ def get_attestation_signature(state: BeaconState, attestation_data: AttestationD
 #### Broadcast attestation
-Finally, the validator broadcasts `attestation` to the associated attestation subnet -- the `committee_index{attestation.data.index % ATTESTATION_SUBNET_COUNT}_beacon_attestation` pubsub topic.
+Finally, the validator broadcasts `attestation` to the associated attestation subnet -- the `beacon_attestation_{compute_subnet_for_attestation(state, attestation)}` pubsub topic.
 ```python
 def compute_subnet_for_attestation(state: BeaconState, attestation: Attestation) -> uint64:
    """
    Compute the correct subnet for an attestation for Phase 0.
    Note, this mimics expected Phase 1 behavior where attestations will be mapped to their shard subnet.
    """
    slots_since_epoch_start = attestation.data.slot % SLOTS_PER_EPOCH
    committees_since_epoch_start = get_committee_count_at_slot(state, attestation.data.slot) * slots_since_epoch_start
    return (committees_since_epoch_start + attestation.data.index) % ATTESTATION_SUBNET_COUNT
 ```
 ### Attestation aggregation
@ -445,7 +465,7 @@ def is_aggregator(state: BeaconState, slot: Slot, index: CommitteeIndex, slot_si
 If the validator is selected to aggregate (`is_aggregator()`), they construct an aggregate attestation via the following.
-Collect `attestations` seen via gossip during the `slot` that have an equivalent `attestation_data` to that constructed by the validator, and create an `aggregate_attestation: Attestation` with the following fields.
+Collect `attestations` seen via gossip during the `slot` that have an equivalent `attestation_data` to that constructed by the validator. If `len(attestations) > 0`, create an `aggregate_attestation: Attestation` with the following fields.
 ##### Data
@ -518,12 +538,14 @@ class SignedAggregateAndProof(Container):
 ## Phase 0 attestation subnet stability
-Because Phase 0 does not have shards and thus does not have Shard Committees, there is no stable backbone to the attestation subnets (`committee_index{subnet_id}_beacon_attestation`). To provide this stability, each validator must:
+Because Phase 0 does not have shards and thus does not have Shard Committees, there is no stable backbone to the attestation subnets (`beacon_attestation_{subnet_id}`). To provide this stability, each validator must:
 * Randomly select and remain subscribed to `RANDOM_SUBNETS_PER_VALIDATOR` attestation subnets
 * Maintain advertisement of the randomly selected subnets in their node's ENR `attnets` entry by setting the randomly selected `subnet_id` bits to `True` (e.g. `ENR["attnets"][subnet_id] = True`) for all persistent attestation subnets
 * Set the lifetime of each random subscription to a random number of epochs between `EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION` and `2 * EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION]`. At the end of life for a subscription, select a new random subnet, update subnet subscriptions, and publish an updated ENR
 *Note*: Short lived beacon committee assignments should not be added in into the ENR `attnets` entry.
 *Note*: When preparing for a hard fork, a validator must select and subscribe to random subnets of the future fork versioning at least `EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION` epochs in advance of the fork. These new subnets for the fork are maintained in addition to those for the current fork until the fork occurs. After the fork occurs, let the subnets from the previous fork reach the end of life with no replacements.
 ## How to avoid slashing
--- a/specs/phase1/beacon-chain.md
+++ b/specs/phase1/beacon-chain.md
@ -17,51 +17,61 @@
  - [Extended `AttestationData`](#extended-attestationdata)
  - [Extended `Attestation`](#extended-attestation)
  - [Extended `PendingAttestation`](#extended-pendingattestation)
-  - [`IndexedAttestation`](#indexedattestation)
+  - [Extended `IndexedAttestation`](#extended-indexedattestation)
-    - [Extended `AttesterSlashing`](#extended-attesterslashing)
+  - [Extended `AttesterSlashing`](#extended-attesterslashing)
  - [Extended `Validator`](#extended-validator)
  - [Extended `BeaconBlockBody`](#extended-beaconblockbody)
  - [Extended `BeaconBlock`](#extended-beaconblock)
    - [Extended `SignedBeaconBlock`](#extended-signedbeaconblock)
  - [Extended `BeaconState`](#extended-beaconstate)
 - [New containers](#new-containers)
-  - [`ShardBlockWrapper`](#shardblockwrapper)
+  - [`ShardBlock`](#shardblock)
-  - [`ShardSignableHeader`](#shardsignableheader)
+  - [`SignedShardBlock`](#signedshardblock)
  - [`ShardBlockHeader`](#shardblockheader)
  - [`ShardState`](#shardstate)
  - [`ShardTransition`](#shardtransition)
  - [`CompactCommittee`](#compactcommittee)
  - [`AttestationCustodyBitWrapper`](#attestationcustodybitwrapper)
 - [Helper functions](#helper-functions)
  - [Misc](#misc-1)
-    - [`get_previous_slot`](#get_previous_slot)
+    - [`compute_previous_slot`](#compute_previous_slot)
    - [`pack_compact_validator`](#pack_compact_validator)
    - [`unpack_compact_validator`](#unpack_compact_validator)
    - [`committee_to_compact_committee`](#committee_to_compact_committee)
    - [`compute_shard_from_committee_index`](#compute_shard_from_committee_index)
    - [`compute_offset_slots`](#compute_offset_slots)
    - [`compute_updated_gasprice`](#compute_updated_gasprice)
    - [`compute_committee_source_epoch`](#compute_committee_source_epoch)
  - [Beacon state accessors](#beacon-state-accessors)
    - [`get_active_shard_count`](#get_active_shard_count)
    - [`get_online_validator_indices`](#get_online_validator_indices)
    - [`get_shard_committee`](#get_shard_committee)
    - [`get_shard_proposer_index`](#get_shard_proposer_index)
    - [`get_light_client_committee`](#get_light_client_committee)
    - [`get_shard_proposer_index`](#get_shard_proposer_index)
    - [`get_indexed_attestation`](#get_indexed_attestation)
    - [`get_updated_gasprice`](#get_updated_gasprice)
    - [`get_start_shard`](#get_start_shard)
    - [`get_shard`](#get_shard)
    - [`get_latest_slot_for_shard`](#get_latest_slot_for_shard)
    - [`get_offset_slots`](#get_offset_slots)
  - [Predicates](#predicates)
    - [`verify_attestation_custody`](#verify_attestation_custody)
    - [Updated `is_valid_indexed_attestation`](#updated-is_valid_indexed_attestation)
    - [`is_on_time_attestation`](#is_on_time_attestation)
    - [`is_winning_attestation`](#is_winning_attestation)
    - [`optional_aggregate_verify`](#optional_aggregate_verify)
    - [`optional_fast_aggregate_verify`](#optional_fast_aggregate_verify)
  - [Block processing](#block-processing)
    - [Operations](#operations)
      - [New Attestation processing](#new-attestation-processing)
        - [`validate_attestation`](#validate_attestation)
        - [Updated `process_attestation`](#updated-process_attestation)
      - [Shard transition processing](#shard-transition-processing)
        - [`apply_shard_transition`](#apply_shard_transition)
        - [`process_crosslink_for_shard`](#process_crosslink_for_shard)
        - [`process_crosslinks`](#process_crosslinks)
-        - [`process_attestation`](#process_attestation)
+        - [`verify_empty_shard_transition`](#verify_empty_shard_transition)
        - [`process_shard_transitions`](#process_shard_transitions)
      - [New Attester slashing processing](#new-attester-slashing-processing)
    - [Shard transition false positives](#shard-transition-false-positives)
    - [Light client processing](#light-client-processing)
  - [Epoch transition](#epoch-transition)
    - [Custody game updates](#custody-game-updates)
@ -97,7 +107,6 @@ Configuration is not namespaced. Instead it is strictly an extension;
 | `ONLINE_PERIOD` | `OnlineEpochs(2**3)` (= 8) | online epochs | ~51 min |
 | `LIGHT_CLIENT_COMMITTEE_SIZE` | `2**7` (= 128) |
 | `LIGHT_CLIENT_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
 | `SHARD_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
 | `MAX_SHARD_BLOCK_SIZE` | `2**20` (= 1,048,576) | |
 | `TARGET_SHARD_BLOCK_SIZE` | `2**18` (= 262,144) | |
 | `SHARD_BLOCK_OFFSETS` | `[1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233]` | |
@ -105,6 +114,7 @@ Configuration is not namespaced. Instead it is strictly an extension;
 | `MAX_GASPRICE` | `Gwei(2**14)` (= 16,384) | Gwei | |
 | `MIN_GASPRICE` | `Gwei(2**3)` (= 8) | Gwei | |
 | `GASPRICE_ADJUSTMENT_COEFFICIENT` | `2**3` (= 8) | |
 | `NO_SIGNATURE` | `BLSSignature(b'\x00' * 96)` | |
 ### Domain types
@ -132,7 +142,7 @@ class AttestationData(Container):
    source: Checkpoint
    target: Checkpoint
    # Current-slot shard block root
-    head_shard_root: Root
+    shard_head_root: Root
    # Shard transition root
    shard_transition_root: Root
 ```
@ -155,10 +165,11 @@ class PendingAttestation(Container):
    data: AttestationData
    inclusion_delay: Slot
    proposer_index: ValidatorIndex
    # Phase 1
    crosslink_success: boolean
 ```
-### `IndexedAttestation`
+### Extended `IndexedAttestation`
 ```python
 class IndexedAttestation(Container):
@ -166,7 +177,7 @@ class IndexedAttestation(Container):
    attestation: Attestation
 ```
-#### Extended `AttesterSlashing`
+### Extended `AttesterSlashing`
 Note that the `attestation_1` and `attestation_2` have a new `IndexedAttestation` definition.
@ -297,26 +308,35 @@ class BeaconState(Container):
 The following containers are new in Phase 1.
-### `ShardBlockWrapper`
+### `ShardBlock`
 _Wrapper for being broadcasted over the network._
 ```python
-class ShardBlockWrapper(Container):
+class ShardBlock(Container):
    shard_parent_root: Root
    beacon_parent_root: Root
    slot: Slot
    shard: Shard
    proposer_index: ValidatorIndex
    body: ByteList[MAX_SHARD_BLOCK_SIZE]
 ```
 ### `SignedShardBlock`
 ```python
 class SignedShardBlock(Container):
    message: ShardBlock
    signature: BLSSignature
 ```
-### `ShardSignableHeader`
+### `ShardBlockHeader`
 ```python
-class ShardSignableHeader(Container):
+class ShardBlockHeader(Container):
    shard_parent_root: Root
    beacon_parent_root: Root
    slot: Slot
    shard: Shard
    proposer_index: ValidatorIndex
    body_root: Root
 ```
@ -326,7 +346,7 @@ class ShardSignableHeader(Container):
 class ShardState(Container):
    slot: Slot
    gasprice: Gwei
-    data: Bytes32
+    transition_digest: Bytes32
    latest_block_root: Root
 ```
@ -367,10 +387,10 @@ class AttestationCustodyBitWrapper(Container):
 ### Misc
-#### `get_previous_slot`
+#### `compute_previous_slot`
 ```python
-def get_previous_slot(slot: Slot) -> Slot:
+def compute_previous_slot(slot: Slot) -> Slot:
    if slot > 0:
        return Slot(slot - 1)
    else:
@ -408,7 +428,7 @@ def unpack_compact_validator(compact_validator: uint64) -> Tuple[ValidatorIndex,
 ```python
 def committee_to_compact_committee(state: BeaconState, committee: Sequence[ValidatorIndex]) -> CompactCommittee:
    """
-    Given a state and a list of validator indices, outputs the CompactCommittee representing them.
+    Given a state and a list of validator indices, outputs the ``CompactCommittee`` representing them.
    """
    validators = [state.validators[i] for i in committee]
    compact_validators = [
@ -427,6 +447,43 @@ def compute_shard_from_committee_index(state: BeaconState, index: CommitteeIndex
    return Shard((index + get_start_shard(state, slot)) % active_shards)
 ```
 #### `compute_offset_slots`
 ```python
 def compute_offset_slots(start_slot: Slot, end_slot: Slot) -> Sequence[Slot]:
    """
    Return the offset slots that are greater than ``start_slot`` and less than ``end_slot``.
    """
    return [Slot(start_slot + x) for x in SHARD_BLOCK_OFFSETS if start_slot + x < end_slot]
 ```
 #### `compute_updated_gasprice`
 ```python
 def compute_updated_gasprice(prev_gasprice: Gwei, shard_block_length: uint8) -> Gwei:
    if shard_block_length > TARGET_SHARD_BLOCK_SIZE:
        delta = (prev_gasprice * (shard_block_length - TARGET_SHARD_BLOCK_SIZE)
                 // TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
        return min(prev_gasprice + delta, MAX_GASPRICE)
    else:
        delta = (prev_gasprice * (TARGET_SHARD_BLOCK_SIZE - shard_block_length)
                 // TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
        return max(prev_gasprice, MIN_GASPRICE + delta) - delta
 ```
 #### `compute_committee_source_epoch`
 ```python
 def compute_committee_source_epoch(epoch: Epoch, period: uint64) -> Epoch:
    """
    Return the source epoch for computing the committee.
    """
    source_epoch = epoch - epoch % period
    if source_epoch >= period:
        source_epoch -= period  # `period` epochs lookahead
    return source_epoch
 ```
 ### Beacon state accessors
 #### `get_active_shard_count`
@ -448,12 +505,37 @@ def get_online_validator_indices(state: BeaconState) -> Set[ValidatorIndex]:
 ```python
 def get_shard_committee(beacon_state: BeaconState, epoch: Epoch, shard: Shard) -> Sequence[ValidatorIndex]:
-    source_epoch = epoch - epoch % SHARD_COMMITTEE_PERIOD 
+    """
-    if source_epoch > 0:
+    Return the shard committee of the given ``epoch`` of the given ``shard``.
-        source_epoch -= SHARD_COMMITTEE_PERIOD
+    """
    source_epoch = compute_committee_source_epoch(epoch, SHARD_COMMITTEE_PERIOD)
    active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
    seed = get_seed(beacon_state, source_epoch, DOMAIN_SHARD_COMMITTEE)
-    return compute_committee(active_validator_indices, seed, shard, get_active_shard_count(beacon_state))
+    active_shard_count = get_active_shard_count(beacon_state)
    return compute_committee(
        indices=active_validator_indices,
        seed=seed,
        index=shard,
        count=active_shard_count,
    )
 ```
 #### `get_light_client_committee`
 ```python
 def get_light_client_committee(beacon_state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
    """
    Return the light client committee of no more than ``TARGET_COMMITTEE_SIZE`` validators.
    """
    source_epoch = compute_committee_source_epoch(epoch, LIGHT_CLIENT_COMMITTEE_PERIOD)
    active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
    seed = get_seed(beacon_state, source_epoch, DOMAIN_LIGHT_CLIENT)
    return compute_committee(
        indices=active_validator_indices,
        seed=seed,
        index=0,
        count=get_active_shard_count(beacon_state),
    )[:TARGET_COMMITTEE_SIZE]
 ```
 #### `get_shard_proposer_index`
@ -465,19 +547,6 @@ def get_shard_proposer_index(beacon_state: BeaconState, slot: Slot, shard: Shard
    return committee[r % len(committee)]
 ```
 #### `get_light_client_committee`
 ```python
 def get_light_client_committee(beacon_state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
    source_epoch = epoch - epoch % LIGHT_CLIENT_COMMITTEE_PERIOD 
    if source_epoch > 0:
        source_epoch -= LIGHT_CLIENT_COMMITTEE_PERIOD
    active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
    seed = get_seed(beacon_state, source_epoch, DOMAIN_LIGHT_CLIENT)
    active_shards = get_active_shard_count(beacon_state)
    return compute_committee(active_validator_indices, seed, 0, active_shards)[:TARGET_COMMITTEE_SIZE]
 ```
 #### `get_indexed_attestation`
 ```python
@ -489,20 +558,6 @@ def get_indexed_attestation(beacon_state: BeaconState, attestation: Attestation)
    )
 ```
 #### `get_updated_gasprice`
 ```python
 def get_updated_gasprice(prev_gasprice: Gwei, length: uint8) -> Gwei:
    if length > TARGET_SHARD_BLOCK_SIZE:
        delta = (prev_gasprice * (length - TARGET_SHARD_BLOCK_SIZE) 
                 // TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
        return min(prev_gasprice + delta, MAX_GASPRICE)
    else:
        delta = (prev_gasprice * (TARGET_SHARD_BLOCK_SIZE - length)
                 // TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
        return max(prev_gasprice, MIN_GASPRICE + delta) - delta
 ```
 #### `get_start_shard`
 ```python
@ -528,12 +583,46 @@ def get_latest_slot_for_shard(state: BeaconState, shard: Shard) -> Slot:
 #### `get_offset_slots`
 ```python
-def get_offset_slots(state: BeaconState, latest_shard_slot: Slot) -> Sequence[Slot]:
+def get_offset_slots(state: BeaconState, shard: Shard) -> Sequence[Slot]:
-    return [Slot(latest_shard_slot + x) for x in SHARD_BLOCK_OFFSETS if latest_shard_slot + x < state.slot]
+    """
    Return the offset slots of the given ``shard`` between that latest included slot and current slot.
    """
    return compute_offset_slots(get_latest_slot_for_shard(state, shard), state.slot)
 ```
 ### Predicates
 #### `verify_attestation_custody`
 ```python
 def verify_attestation_custody(state: BeaconState, indexed_attestation: IndexedAttestation) -> bool:
    """
    Check if ``indexed_attestation`` has valid signature against non-empty custody bits.
    """
    attestation = indexed_attestation.attestation
    aggregation_bits = attestation.aggregation_bits
    domain = get_domain(state, DOMAIN_BEACON_ATTESTER, attestation.data.target.epoch)
    all_pubkeys = []
    all_signing_roots = []
    for block_index, custody_bits in enumerate(attestation.custody_bits_blocks):
        assert len(custody_bits) == len(indexed_attestation.committee)
        for participant, aggregation_bit, custody_bit in zip(
            indexed_attestation.committee, aggregation_bits, custody_bits
        ):
            if aggregation_bit:
                all_pubkeys.append(state.validators[participant].pubkey)
                # Note: only 2N distinct message hashes
                attestation_wrapper = AttestationCustodyBitWrapper(
                    attestation_data_root=hash_tree_root(attestation.data),
                    block_index=block_index,
                    bit=custody_bit,
                )
                all_signing_roots.append(compute_signing_root(attestation_wrapper, domain))
            else:
                assert not custody_bit
    return bls.AggregateVerify(all_pubkeys, all_signing_roots, signature=attestation.signature)
 ```
 #### Updated `is_valid_indexed_attestation`
 Note that this replaces the Phase 0 `is_valid_indexed_attestation`.
@ -544,38 +633,83 @@ def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: Indexe
    Check if ``indexed_attestation`` has valid indices and signature.
    """
    # Verify aggregate signature
    all_pubkeys = []
    all_signing_roots = []
    attestation = indexed_attestation.attestation
    domain = get_domain(state, DOMAIN_BEACON_ATTESTER, attestation.data.target.epoch)
    aggregation_bits = attestation.aggregation_bits
-    assert len(aggregation_bits) == len(indexed_attestation.committee)
+    if not any(aggregation_bits) or len(aggregation_bits) != len(indexed_attestation.committee):
        return False
    if len(attestation.custody_bits_blocks) == 0:
        # fall back on phase0 behavior if there is no shard data.
-        for participant, abit in zip(indexed_attestation.committee, aggregation_bits):
+        domain = get_domain(state, DOMAIN_BEACON_ATTESTER, attestation.data.target.epoch)
-            if abit:
+        all_pubkeys = []
        for participant, aggregation_bit in zip(indexed_attestation.committee, aggregation_bits):
            if aggregation_bit:
                all_pubkeys.append(state.validators[participant].pubkey)
        signing_root = compute_signing_root(indexed_attestation.attestation.data, domain)
        return bls.FastAggregateVerify(all_pubkeys, signing_root, signature=attestation.signature)
    else:
-        for i, custody_bits in enumerate(attestation.custody_bits_blocks):
+        return verify_attestation_custody(state, indexed_attestation)
            assert len(custody_bits) == len(indexed_attestation.committee)
            for participant, abit, cbit in zip(indexed_attestation.committee, aggregation_bits, custody_bits):
                if abit:
                    all_pubkeys.append(state.validators[participant].pubkey)
                    # Note: only 2N distinct message hashes
                    attestation_wrapper = AttestationCustodyBitWrapper(
                        attestation_data_root=hash_tree_root(attestation.data),
                        block_index=i,
                        bit=cbit
                    )
                    all_signing_roots.append(compute_signing_root(attestation_wrapper, domain))
                else:
                    assert not cbit
        return bls.AggregateVerify(zip(all_pubkeys, all_signing_roots), signature=attestation.signature)
 ```
 #### `is_on_time_attestation`
 ```python
 def is_on_time_attestation(state: BeaconState,
                           attestation: Attestation) -> bool:
    """
    Check if the given attestation is on-time.
    """
    # TODO: MIN_ATTESTATION_INCLUSION_DELAY should always be 1
    return attestation.data.slot + MIN_ATTESTATION_INCLUSION_DELAY == state.slot
 ```
 #### `is_winning_attestation`
 ```python
 def is_winning_attestation(state: BeaconState,
                           attestation: PendingAttestation,
                           committee_index: CommitteeIndex,
                           winning_root: Root) -> bool:
    """
    Check if ``attestation`` helped contribute to the successful crosslink of
    ``winning_root`` formed by ``committee_index`` committee at the current slot.
    """
    return (
        attestation.data.slot == state.slot
        and attestation.data.index == committee_index
        and attestation.data.shard_transition_root == winning_root
    )
 ```
 #### `optional_aggregate_verify`
 ```python
 def optional_aggregate_verify(pubkeys: Sequence[BLSPubkey],
                              messages: Sequence[Bytes32],
                              signature: BLSSignature) -> bool:
    """
    If ``pubkeys`` is an empty list, the given ``signature`` should be a stub ``NO_SIGNATURE``.
    Otherwise, verify it with standard BLS AggregateVerify API.
    """
    if len(pubkeys) == 0:
        return signature == NO_SIGNATURE
    else:
        return bls.AggregateVerify(pubkeys, messages, signature)
 ```
 #### `optional_fast_aggregate_verify`
 ```python
 def optional_fast_aggregate_verify(pubkeys: Sequence[BLSPubkey], message: Bytes32, signature: BLSSignature) -> bool:
    """
    If ``pubkeys`` is an empty list, the given ``signature`` should be a stub ``NO_SIGNATURE``.
    Otherwise, verify it with standard BLS FastAggregateVerify API.
    """
    if len(pubkeys) == 0:
        return signature == NO_SIGNATURE
    else:
        return bls.FastAggregateVerify(pubkeys, message, signature)
 ```
 ### Block processing
@ -584,12 +718,10 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
    process_block_header(state, block)
    process_randao(state, block.body)
    process_eth1_data(state, block.body)
    verify_shard_transition_false_positives(state, block.body)
    process_light_client_aggregate(state, block.body)
    process_operations(state, block.body)
 ```
 #### Operations
 ```python
@ -611,7 +743,7 @@ def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
    # See custody game spec.
    process_custody_game_operations(state, body)
-    process_crosslinks(state, body.shard_transitions, body.attestations)
+    process_shard_transitions(state, body.shard_transitions, body.attestations)
    # TODO process_operations(body.shard_receipt_proofs, process_shard_receipt_proofs)
 ```
@ -638,17 +770,16 @@ def validate_attestation(state: BeaconState, attestation: Attestation) -> None:
        assert attestation.data.source == state.previous_justified_checkpoint
    shard = get_shard(state, attestation)
    latest_shard_slot = get_latest_slot_for_shard(state, shard)
-    # Type 1: on-time attestations
+    # Type 1: on-time attestations, the custody bits should be non-empty.
    if attestation.custody_bits_blocks != []:
        # Ensure on-time attestation
-        assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY == state.slot
+        assert is_on_time_attestation(state, attestation)
        # Correct data root count
-        assert len(attestation.custody_bits_blocks) == len(get_offset_slots(state, latest_shard_slot))
+        assert len(attestation.custody_bits_blocks) == len(get_offset_slots(state, shard))
        # Correct parent block root
-        assert data.beacon_block_root == get_block_root_at_slot(state, get_previous_slot(state.slot))
+        assert data.beacon_block_root == get_block_root_at_slot(state, compute_previous_slot(state.slot))
-    # Type 2: no shard transition, no custody bits  # TODO: could only allow for older attestations.
+    # Type 2: no shard transition, no custody bits
    else:
        # Ensure delayed attestation
        assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY < state.slot  
@ -659,15 +790,36 @@ def validate_attestation(state: BeaconState, attestation: Attestation) -> None:
    assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
 ```
 ###### Updated `process_attestation`
 ```python
 def process_attestation(state: BeaconState, attestation: Attestation) -> None:
    validate_attestation(state, attestation)
    # Store pending attestation for epoch processing
    pending_attestation = PendingAttestation(
        aggregation_bits=attestation.aggregation_bits,
        data=attestation.data,
        inclusion_delay=state.slot - attestation.data.slot,
        proposer_index=get_beacon_proposer_index(state),
        crosslink_success=False,  # To be filled in during process_shard_transitions
    )
    if attestation.data.target.epoch == get_current_epoch(state):
        state.current_epoch_attestations.append(pending_attestation)
    else:
        state.previous_epoch_attestations.append(pending_attestation)
 ```
 ##### Shard transition processing
 ###### `apply_shard_transition`
 ```python
 def apply_shard_transition(state: BeaconState, shard: Shard, transition: ShardTransition) -> None:
-    # Slot the attestation starts counting from
+    # TODO: only need to check it once when phase 1 starts
-    latest_slot = get_latest_slot_for_shard(state, shard)
+    assert state.slot > PHASE_1_GENESIS_SLOT
    # Correct data root count
-    offset_slots = get_offset_slots(state, latest_slot)
+    offset_slots = get_offset_slots(state, shard)
    assert (
        len(transition.shard_data_roots)
        == len(transition.shard_states)
@ -676,28 +828,33 @@ def apply_shard_transition(state: BeaconState, shard: Shard, transition: ShardTr
    )
    assert transition.start_slot == offset_slots[0]
    # Reconstruct shard headers
    headers = []
    proposers = []
    shard_parent_root = state.shard_states[shard].latest_block_root
    for i in range(len(offset_slots)):
        if any(transition.shard_data_roots):
            headers.append(ShardSignableHeader(
                shard_parent_root=shard_parent_root,
                parent_hash=get_block_root_at_slot(state, get_previous_slot(state.slot)),
                slot=offset_slots[i],
                body_root=transition.shard_data_roots[i]
            ))
            proposers.append(get_shard_proposer_index(state, shard, offset_slots[i]))
            shard_parent_root = hash_tree_root(headers[-1])
    # Verify correct calculation of gas prices and slots
    prev_gasprice = state.shard_states[shard].gasprice
-    for i in range(len(offset_slots)):
+    shard_parent_root = state.shard_states[shard].latest_block_root
    for i, offset_slot in enumerate(offset_slots):
        shard_block_length = transition.shard_block_lengths[i]
        shard_state = transition.shard_states[i]
-        block_length = transition.shard_block_lengths[i]
+        # Verify correct calculation of gas prices and slots
-        assert shard_state.gasprice == get_updated_gasprice(prev_gasprice, block_length)
+        assert shard_state.gasprice == compute_updated_gasprice(prev_gasprice, shard_block_length)
-        assert shard_state.slot == offset_slots[i]
+        assert shard_state.slot == offset_slot
        # Collect the non-empty proposals result
        is_empty_proposal = shard_block_length == 0
        if not is_empty_proposal:
            proposal_index = get_shard_proposer_index(state, offset_slot, shard)
            # Reconstruct shard headers
            header = ShardBlockHeader(
                shard_parent_root=shard_parent_root,
                beacon_parent_root=get_block_root_at_slot(state, offset_slot),
                slot=offset_slot,
                shard=shard,
                proposer_index=proposal_index,
                body_root=transition.shard_data_roots[i]
            )
            shard_parent_root = hash_tree_root(header)
            headers.append(header)
            proposers.append(proposal_index)
        prev_gasprice = shard_state.gasprice
    pubkeys = [state.validators[proposer].pubkey for proposer in proposers]
@ -706,11 +863,11 @@ def apply_shard_transition(state: BeaconState, shard: Shard, transition: ShardTr
        for header in headers
    ]
    # Verify combined proposer signature
-    assert bls.AggregateVerify(zip(pubkeys, signing_roots), signature=transition.proposer_signature_aggregate)
+    assert optional_aggregate_verify(pubkeys, signing_roots, transition.proposer_signature_aggregate)
    # Save updated state
-    state.shard_states[shard] = transition.shard_states[-1]
+    state.shard_states[shard] = transition.shard_states[len(transition.shard_states) - 1]
-    state.shard_states[shard].slot = state.slot - 1
+    state.shard_states[shard].slot = compute_previous_slot(state.slot)
 ```
 ###### `process_crosslink_for_shard`
@ -732,6 +889,9 @@ def process_crosslink_for_shard(state: BeaconState,
        for attestation in transition_attestations:
            participants = get_attesting_indices(state, attestation.data, attestation.aggregation_bits)
            transition_participants = transition_participants.union(participants)
            assert attestation.data.shard_head_root == shard_transition.shard_data_roots[
                len(shard_transition.shard_data_roots) - 1
            ]
        enough_online_stake = (
            get_total_balance(state, online_indices.intersection(transition_participants)) * 3 >=
@ -743,7 +903,6 @@ def process_crosslink_for_shard(state: BeaconState,
        # Attestation <-> shard transition consistency
        assert shard_transition_root == hash_tree_root(shard_transition)
        assert attestation.data.head_shard_root == shard_transition.shard_data_roots[-1]
        # Apply transition
        apply_shard_transition(state, shard, shard_transition)
@ -754,11 +913,11 @@ def process_crosslink_for_shard(state: BeaconState,
        increase_balance(state, beacon_proposer_index, proposer_reward)
        states_slots_lengths = zip(
            shard_transition.shard_states,
-            get_offset_slots(state, get_latest_slot_for_shard(state, shard)),
+            get_offset_slots(state, shard),
            shard_transition.shard_block_lengths
        )
        for shard_state, slot, length in states_slots_lengths:
-            proposer_index = get_shard_proposer_index(state, shard, slot)
+            proposer_index = get_shard_proposer_index(state, slot, shard)
            decrease_balance(state, proposer_index, shard_state.gasprice * length)
        # Return winning transition root
@ -781,38 +940,41 @@ def process_crosslinks(state: BeaconState,
        # All attestations in the block for this committee/shard and current slot
        shard_attestations = [
            attestation for attestation in attestations
-            if attestation.data.index == committee_index and attestation.data.slot == state.slot
+            if is_on_time_attestation(state, attestation) and attestation.data.index == committee_index
        ]
-        shard_transition = shard_transitions[shard]
+
-        winning_root = process_crosslink_for_shard(state, committee_index, shard_transition, shard_attestations)
+        winning_root = process_crosslink_for_shard(state, committee_index, shard_transitions[shard], shard_attestations)
        if winning_root != Root():
            # Mark relevant pending attestations as creating a successful crosslink
            for pending_attestation in state.current_epoch_attestations:
-                if (
+                if is_winning_attestation(state, pending_attestation, committee_index, winning_root):
                    pending_attestation.slot == state.slot and pending_attestation
                    and pending_attestation.data.index == committee_index
                    and pending_attestation.data.shard_transition_root == winning_root
                ):
                    pending_attestation.crosslink_success = True
 ```
-###### `process_attestation`
+###### `verify_empty_shard_transition`
 ```python
-def process_attestation(state: BeaconState, attestation: Attestation) -> None:
+def verify_empty_shard_transition(state: BeaconState, shard_transitions: Sequence[ShardTransition]) -> bool:
-    validate_attestation(state, attestation)
+    """
-    # Store pending attestation for epoch processing
+    Verify that a `shard_transition` in a block is empty if an attestation was not processed for it.
-    pending_attestation = PendingAttestation(
+    """
-        aggregation_bits=attestation.aggregation_bits,
+    for shard in range(get_active_shard_count(state)):
-        data=attestation.data,
+        if state.shard_states[shard].slot != compute_previous_slot(state.slot):
-        inclusion_delay=state.slot - attestation.data.slot,
+            if shard_transitions[shard] != ShardTransition():
-        crosslink_success=False,  # To be filled in during process_crosslinks
+                return False
-        proposer_index=get_beacon_proposer_index(state),
+    return True
-    )
+```
-    if attestation.data.target.epoch == get_current_epoch(state):
+
-        state.current_epoch_attestations.append(pending_attestation)
+###### `process_shard_transitions`
-    else:
+
-        state.previous_epoch_attestations.append(pending_attestation)
+```python
 def process_shard_transitions(state: BeaconState,
                              shard_transitions: Sequence[ShardTransition],
                              attestations: Sequence[Attestation]) -> None:
    # Process crosslinks
    process_crosslinks(state, shard_transitions, attestations)
    # Verify the empty proposal shard states
    assert verify_empty_shard_transition(state, shard_transitions)
 ```
 ##### New Attester slashing processing
@ -820,11 +982,9 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
 ```python
 def get_indices_from_committee(
        committee: List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE],
-        bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]) -> List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE]:
+        bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]) -> Sequence[ValidatorIndex]:
    assert len(bits) == len(committee)
-    return List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE](
+    return [validator_index for i, validator_index in enumerate(committee) if bits[i]]
        [validator_index for i, validator_index in enumerate(committee) if bits[i]]
    )
 ```
 ```python
@ -857,22 +1017,12 @@ def process_attester_slashing(state: BeaconState, attester_slashing: AttesterSla
    assert slashed_any
 ```
 #### Shard transition false positives
 ```python
 def verify_shard_transition_false_positives(state: BeaconState, block_body: BeaconBlockBody) -> None:
    # Verify that a `shard_transition` in a block is empty if an attestation was not processed for it
    for shard in range(get_active_shard_count(state)):
        if state.shard_states[shard].slot != state.slot - 1:
            assert block_body.shard_transitions[shard] == ShardTransition()
 ```
 #### Light client processing
 ```python
 def process_light_client_aggregate(state: BeaconState, block_body: BeaconBlockBody) -> None:
    committee = get_light_client_committee(state, get_current_epoch(state))
-    previous_slot = get_previous_slot(state.slot)
+    previous_slot = compute_previous_slot(state.slot)
    previous_block_root = get_block_root_at_slot(state, previous_slot)
    total_reward = Gwei(0)
@ -888,10 +1038,9 @@ def process_light_client_aggregate(state: BeaconState, block_body: BeaconBlockBo
    signing_root = compute_signing_root(previous_block_root,
                                        get_domain(state, DOMAIN_LIGHT_CLIENT, compute_epoch_at_slot(previous_slot)))
-    assert bls.FastAggregateVerify(signer_pubkeys, signing_root, signature=block_body.light_client_signature)
+    assert optional_fast_aggregate_verify(signer_pubkeys, signing_root, block_body.light_client_signature)
 ```
 ### Epoch transition
 This epoch transition overrides the phase0 epoch transition:
@ -911,7 +1060,7 @@ def process_epoch(state: BeaconState) -> None:
 #### Custody game updates
-`process_reveal_deadlines` and `process_custody_final_updates` are defined in [the Custody Game spec](./1_custody-game.md), 
+`process_reveal_deadlines` and `process_custody_final_updates` are defined in [the Custody Game spec](./custody-game.md), 
 #### Online-tracking
@ -932,7 +1081,9 @@ def process_online_tracking(state: BeaconState) -> None:
 ```python
 def process_light_client_committee_updates(state: BeaconState) -> None:
-    # Update light client committees
+    """
    Update light client committees.
    """
    if get_current_epoch(state) % LIGHT_CLIENT_COMMITTEE_PERIOD == 0:
        state.current_light_committee = state.next_light_committee
        new_committee = get_light_client_committee(state, get_current_epoch(state) + LIGHT_CLIENT_COMMITTEE_PERIOD)
--- a/specs/phase1/custody-game.md
+++ b/specs/phase1/custody-game.md
@ -300,7 +300,7 @@ def process_early_derived_secret_reveal(state: BeaconState, reveal: EarlyDerived
    domain = get_domain(state, DOMAIN_RANDAO, reveal.epoch)
    signing_roots = [compute_signing_root(root, domain) for root in [hash_tree_root(reveal.epoch), reveal.mask]]
-    assert bls.AggregateVerify(zip(pubkeys, signing_roots), reveal.reveal)
+    assert bls.AggregateVerify(pubkeys, signing_roots, reveal.reveal)
    if reveal.epoch >= get_current_epoch(state) + CUSTODY_PERIOD_TO_RANDAO_PADDING:
        # Full slashing when the secret was revealed so early it may be a valid custody
--- a/specs/phase1/fraud-proofs.md
+++ b/specs/phase1/fraud-proofs.md
@ -1,70 +0,0 @@
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 **Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*
 - [Ethereum 2.0 Phase 1 -- Shard Transition and Fraud Proofs](#ethereum-20-phase-1----shard-transition-and-fraud-proofs)
  - [Table of contents](#table-of-contents)
  - [Introduction](#introduction)
  - [Fraud proofs](#fraud-proofs)
  - [Shard state transition function](#shard-state-transition-function)
  - [Honest committee member behavior](#honest-committee-member-behavior)
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 # Ethereum 2.0 Phase 1 -- Shard Transition and Fraud Proofs
 **Notice**: This document is a work-in-progress for researchers and implementers.
 ## Table of contents
 <!-- TOC -->
 TODO
 <!-- /TOC -->
 ## Introduction
 This document describes the shard transition function and fraud proofs as part of Phase 1 of Ethereum 2.0.
 ## Fraud proofs
 TODO. The intent is to have a single universal fraud proof type, which contains the following parts:
 1. An on-time attestation on some `shard` signing a `ShardTransition`
 2. An index `i` of a particular position to focus on
 3. The `ShardTransition` itself
 4. The full body of the block
 5. A Merkle proof to the `shard_states` in the parent block the attestation is referencing
 The proof verifies that one of the two conditions is false:
 1. `custody_bits[i][j] != generate_custody_bit(subkey, block_contents)` for any `j`
 2. `execute_state_transition(shard, slot, transition.shard_states[i-1].data, hash_tree_root(parent), get_shard_proposer_index(state, shard, slot), block_contents) != transition.shard_states[i].data` (if `i=0` then instead use `parent.shard_states[shard][-1].data`)
 ## Shard state transition function
 ```python
 def shard_state_transition(shard: Shard,
                           slot: Slot,
                           pre_state: Root,
                           previous_beacon_root: Root,
                           proposer_pubkey: BLSPubkey,
                           block_data: ByteList[MAX_SHARD_BLOCK_SIZE]) -> Root:
    # We will add something more substantive in phase 2
    return hash(pre_state + hash_tree_root(previous_beacon_root) + hash_tree_root(block_data))
 ```
 ## Honest committee member behavior
 Suppose you are a committee member on shard `shard` at slot `current_slot`. Let `state` be the head beacon state you are building on, and let `QUARTER_PERIOD = SECONDS_PER_SLOT // 4`. `2 * QUARTER_PERIOD` seconds into slot `slot`, run the following procedure:
 * Initialize `proposals = []`, `shard_states = []`, `shard_state = state.shard_states[shard][-1]`, `start_slot = shard_state.slot`.
 * For `slot in get_offset_slots(state, start_slot)`, do the following:
    * Look for all valid proposals for `slot`; that is, a Bytes `proposal` where `shard_state_transition(shard, slot, shard_state, get_block_root_at_slot(state, state.slot - 1), get_shard_proposer_index(state, shard, slot), proposal)` returns a result and does not throw an exception. Let `choices` be the set of non-empty valid proposals you discover.
    * If `len(choices) == 0`, do `proposals.append(make_empty_proposal(shard_state, slot))`
    * If `len(choices) == 1`, do `proposals.append(choices[0])`
    * If `len(choices) > 1`, let `winning_proposal` be the proposal with the largest number of total attestations from slots in `state.shard_next_slots[shard]....slot-1` supporting it or any of its descendants, breaking ties by choosing the first proposal locally seen. Do `proposals.append(winning_proposal)`.
    * If `proposals[-1]` is NOT an empty proposal, set `shard_state = shard_state_transition(shard, slot, shard_state, get_block_root_at_slot(state, state.slot - 1), get_shard_proposer_index(state, shard, slot), proposals[-1])` and do `shard_states.append(shard_state)`. If it is an empty proposal, leave `shard_state` unchanged.
 Make an attestation using `shard_data_roots = [hash_tree_root(proposal) for proposal in proposals]` and `shard_state_roots = shard_states`.
--- a/specs/phase1/phase1-fork.md
+++ b/specs/phase1/phase1-fork.md
@ -7,7 +7,7 @@
  - [Introduction](#introduction)
  - [Configuration](#configuration)
  - [Fork to Phase 1](#fork-to-phase-1)
-    - [Fork trigger.](#fork-trigger)
+    - [Fork trigger](#fork-trigger)
    - [Upgrading the state](#upgrading-the-state)
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
@ -35,17 +35,18 @@ Warning: this configuration is not definitive.
 | Name | Value |
 | - | - |
 | `PHASE_1_FORK_VERSION` | `Version('0x01000000')` |
 | `PHASE_1_GENESIS_SLOT` | `2**5` **TBD** |
 | `INITIAL_ACTIVE_SHARDS` | `2**6` (= 64) |
 ## Fork to Phase 1
-### Fork trigger.
+### Fork trigger
-TBD. Social consensus, along with state conditions such as epoch boundary, finality, deposits, active validator count, etc. may be part of the decision process to trigger the fork.
+TBD. Social consensus, along with state conditions such as epoch boundary, finality, deposits, active validator count, etc. may be part of the decision process to trigger the fork. For now we assume the condition will be triggered at slot `PHASE_1_GENESIS_SLOT`, where `PHASE_1_GENESIS_SLOT % SLOTS_PER_EPOCH == 0`.
 ### Upgrading the state
-After `process_slots` of Phase 0 finishes, but before the first Phase 1 block is processed, an irregular state change is made to upgrade to Phase 1.
+After `process_slots` of Phase 0 finishes, if `state.slot == PHASE_1_GENESIS_SLOT`, an irregular state change is made to upgrade to Phase 1.
 ```python
 def upgrade_to_phase1(pre: phase0.BeaconState) -> BeaconState:
@ -102,7 +103,7 @@ def upgrade_to_phase1(pre: phase0.BeaconState) -> BeaconState:
            ShardState(
                slot=pre.slot,
                gasprice=MIN_GASPRICE,
-                data=Root(),
+                transition_digest=Root(),
                latest_block_root=Root(),
            ) for i in range(INITIAL_ACTIVE_SHARDS)
        ),
@ -110,7 +111,7 @@ def upgrade_to_phase1(pre: phase0.BeaconState) -> BeaconState:
        current_light_committee=CompactCommittee(),  # computed after state creation
        next_light_committee=CompactCommittee(),
        # Custody game
-        custody_challenge_index=0,
+        exposed_derived_secrets=[] * EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS,
        # exposed_derived_secrets will fully default to zeroes
    )
    next_epoch = Epoch(epoch + 1)
--- a/specs/phase1/shard-transition.md
+++ b/specs/phase1/shard-transition.md
@ -0,0 +1,294 @@
 # Ethereum 2.0 Phase 1 -- Shard Transition and Fraud Proofs
 **Notice**: This document is a work-in-progress for researchers and implementers.
 ## Table of contents
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 **Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*
 - [Introduction](#introduction)
 - [Helper functions](#helper-functions)
  - [Misc](#misc)
  - [Shard block verification functions](#shard-block-verification-functions)
 - [Shard state transition](#shard-state-transition)
 - [Fraud proofs](#fraud-proofs)
  - [Verifying the proof](#verifying-the-proof)
 - [Honest committee member behavior](#honest-committee-member-behavior)
  - [Helper functions](#helper-functions-1)
  - [Make attestations](#make-attestations)
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 ## Introduction
 This document describes the shard transition function and fraud proofs as part of Phase 1 of Ethereum 2.0.
 ## Helper functions
 ### Misc
 ```python
 def compute_shard_transition_digest(beacon_state: BeaconState,
                                    shard_state: ShardState,
                                    beacon_parent_root: Root,
                                    shard_body_root: Root) -> Bytes32:
    # TODO: use SSZ hash tree root
    return hash(
        hash_tree_root(shard_state) + beacon_parent_root + shard_body_root
    )
 ```
 ### Shard block verification functions
 ```python
 def verify_shard_block_message(beacon_state: BeaconState,
                               shard_state: ShardState,
                               block: ShardBlock,
                               slot: Slot,
                               shard: Shard) -> bool:
    assert block.shard_parent_root == shard_state.latest_block_root
    assert block.slot == slot
    assert block.shard == shard
    assert block.proposer_index == get_shard_proposer_index(beacon_state, slot, shard)
    assert 0 < len(block.body) <= MAX_SHARD_BLOCK_SIZE
    return True
 ```
 ```python
 def verify_shard_block_signature(beacon_state: BeaconState,
                                 signed_block: SignedShardBlock) -> bool:
    proposer = beacon_state.validators[signed_block.message.proposer_index]
    domain = get_domain(beacon_state, DOMAIN_SHARD_PROPOSAL, compute_epoch_at_slot(signed_block.message.slot))
    signing_root = compute_signing_root(signed_block.message, domain)
    return bls.Verify(proposer.pubkey, signing_root, signed_block.signature)
 ```
 ## Shard state transition
 ```python
 def shard_state_transition(beacon_state: BeaconState,
                           shard_state: ShardState,
                           block: ShardBlock) -> None:
    """
    Update ``shard_state`` with shard ``block`` and ``beacon_state`.
    """
    shard_state.slot = block.slot
    prev_gasprice = shard_state.gasprice
    shard_state.gasprice = compute_updated_gasprice(prev_gasprice, len(block.body))
    if len(block.body) == 0:
        latest_block_root = shard_state.latest_block_root
    else:
        latest_block_root = hash_tree_root(block)
    shard_state.latest_block_root = latest_block_root
    shard_state.transition_digest = compute_shard_transition_digest(
        beacon_state,
        shard_state,
        block.beacon_parent_root,
        hash_tree_root(block.body),
    )
 ```
 We have a pure function `get_post_shard_state` for describing the fraud proof verification and honest validator behavior.
 ```python
 def get_post_shard_state(beacon_state: BeaconState,
                         shard_state: ShardState,
                         block: ShardBlock) -> ShardState:
    """
    A pure function that returns a new post ShardState instead of modifying the given `shard_state`.
    """
    post_state = shard_state.copy()
    shard_state_transition(beacon_state, post_state, block)
    return post_state
 ```
 ## Fraud proofs
 ### Verifying the proof
 TODO. The intent is to have a single universal fraud proof type, which contains the following parts:
 1. An on-time attestation `attestation` on some shard `shard` signing a `transition: ShardTransition`
 2. An index `offset_index` of a particular position to focus on
 3. The `transition: ShardTransition` itself
 4. The full body of the shard block `shard_block`
 5. A Merkle proof to the `shard_states` in the parent block the attestation is referencing
 6. The `subkey` to generate the custody bit
 Call the following function to verify the proof:
 ```python
 def is_valid_fraud_proof(beacon_state: BeaconState,
                         attestation: Attestation,
                         offset_index: uint64,
                         transition: ShardTransition,
                         block: ShardBlock,
                         subkey: BLSPubkey,
                         beacon_parent_block: BeaconBlock) -> bool:
    # 1. Check if `custody_bits[offset_index][j] != generate_custody_bit(subkey, block_contents)` for any `j`.
    custody_bits = attestation.custody_bits_blocks
    for j in range(len(custody_bits[offset_index])):
        if custody_bits[offset_index][j] != generate_custody_bit(subkey, block):
            return True
    # 2. Check if the shard state transition result is wrong between
    # `transition.shard_states[offset_index - 1]` to `transition.shard_states[offset_index]`.
    if offset_index == 0:
        shard = get_shard(beacon_state, attestation)
        shard_states = beacon_parent_block.body.shard_transitions[shard].shard_states
        shard_state = shard_states[len(shard_states) - 1]
    else:
        shard_state = transition.shard_states[offset_index - 1]  # Not doing the actual state updates here.
    shard_state = get_post_shard_state(beacon_state, shard_state, block)
    if shard_state.transition_digest != transition.shard_states[offset_index].transition_digest:
        return True
    return False
 ```
 ```python
 def generate_custody_bit(subkey: BLSPubkey, block: ShardBlock) -> bool:
    # TODO
    ...
 ```
 ## Honest committee member behavior
 ### Helper functions
 ```python
 def get_winning_proposal(beacon_state: BeaconState, proposals: Sequence[SignedShardBlock]) -> SignedShardBlock:
    # TODO: Let `winning_proposal` be the proposal with the largest number of total attestations from slots in
    # `state.shard_next_slots[shard]....slot-1` supporting it or any of its descendants, breaking ties by choosing
    # the first proposal locally seen. Do `proposals.append(winning_proposal)`.
    return proposals[-1]  # stub
 ```
 ```python
 def compute_shard_body_roots(proposals: Sequence[SignedShardBlock]) -> Sequence[Root]:
    return [hash_tree_root(proposal.message.body) for proposal in proposals]
 ```
 ```python
 def get_proposal_choices_at_slot(beacon_state: BeaconState,
                                 shard_state: ShardState,
                                 slot: Slot,
                                 shard: Shard,
                                 shard_blocks: Sequence[SignedShardBlock],
                                 validate_signature: bool=True) -> Sequence[SignedShardBlock]:
    """
    Return the valid shard blocks at the given ``slot``.
    Note that this function doesn't change the state.
    """
    choices = []
    shard_blocks_at_slot = [block for block in shard_blocks if block.message.slot == slot]
    for block in shard_blocks_at_slot:
        try:
            # Verify block message and signature
            # TODO these validations should have been checked upon receiving shard blocks.
            assert verify_shard_block_message(beacon_state, shard_state, block.message, slot, shard)
            if validate_signature:
                assert verify_shard_block_signature(beacon_state, block)
            shard_state = get_post_shard_state(beacon_state, shard_state, block.message)
        except Exception:
            pass  # TODO: throw error in the test helper
        else:
            choices.append(block)
    return choices
 ```
 ```python
 def get_proposal_at_slot(beacon_state: BeaconState,
                         shard_state: ShardState,
                         slot: Shard,
                         shard: Shard,
                         shard_blocks: Sequence[SignedShardBlock],
                         validate_signature: bool=True) -> Tuple[SignedShardBlock, ShardState]:
    """
    Return ``proposal``, ``shard_state`` of the given ``slot``.
    Note that this function doesn't change the state.
    """
    choices = get_proposal_choices_at_slot(
        beacon_state=beacon_state,
        shard_state=shard_state,
        slot=slot,
        shard=shard,
        shard_blocks=shard_blocks,
        validate_signature=validate_signature,
    )
    if len(choices) == 0:
        block = ShardBlock(slot=slot)
        proposal = SignedShardBlock(message=block)
    elif len(choices) == 1:
        proposal = choices[0]
    else:
        proposal = get_winning_proposal(beacon_state, choices)
    # Apply state transition
    shard_state = get_post_shard_state(beacon_state, shard_state, proposal.message)
    return proposal, shard_state
 ```
 ```python
 def get_shard_state_transition_result(
    beacon_state: BeaconState,
    shard: Shard,
    shard_blocks: Sequence[SignedShardBlock],
    validate_signature: bool=True,
 ) -> Tuple[Sequence[SignedShardBlock], Sequence[ShardState], Sequence[Root]]:
    proposals = []
    shard_states = []
    shard_state = beacon_state.shard_states[shard]
    for slot in get_offset_slots(beacon_state, shard):
        proposal, shard_state = get_proposal_at_slot(
            beacon_state=beacon_state,
            shard_state=shard_state,
            slot=slot,
            shard=shard,
            shard_blocks=shard_blocks,
            validate_signature=validate_signature,
        )
        shard_states.append(shard_state)
        proposals.append(proposal)
    shard_data_roots = compute_shard_body_roots(proposals)
    return proposals, shard_states, shard_data_roots
 ```
 ### Make attestations
 Suppose you are a committee member on shard `shard` at slot `current_slot` and you have received shard blocks `shard_blocks` since the latest successful crosslink for `shard` into the beacon chain. Let `beacon_state` be the head beacon state you are building on, and let `QUARTER_PERIOD = SECONDS_PER_SLOT // 4`. `2 * QUARTER_PERIOD` seconds into slot `current_slot`, run `get_shard_transition(beacon_state, shard, shard_blocks)` to get `shard_transition`.
 ```python
 def get_shard_transition(beacon_state: BeaconState,
                         shard: Shard,
                         shard_blocks: Sequence[SignedShardBlock]) -> ShardTransition:
    offset_slots = get_offset_slots(beacon_state, shard)
    proposals, shard_states, shard_data_roots = get_shard_state_transition_result(beacon_state, shard, shard_blocks)
    shard_block_lengths = []
    proposer_signatures = []
    for proposal in proposals:
        shard_block_lengths.append(len(proposal.message.body))
        if proposal.signature != NO_SIGNATURE:
            proposer_signatures.append(proposal.signature)
    if len(proposer_signatures) > 0:
        proposer_signature_aggregate = bls.Aggregate(proposer_signatures)
    else:
        proposer_signature_aggregate = NO_SIGNATURE
    return ShardTransition(
        start_slot=offset_slots[0],
        shard_block_lengths=shard_block_lengths,
        shard_data_roots=shard_data_roots,
        shard_states=shard_states,
        proposer_signature_aggregate=proposer_signature_aggregate,
    )
 ```
--- a/ssz/simple-serialize.md
+++ b/ssz/simple-serialize.md
@ -211,8 +211,8 @@ We first define helper functions:
   * `List[B, N]` and `Vector[B, N]`, where `B` is a basic type: `(N * size_of(B) + 31) // 32` (dividing by chunk size, rounding up)
   * `List[C, N]` and `Vector[C, N]`, where `C` is a composite type: `N`
   * containers: `len(fields)`
-* `bitfield_bytes(bits)`: return the bits of the bitlist or bitvector, packed in bytes, aligned to the start. Length-delimiting bit for bitlists is excluded.
+* `pack(value)`: given ordered objects of the same basic type, serialize them, pack them into `BYTES_PER_CHUNK`-byte chunks, right-pad the last chunk with zero bytes, and return the chunks.
-* `pack`: Given ordered objects of the same basic type, serialize them, pack them into `BYTES_PER_CHUNK`-byte chunks, right-pad the last chunk with zero bytes, and return the chunks.
+* `pack_bits(bits)`: Given the `bits` of bitlist or bitvector, get `bitfield_bytes` by packing them in bytes and aligning to the start. The length-delimiting bit for bitlists is excluded. And then pack `bitfield_bytes` into `BYTES_PER_CHUNK`-byte chunks, right-pad the last chunk with zero bytes, and return the chunks.
 * `next_pow_of_two(i)`: get the next power of 2 of `i`, if not already a power of 2, with 0 mapping to 1. Examples: `0->1, 1->1, 2->2, 3->4, 4->4, 6->8, 9->16`
 * `merkleize(chunks, limit=None)`: Given ordered `BYTES_PER_CHUNK`-byte chunks, merkleize the chunks, and return the root:
    * The merkleization depends on the effective input, which can be padded/limited:
@ -228,9 +228,9 @@ We first define helper functions:
 We now define Merkleization `hash_tree_root(value)` of an object `value` recursively:
 * `merkleize(pack(value))` if `value` is a basic object or a vector of basic objects.
-* `merkleize(bitfield_bytes(value), limit=chunk_count(type))` if `value` is a bitvector.
+* `merkleize(pack_bits(value), limit=chunk_count(type))` if `value` is a bitvector.
 * `mix_in_length(merkleize(pack(value), limit=chunk_count(type)), len(value))` if `value` is a list of basic objects.
-* `mix_in_length(merkleize(bitfield_bytes(value), limit=chunk_count(type)), len(value))` if `value` is a bitlist.
+* `mix_in_length(merkleize(pack_bits(value), limit=chunk_count(type)), len(value))` if `value` is a bitlist.
 * `merkleize([hash_tree_root(element) for element in value])` if `value` is a vector of composite objects or a container.
 * `mix_in_length(merkleize([hash_tree_root(element) for element in value], limit=chunk_count(type)), len(value))` if `value` is a list of composite objects.
 * `mix_in_type(merkleize(value.value), value.type_index)` if `value` is of union type.
--- a/tests/core/pyspec/README.md
+++ b/tests/core/pyspec/README.md
@ -55,6 +55,11 @@ Run the test command from the `tests/core/pyspec` directory:
 pytest --config=minimal eth2spec
 ```
 Options:
 - `--config`, to change the config. Defaults to `minimal`, can be set to `mainnet`, or other configs from the configs directory.
 - `--disable-bls`, to disable BLS (only for tests that can run without)
 - `--bls-type`, `milagro` or `py_ecc` (default)
 ### How to view code coverage report
 Run `make open_cov` from the root of the specs repository after running `make test` to open the html code coverage report.
--- a/tests/core/pyspec/eth2spec/VERSION.txt
+++ b/tests/core/pyspec/eth2spec/VERSION.txt
@ -1 +1 @@
-0.11.1
+0.12.1
--- a/tests/core/pyspec/eth2spec/config/README.md
+++ b/tests/core/pyspec/eth2spec/config/README.md
@ -12,7 +12,7 @@ configs_path = 'configs/'
 from eth2spec.config import config_util
 from eth2spec.phase0 import spec
 from importlib import reload
-my_presets = config_util.prepare_config(configs_path, 'mainnet')
+config_util.prepare_config(configs_path, 'mainnet')
 # reload spec to make loaded config effective
 reload(spec)
 ```
--- a/tests/core/pyspec/eth2spec/config/config_util.py
+++ b/tests/core/pyspec/eth2spec/config/config_util.py
@ -8,23 +8,28 @@ config: Dict[str, Any] = {}
 # Access to overwrite spec constants based on configuration
 # This is called by the spec module after declaring its globals, and applies the loaded presets.
-def apply_constants_config(spec_globals: Dict[str, Any]) -> None:
+def apply_constants_config(spec_globals: Dict[str, Any], warn_if_unknown: bool = False) -> None:
    global config
    for k, v in config.items():
-        if k.startswith('DOMAIN_'):
+        # the spec should have default values for everything, if not, the config key is invalid.
-            spec_globals[k] = spec_globals['DomainType'](v)  # domain types are defined as bytes in the configs
+        if k in spec_globals:
            # Keep the same type as the default value indicates (which may be an SSZ basic type subclass, e.g. 'Gwei')
            spec_globals[k] = spec_globals[k].__class__(v)
        else:
-            spec_globals[k] = v
+            # Note: Phase 0 spec will not know the phase 1 config values.
            # Yet, during debugging you can enable explicit warnings.
            if warn_if_unknown:
                print(f"WARNING: unknown config key: '{k}' with value: '{v}'")
 # Load presets from a file, and then prepares the global config setting. This does not apply the config.
 # To apply the config, reload the spec module (it will re-initialize with the config taken from here).
-def prepare_config(configs_path, config_name):
+def prepare_config(configs_path: str, config_name: str) -> None:
    global config
    config = load_config_file(configs_path, config_name)
-def load_config_file(configs_dir, presets_name) -> Dict[str, Any]:
+def load_config_file(configs_dir: str, presets_name: str) -> Dict[str, Any]:
    """
    Loads the given preset
    :param presets_name: The name of the presets. (lowercase snake_case)
@ -33,7 +38,7 @@ def load_config_file(configs_dir, presets_name) -> Dict[str, Any]:
    path = Path(join(configs_dir, presets_name + '.yaml'))
    yaml = YAML(typ='base')
    loaded = yaml.load(path)
-    out = dict()
+    out: Dict[str, Any] = dict()
    for k, v in loaded.items():
        if isinstance(v, list):
            # Clean up integer values. YAML parser renders lists of ints as list of str
--- a/tests/core/pyspec/eth2spec/test/conftest.py
+++ b/tests/core/pyspec/eth2spec/test/conftest.py
@ -1,6 +1,6 @@
 from eth2spec.config import config_util
-from eth2spec.test.context import reload_specs
+from eth2spec.test import context
-
+from eth2spec.utils import bls as bls_utils
 # We import pytest only when it's present, i.e. when we are running tests.
 # The test-cases themselves can be generated without installing pytest.
@ -27,7 +27,16 @@ def fixture(*args, **kwargs):
 def pytest_addoption(parser):
    parser.addoption(
-        "--config", action="store", default="minimal", help="config: make the pyspec use the specified configuration"
+        "--config", action="store", type=str, default="minimal",
        help="config: make the pyspec use the specified configuration"
    )
    parser.addoption(
        "--disable-bls", action="store_true",
        help="bls-default: make tests that are not dependent on BLS run without BLS"
    )
    parser.addoption(
        "--bls-type", action="store", type=str, default="py_ecc", choices=["py_ecc", "milagro"],
        help="bls-type: use 'pyecc' or 'milagro' implementation for BLS"
    )
@ -36,4 +45,22 @@ def config(request):
    config_name = request.config.getoption("--config")
    config_util.prepare_config('../../../configs/', config_name)
    # now that the presets are loaded, reload the specs to apply them
-    reload_specs()
+    context.reload_specs()
@fixture(autouse=True)
 def bls_default(request):
    disable_bls = request.config.getoption("--disable-bls")
    if disable_bls:
        context.DEFAULT_BLS_ACTIVE = False
@fixture(autouse=True)
 def bls_type(request):
    bls_type = request.config.getoption("--bls-type")
    if bls_type == "py_ecc":
        bls_utils.bls = bls_utils.py_ecc_bls
    elif bls_type == "milagro":
        bls_utils.bls = bls_utils.milagro_bls
    else:
        raise Exception(f"unrecognized bls type: {bls_type}")
--- a/tests/core/pyspec/eth2spec/test/context.py
+++ b/tests/core/pyspec/eth2spec/test/context.py
@ -7,7 +7,9 @@ from .helpers.genesis import create_genesis_state
 from .utils import vector_test, with_meta_tags
 from random import Random
-from typing import Any, Callable, Sequence, TypedDict, Protocol
+from typing import Any, Callable, NewType, Sequence, TypedDict, Protocol
 from lru import LRU
 from importlib import reload
@ -19,48 +21,75 @@ def reload_specs():
 # Some of the Spec module functionality is exposed here to deal with phase-specific changes.
 SpecForkName = NewType("SpecForkName", str)
 PHASE0 = SpecForkName('phase0')
 PHASE1 = SpecForkName('phase1')
 ALL_PHASES = (PHASE0, PHASE1)
 # TODO: currently phases are defined as python modules.
 # It would be better if they would be more well-defined interfaces for stronger typing.
 class Spec(Protocol):
    version: str
-class Phase0(Spec):
+class SpecPhase0(Spec):
    ...
-class Phase1(Spec):
+class SpecPhase1(Spec):
    def upgrade_to_phase1(self, state: spec_phase0.BeaconState) -> spec_phase1.BeaconState:
        ...
 # add transfer, bridge, etc. as the spec evolves
 class SpecForks(TypedDict, total=False):
-    phase0: Phase0
+    PHASE0: SpecPhase0
-    phase1: Phase1
+    PHASE1: SpecPhase1
 def _prepare_state(balances_fn: Callable[[Any], Sequence[int]], threshold_fn: Callable[[Any], int],
                   spec: Spec, phases: SpecForks):
    p0 = phases[PHASE0]
    balances = balances_fn(p0)
    activation_threshold = threshold_fn(p0)
    state = create_genesis_state(spec=p0, validator_balances=balances,
                                 activation_threshold=activation_threshold)
    if spec.fork == PHASE1:
        # TODO: instead of upgrading a test phase0 genesis state we can also write a phase1 state helper.
        # Decide based on performance/consistency results later.
        state = phases[PHASE1].upgrade_to_phase1(state)
        # Shard state slot must lag behind BeaconState slot by at least 1
        # Will handle this more elegantly with fork mechanics
        spec.process_slots(state, state.slot + 1)
    return state
 _custom_state_cache_dict = LRU(size=10)
 def with_custom_state(balances_fn: Callable[[Any], Sequence[int]],
                      threshold_fn: Callable[[Any], int]):
    def deco(fn):
        def entry(*args, spec: Spec, phases: SpecForks, **kw):
            try:
                p0 = phases["phase0"]
                balances = balances_fn(p0)
                activation_threshold = threshold_fn(p0)
-                state = create_genesis_state(spec=p0, validator_balances=balances,
+        def entry(*args, spec: Spec, phases: SpecForks, **kw):
-                                             activation_threshold=activation_threshold)
+            # make a key for the state
-                if spec.fork == 'phase1':
+            # genesis fork version separates configs during test-generation runtime.
-                    # TODO: instead of upgrading a test phase0 genesis state we can also write a phase1 state helper.
+            key = (spec.fork, spec.GENESIS_FORK_VERSION, spec.__file__, balances_fn, threshold_fn)
-                    # Decide based on performance/consistency results later.
+            global _custom_state_cache_dict
-                    state = phases["phase1"].upgrade_to_phase1(state)
+            if key not in _custom_state_cache_dict:
-                    # Shard state slot must lag behind BeaconState slot by at least 1
+                state = _prepare_state(balances_fn, threshold_fn, spec, phases)
-                    # Will handle this more elegantly with fork mechanics
+                _custom_state_cache_dict[key] = state.get_backing()
-                    spec.process_slots(state, state.slot + 1)
+
-                kw['state'] = state
+            # Take an entry out of the LRU.
-            except KeyError:
+            # No copy is necessary, as we wrap the immutable backing with a new view.
-                raise TypeError('Spec decorator must come within state decorator to inject spec into state.')
+            state = spec.BeaconState(backing=_custom_state_cache_dict[key])
            kw['state'] = state
            return fn(*args, spec=spec, phases=phases, **kw)
        return entry
    return deco
@ -138,14 +167,15 @@ def single_phase(fn):
    return entry
-# BLS is turned off by default *for performance purposes during TESTING*.
+# BLS is turned on by default, it can be disabled in tests by overriding this, or using `--disable-bls`.
 # *This is for performance purposes during TESTING, DO NOT DISABLE IN PRODUCTION*.
 # The runner of the test can indicate the preferred setting (test generators prefer BLS to be ON).
 # - Some tests are marked as BLS-requiring, and ignore this setting.
 #    (tests that express differences caused by BLS, e.g. invalid signatures being rejected)
 # - Some other tests are marked as BLS-ignoring, and ignore this setting.
 #    (tests that are heavily performance impacted / require unsigned state transitions)
 # - Most tests respect the BLS setting.
-DEFAULT_BLS_ACTIVE = False
+DEFAULT_BLS_ACTIVE = True
 def spec_test(fn):
@ -219,14 +249,11 @@ def bls_switch(fn):
    return entry
 all_phases = ['phase0', 'phase1']
 def with_all_phases(fn):
    """
    A decorator for running a test with every phase
    """
-    return with_phases(all_phases)(fn)
+    return with_phases(ALL_PHASES)(fn)
 def with_all_phases_except(exclusion_phases):
@ -234,7 +261,7 @@ def with_all_phases_except(exclusion_phases):
    A decorator factory for running a tests with every phase except the ones listed
    """
    def decorator(fn):
-        return with_phases([phase for phase in all_phases if phase not in exclusion_phases])(fn)
+        return with_phases([phase for phase in ALL_PHASES if phase not in exclusion_phases])(fn)
    return decorator
@ -260,18 +287,18 @@ def with_phases(phases, other_phases=None):
            # TODO: test state is dependent on phase0 but is immediately transitioned to phase1.
            #  A new state-creation helper for phase 1 may be in place, and then phase1+ tests can run without phase0
-            available_phases.add('phase0')
+            available_phases.add(PHASE0)
            phase_dir = {}
-            if 'phase0' in available_phases:
+            if PHASE0 in available_phases:
-                phase_dir['phase0'] = spec_phase0
+                phase_dir[PHASE0] = spec_phase0
-            if 'phase1' in available_phases:
+            if PHASE1 in available_phases:
-                phase_dir['phase1'] = spec_phase1
+                phase_dir[PHASE1] = spec_phase1
            # return is ignored whenever multiple phases are ran. If
-            if 'phase0' in run_phases:
+            if PHASE0 in run_phases:
                ret = fn(spec=spec_phase0, phases=phase_dir, *args, **kw)
-            if 'phase1' in run_phases:
+            if PHASE1 in run_phases:
                ret = fn(spec=spec_phase1, phases=phase_dir, *args, **kw)
            return ret
        return wrapper
--- a/tests/core/pyspec/eth2spec/test/fork_choice/test_get_head.py
+++ b/tests/core/pyspec/eth2spec/test/fork_choice/test_get_head.py
@ -183,7 +183,7 @@ def test_filtered_block_tree(spec, state):
    for i in range(spec.SLOTS_PER_EPOCH):
        slot = rogue_block.slot + i
        for index in range(spec.get_committee_count_at_slot(non_viable_state, slot)):
-            attestation = get_valid_attestation(spec, non_viable_state, rogue_block.slot + i, index)
+            attestation = get_valid_attestation(spec, non_viable_state, slot, index, signed=True)
            attestations.append(attestation)
    # tick time forward to be able to include up to the latest attestation
--- a/tests/core/pyspec/eth2spec/test/fork_choice/test_on_attestation.py
+++ b/tests/core/pyspec/eth2spec/test/fork_choice/test_on_attestation.py
@ -1,7 +1,7 @@
-from eth2spec.test.context import with_all_phases, spec_state_test
+from eth2spec.test.context import PHASE0, with_all_phases, spec_state_test
 from eth2spec.test.helpers.block import build_empty_block_for_next_slot
 from eth2spec.test.helpers.attestations import get_valid_attestation, sign_attestation
-from eth2spec.test.helpers.state import transition_to, state_transition_and_sign_block, next_epoch
+from eth2spec.test.helpers.state import transition_to, state_transition_and_sign_block, next_epoch, next_slot
 def run_on_attestation(spec, state, store, attestation, valid=True):
@ -16,7 +16,7 @@ def run_on_attestation(spec, state, store, attestation, valid=True):
    indexed_attestation = spec.get_indexed_attestation(state, attestation)
    spec.on_attestation(store, attestation)
-    if spec.fork == 'phase0':
+    if spec.fork == PHASE0:
        sample_index = indexed_attestation.attesting_indices[0]
    else:
        attesting_indices = [
@ -116,6 +116,44 @@ def test_on_attestation_mismatched_target_and_slot(spec, state):
    run_on_attestation(spec, state, store, attestation, False)
@with_all_phases
@spec_state_test
 def test_on_attestation_inconsistent_target_and_head(spec, state):
    store = spec.get_forkchoice_store(state)
    spec.on_tick(store, store.time + 2 * spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH)
    # Create chain 1 as empty chain between genesis and start of 1st epoch
    target_state_1 = state.copy()
    next_epoch(spec, target_state_1)
    # Create chain 2 with different block in chain from chain 1 from chain 1 from chain 1 from chain 1
    target_state_2 = state.copy()
    diff_block = build_empty_block_for_next_slot(spec, target_state_2)
    signed_diff_block = state_transition_and_sign_block(spec, target_state_2, diff_block)
    spec.on_block(store, signed_diff_block)
    next_epoch(spec, target_state_2)
    next_slot(spec, target_state_2)
    # Create and store block new head block on target state 1
    head_block = build_empty_block_for_next_slot(spec, target_state_1)
    signed_head_block = state_transition_and_sign_block(spec, target_state_1, head_block)
    spec.on_block(store, signed_head_block)
    # Attest to head of chain 1
    attestation = get_valid_attestation(spec, target_state_1, slot=head_block.slot, signed=False)
    epoch = spec.compute_epoch_at_slot(attestation.data.slot)
    # Set attestation target to be from chain 2
    attestation.data.target = spec.Checkpoint(epoch=epoch, root=spec.get_block_root(target_state_2, epoch))
    sign_attestation(spec, state, attestation)
    assert attestation.data.target.epoch == spec.GENESIS_EPOCH + 1
    assert spec.compute_epoch_at_slot(attestation.data.slot) == spec.GENESIS_EPOCH + 1
    assert spec.get_block_root(target_state_1, epoch) != attestation.data.target.root
    run_on_attestation(spec, state, store, attestation, False)
@with_all_phases
@spec_state_test
 def test_on_attestation_target_not_in_store(spec, state):
--- a/tests/core/pyspec/eth2spec/test/fork_choice/test_on_block.py
+++ b/tests/core/pyspec/eth2spec/test/fork_choice/test_on_block.py
@ -184,7 +184,7 @@ def test_on_block_finalized_skip_slots_not_in_skip_chain(spec, state):
 def test_on_block_update_justified_checkpoint_within_safe_slots(spec, state):
    # Initialization
    store = spec.get_forkchoice_store(state)
-    time = 100
+    time = 0
    spec.on_tick(store, time)
    next_epoch(spec, state)
@ -215,7 +215,7 @@ def test_on_block_update_justified_checkpoint_within_safe_slots(spec, state):
 def test_on_block_outside_safe_slots_and_multiple_better_justified(spec, state):
    # Initialization
    store = spec.get_forkchoice_store(state)
-    time = 100
+    time = 0
    spec.on_tick(store, time)
    next_epoch(spec, state)
--- a/tests/core/pyspec/eth2spec/test/genesis/test_initialization.py
+++ b/tests/core/pyspec/eth2spec/test/genesis/test_initialization.py
@ -1,10 +1,10 @@
-from eth2spec.test.context import spec_test, with_phases, single_phase
+from eth2spec.test.context import PHASE0, spec_test, with_phases, single_phase
 from eth2spec.test.helpers.deposits import (
    prepare_genesis_deposits,
 )
-@with_phases(['phase0'])
+@with_phases(([PHASE0]))
@spec_test
@single_phase
 def test_initialize_beacon_state_from_eth1(spec):
@ -21,7 +21,7 @@ def test_initialize_beacon_state_from_eth1(spec):
    # initialize beacon_state
    state = spec.initialize_beacon_state_from_eth1(eth1_block_hash, eth1_timestamp, deposits)
-    assert state.genesis_time == eth1_timestamp - eth1_timestamp % spec.MIN_GENESIS_DELAY + 2 * spec.MIN_GENESIS_DELAY
+    assert state.genesis_time == eth1_timestamp + spec.GENESIS_DELAY
    assert len(state.validators) == deposit_count
    assert state.eth1_data.deposit_root == deposit_root
    assert state.eth1_data.deposit_count == deposit_count
@ -32,7 +32,7 @@ def test_initialize_beacon_state_from_eth1(spec):
    yield 'state', state
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_test
@single_phase
 def test_initialize_beacon_state_some_small_balances(spec):
@ -57,7 +57,7 @@ def test_initialize_beacon_state_some_small_balances(spec):
    # initialize beacon_state
    state = spec.initialize_beacon_state_from_eth1(eth1_block_hash, eth1_timestamp, deposits)
-    assert state.genesis_time == eth1_timestamp - eth1_timestamp % spec.MIN_GENESIS_DELAY + 2 * spec.MIN_GENESIS_DELAY
+    assert state.genesis_time == eth1_timestamp + spec.GENESIS_DELAY
    assert len(state.validators) == small_deposit_count
    assert state.eth1_data.deposit_root == deposit_root
    assert state.eth1_data.deposit_count == len(deposits)
--- a/tests/core/pyspec/eth2spec/test/genesis/test_validity.py
+++ b/tests/core/pyspec/eth2spec/test/genesis/test_validity.py
@ -1,4 +1,4 @@
-from eth2spec.test.context import spec_test, with_phases, single_phase
+from eth2spec.test.context import PHASE0, spec_test, with_phases, single_phase
 from eth2spec.test.helpers.deposits import (
    prepare_genesis_deposits,
 )
@ -25,7 +25,7 @@ def run_is_valid_genesis_state(spec, state, valid=True):
    assert is_valid == valid
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_test
@single_phase
 def test_is_valid_genesis_state_true(spec):
@ -34,7 +34,7 @@ def test_is_valid_genesis_state_true(spec):
    yield from run_is_valid_genesis_state(spec, state, valid=True)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_test
@single_phase
 def test_is_valid_genesis_state_false_invalid_timestamp(spec):
@ -44,7 +44,7 @@ def test_is_valid_genesis_state_false_invalid_timestamp(spec):
    yield from run_is_valid_genesis_state(spec, state, valid=False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_test
@single_phase
 def test_is_valid_genesis_state_true_more_balance(spec):
@ -55,7 +55,7 @@ def test_is_valid_genesis_state_true_more_balance(spec):
 # TODO: not part of the genesis function yet. Erroneously merged.
-# @with_phases(['phase0'])
+# @with_phases([PHASE0])
 # @spec_test
 # def test_is_valid_genesis_state_false_not_enough_balance(spec):
 #     state = create_valid_beacon_state(spec)
@ -64,7 +64,7 @@ def test_is_valid_genesis_state_true_more_balance(spec):
 #     yield from run_is_valid_genesis_state(spec, state, valid=False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_test
@single_phase
 def test_is_valid_genesis_state_true_one_more_validator(spec):
@ -78,7 +78,7 @@ def test_is_valid_genesis_state_true_one_more_validator(spec):
    yield from run_is_valid_genesis_state(spec, state, valid=True)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_test
@single_phase
 def test_is_valid_genesis_state_false_not_enough_validator(spec):
--- a/tests/core/pyspec/eth2spec/test/helpers/attestations.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/attestations.py
@ -1,11 +1,12 @@
 from typing import List
-from eth2spec.test.context import expect_assertion_error
+from eth2spec.test.context import expect_assertion_error, PHASE0, PHASE1
-from eth2spec.test.helpers.state import next_slot, state_transition_and_sign_block
+from eth2spec.test.helpers.state import state_transition_and_sign_block, next_epoch, next_slot, transition_to
 from eth2spec.test.helpers.block import build_empty_block_for_next_slot
 from eth2spec.test.helpers.keys import privkeys
 from eth2spec.utils import bls
 from eth2spec.utils.ssz.ssz_typing import Bitlist
 from lru import LRU
 def run_attestation_processing(spec, state, attestation, valid=True):
@ -43,7 +44,7 @@ def run_attestation_processing(spec, state, attestation, valid=True):
    yield 'post', state
-def build_attestation_data(spec, state, slot, index):
+def build_attestation_data(spec, state, slot, index, shard_transition=None, on_time=True):
    assert state.slot >= slot
    if slot == state.slot:
@ -66,7 +67,7 @@ def build_attestation_data(spec, state, slot, index):
        source_epoch = state.current_justified_checkpoint.epoch
        source_root = state.current_justified_checkpoint.root
-    return spec.AttestationData(
+    attestation_data = spec.AttestationData(
        slot=slot,
        index=index,
        beacon_block_root=block_root,
@ -74,14 +75,34 @@ def build_attestation_data(spec, state, slot, index):
        target=spec.Checkpoint(epoch=spec.compute_epoch_at_slot(slot), root=epoch_boundary_root),
    )
    if spec.fork == PHASE1:
        if shard_transition is not None:
            lastest_shard_data_root_index = len(shard_transition.shard_data_roots) - 1
            attestation_data.shard_head_root = shard_transition.shard_data_roots[lastest_shard_data_root_index]
            attestation_data.shard_transition_root = shard_transition.hash_tree_root()
        else:
            # No shard transition
            shard = spec.get_shard(state, spec.Attestation(data=attestation_data))
            if on_time:
                temp_state = state.copy()
                next_slot(spec, temp_state)
                shard_transition = spec.get_shard_transition(temp_state, shard, [])
                lastest_shard_data_root_index = len(shard_transition.shard_data_roots) - 1
                attestation_data.shard_head_root = shard_transition.shard_data_roots[lastest_shard_data_root_index]
                attestation_data.shard_transition_root = shard_transition.hash_tree_root()
            else:
                attestation_data.shard_head_root = state.shard_states[shard].transition_digest
                attestation_data.shard_transition_root = spec.Root()
    return attestation_data
 def convert_to_valid_on_time_attestation(spec, state, attestation, signed=False):
    shard = spec.get_shard(state, attestation)
-
+    offset_slots = spec.compute_offset_slots(
-    next_state = state.copy()
+        spec.get_latest_slot_for_shard(state, shard),
-    next_slot(spec, next_state)
+        attestation.data.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY,
-    offset_slots = spec.get_offset_slots(next_state, spec.get_latest_slot_for_shard(next_state, shard))
+    )
-    for offset_slot in offset_slots:
+    for _ in offset_slots:
        attestation.custody_bits_blocks.append(
            Bitlist[spec.MAX_VALIDATORS_PER_COMMITTEE]([0 for _ in attestation.aggregation_bits])
        )
@ -92,7 +113,7 @@ def convert_to_valid_on_time_attestation(spec, state, attestation, signed=False)
    return attestation
-def get_valid_on_time_attestation(spec, state, slot=None, index=None, signed=False):
+def get_valid_on_time_attestation(spec, state, slot=None, index=None, shard_transition=None, signed=False):
    '''
    Construct on-time attestation for next slot
    '''
@ -101,7 +122,15 @@ def get_valid_on_time_attestation(spec, state, slot=None, index=None, signed=Fal
    if index is None:
        index = 0
-    return get_valid_attestation(spec, state, slot=slot, index=index, signed=signed, on_time=True)
+    return get_valid_attestation(
        spec,
        state,
        slot=slot,
        index=index,
        shard_transition=shard_transition,
        signed=signed,
        on_time=True,
    )
 def get_valid_late_attestation(spec, state, slot=None, index=None, signed=False):
@ -116,13 +145,24 @@ def get_valid_late_attestation(spec, state, slot=None, index=None, signed=False)
    return get_valid_attestation(spec, state, slot=slot, index=index, signed=signed, on_time=False)
-def get_valid_attestation(spec, state, slot=None, index=None, empty=False, signed=False, on_time=True):
+def get_valid_attestation(spec,
                          state,
                          slot=None,
                          index=None,
                          filter_participant_set=None,
                          shard_transition=None,
                          signed=False,
                          on_time=True):
    # If filter_participant_set filters everything, the attestation has 0 participants, and cannot be signed.
    # Thus strictly speaking invalid when no participant is added later.
    if slot is None:
        slot = state.slot
    if index is None:
        index = 0
-    attestation_data = build_attestation_data(spec, state, slot, index)
+    attestation_data = build_attestation_data(
        spec, state, slot=slot, index=index, shard_transition=shard_transition, on_time=on_time
    )
    beacon_committee = spec.get_beacon_committee(
        state,
@ -136,12 +176,10 @@ def get_valid_attestation(spec, state, slot=None, index=None, empty=False, signe
        aggregation_bits=aggregation_bits,
        data=attestation_data,
    )
-    if not empty:
+    # fill the attestation with (optionally filtered) participants, and optionally sign it
-        fill_aggregate_attestation(spec, state, attestation)
+    fill_aggregate_attestation(spec, state, attestation, signed=signed, filter_participant_set=filter_participant_set)
    if signed:
        sign_attestation(spec, state, attestation)
-    if spec.fork == 'phase1' and on_time:
+    if spec.fork == PHASE1 and on_time:
        attestation = convert_to_valid_on_time_attestation(spec, state, attestation, signed)
    return attestation
@ -163,7 +201,7 @@ def sign_aggregate_attestation(spec, state, attestation_data, participants: List
 def sign_indexed_attestation(spec, state, indexed_attestation):
-    if spec.fork == 'phase0':
+    if spec.fork == PHASE0:
        participants = indexed_attestation.attesting_indices
        data = indexed_attestation.data
        indexed_attestation.signature = sign_aggregate_attestation(spec, state, data, participants)
@ -173,7 +211,10 @@ def sign_indexed_attestation(spec, state, indexed_attestation):
            indexed_attestation.attestation.aggregation_bits,
        )
        data = indexed_attestation.attestation.data
-        indexed_attestation.attestation.signature = sign_aggregate_attestation(spec, state, data, participants)
+        if any(indexed_attestation.attestation.custody_bits_blocks):
            sign_on_time_attestation(spec, state, indexed_attestation.attestation)
        else:
            indexed_attestation.attestation.signature = sign_aggregate_attestation(spec, state, data, participants)
 def sign_on_time_attestation(spec, state, attestation):
@ -213,7 +254,7 @@ def get_attestation_custody_signature(spec, state, attestation_data, block_index
 def sign_attestation(spec, state, attestation):
-    if spec.fork == 'phase1' and any(attestation.custody_bits_blocks):
+    if spec.fork == PHASE1 and any(attestation.custody_bits_blocks):
        sign_on_time_attestation(spec, state, attestation)
        return
@ -232,21 +273,31 @@ def get_attestation_signature(spec, state, attestation_data, privkey):
    return bls.Sign(privkey, signing_root)
-def fill_aggregate_attestation(spec, state, attestation, signed=False):
+def fill_aggregate_attestation(spec, state, attestation, signed=False, filter_participant_set=None):
    """
     `signed`: Signing is optional.
     `filter_participant_set`: Optional, filters the full committee indices set (default) to a subset that participates
    """
    beacon_committee = spec.get_beacon_committee(
        state,
        attestation.data.slot,
        attestation.data.index,
    )
    # By default, have everyone participate
    participants = set(beacon_committee)
    # But optionally filter the participants to a smaller amount
    if filter_participant_set is not None:
        participants = filter_participant_set(participants)
    for i in range(len(beacon_committee)):
-        attestation.aggregation_bits[i] = True
+        attestation.aggregation_bits[i] = beacon_committee[i] in participants
-    if signed:
+    if signed and len(participants) > 0:
        sign_attestation(spec, state, attestation)
 def add_attestations_to_state(spec, state, attestations, slot):
-    spec.process_slots(state, slot)
+    if state.slot < slot:
        spec.process_slots(state, slot)
    for attestation in attestations:
        spec.process_attestation(state, attestation)
@ -277,7 +328,82 @@ def next_epoch_with_attestations(spec,
                    spec, post_state, slot_to_attest, index=index, signed=True, on_time=False)
                block.body.attestations.append(prev_attestation)
        if spec.fork == PHASE1:
            fill_block_shard_transitions_by_attestations(spec, post_state, block)
        signed_block = state_transition_and_sign_block(spec, post_state, block)
        signed_blocks.append(signed_block)
    return state, signed_blocks, post_state
 def prepare_state_with_attestations(spec, state, participation_fn=None):
    """
    Prepare state with attestations according to the ``participation_fn``.
    If no ``participation_fn``, default to "full" -- max committee participation at each slot.
    participation_fn: (slot, committee_index, committee_indices_set) -> participants_indices_set
    """
    # Go to start of next epoch to ensure can have full participation
    next_epoch(spec, state)
    start_slot = state.slot
    start_epoch = spec.get_current_epoch(state)
    next_epoch_start_slot = spec.compute_start_slot_at_epoch(start_epoch + 1)
    attestations = []
    for _ in range(spec.SLOTS_PER_EPOCH + spec.MIN_ATTESTATION_INCLUSION_DELAY):
        # create an attestation for each index in each slot in epoch
        if state.slot < next_epoch_start_slot:
            for committee_index in range(spec.get_committee_count_at_slot(state, state.slot)):
                def temp_participants_filter(comm):
                    if participation_fn is None:
                        return comm
                    else:
                        return participation_fn(state.slot, committee_index, comm)
                attestation = get_valid_attestation(spec, state, index=committee_index,
                                                    filter_participant_set=temp_participants_filter, signed=True)
                if any(attestation.aggregation_bits):  # Only if there is at least 1 participant.
                    attestations.append(attestation)
        # fill each created slot in state after inclusion delay
        if state.slot >= start_slot + spec.MIN_ATTESTATION_INCLUSION_DELAY:
            inclusion_slot = state.slot - spec.MIN_ATTESTATION_INCLUSION_DELAY
            include_attestations = [att for att in attestations if att.data.slot == inclusion_slot]
            add_attestations_to_state(spec, state, include_attestations, state.slot)
        next_slot(spec, state)
    assert state.slot == next_epoch_start_slot + spec.MIN_ATTESTATION_INCLUSION_DELAY
    assert len(state.previous_epoch_attestations) == len(attestations)
    return attestations
 _prep_state_cache_dict = LRU(size=10)
 def cached_prepare_state_with_attestations(spec, state):
    """
    Cached version of prepare_state_with_attestations,
    but does not return anything, and does not support a participation fn argument
    """
    # If the pre-state is not already known in the LRU, then take it,
    # prepare it with attestations, and put it in the LRU.
    # The input state is likely already cached, so the hash-tree-root does not affect speed.
    key = (spec.fork, state.hash_tree_root())
    global _prep_state_cache_dict
    if key not in _prep_state_cache_dict:
        prepare_state_with_attestations(spec, state)
        _prep_state_cache_dict[key] = state.get_backing()  # cache the tree structure, not the view wrapping it.
    # Put the LRU cache result into the state view, as if we transitioned the original view
    state.set_backing(_prep_state_cache_dict[key])
 def fill_block_shard_transitions_by_attestations(spec, state, block):
    block.body.shard_transitions = [spec.ShardTransition()] * spec.MAX_SHARDS
    for attestation in block.body.attestations:
        shard = spec.get_shard(state, attestation)
        if attestation.data.slot == state.slot:
            temp_state = state.copy()
            transition_to(spec, temp_state, slot=block.slot)
            shard_transition = spec.get_shard_transition(temp_state, shard, [])
            block.body.shard_transitions[shard] = shard_transition
--- a/tests/core/pyspec/eth2spec/test/helpers/attester_slashings.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/attester_slashings.py
@ -1,4 +1,5 @@
-from eth2spec.test.helpers.attestations import get_valid_attestation, sign_attestation
+from eth2spec.test.context import PHASE1
 from eth2spec.test.helpers.attestations import get_valid_attestation, sign_attestation, sign_indexed_attestation
 def get_valid_attester_slashing(spec, state, signed_1=False, signed_2=False):
@ -16,11 +17,31 @@ def get_valid_attester_slashing(spec, state, signed_1=False, signed_2=False):
    )
 def get_valid_attester_slashing_by_indices(spec, state, indices_1, indices_2=None, signed_1=False, signed_2=False):
    if indices_2 is None:
        indices_2 = indices_1
    assert indices_1 == sorted(indices_1)
    assert indices_2 == sorted(indices_2)
    attester_slashing = get_valid_attester_slashing(spec, state)
    attester_slashing.attestation_1.attesting_indices = indices_1
    attester_slashing.attestation_2.attesting_indices = indices_2
    if signed_1:
        sign_indexed_attestation(spec, state, attester_slashing.attestation_1)
    if signed_2:
        sign_indexed_attestation(spec, state, attester_slashing.attestation_2)
    return attester_slashing
 def get_indexed_attestation_participants(spec, indexed_att):
    """
    Wrapper around index-attestation to return the list of participant indices, regardless of spec phase.
    """
-    if spec.fork == "phase1":
+    if spec.fork == PHASE1:
        return list(spec.get_indices_from_committee(
            indexed_att.committee,
            indexed_att.attestation.aggregation_bits,
@ -33,21 +54,21 @@ def set_indexed_attestation_participants(spec, indexed_att, participants):
    """
    Wrapper around index-attestation to return the list of participant indices, regardless of spec phase.
    """
-    if spec.fork == "phase1":
+    if spec.fork == PHASE1:
        indexed_att.attestation.aggregation_bits = [bool(i in participants) for i in indexed_att.committee]
    else:
        indexed_att.attesting_indices = participants
 def get_attestation_1_data(spec, att_slashing):
-    if spec.fork == "phase1":
+    if spec.fork == PHASE1:
        return att_slashing.attestation_1.attestation.data
    else:
        return att_slashing.attestation_1.data
 def get_attestation_2_data(spec, att_slashing):
-    if spec.fork == "phase1":
+    if spec.fork == PHASE1:
        return att_slashing.attestation_2.attestation.data
    else:
        return att_slashing.attestation_2.data
--- a/tests/core/pyspec/eth2spec/test/helpers/block.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/block.py
@ -15,7 +15,8 @@ def get_proposer_index_maybe(spec, state, slot, proposer_index=None):
                      " Signing block is slow due to transition for proposer index calculation.")
            # use stub state to get proposer index of future slot
            stub_state = state.copy()
-            spec.process_slots(stub_state, slot)
+            if stub_state.slot < slot:
                spec.process_slots(stub_state, slot)
            proposer_index = spec.get_beacon_proposer_index(stub_state)
    return proposer_index
@ -52,15 +53,19 @@ def sign_block(spec, state, block, proposer_index=None):
 def transition_unsigned_block(spec, state, block):
-    spec.process_slots(state, block.slot)
+    assert state.slot < block.slot  # Preserve assertion from state transition to avoid strange pre-states from testing
    if state.slot < block.slot:
        spec.process_slots(state, block.slot)
    assert state.latest_block_header.slot < block.slot  # There may not already be a block in this slot or past it.
    assert state.slot == block.slot  # The block must be for this slot
    spec.process_block(state, block)
-def apply_empty_block(spec, state):
+def apply_empty_block(spec, state, slot=None):
    """
    Transition via an empty block (on current slot, assuming no block has been applied yet).
    """
-    block = build_empty_block(spec, state)
+    block = build_empty_block(spec, state, slot)
    transition_unsigned_block(spec, state, block)
@ -73,22 +78,35 @@ def build_empty_block(spec, state, slot=None):
        slot = state.slot
    if slot < state.slot:
        raise Exception("build_empty_block cannot build blocks for past slots")
-    if slot > state.slot:
+    if state.slot < slot:
        # transition forward in copied state to grab relevant data from state
        state = state.copy()
        spec.process_slots(state, slot)
    state, parent_block_root = get_state_and_beacon_parent_root_at_slot(spec, state, slot)
    empty_block = spec.BeaconBlock()
    empty_block.slot = slot
    empty_block.proposer_index = spec.get_beacon_proposer_index(state)
    empty_block.body.eth1_data.deposit_count = state.eth1_deposit_index
-    previous_block_header = state.latest_block_header.copy()
+    empty_block.parent_root = parent_block_root
    if previous_block_header.state_root == spec.Root():
        previous_block_header.state_root = hash_tree_root(state)
    empty_block.parent_root = hash_tree_root(previous_block_header)
    apply_randao_reveal(spec, state, empty_block)
    return empty_block
 def build_empty_block_for_next_slot(spec, state):
    return build_empty_block(spec, state, state.slot + 1)
 def get_state_and_beacon_parent_root_at_slot(spec, state, slot):
    if slot < state.slot:
        raise Exception("Cannot build blocks for past slots")
    if slot > state.slot:
        # transition forward in copied state to grab relevant data from state
        state = state.copy()
        spec.process_slots(state, slot)
    previous_block_header = state.latest_block_header.copy()
    if previous_block_header.state_root == spec.Root():
        previous_block_header.state_root = hash_tree_root(state)
    beacon_parent_root = hash_tree_root(previous_block_header)
    return state, beacon_parent_root
--- a/tests/core/pyspec/eth2spec/test/helpers/deposits.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/deposits.py
@ -5,6 +5,17 @@ from eth2spec.utils.ssz.ssz_impl import hash_tree_root
 from eth2spec.utils.ssz.ssz_typing import List
 def mock_deposit(spec, state, index):
    """
    Mock validator at ``index`` as having just made a deposit
    """
    assert spec.is_active_validator(state.validators[index], spec.get_current_epoch(state))
    state.validators[index].activation_eligibility_epoch = spec.FAR_FUTURE_EPOCH
    state.validators[index].activation_epoch = spec.FAR_FUTURE_EPOCH
    state.validators[index].effective_balance = spec.MAX_EFFECTIVE_BALANCE
    assert not spec.is_active_validator(state.validators[index], spec.get_current_epoch(state))
 def build_deposit_data(spec, pubkey, privkey, amount, withdrawal_credentials, signed=False):
    deposit_data = spec.DepositData(
        pubkey=pubkey,
--- a/tests/core/pyspec/eth2spec/test/helpers/keys.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/keys.py
@ -2,5 +2,5 @@ from py_ecc.bls import G2ProofOfPossession as bls
 from eth2spec.phase0 import spec
 privkeys = [i + 1 for i in range(spec.SLOTS_PER_EPOCH * 256)]
-pubkeys = [bls.PrivToPub(privkey) for privkey in privkeys]
+pubkeys = [bls.SkToPk(privkey) for privkey in privkeys]
 pubkey_to_privkey = {pubkey: privkey for privkey, pubkey in zip(privkeys, pubkeys)}
--- a/tests/core/pyspec/eth2spec/test/helpers/phase1/attestations.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/phase1/attestations.py
@ -1,66 +0,0 @@
 from eth2spec.utils.ssz.ssz_typing import Bitlist
 from eth2spec.utils import bls
 from eth2spec.test.helpers.keys import privkeys
 import eth2spec.test.helpers.attestations as phase0_attestations
 from eth2spec.test.helpers.state import next_slot
 def get_valid_on_time_attestation(spec, state, index=None, signed=False):
    '''
    Construct on-time attestation for next slot
    '''
    if index is None:
        index = 0
    attestation = phase0_attestations.get_valid_attestation(spec, state, state.slot, index, False)
    shard = spec.get_shard(state, attestation)
    next_state = state.copy()
    next_slot(spec, next_state)
    offset_slots = spec.get_offset_slots(next_state, spec.get_latest_slot_for_shard(next_state, shard))
    for offset_slot in offset_slots:
        attestation.custody_bits_blocks.append(
            Bitlist[spec.MAX_VALIDATORS_PER_COMMITTEE]([0 for _ in attestation.aggregation_bits])
        )
    if signed:
        sign_attestation(spec, state, attestation)
    return attestation
 def sign_attestation(spec, state, attestation):
    if not any(attestation.custody_bits_blocks):
        phase0_attestations.sign_attestation(spec, state, attestation)
        return
    committee = spec.get_beacon_committee(state, attestation.data.slot, attestation.data.index)
    signatures = []
    for block_index, custody_bits in enumerate(attestation.custody_bits_blocks):
        for participant, abit, cbit in zip(committee, attestation.aggregation_bits, custody_bits):
            if not abit:
                continue
            signatures.append(get_attestation_custody_signature(
                spec,
                state,
                attestation.data,
                block_index,
                cbit,
                privkeys[participant]
            ))
    attestation.signature = bls.Aggregate(signatures)
 def get_attestation_custody_signature(spec, state, attestation_data, block_index, bit, privkey):
    domain = spec.get_domain(state, spec.DOMAIN_BEACON_ATTESTER, attestation_data.target.epoch)
    signing_root = spec.compute_signing_root(
        spec.AttestationCustodyBitWrapper(
            attestation_data.hash_tree_root(),
            block_index,
            bit,
        ),
        domain,
    )
    return bls.Sign(privkey, signing_root)
--- a/tests/core/pyspec/eth2spec/test/helpers/phase1/shard_block.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/phase1/shard_block.py
@ -1,71 +0,0 @@
 from eth2spec.test.helpers.keys import privkeys
 from eth2spec.utils import bls
 from eth2spec.utils.bls import only_with_bls
 from eth2spec.utils.ssz.ssz_impl import (
    hash_tree_root,
 )
 from .attestations import (
    sign_shard_attestation,
 )
@only_with_bls()
 def sign_shard_block(spec, beacon_state, shard_state, block, proposer_index=None):
    if proposer_index is None:
        proposer_index = spec.get_shard_proposer_index(beacon_state, shard_state.shard, block.slot)
    privkey = privkeys[proposer_index]
    domain = spec.get_domain(beacon_state, spec.DOMAIN_SHARD_PROPOSER, spec.compute_epoch_of_shard_slot(block.slot))
    signing_root = spec.compute_signing_root(block, domain)
    block.signature = bls.Sign(privkey, signing_root)
 def build_empty_shard_block(spec,
                            beacon_state,
                            shard_state,
                            slot,
                            signed=False,
                            full_attestation=False):
    if slot is None:
        slot = shard_state.slot
    previous_beacon_header = beacon_state.latest_block_header.copy()
    if previous_beacon_header.state_root == spec.Bytes32():
        previous_beacon_header.state_root = beacon_state.hash_tree_root()
    beacon_block_root = hash_tree_root(previous_beacon_header)
    previous_block_header = shard_state.latest_block_header.copy()
    if previous_block_header.state_root == spec.Bytes32():
        previous_block_header.state_root = shard_state.hash_tree_root()
    parent_root = hash_tree_root(previous_block_header)
    block = spec.ShardBlock(
        shard=shard_state.shard,
        slot=slot,
        beacon_block_root=beacon_block_root,
        parent_root=parent_root,
        block_size_sum=shard_state.block_size_sum + spec.SHARD_HEADER_SIZE,
    )
    if full_attestation:
        shard_committee = spec.get_shard_committee(beacon_state, shard_state.shard, block.slot)
        block.aggregation_bits = list(
            (True,) * len(shard_committee) +
            (False,) * (spec.MAX_PERIOD_COMMITTEE_SIZE * 2 - len(shard_committee))
        )
    else:
        shard_committee = []
    block.attestations = sign_shard_attestation(
        spec,
        beacon_state,
        shard_state,
        block,
        participants=shard_committee,
    )
    if signed:
        sign_shard_block(spec, beacon_state, shard_state, block)
    return block
--- a/tests/core/pyspec/eth2spec/test/helpers/phase1/shard_state.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/phase1/shard_state.py
@ -1,18 +0,0 @@
 from eth2spec.test.helpers.phase1.shard_block import sign_shard_block
 def configure_shard_state(spec, beacon_state, shard=0):
    beacon_state.slot = spec.Slot(spec.SHARD_GENESIS_EPOCH * spec.SLOTS_PER_EPOCH)
    shard_state = spec.get_genesis_shard_state(spec.Shard(shard))
    shard_state.slot = spec.ShardSlot(spec.SHARD_GENESIS_EPOCH * spec.SHARD_SLOTS_PER_EPOCH)
    return beacon_state, shard_state
 def shard_state_transition_and_sign_block(spec, beacon_state, shard_state, block):
    """
    Shard state transition via the provided ``block``
    then package the block with the state root and signature.
    """
    spec.shard_state_transition(beacon_state, shard_state, block)
    block.state_root = shard_state.hash_tree_root()
    sign_shard_block(spec, beacon_state, shard_state, block)
--- a/tests/core/pyspec/eth2spec/test/helpers/proposer_slashings.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/proposer_slashings.py
@ -1,22 +1,55 @@
 from eth2spec.test.helpers.block_header import sign_block_header
 from eth2spec.test.helpers.keys import pubkey_to_privkey
 from eth2spec.test.helpers.state import get_balance
-def get_valid_proposer_slashing(spec, state, signed_1=False, signed_2=False):
+def check_proposer_slashing_effect(spec, pre_state, state, slashed_index):
-    current_epoch = spec.get_current_epoch(state)
+    slashed_validator = state.validators[slashed_index]
-    validator_index = spec.get_active_validator_indices(state, current_epoch)[-1]
+    assert slashed_validator.slashed
-    privkey = pubkey_to_privkey[state.validators[validator_index].pubkey]
+    assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
    assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
    proposer_index = spec.get_beacon_proposer_index(state)
    slash_penalty = state.validators[slashed_index].effective_balance // spec.MIN_SLASHING_PENALTY_QUOTIENT
    whistleblower_reward = state.validators[slashed_index].effective_balance // spec.WHISTLEBLOWER_REWARD_QUOTIENT
    if proposer_index != slashed_index:
        # slashed validator lost initial slash penalty
        assert (
            get_balance(state, slashed_index)
            == get_balance(pre_state, slashed_index) - slash_penalty
        )
        # block proposer gained whistleblower reward
        # >= because proposer could have reported multiple
        assert (
            get_balance(state, proposer_index)
            >= get_balance(pre_state, proposer_index) + whistleblower_reward
        )
    else:
        # proposer reported themself so get penalty and reward
        # >= because proposer could have reported multiple
        assert (
            get_balance(state, slashed_index)
            >= get_balance(pre_state, slashed_index) - slash_penalty + whistleblower_reward
        )
 def get_valid_proposer_slashing(spec, state, random_root=b'\x99' * 32,
                                slashed_index=None, signed_1=False, signed_2=False):
    if slashed_index is None:
        current_epoch = spec.get_current_epoch(state)
        slashed_index = spec.get_active_validator_indices(state, current_epoch)[-1]
    privkey = pubkey_to_privkey[state.validators[slashed_index].pubkey]
    slot = state.slot
    header_1 = spec.BeaconBlockHeader(
        slot=slot,
-        proposer_index=validator_index,
+        proposer_index=slashed_index,
        parent_root=b'\x33' * 32,
        state_root=b'\x44' * 32,
        body_root=b'\x55' * 32,
    )
    header_2 = header_1.copy()
-    header_2.parent_root = b'\x99' * 32
+    header_2.parent_root = random_root
    if signed_1:
        signed_header_1 = sign_block_header(spec, state, header_1, privkey)
--- a/tests/core/pyspec/eth2spec/test/helpers/rewards.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/rewards.py
@ -0,0 +1,457 @@
 from random import Random
 from lru import LRU
 from eth2spec.phase0 import spec as spec_phase0
 from eth2spec.test.helpers.attestations import cached_prepare_state_with_attestations
 from eth2spec.test.helpers.deposits import mock_deposit
 from eth2spec.test.helpers.state import next_epoch
 from eth2spec.utils.ssz.ssz_typing import Container, uint64, List
 class Deltas(Container):
    rewards: List[uint64, spec_phase0.VALIDATOR_REGISTRY_LIMIT]
    penalties: List[uint64, spec_phase0.VALIDATOR_REGISTRY_LIMIT]
 def has_enough_for_reward(spec, state, index):
    """
    Check if base_reward will be non-zero.
    At very low balances, it is possible for a validator have a positive effective_balance
    but a zero base reward.
    """
    return (
        state.validators[index].effective_balance * spec.BASE_REWARD_FACTOR
        > spec.integer_squareroot(spec.get_total_active_balance(state)) // spec.BASE_REWARDS_PER_EPOCH
    )
 def run_deltas(spec, state):
    """
    Run all deltas functions yielding:
      - pre-state ('pre')
      - source deltas ('source_deltas')
      - target deltas ('target_deltas')
      - head deltas ('head_deltas')
      - inclusion delay deltas ('inclusion_delay_deltas')
      - inactivity penalty deltas ('inactivity_penalty_deltas')
    """
    yield 'pre', state
    yield from run_attestation_component_deltas(
        spec,
        state,
        spec.get_source_deltas,
        spec.get_matching_source_attestations,
        'source_deltas',
    )
    yield from run_attestation_component_deltas(
        spec,
        state,
        spec.get_target_deltas,
        spec.get_matching_target_attestations,
        'target_deltas',
    )
    yield from run_attestation_component_deltas(
        spec,
        state,
        spec.get_head_deltas,
        spec.get_matching_head_attestations,
        'head_deltas',
    )
    yield from run_get_inclusion_delay_deltas(spec, state)
    yield from run_get_inactivity_penalty_deltas(spec, state)
 def run_attestation_component_deltas(spec, state, component_delta_fn, matching_att_fn, deltas_name):
    """
    Run ``component_delta_fn``, yielding:
      - deltas ('{``deltas_name``}')
    """
    rewards, penalties = component_delta_fn(state)
    yield deltas_name, Deltas(rewards=rewards, penalties=penalties)
    matching_attestations = matching_att_fn(state, spec.get_previous_epoch(state))
    matching_indices = spec.get_unslashed_attesting_indices(state, matching_attestations)
    eligible_indices = spec.get_eligible_validator_indices(state)
    for index in range(len(state.validators)):
        if index not in eligible_indices:
            assert rewards[index] == 0
            assert penalties[index] == 0
            continue
        validator = state.validators[index]
        enough_for_reward = has_enough_for_reward(spec, state, index)
        if index in matching_indices and not validator.slashed:
            if enough_for_reward:
                assert rewards[index] > 0
            else:
                assert rewards[index] == 0
            assert penalties[index] == 0
        else:
            assert rewards[index] == 0
            if enough_for_reward:
                assert penalties[index] > 0
            else:
                assert penalties[index] == 0
 def run_get_inclusion_delay_deltas(spec, state):
    """
    Run ``get_inclusion_delay_deltas``, yielding:
      - inclusion delay deltas ('inclusion_delay_deltas')
    """
    rewards, penalties = spec.get_inclusion_delay_deltas(state)
    yield 'inclusion_delay_deltas', Deltas(rewards=rewards, penalties=penalties)
    eligible_attestations = spec.get_matching_source_attestations(state, spec.get_previous_epoch(state))
    attesting_indices = spec.get_unslashed_attesting_indices(state, eligible_attestations)
    rewarded_indices = set()
    rewarded_proposer_indices = set()
    # Ensure attesters with enough balance are rewarded for attestations
    # Track those that are rewarded and track proposers that should be rewarded
    for index in range(len(state.validators)):
        if index in attesting_indices and has_enough_for_reward(spec, state, index):
            assert rewards[index] > 0
            rewarded_indices.add(index)
            # Track proposer of earliest included attestation for the validator defined by index
            earliest_attestation = min([
                a for a in eligible_attestations
                if index in spec.get_attesting_indices(state, a.data, a.aggregation_bits)
            ], key=lambda a: a.inclusion_delay)
            rewarded_proposer_indices.add(earliest_attestation.proposer_index)
    # Ensure all expected proposers have been rewarded
    # Track rewarde indices
    proposing_indices = [a.proposer_index for a in eligible_attestations]
    for index in proposing_indices:
        if index in rewarded_proposer_indices:
            assert rewards[index] > 0
            rewarded_indices.add(index)
    # Ensure all expected non-rewarded indices received no reward
    for index in range(len(state.validators)):
        assert penalties[index] == 0
        if index not in rewarded_indices:
            assert rewards[index] == 0
 def run_get_inactivity_penalty_deltas(spec, state):
    """
    Run ``get_inactivity_penalty_deltas``, yielding:
      - inactivity penalty deltas ('inactivity_penalty_deltas')
    """
    rewards, penalties = spec.get_inactivity_penalty_deltas(state)
    yield 'inactivity_penalty_deltas', Deltas(rewards=rewards, penalties=penalties)
    matching_attestations = spec.get_matching_target_attestations(state, spec.get_previous_epoch(state))
    matching_attesting_indices = spec.get_unslashed_attesting_indices(state, matching_attestations)
    eligible_indices = spec.get_eligible_validator_indices(state)
    for index in range(len(state.validators)):
        assert rewards[index] == 0
        if index not in eligible_indices:
            assert penalties[index] == 0
            continue
        if spec.is_in_inactivity_leak(state):
            base_reward = spec.get_base_reward(state, index)
            base_penalty = spec.BASE_REWARDS_PER_EPOCH * base_reward - spec.get_proposer_reward(state, index)
            if not has_enough_for_reward(spec, state, index):
                assert penalties[index] == 0
            elif index in matching_attesting_indices:
                assert penalties[index] == base_penalty
            else:
                assert penalties[index] > base_penalty
        else:
            assert penalties[index] == 0
 def transition_state_to_leak(spec, state, epochs=None):
    if epochs is None:
        epochs = spec.MIN_EPOCHS_TO_INACTIVITY_PENALTY
    assert epochs >= spec.MIN_EPOCHS_TO_INACTIVITY_PENALTY
    for _ in range(epochs):
        next_epoch(spec, state)
 _cache_dict = LRU(size=10)
 def leaking(epochs=None):
    def deco(fn):
        def entry(*args, spec, state, **kw):
            # If the pre-state is not already known in the LRU, then take it,
            # transition it to leak, and put it in the LRU.
            # The input state is likely already cached, so the hash-tree-root does not affect speed.
            key = (state.hash_tree_root(), spec.MIN_EPOCHS_TO_INACTIVITY_PENALTY, spec.SLOTS_PER_EPOCH, epochs)
            global _cache_dict
            if key not in _cache_dict:
                transition_state_to_leak(spec, state, epochs=epochs)
                _cache_dict[key] = state.get_backing()  # cache the tree structure, not the view wrapping it.
            # Take an entry out of the LRU.
            # No copy is necessary, as we wrap the immutable backing with a new view.
            state = spec.BeaconState(backing=_cache_dict[key])
            return fn(*args, spec=spec, state=state, **kw)
        return entry
    return deco
 def set_some_new_deposits(spec, state, rng):
    num_validators = len(state.validators)
    # Set ~1/10 to just recently deposited
    for index in range(num_validators):
        # If not already active, skip
        if not spec.is_active_validator(state.validators[index], spec.get_current_epoch(state)):
            continue
        if rng.randrange(num_validators) < num_validators // 10:
            mock_deposit(spec, state, index)
            # Set ~half of selected to eligible for activation
            if rng.choice([True, False]):
                state.validators[index].activation_eligibility_epoch = spec.get_current_epoch(state)
 def exit_random_validators(spec, state, rng):
    if spec.get_current_epoch(state) < 5:
        # Move epochs forward to allow for some validators already exited/withdrawable
        for _ in range(5):
            next_epoch(spec, state)
    current_epoch = spec.get_current_epoch(state)
    # Exit ~1/2 of validators
    for index in spec.get_active_validator_indices(state, current_epoch):
        if rng.choice([True, False]):
            continue
        validator = state.validators[index]
        validator.exit_epoch = rng.choice([current_epoch - 1, current_epoch - 2, current_epoch - 3])
        # ~1/2 are withdrawable
        if rng.choice([True, False]):
            validator.withdrawable_epoch = current_epoch
        else:
            validator.withdrawable_epoch = current_epoch + 1
 def slash_random_validators(spec, state, rng):
    # Slash ~1/2 of validators
    for index in range(len(state.validators)):
        # slash at least one validator
        if index == 0 or rng.choice([True, False]):
            spec.slash_validator(state, index)
 def run_test_empty(spec, state):
    # Do not add any attestations to state
    yield from run_deltas(spec, state)
 def run_test_full_all_correct(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    yield from run_deltas(spec, state)
 def run_test_full_but_partial_participation(spec, state, rng=Random(5522)):
    cached_prepare_state_with_attestations(spec, state)
    for a in state.previous_epoch_attestations:
        a.aggregation_bits = [rng.choice([True, False]) for _ in a.aggregation_bits]
    yield from run_deltas(spec, state)
 def run_test_partial(spec, state, fraction_filled):
    cached_prepare_state_with_attestations(spec, state)
    # Remove portion of attestations
    num_attestations = int(len(state.previous_epoch_attestations) * fraction_filled)
    state.previous_epoch_attestations = state.previous_epoch_attestations[:num_attestations]
    yield from run_deltas(spec, state)
 def run_test_half_full(spec, state):
    yield from run_test_partial(spec, state, 0.5)
 def run_test_one_attestation_one_correct(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    # Remove all attestations except for the first one
    state.previous_epoch_attestations = state.previous_epoch_attestations[:1]
    yield from run_deltas(spec, state)
 def run_test_with_not_yet_activated_validators(spec, state, rng=Random(5555)):
    set_some_new_deposits(spec, state, rng)
    cached_prepare_state_with_attestations(spec, state)
    yield from run_deltas(spec, state)
 def run_test_with_exited_validators(spec, state, rng=Random(1337)):
    exit_random_validators(spec, state, rng)
    cached_prepare_state_with_attestations(spec, state)
    yield from run_deltas(spec, state)
 def run_test_with_slashed_validators(spec, state, rng=Random(3322)):
    exit_random_validators(spec, state, rng)
    slash_random_validators(spec, state, rng)
    cached_prepare_state_with_attestations(spec, state)
    yield from run_deltas(spec, state)
 def run_test_some_very_low_effective_balances_that_attested(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    # Set some balances to be very low (including 0)
    assert len(state.validators) >= 5
    for i, index in enumerate(range(5)):
        state.validators[index].effective_balance = i
    yield from run_deltas(spec, state)
 def run_test_some_very_low_effective_balances_that_did_not_attest(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    # Remove attestation
    attestation = state.previous_epoch_attestations[0]
    state.previous_epoch_attestations = state.previous_epoch_attestations[1:]
    # Set removed indices effective balance to very low amount
    indices = spec.get_unslashed_attesting_indices(state, [attestation])
    for i, index in enumerate(indices):
        state.validators[index].effective_balance = i
    yield from run_deltas(spec, state)
 def run_test_full_fraction_incorrect(spec, state, correct_target, correct_head, fraction_incorrect):
    cached_prepare_state_with_attestations(spec, state)
    # Make fraction_incorrect of pending attestations have bad target/head as specified
    num_incorrect = int(fraction_incorrect * len(state.previous_epoch_attestations))
    for pending_attestation in state.previous_epoch_attestations[:num_incorrect]:
        if not correct_target:
            pending_attestation.data.target.root = b'\x55' * 32
        if not correct_head:
            pending_attestation.data.beacon_block_root = b'\x66' * 32
    yield from run_deltas(spec, state)
 def run_test_full_delay_one_slot(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    for a in state.previous_epoch_attestations:
        a.inclusion_delay += 1
    yield from run_deltas(spec, state)
 def run_test_full_delay_max_slots(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    for a in state.previous_epoch_attestations:
        a.inclusion_delay += spec.SLOTS_PER_EPOCH
    yield from run_deltas(spec, state)
 def run_test_full_mixed_delay(spec, state, rng=Random(1234)):
    cached_prepare_state_with_attestations(spec, state)
    for a in state.previous_epoch_attestations:
        a.inclusion_delay = rng.randint(1, spec.SLOTS_PER_EPOCH)
    yield from run_deltas(spec, state)
 def run_test_proposer_not_in_attestations(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    # Get an attestation where the proposer is not in the committee
    non_proposer_attestations = []
    for a in state.previous_epoch_attestations:
        if a.proposer_index not in spec.get_unslashed_attesting_indices(state, [a]):
            non_proposer_attestations.append(a)
    assert any(non_proposer_attestations)
    state.previous_epoch_attestations = non_proposer_attestations
    yield from run_deltas(spec, state)
 def run_test_duplicate_attestations_at_later_slots(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    # Remove 2/3 of attestations to make it more interesting
    num_attestations = int(len(state.previous_epoch_attestations) * 0.33)
    state.previous_epoch_attestations = state.previous_epoch_attestations[:num_attestations]
    # Get map of the proposer at each slot to make valid-looking duplicate attestations
    per_slot_proposers = {
        (a.data.slot + a.inclusion_delay): a.proposer_index
        for a in state.previous_epoch_attestations
    }
    max_slot = max([a.data.slot + a.inclusion_delay for a in state.previous_epoch_attestations])
    later_attestations = []
    for a in state.previous_epoch_attestations:
        # Only have proposers for previous epoch so do not create later
        # duplicate if slot exceeds the max slot in previous_epoch_attestations
        if a.data.slot + a.inclusion_delay >= max_slot:
            continue
        later_a = a.copy()
        later_a.inclusion_delay += 1
        later_a.proposer_index = per_slot_proposers[later_a.data.slot + later_a.inclusion_delay]
        later_attestations.append(later_a)
    assert any(later_attestations)
    state.previous_epoch_attestations = sorted(
        state.previous_epoch_attestations + later_attestations,
        key=lambda a: a.data.slot + a.inclusion_delay
    )
    yield from run_deltas(spec, state)
 def run_test_all_balances_too_low_for_reward(spec, state):
    cached_prepare_state_with_attestations(spec, state)
    for index in range(len(state.validators)):
        state.validators[index].effective_balance = 10
    yield from run_deltas(spec, state)
 def run_test_full_random(spec, state, rng=Random(8020)):
    set_some_new_deposits(spec, state, rng)
    exit_random_validators(spec, state, rng)
    slash_random_validators(spec, state, rng)
    cached_prepare_state_with_attestations(spec, state)
    for pending_attestation in state.previous_epoch_attestations:
        # ~1/3 have bad target
        if rng.randint(0, 2) == 0:
            pending_attestation.data.target.root = b'\x55' * 32
        # ~1/3 have bad head
        if rng.randint(0, 2) == 0:
            pending_attestation.data.beacon_block_root = b'\x66' * 32
        # ~50% participation
        pending_attestation.aggregation_bits = [rng.choice([True, False]) for _ in pending_attestation.aggregation_bits]
        # Random inclusion delay
        pending_attestation.inclusion_delay = rng.randint(1, spec.SLOTS_PER_EPOCH)
    yield from run_deltas(spec, state)
--- a/tests/core/pyspec/eth2spec/test/helpers/shard_block.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/shard_block.py
@ -0,0 +1,86 @@
 from eth2spec.test.helpers.attestations import get_valid_on_time_attestation
 from eth2spec.test.helpers.block import get_state_and_beacon_parent_root_at_slot
 from eth2spec.test.helpers.state import transition_to
 from eth2spec.test.helpers.keys import privkeys
 from eth2spec.utils import bls
 from eth2spec.utils.bls import only_with_bls
@only_with_bls()
 def sign_shard_block(spec, beacon_state, shard, block, proposer_index=None):
    slot = block.message.slot
    if proposer_index is None:
        proposer_index = spec.get_shard_proposer_index(beacon_state, slot, shard)
    privkey = privkeys[proposer_index]
    domain = spec.get_domain(beacon_state, spec.DOMAIN_SHARD_PROPOSAL, spec.compute_epoch_at_slot(slot))
    signing_root = spec.compute_signing_root(block.message, domain)
    block.signature = bls.Sign(privkey, signing_root)
 def build_shard_block(spec,
                      beacon_state,
                      shard,
                      slot=None,
                      body=None,
                      signed=False):
    shard_state = beacon_state.shard_states[shard]
    if slot is None:
        slot = shard_state.slot + 1
    if body is None:
        body = b'\x56' * 128
    proposer_index = spec.get_shard_proposer_index(beacon_state, slot, shard)
    beacon_state, beacon_parent_root = get_state_and_beacon_parent_root_at_slot(spec, beacon_state, slot)
    block = spec.ShardBlock(
        shard_parent_root=shard_state.latest_block_root,
        beacon_parent_root=beacon_parent_root,
        slot=slot,
        shard=shard,
        proposer_index=proposer_index,
        body=body,
    )
    signed_block = spec.SignedShardBlock(
        message=block,
    )
    if signed:
        sign_shard_block(spec, beacon_state, shard, signed_block, proposer_index=proposer_index)
    return signed_block
 def build_shard_transitions_till_slot(spec, state, shard_blocks, on_time_slot):
    temp_state = state.copy()
    transition_to(spec, temp_state, on_time_slot)
    shard_transitions = [spec.ShardTransition()] * spec.MAX_SHARDS
    for shard, blocks in shard_blocks.items():
        offset_slots = spec.get_offset_slots(temp_state, shard)
        len_offset_slots = len(offset_slots)
        assert len_offset_slots == on_time_slot - state.shard_states[shard].slot - 1
        shard_transition = spec.get_shard_transition(temp_state, shard, blocks)
        if len(blocks) > 0:
            shard_block_root = blocks[-1].message.hash_tree_root()
            assert shard_transition.shard_states[len_offset_slots - 1].latest_block_root == shard_block_root
            assert shard_transition.shard_states[len_offset_slots - 1].slot == offset_slots[-1]
        shard_transitions[shard] = shard_transition
    return shard_transitions
 def build_attestation_with_shard_transition(spec, state, index, on_time_slot, shard_transition=None):
    temp_state = state.copy()
    transition_to(spec, temp_state, on_time_slot - 1)
    attestation = get_valid_on_time_attestation(
        spec,
        temp_state,
        index=index,
        shard_transition=shard_transition,
        signed=True,
    )
    assert attestation.data.slot == temp_state.slot
    if shard_transition is not None:
        assert attestation.data.shard_transition_root == shard_transition.hash_tree_root()
    return attestation
--- a/tests/core/pyspec/eth2spec/test/helpers/shard_transitions.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/shard_transitions.py
@ -0,0 +1,28 @@
 from eth2spec.test.context import expect_assertion_error
 def run_shard_transitions_processing(spec, state, shard_transitions, attestations, valid=True):
    """
    Run ``process_shard_transitions``, yielding:
      - pre-state ('pre')
      - shard_transitions ('shard_transitions')
      - attestations ('attestations')
      - post-state ('post').
    If ``valid == False``, run expecting ``AssertionError``
    """
    # yield pre-state
    yield 'pre', state
    yield 'shard_transitions', shard_transitions
    yield 'attestations', attestations
    # If the attestation is invalid, processing is aborted, and there is no post-state.
    if not valid:
        expect_assertion_error(lambda: spec.process_shard_transitions(state, shard_transitions, attestations))
        yield 'post', None
        return
    # process crosslinks
    spec.process_shard_transitions(state, shard_transitions, attestations)
    # yield post-state
    yield 'post', state
--- a/tests/core/pyspec/eth2spec/test/helpers/state.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/state.py
@ -1,5 +1,5 @@
 from eth2spec.test.context import expect_assertion_error
-from eth2spec.test.helpers.block import sign_block, transition_unsigned_block
+from eth2spec.test.helpers.block import apply_empty_block, sign_block, transition_unsigned_block
 def get_balance(state, index):
@ -17,7 +17,8 @@ def next_slots(spec, state, slots):
    """
    Transition given slots forward.
    """
-    spec.process_slots(state, state.slot + slots)
+    if slots > 0:
        spec.process_slots(state, state.slot + slots)
 def transition_to(spec, state, slot):
@ -30,12 +31,39 @@ def transition_to(spec, state, slot):
    assert state.slot == slot
 def transition_to_slot_via_block(spec, state, slot):
    """
    Transition to ``slot`` via an empty block transition
    """
    assert state.slot < slot
    apply_empty_block(spec, state, slot)
    assert state.slot == slot
 def transition_to_valid_shard_slot(spec, state):
    """
    Transition to slot `spec.PHASE_1_GENESIS_SLOT + 1` and fork at `spec.PHASE_1_GENESIS_SLOT`.
    """
    transition_to(spec, state, spec.PHASE_1_GENESIS_SLOT)
    state = spec.upgrade_to_phase1(state)  # `upgrade_to_phase1` is a pure function
    next_slot(spec, state)
    return state
 def next_epoch(spec, state):
    """
    Transition to the start slot of the next epoch
    """
    slot = state.slot + spec.SLOTS_PER_EPOCH - (state.slot % spec.SLOTS_PER_EPOCH)
-    spec.process_slots(state, slot)
+    if slot > state.slot:
        spec.process_slots(state, slot)
 def next_epoch_via_block(spec, state):
    """
    Transition to the start slot of the next epoch via a full block transition
    """
    apply_empty_block(spec, state, state.slot + spec.SLOTS_PER_EPOCH - state.slot % spec.SLOTS_PER_EPOCH)
 def get_state_root(spec, state, slot) -> bytes:
--- a/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_attestation.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_attestation.py
@ -13,12 +13,10 @@ from eth2spec.test.helpers.attestations import (
    sign_attestation,
 )
 from eth2spec.test.helpers.state import (
    next_slot,
    next_slots,
-    next_epoch,
+    next_epoch_via_block,
-    transition_to,
+    transition_to_slot_via_block,
 )
 from eth2spec.test.helpers.block import apply_empty_block
 from eth2spec.utils.ssz.ssz_typing import Bitlist
@ -47,9 +45,7 @@ def test_success_multi_proposer_index_iterations(spec, state):
@spec_state_test
 def test_success_previous_epoch(spec, state):
    attestation = get_valid_attestation(spec, state, signed=True, on_time=False)
-    transition_to(spec, state, spec.SLOTS_PER_EPOCH - 1)
+    next_epoch_via_block(spec, state)
    next_epoch(spec, state)
    apply_empty_block(spec, state)
    yield from run_attestation_processing(spec, state, attestation)
@ -64,6 +60,29 @@ def test_invalid_attestation_signature(spec, state):
    yield from run_attestation_processing(spec, state, attestation, False)
@with_all_phases
@spec_state_test
@always_bls
 def test_empty_participants_zeroes_sig(spec, state):
    attestation = get_valid_attestation(spec, state, filter_participant_set=lambda comm: [])  # 0 participants
    attestation.signature = spec.BLSSignature(b'\x00' * 96)
    next_slots(spec, state, spec.MIN_ATTESTATION_INCLUSION_DELAY)
    yield from run_attestation_processing(spec, state, attestation, False)
@with_all_phases
@spec_state_test
@always_bls
 def test_empty_participants_seemingly_valid_sig(spec, state):
    attestation = get_valid_attestation(spec, state, filter_participant_set=lambda comm: [])  # 0 participants
    # Special BLS value, valid for zero pubkeys on some (but not all) BLS implementations.
    attestation.signature = spec.BLSSignature(b'\xc0' + b'\x00' * 95)
    next_slots(spec, state, spec.MIN_ATTESTATION_INCLUSION_DELAY)
    yield from run_attestation_processing(spec, state, attestation, False)
@with_all_phases
@spec_state_test
 def test_before_inclusion_delay(spec, state):
@ -79,8 +98,7 @@ def test_after_epoch_slots(spec, state):
    attestation = get_valid_attestation(spec, state, signed=True, on_time=False)
    # increment past latest inclusion slot
-    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH + 1)
+    transition_to_slot_via_block(spec, state, state.slot + spec.SLOTS_PER_EPOCH + 1)
    apply_empty_block(spec, state)
    yield from run_attestation_processing(spec, state, attestation, False)
@ -151,8 +169,8 @@ def test_invalid_index(spec, state):
@with_all_phases
@spec_state_test
 def test_mismatched_target_and_slot(spec, state):
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
    attestation = get_valid_attestation(spec, state, on_time=False)
    attestation.data.slot = attestation.data.slot - spec.SLOTS_PER_EPOCH
@ -260,19 +278,6 @@ def test_bad_source_root(spec, state):
    yield from run_attestation_processing(spec, state, attestation, False)
@with_all_phases
@spec_state_test
 def test_empty_aggregation_bits(spec, state):
    next_slot(spec, state)
    attestation = get_valid_attestation(spec, state, empty=True)
    next_slots(spec, state, spec.MIN_ATTESTATION_INCLUSION_DELAY)
    assert attestation.aggregation_bits == Bitlist[spec.MAX_VALIDATORS_PER_COMMITTEE](
        *([0b0] * len(attestation.aggregation_bits)))
    yield from run_attestation_processing(spec, state, attestation)
@with_all_phases
@spec_state_test
 def test_too_many_aggregation_bits(spec, state):
--- a/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_attester_slashing.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_attester_slashing.py
@ -1,11 +1,13 @@
-from eth2spec.test.context import spec_state_test, expect_assertion_error, always_bls, with_all_phases, with_phases
+from eth2spec.test.context import (
    PHASE0, PHASE1,
    spec_state_test, expect_assertion_error, always_bls, with_all_phases, with_phases
 )
 from eth2spec.test.helpers.attestations import sign_indexed_attestation
 from eth2spec.test.helpers.attester_slashings import get_valid_attester_slashing, \
    get_indexed_attestation_participants, get_attestation_2_data, get_attestation_1_data
 from eth2spec.test.helpers.block import apply_empty_block
 from eth2spec.test.helpers.state import (
    get_balance,
-    next_epoch,
+    next_epoch_via_block,
 )
@ -88,8 +90,7 @@ def test_success_double(spec, state):
@with_all_phases
@spec_state_test
 def test_success_surround(spec, state):
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
    apply_empty_block(spec, state)
    state.current_justified_checkpoint.epoch += 1
    attester_slashing = get_valid_attester_slashing(spec, state, signed_1=False, signed_2=True)
@ -161,7 +162,7 @@ def test_same_data(spec, state):
    indexed_att_1 = attester_slashing.attestation_1
    att_2_data = get_attestation_2_data(spec, attester_slashing)
-    if spec.fork == 'phase1':
+    if spec.fork == PHASE1:
        indexed_att_1.attestation.data = att_2_data
    else:
        indexed_att_1.data = att_2_data
@ -199,7 +200,7 @@ def test_participants_already_slashed(spec, state):
 # Some of the following tests are phase0 only: phase 1 lists participants with bitfields instead of index list.
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att1_bad_extra_index(spec, state):
@ -215,7 +216,7 @@ def test_att1_bad_extra_index(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att1_bad_replaced_index(spec, state):
@ -231,7 +232,7 @@ def test_att1_bad_replaced_index(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att2_bad_extra_index(spec, state):
@ -247,7 +248,7 @@ def test_att2_bad_extra_index(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att2_bad_replaced_index(spec, state):
@ -263,7 +264,7 @@ def test_att2_bad_replaced_index(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att1_duplicate_index_normal_signed(spec, state):
@ -283,7 +284,7 @@ def test_att1_duplicate_index_normal_signed(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att2_duplicate_index_normal_signed(spec, state):
@ -303,7 +304,7 @@ def test_att2_duplicate_index_normal_signed(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att1_duplicate_index_double_signed(spec, state):
@ -318,7 +319,7 @@ def test_att1_duplicate_index_double_signed(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
@always_bls
 def test_att2_duplicate_index_double_signed(spec, state):
@ -333,7 +334,7 @@ def test_att2_duplicate_index_double_signed(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
 def test_unsorted_att_1(spec, state):
    attester_slashing = get_valid_attester_slashing(spec, state, signed_1=False, signed_2=True)
@ -346,7 +347,7 @@ def test_unsorted_att_1(spec, state):
    yield from run_attester_slashing_processing(spec, state, attester_slashing, False)
-@with_phases(['phase0'])
+@with_phases([PHASE0])
@spec_state_test
 def test_unsorted_att_2(spec, state):
    attester_slashing = get_valid_attester_slashing(spec, state, signed_1=True, signed_2=False)
--- a/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_block_header.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_block_header.py
@ -9,7 +9,7 @@ def prepare_state_for_header_processing(spec, state):
    spec.process_slots(state, state.slot + 1)
-def run_block_header_processing(spec, state, block, valid=True):
+def run_block_header_processing(spec, state, block, prepare_state=True, valid=True):
    """
    Run ``process_block_header``, yielding:
      - pre-state ('pre')
@ -17,7 +17,8 @@ def run_block_header_processing(spec, state, block, valid=True):
      - post-state ('post').
    If ``valid == False``, run expecting ``AssertionError``
    """
-    prepare_state_for_header_processing(spec, state)
+    if prepare_state:
        prepare_state_for_header_processing(spec, state)
    yield 'pre', state
    yield 'block', block
@ -68,6 +69,22 @@ def test_invalid_parent_root(spec, state):
    yield from run_block_header_processing(spec, state, block, valid=False)
@with_all_phases
@spec_state_test
 def test_invalid_multiple_blocks_single_slot(spec, state):
    block = build_empty_block_for_next_slot(spec, state)
    prepare_state_for_header_processing(spec, state)
    spec.process_block_header(state, block)
    assert state.latest_block_header.slot == state.slot
    child_block = block.copy()
    child_block.parent_root = block.hash_tree_root()
    yield from run_block_header_processing(spec, state, child_block, prepare_state=False, valid=False)
@with_all_phases
@spec_state_test
 def test_proposer_slashed(spec, state):
--- a/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_proposer_slashing.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_proposer_slashing.py
@ -1,8 +1,9 @@
 from eth2spec.test.context import spec_state_test, expect_assertion_error, always_bls, with_all_phases
 from eth2spec.test.helpers.block import build_empty_block_for_next_slot
 from eth2spec.test.helpers.block_header import sign_block_header
 from eth2spec.test.helpers.keys import privkeys
-from eth2spec.test.helpers.proposer_slashings import get_valid_proposer_slashing
+from eth2spec.test.helpers.proposer_slashings import get_valid_proposer_slashing, check_proposer_slashing_effect
-from eth2spec.test.helpers.state import get_balance, next_epoch
+from eth2spec.test.helpers.state import next_epoch
 def run_proposer_slashing_processing(spec, state, proposer_slashing, valid=True):
@ -14,6 +15,8 @@ def run_proposer_slashing_processing(spec, state, proposer_slashing, valid=True)
    If ``valid == False``, run expecting ``AssertionError``
    """
    pre_state = state.copy()
    yield 'pre', state
    yield 'proposer_slashing', proposer_slashing
@ -22,25 +25,31 @@ def run_proposer_slashing_processing(spec, state, proposer_slashing, valid=True)
        yield 'post', None
        return
    proposer_index = proposer_slashing.signed_header_1.message.proposer_index
    pre_proposer_balance = get_balance(state, proposer_index)
    spec.process_proposer_slashing(state, proposer_slashing)
    yield 'post', state
-    # check if slashed
+    slashed_proposer_index = proposer_slashing.signed_header_1.message.proposer_index
-    slashed_validator = state.validators[proposer_index]
+    check_proposer_slashing_effect(spec, pre_state, state, slashed_proposer_index)
    assert slashed_validator.slashed
    assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
    assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
    # lost whistleblower reward
    assert get_balance(state, proposer_index) < pre_proposer_balance
@with_all_phases
@spec_state_test
 def test_success(spec, state):
    # Get proposer for next slot
    block = build_empty_block_for_next_slot(spec, state)
    proposer_index = block.proposer_index
    # Create slashing for same proposer
    proposer_slashing = get_valid_proposer_slashing(spec, state,
                                                    slashed_index=proposer_index,
                                                    signed_1=True, signed_2=True)
    yield from run_proposer_slashing_processing(spec, state, proposer_slashing)
@with_all_phases
@spec_state_test
 def test_success_slashed_and_proposer_index_the_same(spec, state):
    proposer_slashing = get_valid_proposer_slashing(spec, state, signed_1=True, signed_2=True)
    yield from run_proposer_slashing_processing(spec, state, proposer_slashing)
--- a/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_voluntary_exit.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/block_processing/test_process_voluntary_exit.py
@ -34,8 +34,8 @@ def run_voluntary_exit_processing(spec, state, signed_voluntary_exit, valid=True
@with_all_phases
@spec_state_test
 def test_success(spec, state):
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    current_epoch = spec.get_current_epoch(state)
    validator_index = spec.get_active_validator_indices(state, current_epoch)[0]
@ -53,8 +53,8 @@ def test_success(spec, state):
@spec_state_test
@always_bls
 def test_invalid_signature(spec, state):
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    current_epoch = spec.get_current_epoch(state)
    validator_index = spec.get_active_validator_indices(state, current_epoch)[0]
@ -71,8 +71,8 @@ def test_invalid_signature(spec, state):
@with_all_phases
@spec_state_test
 def test_success_exit_queue(spec, state):
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    current_epoch = spec.get_current_epoch(state)
@ -115,8 +115,8 @@ def test_success_exit_queue(spec, state):
@with_all_phases
@spec_state_test
 def test_default_exit_epoch_subsequent_exit(spec, state):
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    current_epoch = spec.get_current_epoch(state)
    validator_index = spec.get_active_validator_indices(state, current_epoch)[0]
@ -137,8 +137,8 @@ def test_default_exit_epoch_subsequent_exit(spec, state):
@with_all_phases
@spec_state_test
 def test_validator_exit_in_future(spec, state):
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    current_epoch = spec.get_current_epoch(state)
    validator_index = spec.get_active_validator_indices(state, current_epoch)[0]
@ -156,8 +156,8 @@ def test_validator_exit_in_future(spec, state):
@with_all_phases
@spec_state_test
 def test_validator_invalid_validator_index(spec, state):
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    current_epoch = spec.get_current_epoch(state)
    validator_index = spec.get_active_validator_indices(state, current_epoch)[0]
@ -190,8 +190,8 @@ def test_validator_not_active(spec, state):
@with_all_phases
@spec_state_test
 def test_validator_already_exited(spec, state):
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow validator able to exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow validator able to exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    current_epoch = spec.get_current_epoch(state)
    validator_index = spec.get_active_validator_indices(state, current_epoch)[0]
@ -218,7 +218,7 @@ def test_validator_not_active_long_enough(spec, state):
    assert (
        current_epoch - state.validators[validator_index].activation_epoch <
-        spec.PERSISTENT_COMMITTEE_PERIOD
+        spec.SHARD_COMMITTEE_PERIOD
    )
    yield from run_voluntary_exit_processing(spec, state, signed_voluntary_exit, False)
--- a/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/run_epoch_process_base.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/run_epoch_process_base.py
@ -18,7 +18,8 @@ def run_epoch_processing_to(spec, state, process_name: str):
    slot = state.slot + (spec.SLOTS_PER_EPOCH - state.slot % spec.SLOTS_PER_EPOCH)
    # transition state to slot before epoch state transition
-    spec.process_slots(state, slot - 1)
+    if state.slot < slot - 1:
        spec.process_slots(state, slot - 1)
    # start transitioning, do one slot update before the epoch itself.
    spec.process_slot(state)
--- a/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_justification_and_finalization.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_justification_and_finalization.py
@ -24,7 +24,7 @@ def add_mock_attestations(spec, state, epoch, source, target, sufficient_support
        raise Exception(f"cannot include attestations in epoch ${epoch} from epoch ${current_epoch}")
    total_balance = spec.get_total_active_balance(state)
-    remaining_balance = total_balance * 2 // 3
+    remaining_balance = int(total_balance * 2 // 3)  # can become negative
    start_slot = spec.compute_start_slot_at_epoch(epoch)
    for slot in range(start_slot, start_slot + spec.SLOTS_PER_EPOCH):
@ -42,7 +42,7 @@ def add_mock_attestations(spec, state, epoch, source, target, sufficient_support
            aggregation_bits = [0] * len(committee)
            for v in range(len(committee) * 2 // 3 + 1):
                if remaining_balance > 0:
-                    remaining_balance -= state.validators[v].effective_balance
+                    remaining_balance -= int(state.validators[v].effective_balance)
                    aggregation_bits[v] = 1
                else:
                    break
--- a/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_registry_updates.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_registry_updates.py
@ -1,3 +1,4 @@
 from eth2spec.test.helpers.deposits import mock_deposit
 from eth2spec.test.helpers.state import next_epoch, next_slots
 from eth2spec.test.context import spec_state_test, with_all_phases
 from eth2spec.test.phase_0.epoch_processing.run_epoch_process_base import run_epoch_processing_with
@ -7,14 +8,6 @@ def run_process_registry_updates(spec, state):
    yield from run_epoch_processing_with(spec, state, 'process_registry_updates')
 def mock_deposit(spec, state, index):
    assert spec.is_active_validator(state.validators[index], spec.get_current_epoch(state))
    state.validators[index].activation_eligibility_epoch = spec.FAR_FUTURE_EPOCH
    state.validators[index].activation_epoch = spec.FAR_FUTURE_EPOCH
    state.validators[index].effective_balance = spec.MAX_EFFECTIVE_BALANCE
    assert not spec.is_active_validator(state.validators[index], spec.get_current_epoch(state))
@with_all_phases
@spec_state_test
 def test_add_to_activation_queue(spec, state):
--- a/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_rewards_and_penalties.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_rewards_and_penalties.py
@ -12,39 +12,18 @@ from eth2spec.test.helpers.state import (
 from eth2spec.test.helpers.attestations import (
    add_attestations_to_state,
    get_valid_attestation,
    prepare_state_with_attestations,
 )
 from eth2spec.test.helpers.rewards import leaking
 from eth2spec.test.helpers.attester_slashings import get_indexed_attestation_participants
 from eth2spec.test.phase_0.epoch_processing.run_epoch_process_base import run_epoch_processing_with
 from random import Random
 def run_process_rewards_and_penalties(spec, state):
    yield from run_epoch_processing_with(spec, state, 'process_rewards_and_penalties')
 def prepare_state_with_full_attestations(spec, state, empty=False):
    start_slot = state.slot
    start_epoch = spec.get_current_epoch(state)
    next_start_epoch = spec.compute_start_slot_at_epoch(start_epoch + 1)
    attestations = []
    for slot in range(spec.SLOTS_PER_EPOCH + spec.MIN_ATTESTATION_INCLUSION_DELAY):
        # create an attestation for each index in each slot in epoch
        if state.slot < next_start_epoch:
            for committee_index in range(spec.get_committee_count_at_slot(state, state.slot)):
                attestation = get_valid_attestation(spec, state, index=committee_index, empty=empty, signed=True)
                attestations.append(attestation)
        # fill each created slot in state after inclusion delay
        if state.slot >= start_slot + spec.MIN_ATTESTATION_INCLUSION_DELAY:
            inclusion_slot = state.slot - spec.MIN_ATTESTATION_INCLUSION_DELAY
            include_attestations = [att for att in attestations if att.data.slot == inclusion_slot]
            add_attestations_to_state(spec, state, include_attestations, state.slot)
        next_slot(spec, state)
    assert spec.compute_epoch_at_slot(state.slot) == start_epoch + 1
    assert len(state.previous_epoch_attestations) == len(attestations)
    return attestations
@with_phases(['phase0'])
@spec_state_test
 def test_genesis_epoch_no_attestations_no_penalties(spec, state):
@ -84,30 +63,10 @@ def test_genesis_epoch_full_attestations_no_rewards(spec, state):
        assert state.balances[index] == pre_state.balances[index]
@with_all_phases
@spec_state_test
 def test_full_attestations(spec, state):
    # Go to start of next epoch to ensure can have full participation
    next_epoch(spec, state)
    attestations = prepare_state_with_full_attestations(spec, state)
    pre_state = state.copy()
    yield from run_process_rewards_and_penalties(spec, state)
    attesting_indices = spec.get_unslashed_attesting_indices(state, attestations)
    assert len(attesting_indices) == len(pre_state.validators)
    for index in range(len(pre_state.validators)):
        if index in attesting_indices:
            assert state.balances[index] > pre_state.balances[index]
        else:
            assert state.balances[index] < pre_state.balances[index]
@with_all_phases
@spec_state_test
 def test_full_attestations_random_incorrect_fields(spec, state):
-    attestations = prepare_state_with_full_attestations(spec, state)
+    attestations = prepare_state_with_attestations(spec, state)
    for i, attestation in enumerate(state.previous_epoch_attestations):
        if i % 3 == 0:
            # Mess up some head votes
@ -132,9 +91,7 @@ def test_full_attestations_random_incorrect_fields(spec, state):
@with_custom_state(balances_fn=misc_balances, threshold_fn=lambda spec: spec.MAX_EFFECTIVE_BALANCE // 2)
@single_phase
 def test_full_attestations_misc_balances(spec, state):
-    # Go to start of next epoch to ensure can have full participation
+    attestations = prepare_state_with_attestations(spec, state)
    next_epoch(spec, state)
    attestations = prepare_state_with_full_attestations(spec, state)
    pre_state = state.copy()
@ -166,7 +123,7 @@ def test_full_attestations_misc_balances(spec, state):
@with_custom_state(balances_fn=low_single_balance, threshold_fn=zero_activation_threshold)
@single_phase
 def test_full_attestations_one_validaor_one_gwei(spec, state):
-    attestations = prepare_state_with_full_attestations(spec, state)
+    attestations = prepare_state_with_attestations(spec, state)
    yield from run_process_rewards_and_penalties(spec, state)
@ -178,6 +135,7 @@ def test_full_attestations_one_validaor_one_gwei(spec, state):
@with_all_phases
@spec_state_test
 def test_no_attestations_all_penalties(spec, state):
    # Move to next epoch to ensure rewards/penalties are processed
    next_epoch(spec, state)
    pre_state = state.copy()
@ -189,20 +147,97 @@ def test_no_attestations_all_penalties(spec, state):
        assert state.balances[index] < pre_state.balances[index]
-@with_all_phases
+def run_with_participation(spec, state, participation_fn):
-@spec_state_test
+    participated = set()
-def test_empty_attestations(spec, state):
+
-    attestations = prepare_state_with_full_attestations(spec, state, empty=True)
+    def participation_tracker(slot, comm_index, comm):
        att_participants = participation_fn(slot, comm_index, comm)
        participated.update(att_participants)
        return att_participants
    attestations = prepare_state_with_attestations(spec, state, participation_fn=participation_tracker)
    proposer_indices = [a.proposer_index for a in state.previous_epoch_attestations]
    pre_state = state.copy()
    yield from run_process_rewards_and_penalties(spec, state)
    attesting_indices = spec.get_unslashed_attesting_indices(state, attestations)
-    assert len(attesting_indices) == 0
+    assert len(attesting_indices) == len(participated)
    for index in range(len(pre_state.validators)):
-        assert state.balances[index] < pre_state.balances[index]
+        if spec.is_in_inactivity_leak(state):
            # Proposers can still make money during a leak
            if index in proposer_indices and index in participated:
                assert state.balances[index] > pre_state.balances[index]
            # If not proposer but participated optimally, should have exactly neutral balance
            elif index in attesting_indices:
                assert state.balances[index] == pre_state.balances[index]
            else:
                assert state.balances[index] < pre_state.balances[index]
        else:
            if index in participated:
                assert state.balances[index] > pre_state.balances[index]
            else:
                assert state.balances[index] < pre_state.balances[index]
@with_all_phases
@spec_state_test
 def test_almost_empty_attestations(spec, state):
    rng = Random(1234)
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: rng.sample(comm, 1))
@with_all_phases
@spec_state_test
@leaking()
 def test_almost_empty_attestations_with_leak(spec, state):
    rng = Random(1234)
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: rng.sample(comm, 1))
@with_all_phases
@spec_state_test
 def test_random_fill_attestations(spec, state):
    rng = Random(4567)
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: rng.sample(comm, len(comm) // 3))
@with_all_phases
@spec_state_test
@leaking()
 def test_random_fill_attestations_with_leak(spec, state):
    rng = Random(4567)
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: rng.sample(comm, len(comm) // 3))
@with_all_phases
@spec_state_test
 def test_almost_full_attestations(spec, state):
    rng = Random(8901)
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: rng.sample(comm, len(comm) - 1))
@with_all_phases
@spec_state_test
@leaking()
 def test_almost_full_attestations_with_leak(spec, state):
    rng = Random(8901)
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: rng.sample(comm, len(comm) - 1))
@with_all_phases
@spec_state_test
 def test_full_attestation_participation(spec, state):
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: comm)
@with_all_phases
@spec_state_test
@leaking()
 def test_full_attestation_participation_with_leak(spec, state):
    yield from run_with_participation(spec, state, lambda slot, comm_index, comm: comm)
@with_all_phases
@ -247,14 +282,13 @@ def test_duplicate_attestation(spec, state):
@spec_state_test
 # Case when some eligible attestations are slashed. Modifies attesting_balance and consequently rewards/penalties.
 def test_attestations_some_slashed(spec, state):
-    attestations = prepare_state_with_full_attestations(spec, state)
+    attestations = prepare_state_with_attestations(spec, state)
    attesting_indices_before_slashings = list(spec.get_unslashed_attesting_indices(state, attestations))
    # Slash maximum amount of validators allowed per epoch.
    for i in range(spec.MIN_PER_EPOCH_CHURN_LIMIT):
        spec.slash_validator(state, attesting_indices_before_slashings[i])
    assert spec.compute_epoch_at_slot(state.slot) == spec.GENESIS_EPOCH + 1
    assert len(state.previous_epoch_attestations) == len(attestations)
    pre_state = state.copy()
--- a/tests/core/pyspec/eth2spec/test/phase_0/rewards/init.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/rewards/init.py
--- a/tests/core/pyspec/eth2spec/test/phase_0/rewards/test_basic.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/rewards/test_basic.py
@ -0,0 +1,155 @@
 from eth2spec.test.context import with_all_phases, spec_state_test
 import eth2spec.test.helpers.rewards as rewards_helpers
@with_all_phases
@spec_state_test
 def test_empty(spec, state):
    yield from rewards_helpers.run_test_empty(spec, state)
@with_all_phases
@spec_state_test
 def test_full_all_correct(spec, state):
    yield from rewards_helpers.run_test_full_all_correct(spec, state)
@with_all_phases
@spec_state_test
 def test_half_full(spec, state):
    yield from rewards_helpers.run_test_half_full(spec, state)
@with_all_phases
@spec_state_test
 def test_quarter_full(spec, state):
    yield from rewards_helpers.run_test_partial(spec, state, 0.25)
@with_all_phases
@spec_state_test
 def test_full_but_partial_participation(spec, state):
    yield from rewards_helpers.run_test_full_but_partial_participation(spec, state)
@with_all_phases
@spec_state_test
 def test_one_attestation_one_correct(spec, state):
    yield from rewards_helpers.run_test_one_attestation_one_correct(spec, state)
@with_all_phases
@spec_state_test
 def test_with_not_yet_activated_validators(spec, state):
    yield from rewards_helpers.run_test_with_not_yet_activated_validators(spec, state)
@with_all_phases
@spec_state_test
 def test_with_exited_validators(spec, state):
    yield from rewards_helpers.run_test_with_exited_validators(spec, state)
@with_all_phases
@spec_state_test
 def test_with_slashed_validators(spec, state):
    yield from rewards_helpers.run_test_with_slashed_validators(spec, state)
@with_all_phases
@spec_state_test
 def test_some_very_low_effective_balances_that_attested(spec, state):
    yield from rewards_helpers.run_test_some_very_low_effective_balances_that_attested(spec, state)
@with_all_phases
@spec_state_test
 def test_some_very_low_effective_balances_that_did_not_attest(spec, state):
    yield from rewards_helpers.run_test_some_very_low_effective_balances_that_did_not_attest(spec, state)
 #
 # NOTE: No source incorrect tests
 # All PendingAttestations in state have source validated
 # We choose to keep this invariant in these tests to not force clients to test with degenerate states
 #
@with_all_phases
@spec_state_test
 def test_full_half_correct_target_incorrect_head(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=True,
        correct_head=False,
        fraction_incorrect=0.5,
    )
@with_all_phases
@spec_state_test
 def test_full_correct_target_incorrect_head(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=True,
        correct_head=False,
        fraction_incorrect=1.0,
    )
@with_all_phases
@spec_state_test
 def test_full_half_incorrect_target_incorrect_head(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=False,
        correct_head=False,
        fraction_incorrect=0.5,
    )
@with_all_phases
@spec_state_test
 def test_full_half_incorrect_target_correct_head(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=False,
        correct_head=True,
        fraction_incorrect=0.5,
    )
@with_all_phases
@spec_state_test
 def test_full_delay_one_slot(spec, state):
    yield from rewards_helpers.run_test_full_delay_one_slot(spec, state)
@with_all_phases
@spec_state_test
 def test_full_delay_max_slots(spec, state):
    yield from rewards_helpers.run_test_full_delay_max_slots(spec, state)
@with_all_phases
@spec_state_test
 def test_full_mixed_delay(spec, state):
    yield from rewards_helpers.run_test_full_mixed_delay(spec, state)
@with_all_phases
@spec_state_test
 def test_proposer_not_in_attestations(spec, state):
    yield from rewards_helpers.run_test_proposer_not_in_attestations(spec, state)
@with_all_phases
@spec_state_test
 def test_duplicate_attestations_at_later_slots(spec, state):
    yield from rewards_helpers.run_test_duplicate_attestations_at_later_slots(spec, state)
@with_all_phases
@spec_state_test
 def test_all_balances_too_low_for_reward(spec, state):
    yield from rewards_helpers.run_test_all_balances_too_low_for_reward(spec, state)
--- a/tests/core/pyspec/eth2spec/test/phase_0/rewards/test_leak.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/rewards/test_leak.py
@ -0,0 +1,156 @@
 from eth2spec.test.context import with_all_phases, spec_state_test
 from eth2spec.test.helpers.rewards import leaking
 import eth2spec.test.helpers.rewards as rewards_helpers
@with_all_phases
@spec_state_test
@leaking()
 def test_empty_leak(spec, state):
    yield from rewards_helpers.run_test_empty(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_full_leak(spec, state):
    yield from rewards_helpers.run_test_full_all_correct(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_half_full_leak(spec, state):
    yield from rewards_helpers.run_test_half_full(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_quarter_full_leak(spec, state):
    yield from rewards_helpers.run_test_partial(spec, state, 0.25)
@with_all_phases
@spec_state_test
@leaking()
 def test_full_but_partial_participation_leak(spec, state):
    yield from rewards_helpers.run_test_full_but_partial_participation(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_one_attestation_one_correct_leak(spec, state):
    yield from rewards_helpers.run_test_one_attestation_one_correct(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_with_not_yet_activated_validators_leak(spec, state):
    yield from rewards_helpers.run_test_with_not_yet_activated_validators(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_with_exited_validators_leak(spec, state):
    yield from rewards_helpers.run_test_with_exited_validators(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_with_slashed_validators_leak(spec, state):
    yield from rewards_helpers.run_test_with_slashed_validators(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_some_very_low_effective_balances_that_attested_leak(spec, state):
    yield from rewards_helpers.run_test_some_very_low_effective_balances_that_attested(spec, state)
@with_all_phases
@spec_state_test
@leaking()
 def test_some_very_low_effective_balances_that_did_not_attest_leak(spec, state):
    yield from rewards_helpers.run_test_some_very_low_effective_balances_that_did_not_attest(spec, state)
 #
 # NOTE: No source incorrect tests
 # All PendingAttestations in state have source validated
 # We choose to keep this invariant in these tests to not force clients to test with degenerate states
 #
@with_all_phases
@spec_state_test
@leaking()
 def test_full_half_correct_target_incorrect_head_leak(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=True,
        correct_head=False,
        fraction_incorrect=0.5,
    )
@with_all_phases
@spec_state_test
@leaking()
 def test_full_correct_target_incorrect_head_leak(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=True,
        correct_head=False,
        fraction_incorrect=1.0,
    )
@with_all_phases
@spec_state_test
@leaking()
 def test_full_half_incorrect_target_incorrect_head_leak(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=False,
        correct_head=False,
        fraction_incorrect=0.5,
    )
@with_all_phases
@spec_state_test
@leaking()
 def test_full_half_incorrect_target_correct_head_leak(spec, state):
    yield from rewards_helpers.run_test_full_fraction_incorrect(
        spec, state,
        correct_target=False,
        correct_head=True,
        fraction_incorrect=0.5,
    )
@with_all_phases
@spec_state_test
@leaking()
 def test_full_random_leak(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state)
@with_all_phases
@spec_state_test
@leaking(epochs=5)
 def test_full_random_five_epoch_leak(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state)
@with_all_phases
@spec_state_test
@leaking(epochs=10)
 def test_full_random_ten_epoch_leak(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state)
--- a/tests/core/pyspec/eth2spec/test/phase_0/rewards/test_random.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/rewards/test_random.py
@ -0,0 +1,45 @@
 from random import Random
 from eth2spec.test.context import (
    with_all_phases,
    spec_test,
    spec_state_test,
    with_custom_state,
    single_phase,
    low_balances, misc_balances,
 )
 import eth2spec.test.helpers.rewards as rewards_helpers
@with_all_phases
@spec_state_test
 def test_full_random_0(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state, rng=Random(1010))
@with_all_phases
@spec_state_test
 def test_full_random_1(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state, rng=Random(2020))
@with_all_phases
@spec_state_test
 def test_full_random_2(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state, rng=Random(3030))
@with_all_phases
@with_custom_state(balances_fn=low_balances, threshold_fn=lambda spec: spec.EJECTION_BALANCE)
@spec_test
@single_phase
 def test_full_random_low_balances(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state)
@with_all_phases
@with_custom_state(balances_fn=misc_balances, threshold_fn=lambda spec: spec.EJECTION_BALANCE)
@spec_test
@single_phase
 def test_full_random_misc_balances(spec, state):
    yield from rewards_helpers.run_test_full_random(spec, state)
--- a/tests/core/pyspec/eth2spec/test/phase_0/sanity/init.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/sanity/init.py
--- a/tests/core/pyspec/eth2spec/test/phase_0/sanity/test_blocks.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/sanity/test_blocks.py
@ -1,17 +1,28 @@
 from copy import deepcopy
 from eth2spec.utils import bls
-from eth2spec.test.helpers.state import get_balance, state_transition_and_sign_block, next_slot, next_epoch
+from eth2spec.test.helpers.state import (
-from eth2spec.test.helpers.block import build_empty_block_for_next_slot, build_empty_block, sign_block, \
+    get_balance, state_transition_and_sign_block,
-    transition_unsigned_block
+    next_slot, next_epoch, next_epoch_via_block,
 )
 from eth2spec.test.helpers.block import (
    build_empty_block_for_next_slot, build_empty_block,
    sign_block,
    transition_unsigned_block,
 )
 from eth2spec.test.helpers.keys import privkeys, pubkeys
-from eth2spec.test.helpers.attester_slashings import get_valid_attester_slashing, get_indexed_attestation_participants
+from eth2spec.test.helpers.attester_slashings import (
-from eth2spec.test.helpers.proposer_slashings import get_valid_proposer_slashing
+    get_valid_attester_slashing_by_indices,
-from eth2spec.test.helpers.attestations import get_valid_attestation
+    get_valid_attester_slashing,
    get_indexed_attestation_participants,
 )
 from eth2spec.test.helpers.proposer_slashings import get_valid_proposer_slashing, check_proposer_slashing_effect
 from eth2spec.test.helpers.attestations import get_valid_attestation, fill_block_shard_transitions_by_attestations
 from eth2spec.test.helpers.deposits import prepare_state_and_deposit
-from eth2spec.test.context import spec_state_test, with_all_phases, expect_assertion_error, always_bls, with_phases
+from eth2spec.test.context import (
    spec_state_test, with_all_phases, expect_assertion_error, always_bls, with_phases,
    PHASE1
 )
@with_all_phases
@ -45,10 +56,12 @@ def test_same_slot_block_transition(spec, state):
    yield 'pre', state
-    signed_block = state_transition_and_sign_block(spec, state, block)
+    assert state.slot == block.slot
    signed_block = state_transition_and_sign_block(spec, state, block, expect_fail=True)
    yield 'blocks', [signed_block]
-    yield 'post', state
+    yield 'post', None
@with_all_phases
@ -71,6 +84,81 @@ def test_empty_block_transition(spec, state):
    assert spec.get_randao_mix(state, spec.get_current_epoch(state)) != spec.Bytes32()
 def process_and_sign_block_without_header_validations(spec, state, block):
    """
    Artificially bypass the restrictions in the state transition to transition and sign block
    WARNING UNSAFE: Only use when generating valid-looking invalid blocks for test vectors
    """
    # Perform single mutation in `process_block_header`
    state.latest_block_header = spec.BeaconBlockHeader(
        slot=block.slot,
        proposer_index=block.proposer_index,
        parent_root=block.parent_root,
        state_root=spec.Bytes32(),
        body_root=block.body.hash_tree_root(),
    )
    # Perform rest of process_block transitions
    spec.process_randao(state, block.body)
    spec.process_eth1_data(state, block.body)
    spec.process_operations(state, block.body)
    # Insert post-state rot
    block.state_root = state.hash_tree_root()
    # Sign block
    return sign_block(spec, state, block)
@with_phases(['phase0'])
@spec_state_test
 def test_proposal_for_genesis_slot(spec, state):
    assert state.slot == spec.GENESIS_SLOT
    yield 'pre', state
    block = build_empty_block(spec, state, spec.GENESIS_SLOT)
    block.parent_root = state.latest_block_header.hash_tree_root()
    # Show that normal path through transition fails
    failed_state = state.copy()
    expect_assertion_error(
        lambda: spec.state_transition(failed_state, spec.SignedBeaconBlock(message=block), validate_result=False)
    )
    # Artificially bypass the restriction in the state transition to transition and sign block for test vectors
    signed_block = process_and_sign_block_without_header_validations(spec, state, block)
    yield 'blocks', [signed_block]
    yield 'post', None
@with_all_phases
@spec_state_test
 def test_parent_from_same_slot(spec, state):
    yield 'pre', state
    parent_block = build_empty_block_for_next_slot(spec, state)
    signed_parent_block = state_transition_and_sign_block(spec, state, parent_block)
    child_block = parent_block.copy()
    child_block.parent_root = state.latest_block_header.hash_tree_root()
    # Show that normal path through transition fails
    failed_state = state.copy()
    expect_assertion_error(
        lambda: spec.state_transition(failed_state, spec.SignedBeaconBlock(message=child_block), validate_result=False)
    )
    # Artificially bypass the restriction in the state transition to transition and sign block for test vectors
    signed_child_block = process_and_sign_block_without_header_validations(spec, state, child_block)
    yield 'blocks', [signed_parent_block, signed_child_block]
    yield 'post', None
@with_all_phases
@spec_state_test
 def test_invalid_state_root(spec, state):
@ -228,11 +316,11 @@ def test_empty_epoch_transition_not_finalizing(spec, state):
@spec_state_test
 def test_proposer_slashing(spec, state):
    # copy for later balance lookups.
-    pre_state = deepcopy(state)
+    pre_state = state.copy()
    proposer_slashing = get_valid_proposer_slashing(spec, state, signed_1=True, signed_2=True)
-    validator_index = proposer_slashing.signed_header_1.message.proposer_index
+    slashed_index = proposer_slashing.signed_header_1.message.proposer_index
-    assert not state.validators[validator_index].slashed
+    assert not state.validators[slashed_index].slashed
    yield 'pre', state
@ -247,25 +335,108 @@ def test_proposer_slashing(spec, state):
    yield 'blocks', [signed_block]
    yield 'post', state
-    # check if slashed
+    check_proposer_slashing_effect(spec, pre_state, state, slashed_index)
-    slashed_validator = state.validators[validator_index]
+
-    assert slashed_validator.slashed
+
-    assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
+@with_all_phases
-    assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+@spec_state_test
-    # lost whistleblower reward
+def test_double_same_proposer_slashings_same_block(spec, state):
-    assert get_balance(state, validator_index) < get_balance(pre_state, validator_index)
+    proposer_slashing = get_valid_proposer_slashing(spec, state, signed_1=True, signed_2=True)
    slashed_index = proposer_slashing.signed_header_1.message.proposer_index
    assert not state.validators[slashed_index].slashed
    yield 'pre', state
    block = build_empty_block_for_next_slot(spec, state)
    block.body.proposer_slashings = [proposer_slashing, proposer_slashing]
    signed_block = state_transition_and_sign_block(spec, state, block, expect_fail=True)
    yield 'blocks', [signed_block]
    yield 'post', None
@with_all_phases
@spec_state_test
 def test_double_similar_proposer_slashings_same_block(spec, state):
    slashed_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
    # Same validator, but different slashable offences in the same block
    proposer_slashing_1 = get_valid_proposer_slashing(spec, state, random_root=b'\xaa' * 32,
                                                      slashed_index=slashed_index,
                                                      signed_1=True, signed_2=True)
    proposer_slashing_2 = get_valid_proposer_slashing(spec, state, random_root=b'\xbb' * 32,
                                                      slashed_index=slashed_index,
                                                      signed_1=True, signed_2=True)
    assert not state.validators[slashed_index].slashed
    yield 'pre', state
    block = build_empty_block_for_next_slot(spec, state)
    block.body.proposer_slashings = [proposer_slashing_1, proposer_slashing_2]
    signed_block = state_transition_and_sign_block(spec, state, block, expect_fail=True)
    yield 'blocks', [signed_block]
    yield 'post', None
@with_all_phases
@spec_state_test
 def test_multiple_different_proposer_slashings_same_block(spec, state):
    pre_state = state.copy()
    num_slashings = 3
    proposer_slashings = []
    for i in range(num_slashings):
        slashed_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[i]
        assert not state.validators[slashed_index].slashed
        proposer_slashing = get_valid_proposer_slashing(spec, state,
                                                        slashed_index=slashed_index,
                                                        signed_1=True, signed_2=True)
        proposer_slashings.append(proposer_slashing)
    yield 'pre', state
    #
    # Add to state via block transition
    #
    block = build_empty_block_for_next_slot(spec, state)
    block.body.proposer_slashings = proposer_slashings
    signed_block = state_transition_and_sign_block(spec, state, block)
    yield 'blocks', [signed_block]
    yield 'post', state
    for proposer_slashing in proposer_slashings:
        slashed_index = proposer_slashing.signed_header_1.message.proposer_index
        check_proposer_slashing_effect(spec, pre_state, state, slashed_index)
 def check_attester_slashing_effect(spec, pre_state, state, slashed_indices):
    for slashed_index in slashed_indices:
        slashed_validator = state.validators[slashed_index]
        assert slashed_validator.slashed
        assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
        assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
        # lost whistleblower reward
        assert get_balance(state, slashed_index) < get_balance(pre_state, slashed_index)
    proposer_index = spec.get_beacon_proposer_index(state)
    # gained whistleblower reward
    assert get_balance(state, proposer_index) > get_balance(pre_state, proposer_index)
@with_all_phases
@spec_state_test
 def test_attester_slashing(spec, state):
    # copy for later balance lookups.
-    pre_state = deepcopy(state)
+    pre_state = state.copy()
    attester_slashing = get_valid_attester_slashing(spec, state, signed_1=True, signed_2=True)
-    validator_index = get_indexed_attestation_participants(spec, attester_slashing.attestation_1)[0]
+    slashed_indices = get_indexed_attestation_participants(spec, attester_slashing.attestation_1)
-    assert not state.validators[validator_index].slashed
+    assert not any(state.validators[i].slashed for i in slashed_indices)
    yield 'pre', state
@ -280,19 +451,118 @@ def test_attester_slashing(spec, state):
    yield 'blocks', [signed_block]
    yield 'post', state
-    slashed_validator = state.validators[validator_index]
+    check_attester_slashing_effect(spec, pre_state, state, slashed_indices)
    assert slashed_validator.slashed
    assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
    assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
    # lost whistleblower reward
    assert get_balance(state, validator_index) < get_balance(pre_state, validator_index)
-    proposer_index = spec.get_beacon_proposer_index(state)
+
-    # gained whistleblower reward
+@with_all_phases
-    assert (
+@spec_state_test
-        get_balance(state, proposer_index) >
+def test_duplicate_attester_slashing(spec, state):
-        get_balance(pre_state, proposer_index)
+    # Skip test if config cannot handle multiple AttesterSlashings per block
    if spec.MAX_ATTESTER_SLASHINGS < 2:
        return
    attester_slashing = get_valid_attester_slashing(spec, state, signed_1=True, signed_2=True)
    attester_slashings = [attester_slashing, attester_slashing.copy()]
    slashed_indices = get_indexed_attestation_participants(spec, attester_slashing.attestation_1)
    assert not any(state.validators[i].slashed for i in slashed_indices)
    yield 'pre', state
    #
    # Add to state via block transition
    #
    block = build_empty_block_for_next_slot(spec, state)
    block.body.attester_slashings = attester_slashings
    signed_block = state_transition_and_sign_block(spec, state, block, expect_fail=True)
    yield 'blocks', [signed_block]
    yield 'post', None
 # All AttesterSlashing tests should be adopted for Phase 1 but helper support is not yet there
@with_phases(['phase0'])
@spec_state_test
 def test_multiple_attester_slashings_no_overlap(spec, state):
    # Skip test if config cannot handle multiple AttesterSlashings per block
    if spec.MAX_ATTESTER_SLASHINGS < 2:
        return
    # copy for later balance lookups.
    pre_state = state.copy()
    full_indices = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[:8]
    half_length = len(full_indices) // 2
    attester_slashing_1 = get_valid_attester_slashing_by_indices(
        spec, state,
        full_indices[:half_length], signed_1=True, signed_2=True,
    )
    attester_slashing_2 = get_valid_attester_slashing_by_indices(
        spec, state,
        full_indices[half_length:], signed_1=True, signed_2=True,
    )
    attester_slashings = [attester_slashing_1, attester_slashing_2]
    assert not any(state.validators[i].slashed for i in full_indices)
    yield 'pre', state
    #
    # Add to state via block transition
    #
    block = build_empty_block_for_next_slot(spec, state)
    block.body.attester_slashings = attester_slashings
    signed_block = state_transition_and_sign_block(spec, state, block)
    yield 'blocks', [signed_block]
    yield 'post', state
    check_attester_slashing_effect(spec, pre_state, state, full_indices)
@with_phases(['phase0'])
@spec_state_test
 def test_multiple_attester_slashings_partial_overlap(spec, state):
    # Skip test if config cannot handle multiple AttesterSlashings per block
    if spec.MAX_ATTESTER_SLASHINGS < 2:
        return
    # copy for later balance lookups.
    pre_state = state.copy()
    full_indices = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[:8]
    one_third_length = len(full_indices) // 3
    attester_slashing_1 = get_valid_attester_slashing_by_indices(
        spec, state,
        full_indices[:one_third_length * 2], signed_1=True, signed_2=True,
    )
    attester_slashing_2 = get_valid_attester_slashing_by_indices(
        spec, state,
        full_indices[one_third_length:], signed_1=True, signed_2=True,
    )
    attester_slashings = [attester_slashing_1, attester_slashing_2]
    assert not any(state.validators[i].slashed for i in full_indices)
    yield 'pre', state
    #
    # Add to state via block transition
    #
    block = build_empty_block_for_next_slot(spec, state)
    block.body.attester_slashings = attester_slashings
    signed_block = state_transition_and_sign_block(spec, state, block)
    yield 'blocks', [signed_block]
    yield 'post', state
    check_attester_slashing_effect(spec, pre_state, state, full_indices)
@with_all_phases
@ -303,22 +573,19 @@ def test_proposer_after_inactive_index(spec, state):
    state.validators[inactive_index].exit_epoch = spec.get_current_epoch(state)
    # skip forward, get brand new proposers
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
    block = build_empty_block_for_next_slot(spec, state)
    state_transition_and_sign_block(spec, state, block)
    while True:
        next_slot(spec, state)
        proposer_index = spec.get_beacon_proposer_index(state)
        if proposer_index > inactive_index:
            # found a proposer that has a higher index than a disabled validator
            yield 'pre', state
            # test if the proposer can be recognized correctly after the inactive validator
-            signed_block = state_transition_and_sign_block(spec, state, build_empty_block(spec, state))
+            signed_block = state_transition_and_sign_block(spec, state, build_empty_block_for_next_slot(spec, state))
            yield 'blocks', [signed_block]
            yield 'post', state
            break
        next_slot(spec, state)
@with_all_phases
@ -336,16 +603,16 @@ def test_high_proposer_index(spec, state):
    active_count = len(spec.get_active_validator_indices(state, current_epoch))
    while True:
        next_slot(spec, state)
        proposer_index = spec.get_beacon_proposer_index(state)
        if proposer_index >= active_count:
            # found a proposer that has a higher index than the active validator count
            yield 'pre', state
            # test if the proposer can be recognized correctly, even while it has a high index.
-            signed_block = state_transition_and_sign_block(spec, state, build_empty_block(spec, state))
+            signed_block = state_transition_and_sign_block(spec, state, build_empty_block_for_next_slot(spec, state))
            yield 'blocks', [signed_block]
            yield 'post', state
            break
        next_slot(spec, state)
@with_all_phases
@ -420,12 +687,14 @@ def test_attestation(spec, state):
    yield 'pre', state
-    attestation = get_valid_attestation(spec, state, signed=True)
+    attestation = get_valid_attestation(spec, state, signed=True, on_time=True)
    # Add to state via block transition
    pre_current_attestations_len = len(state.current_epoch_attestations)
    attestation_block = build_empty_block(spec, state, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
    attestation_block.body.attestations.append(attestation)
    if spec.fork == PHASE1:
        fill_block_shard_transitions_by_attestations(spec, state, attestation_block)
    signed_attestation_block = state_transition_and_sign_block(spec, state, attestation_block)
    assert len(state.current_epoch_attestations) == pre_current_attestations_len + 1
@ -443,35 +712,38 @@ def test_attestation(spec, state):
    assert spec.hash_tree_root(state.previous_epoch_attestations) == pre_current_attestations_root
-# In phase1 a committee is computed for PERSISTENT_COMMITTEE_PERIOD slots ago,
+def prepare_signed_exits(spec, state, indices):
    domain = spec.get_domain(state, spec.DOMAIN_VOLUNTARY_EXIT)
    def create_signed_exit(index):
        exit = spec.VoluntaryExit(
            epoch=spec.get_current_epoch(state),
            validator_index=index,
        )
        signing_root = spec.compute_signing_root(exit, domain)
        return spec.SignedVoluntaryExit(message=exit, signature=bls.Sign(privkeys[index], signing_root))
    return [create_signed_exit(index) for index in indices]
 # In phase1 a committee is computed for SHARD_COMMITTEE_PERIOD slots ago,
 # exceeding the minimal-config randao mixes memory size.
 # Applies to all voluntary-exit sanity block tests.
@with_phases(['phase0'])
@spec_state_test
 def test_voluntary_exit(spec, state):
-    validator_index = spec.get_active_validator_indices(
+    validator_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
        state,
        spec.get_current_epoch(state)
    )[-1]
-    # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
+    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
-    state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
+    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    signed_exits = prepare_signed_exits(spec, state, [validator_index])
    yield 'pre', state
    voluntary_exit = spec.VoluntaryExit(
        epoch=spec.get_current_epoch(state),
        validator_index=validator_index,
    )
    domain = spec.get_domain(state, spec.DOMAIN_VOLUNTARY_EXIT)
    signing_root = spec.compute_signing_root(voluntary_exit, domain)
    signed_voluntary_exit = spec.SignedVoluntaryExit(
        message=voluntary_exit,
        signature=bls.Sign(privkeys[validator_index], signing_root)
    )
    # Add to state via block transition
    initiate_exit_block = build_empty_block_for_next_slot(spec, state)
-    initiate_exit_block.body.voluntary_exits.append(signed_voluntary_exit)
+    initiate_exit_block.body.voluntary_exits = signed_exits
    signed_initiate_exit_block = state_transition_and_sign_block(spec, state, initiate_exit_block)
    assert state.validators[validator_index].exit_epoch < spec.FAR_FUTURE_EPOCH
@ -486,6 +758,59 @@ def test_voluntary_exit(spec, state):
    assert state.validators[validator_index].exit_epoch < spec.FAR_FUTURE_EPOCH
@with_phases(['phase0'])
@spec_state_test
 def test_double_validator_exit_same_block(spec, state):
    validator_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    # Same index tries to exit twice, but should only be able to do so once.
    signed_exits = prepare_signed_exits(spec, state, [validator_index, validator_index])
    yield 'pre', state
    # Add to state via block transition
    initiate_exit_block = build_empty_block_for_next_slot(spec, state)
    initiate_exit_block.body.voluntary_exits = signed_exits
    signed_initiate_exit_block = state_transition_and_sign_block(spec, state, initiate_exit_block, expect_fail=True)
    yield 'blocks', [signed_initiate_exit_block]
    yield 'post', None
@with_phases(['phase0'])
@spec_state_test
 def test_multiple_different_validator_exits_same_block(spec, state):
    validator_indices = [
        spec.get_active_validator_indices(state, spec.get_current_epoch(state))[i]
        for i in range(3)
    ]
    # move state forward SHARD_COMMITTEE_PERIOD epochs to allow for exit
    state.slot += spec.SHARD_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
    signed_exits = prepare_signed_exits(spec, state, validator_indices)
    yield 'pre', state
    # Add to state via block transition
    initiate_exit_block = build_empty_block_for_next_slot(spec, state)
    initiate_exit_block.body.voluntary_exits = signed_exits
    signed_initiate_exit_block = state_transition_and_sign_block(spec, state, initiate_exit_block)
    for index in validator_indices:
        assert state.validators[index].exit_epoch < spec.FAR_FUTURE_EPOCH
    # Process within epoch transition
    exit_block = build_empty_block(spec, state, state.slot + spec.SLOTS_PER_EPOCH)
    signed_exit_block = state_transition_and_sign_block(spec, state, exit_block)
    yield 'blocks', [signed_initiate_exit_block, signed_exit_block]
    yield 'post', state
    for index in validator_indices:
        assert state.validators[index].exit_epoch < spec.FAR_FUTURE_EPOCH
@with_all_phases
@spec_state_test
 def test_balance_driven_status_transitions(spec, state):
--- a/tests/core/pyspec/eth2spec/test/phase_0/sanity/test_slots.py
+++ b/tests/core/pyspec/eth2spec/test/phase_0/sanity/test_slots.py
@ -51,7 +51,8 @@ def test_double_empty_epoch(spec, state):
@with_all_phases
@spec_state_test
 def test_over_epoch_boundary(spec, state):
-    spec.process_slots(state, state.slot + (spec.SLOTS_PER_EPOCH // 2))
+    if spec.SLOTS_PER_EPOCH > 1:
        spec.process_slots(state, state.slot + (spec.SLOTS_PER_EPOCH // 2))
    yield 'pre', state
    slots = spec.SLOTS_PER_EPOCH
    yield 'slots', slots
--- a/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_custody_key_reveal.py
+++ b/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_custody_key_reveal.py
@ -1,5 +1,6 @@
 from eth2spec.test.helpers.custody import get_valid_custody_key_reveal
 from eth2spec.test.context import (
    PHASE0,
    with_all_phases_except,
    spec_state_test,
    expect_assertion_error,
@ -54,7 +55,7 @@ def run_custody_key_reveal_processing(spec, state, custody_key_reveal, valid=Tru
    yield 'post', state
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_success(spec, state):
@ -64,7 +65,7 @@ def test_success(spec, state):
    yield from run_custody_key_reveal_processing(spec, state, custody_key_reveal)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_reveal_too_early(spec, state):
@ -73,7 +74,7 @@ def test_reveal_too_early(spec, state):
    yield from run_custody_key_reveal_processing(spec, state, custody_key_reveal, False)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_wrong_period(spec, state):
@ -82,7 +83,7 @@ def test_wrong_period(spec, state):
    yield from run_custody_key_reveal_processing(spec, state, custody_key_reveal, False)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_late_reveal(spec, state):
@ -92,7 +93,7 @@ def test_late_reveal(spec, state):
    yield from run_custody_key_reveal_processing(spec, state, custody_key_reveal)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_double_reveal(spec, state):
@ -104,7 +105,7 @@ def test_double_reveal(spec, state):
    yield from run_custody_key_reveal_processing(spec, state, custody_key_reveal, False)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_max_decrement(spec, state):
--- a/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_early_derived_secret_reveal.py
+++ b/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_early_derived_secret_reveal.py
@ -1,7 +1,7 @@
 from eth2spec.test.helpers.custody import get_valid_early_derived_secret_reveal
-from eth2spec.test.helpers.block import apply_empty_block
+from eth2spec.test.helpers.state import next_epoch_via_block, get_balance
 from eth2spec.test.helpers.state import next_epoch, get_balance
 from eth2spec.test.context import (
    PHASE0,
    with_all_phases_except,
    spec_state_test,
    expect_assertion_error,
@ -41,7 +41,7 @@ def run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal, v
    yield 'post', state
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_success(spec, state):
@ -50,7 +50,7 @@ def test_success(spec, state):
    yield from run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@never_bls
 def test_reveal_from_current_epoch(spec, state):
@ -59,18 +59,17 @@ def test_reveal_from_current_epoch(spec, state):
    yield from run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal, False)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@never_bls
 def test_reveal_from_past_epoch(spec, state):
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
    apply_empty_block(spec, state)
    randao_key_reveal = get_valid_early_derived_secret_reveal(spec, state, spec.get_current_epoch(state) - 1)
    yield from run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal, False)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_reveal_with_custody_padding(spec, state):
@ -82,7 +81,7 @@ def test_reveal_with_custody_padding(spec, state):
    yield from run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal, True)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_reveal_with_custody_padding_minus_one(spec, state):
@ -94,7 +93,7 @@ def test_reveal_with_custody_padding_minus_one(spec, state):
    yield from run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal, True)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@never_bls
 def test_double_reveal(spec, state):
@ -115,7 +114,7 @@ def test_double_reveal(spec, state):
    yield from run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal2, False)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@never_bls
 def test_revealer_is_slashed(spec, state):
@ -125,7 +124,7 @@ def test_revealer_is_slashed(spec, state):
    yield from run_early_derived_secret_reveal_processing(spec, state, randao_key_reveal, False)
-@with_all_phases_except(['phase0'])
+@with_all_phases_except([PHASE0])
@spec_state_test
@never_bls
 def test_far_future_epoch(spec, state):
--- a/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_shard_transition.py
+++ b/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_shard_transition.py
@ -0,0 +1,73 @@
 from eth2spec.test.context import (
    PHASE0,
    with_all_phases_except,
    spec_state_test,
    always_bls,
 )
 from eth2spec.test.helpers.shard_transitions import run_shard_transitions_processing
 from eth2spec.test.helpers.shard_block import (
    build_attestation_with_shard_transition,
    build_shard_block,
    build_shard_transitions_till_slot,
 )
 from eth2spec.test.helpers.state import transition_to, transition_to_valid_shard_slot
 def run_basic_crosslink_tests(spec, state, target_len_offset_slot, valid=True):
    state = transition_to_valid_shard_slot(spec, state)
    # At the beginning, let `x = state.slot`, `state.shard_states[shard].slot == x - 1`
    slot_x = state.slot
    committee_index = spec.CommitteeIndex(0)
    shard = spec.compute_shard_from_committee_index(state, committee_index, state.slot)
    assert state.shard_states[shard].slot == slot_x - 1
    # Create SignedShardBlock
    body = b'\x56' * spec.MAX_SHARD_BLOCK_SIZE
    shard_block = build_shard_block(spec, state, shard, body=body, signed=True)
    shard_blocks = [shard_block]
    # Create a shard_transitions that would be included at beacon block `state.slot + target_len_offset_slot`
    shard_transitions = build_shard_transitions_till_slot(
        spec,
        state,
        shard_blocks={shard: shard_blocks},
        on_time_slot=state.slot + target_len_offset_slot,
    )
    shard_transition = shard_transitions[shard]
    # Create an attestation that would be included at beacon block `state.slot + target_len_offset_slot`
    attestation = build_attestation_with_shard_transition(
        spec,
        state,
        index=committee_index,
        on_time_slot=state.slot + target_len_offset_slot,
        shard_transition=shard_transition,
    )
    pre_gasprice = state.shard_states[shard].gasprice
    transition_to(spec, state, state.slot + target_len_offset_slot)
    pre_shard_state = state.shard_states[shard]
    yield from run_shard_transitions_processing(spec, state, shard_transitions, [attestation], valid=valid)
    if valid:
        # After state transition,
        assert state.slot == slot_x + target_len_offset_slot
        shard_state = state.shard_states[shard]
        assert shard_state != pre_shard_state
        assert shard_state == shard_transition.shard_states[len(shard_transition.shard_states) - 1]
        if target_len_offset_slot == 1:
            assert shard_state.gasprice > pre_gasprice
@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_basic_crosslinks(spec, state):
    yield from run_basic_crosslink_tests(spec, state, target_len_offset_slot=1, valid=True)
@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_multiple_offset_slots(spec, state):
    yield from run_basic_crosslink_tests(spec, state, target_len_offset_slot=3, valid=True)
--- a/tests/core/pyspec/eth2spec/test/phase_1/sanity/init.py
+++ b/tests/core/pyspec/eth2spec/test/phase_1/sanity/init.py
--- a/tests/core/pyspec/eth2spec/test/phase_1/sanity/test_blocks.py
+++ b/tests/core/pyspec/eth2spec/test/phase_1/sanity/test_blocks.py
@ -0,0 +1,107 @@
 from typing import Dict, Sequence
 from eth2spec.test.context import (
    PHASE0,
    with_all_phases_except,
    spec_state_test,
    always_bls,
 )
 from eth2spec.test.helpers.block import build_empty_block
 from eth2spec.test.helpers.shard_block import (
    build_attestation_with_shard_transition,
    build_shard_block,
    build_shard_transitions_till_slot,
 )
 from eth2spec.test.helpers.state import state_transition_and_sign_block, transition_to_valid_shard_slot
 def run_beacon_block_with_shard_blocks(spec, state, shard_blocks, target_len_offset_slot, committee_index, valid=True):
    shard_transitions = build_shard_transitions_till_slot(
        spec, state, shard_blocks, on_time_slot=state.slot + target_len_offset_slot
    )
    attestations = [
        build_attestation_with_shard_transition(
            spec,
            state,
            on_time_slot=state.slot + target_len_offset_slot,
            index=committee_index,
            shard_transition=shard_transitions[shard],
        )
        for shard in shard_blocks.keys()
    ]
    # Propose beacon block at slot `x + 1`
    beacon_block = build_empty_block(spec, state, slot=state.slot + target_len_offset_slot)
    beacon_block.body.attestations = attestations
    beacon_block.body.shard_transitions = shard_transitions
    pre_shard_states = state.shard_states.copy()
    yield 'pre', state.copy()
    yield 'block', beacon_block
    state_transition_and_sign_block(spec, state, beacon_block)
    if valid:
        yield 'post', state
    else:
        yield 'post', None
        return
    for shard in range(spec.get_active_shard_count(state)):
        post_shard_state = state.shard_states[shard]
        if shard in shard_blocks:
            # Shard state has been changed to state_transition result
            assert post_shard_state == shard_transitions[shard].shard_states[
                len(shard_transitions[shard].shard_states) - 1
            ]
            assert beacon_block.slot == shard_transitions[shard].shard_states[0].slot + target_len_offset_slot
            assert post_shard_state.slot == state.slot - 1
            if len(shard_blocks[shard]) == 0:
                # `latest_block_root` is the same
                assert post_shard_state.latest_block_root == pre_shard_states[shard].latest_block_root
@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_process_beacon_block_with_normal_shard_transition(spec, state):
    state = transition_to_valid_shard_slot(spec, state)
    target_len_offset_slot = 1
    committee_index = spec.CommitteeIndex(0)
    shard = spec.compute_shard_from_committee_index(state, committee_index, state.slot)
    assert state.shard_states[shard].slot == state.slot - 1
    pre_gasprice = state.shard_states[shard].gasprice
    # Create SignedShardBlock at slot `shard_state.slot + 1`
    body = b'\x56' * spec.MAX_SHARD_BLOCK_SIZE
    shard_block = build_shard_block(spec, state, shard, body=body, signed=True)
    shard_blocks: Dict[spec.Shard, Sequence[spec.SignedShardBlock]] = {shard: [shard_block]}
    yield from run_beacon_block_with_shard_blocks(spec, state, shard_blocks, target_len_offset_slot, committee_index)
    shard_state = state.shard_states[shard]
    if target_len_offset_slot == 1 and len(shard_blocks) > 0:
        assert shard_state.gasprice > pre_gasprice
@with_all_phases_except([PHASE0])
@spec_state_test
@always_bls
 def test_process_beacon_block_with_empty_proposal_transition(spec, state):
    state = transition_to_valid_shard_slot(spec, state)
    target_len_offset_slot = 1
    committee_index = spec.CommitteeIndex(0)
    shard = spec.compute_shard_from_committee_index(state, committee_index, state.slot)
    assert state.shard_states[shard].slot == state.slot - 1
    # No new shard block
    shard_blocks = {}
    pre_gasprice = state.shard_states[shard].gasprice
    yield from run_beacon_block_with_shard_blocks(spec, state, shard_blocks, target_len_offset_slot, committee_index)
    if target_len_offset_slot == 1 and len(shard_blocks) > 0:
        assert state.shard_states[shard].gasprice > pre_gasprice
--- a/tests/core/pyspec/eth2spec/test/test_finality.py
+++ b/tests/core/pyspec/eth2spec/test/test_finality.py
@ -1,7 +1,6 @@
 from eth2spec.test.context import spec_state_test, never_bls, with_all_phases, with_phases
-from eth2spec.test.helpers.state import next_epoch
+from eth2spec.test.helpers.state import next_epoch_via_block
 from eth2spec.test.helpers.attestations import next_epoch_with_attestations
 from eth2spec.test.helpers.block import apply_empty_block
 def check_finality(spec,
@ -58,10 +57,8 @@ def test_finality_no_updates_at_genesis(spec, state):
@never_bls
 def test_finality_rule_4(spec, state):
    # get past first two epochs that finality does not run on
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
-    apply_empty_block(spec, state)
+    next_epoch_via_block(spec, state)
    next_epoch(spec, state)
    apply_empty_block(spec, state)
    yield 'pre', state
@ -86,10 +83,8 @@ def test_finality_rule_4(spec, state):
@never_bls
 def test_finality_rule_1(spec, state):
    # get past first two epochs that finality does not run on
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
-    apply_empty_block(spec, state)
+    next_epoch_via_block(spec, state)
    next_epoch(spec, state)
    apply_empty_block(spec, state)
    yield 'pre', state
@ -116,10 +111,8 @@ def test_finality_rule_1(spec, state):
@never_bls
 def test_finality_rule_2(spec, state):
    # get past first two epochs that finality does not run on
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
-    apply_empty_block(spec, state)
+    next_epoch_via_block(spec, state)
    next_epoch(spec, state)
    apply_empty_block(spec, state)
    yield 'pre', state
@ -152,10 +145,8 @@ def test_finality_rule_3(spec, state):
    https://github.com/ethereum/eth2.0-specs/issues/611#issuecomment-463612892
    """
    # get past first two epochs that finality does not run on
-    next_epoch(spec, state)
+    next_epoch_via_block(spec, state)
-    apply_empty_block(spec, state)
+    next_epoch_via_block(spec, state)
    next_epoch(spec, state)
    apply_empty_block(spec, state)
    yield 'pre', state
--- a/tests/core/pyspec/eth2spec/test/validator/test_validator_unittest.py
+++ b/tests/core/pyspec/eth2spec/test/validator/test_validator_unittest.py
@ -0,0 +1,444 @@
 from eth2spec.test.context import spec_state_test, always_bls, with_all_phases
 from eth2spec.test.helpers.attestations import build_attestation_data
 from eth2spec.test.helpers.block import build_empty_block
 from eth2spec.test.helpers.deposits import prepare_state_and_deposit
 from eth2spec.test.helpers.keys import privkeys, pubkeys
 from eth2spec.test.helpers.state import next_epoch
 from eth2spec.utils import bls
 from eth2spec.utils.ssz.ssz_typing import Bitlist
 def run_get_signature_test(spec, state, obj, domain, get_signature_fn, privkey, pubkey, signing_ssz_object=None):
    if signing_ssz_object is None:
        signing_ssz_object = obj
    signature = get_signature_fn(state, obj, privkey)
    signing_root = spec.compute_signing_root(signing_ssz_object, domain)
    assert bls.Verify(pubkey, signing_root, signature)
 def run_get_committee_assignment(spec, state, epoch, validator_index, valid=True):
    try:
        assignment = spec.get_committee_assignment(state, epoch, validator_index)
        committee, committee_index, slot = assignment
        assert spec.compute_epoch_at_slot(slot) == epoch
        assert committee == spec.get_beacon_committee(state, slot, committee_index)
        assert committee_index < spec.get_committee_count_at_slot(state, slot)
        assert validator_index in committee
        assert valid
    except AssertionError:
        assert not valid
    else:
        assert valid
 def run_is_candidate_block(spec, eth1_block, period_start, success=True):
    assert success == spec.is_candidate_block(eth1_block, period_start)
 def get_min_new_period_epochs(spec):
    return int(
        spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE * 2  # to seconds
        / spec.SECONDS_PER_SLOT / spec.SLOTS_PER_EPOCH
    )
 def get_mock_aggregate(spec):
    return spec.Attestation(
        data=spec.AttestationData(
            slot=10,
        )
    )
 #
 # Becoming a validator
 #
@with_all_phases
@spec_state_test
 def test_check_if_validator_active(spec, state):
    active_validator_index = len(state.validators) - 1
    assert spec.check_if_validator_active(state, active_validator_index)
    new_validator_index = len(state.validators)
    amount = spec.MAX_EFFECTIVE_BALANCE
    deposit = prepare_state_and_deposit(spec, state, new_validator_index, amount, signed=True)
    spec.process_deposit(state, deposit)
    assert not spec.check_if_validator_active(state, new_validator_index)
 #
 # Validator assignments
 #
@with_all_phases
@spec_state_test
 def test_get_committee_assignment_current_epoch(spec, state):
    epoch = spec.get_current_epoch(state)
    validator_index = len(state.validators) - 1
    run_get_committee_assignment(spec, state, epoch, validator_index, valid=True)
@with_all_phases
@spec_state_test
 def test_get_committee_assignment_next_epoch(spec, state):
    epoch = spec.get_current_epoch(state) + 1
    validator_index = len(state.validators) - 1
    run_get_committee_assignment(spec, state, epoch, validator_index, valid=True)
@with_all_phases
@spec_state_test
 def test_get_committee_assignment_out_bound_epoch(spec, state):
    epoch = spec.get_current_epoch(state) + 2
    validator_index = len(state.validators) - 1
    run_get_committee_assignment(spec, state, epoch, validator_index, valid=False)
@with_all_phases
@spec_state_test
 def test_is_proposer(spec, state):
    proposer_index = spec.get_beacon_proposer_index(state)
    assert spec.is_proposer(state, proposer_index)
    proposer_index = proposer_index + 1 % len(state.validators)
    assert not spec.is_proposer(state, proposer_index)
 #
 # Beacon chain responsibilities
 #
 # Block proposal
@with_all_phases
@spec_state_test
 def test_get_epoch_signature(spec, state):
    block = spec.BeaconBlock()
    privkey = privkeys[0]
    pubkey = pubkeys[0]
    domain = spec.get_domain(state, spec.DOMAIN_RANDAO, spec.compute_epoch_at_slot(block.slot))
    run_get_signature_test(
        spec=spec,
        state=state,
        obj=block,
        domain=domain,
        get_signature_fn=spec.get_epoch_signature,
        privkey=privkey,
        pubkey=pubkey,
        signing_ssz_object=spec.compute_epoch_at_slot(block.slot),
    )
@with_all_phases
@spec_state_test
 def test_is_candidate_block(spec, state):
    period_start = spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE * 2 + 1000
    run_is_candidate_block(
        spec,
        spec.Eth1Block(timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE),
        period_start,
        success=True,
    )
    run_is_candidate_block(
        spec,
        spec.Eth1Block(timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE + 1),
        period_start,
        success=False,
    )
    run_is_candidate_block(
        spec,
        spec.Eth1Block(timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE * 2),
        period_start,
        success=True,
    )
    run_is_candidate_block(
        spec,
        spec.Eth1Block(timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE * 2 - 1),
        period_start,
        success=False,
    )
@with_all_phases
@spec_state_test
 def test_get_eth1_vote_default_vote(spec, state):
    min_new_period_epochs = get_min_new_period_epochs(spec)
    for _ in range(min_new_period_epochs):
        next_epoch(spec, state)
    state.eth1_data_votes = ()
    eth1_chain = []
    eth1_data = spec.get_eth1_vote(state, eth1_chain)
    assert eth1_data == state.eth1_data
@with_all_phases
@spec_state_test
 def test_get_eth1_vote_consensus_vote(spec, state):
    min_new_period_epochs = get_min_new_period_epochs(spec)
    for _ in range(min_new_period_epochs + 2):
        next_epoch(spec, state)
    period_start = spec.voting_period_start_time(state)
    votes_length = spec.get_current_epoch(state) % spec.EPOCHS_PER_ETH1_VOTING_PERIOD
    assert votes_length >= 3  # We need to have the majority vote
    state.eth1_data_votes = ()
    block_1 = spec.Eth1Block(
        timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE - 1,
        deposit_count=state.eth1_data.deposit_count,
        deposit_root=b'\x04' * 32,
    )
    block_2 = spec.Eth1Block(
        timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE,
        deposit_count=state.eth1_data.deposit_count + 1,
        deposit_root=b'\x05' * 32,
    )
    eth1_chain = [block_1, block_2]
    eth1_data_votes = []
    # Only the first vote is for block_1
    eth1_data_votes.append(spec.get_eth1_data(block_1))
    # Other votes are for block_2
    for _ in range(votes_length - 1):
        eth1_data_votes.append(spec.get_eth1_data(block_2))
    state.eth1_data_votes = eth1_data_votes
    eth1_data = spec.get_eth1_vote(state, eth1_chain)
    assert eth1_data.block_hash == block_2.hash_tree_root()
@with_all_phases
@spec_state_test
 def test_get_eth1_vote_tie(spec, state):
    min_new_period_epochs = get_min_new_period_epochs(spec)
    for _ in range(min_new_period_epochs + 1):
        next_epoch(spec, state)
    period_start = spec.voting_period_start_time(state)
    votes_length = spec.get_current_epoch(state) % spec.EPOCHS_PER_ETH1_VOTING_PERIOD
    assert votes_length > 0 and votes_length % 2 == 0
    state.eth1_data_votes = ()
    block_1 = spec.Eth1Block(
        timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE - 1,
        deposit_count=state.eth1_data.deposit_count,
        deposit_root=b'\x04' * 32,
    )
    block_2 = spec.Eth1Block(
        timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE,
        deposit_count=state.eth1_data.deposit_count + 1,
        deposit_root=b'\x05' * 32,
    )
    eth1_chain = [block_1, block_2]
    eth1_data_votes = []
    # Half votes are for block_1, another half votes are for block_2
    for i in range(votes_length):
        if i % 2 == 0:
            block = block_1
        else:
            block = block_2
        eth1_data_votes.append(spec.get_eth1_data(block))
    state.eth1_data_votes = eth1_data_votes
    eth1_data = spec.get_eth1_vote(state, eth1_chain)
    # Tiebreak by smallest distance -> eth1_chain[0]
    assert eth1_data.block_hash == eth1_chain[0].hash_tree_root()
@with_all_phases
@spec_state_test
 def test_get_eth1_vote_chain_in_past(spec, state):
    min_new_period_epochs = get_min_new_period_epochs(spec)
    for _ in range(min_new_period_epochs + 1):
        next_epoch(spec, state)
    period_start = spec.voting_period_start_time(state)
    votes_length = spec.get_current_epoch(state) % spec.EPOCHS_PER_ETH1_VOTING_PERIOD
    assert votes_length > 0 and votes_length % 2 == 0
    state.eth1_data_votes = ()
    block_1 = spec.Eth1Block(
        timestamp=period_start - spec.SECONDS_PER_ETH1_BLOCK * spec.ETH1_FOLLOW_DISTANCE,
        deposit_count=state.eth1_data.deposit_count - 1,  # Chain prior to current eth1data
        deposit_root=b'\x42' * 32,
    )
    eth1_chain = [block_1]
    eth1_data_votes = []
    state.eth1_data_votes = eth1_data_votes
    eth1_data = spec.get_eth1_vote(state, eth1_chain)
    # Should be default vote
    assert eth1_data == state.eth1_data
@with_all_phases
@spec_state_test
 def test_compute_new_state_root(spec, state):
    pre_state = state.copy()
    post_state = state.copy()
    block = build_empty_block(spec, state, state.slot + 1)
    state_root = spec.compute_new_state_root(state, block)
    assert state_root != pre_state.hash_tree_root()
    assert state == pre_state
    # dumb verification
    spec.process_slots(post_state, block.slot)
    spec.process_block(post_state, block)
    assert state_root == post_state.hash_tree_root()
@with_all_phases
@spec_state_test
@always_bls
 def test_get_block_signature(spec, state):
    privkey = privkeys[0]
    pubkey = pubkeys[0]
    block = build_empty_block(spec, state)
    domain = spec.get_domain(state, spec.DOMAIN_BEACON_PROPOSER, spec.compute_epoch_at_slot(block.slot))
    run_get_signature_test(
        spec=spec,
        state=state,
        obj=block,
        domain=domain,
        get_signature_fn=spec.get_block_signature,
        privkey=privkey,
        pubkey=pubkey,
    )
 # Attesting
@with_all_phases
@spec_state_test
@always_bls
 def test_get_attestation_signature(spec, state):
    privkey = privkeys[0]
    pubkey = pubkeys[0]
    attestation_data = spec.AttestationData(slot=10)
    domain = spec.get_domain(state, spec.DOMAIN_BEACON_ATTESTER, attestation_data.target.epoch)
    run_get_signature_test(
        spec=spec,
        state=state,
        obj=attestation_data,
        domain=domain,
        get_signature_fn=spec.get_attestation_signature,
        privkey=privkey,
        pubkey=pubkey,
    )
 # Attestation aggregation
@with_all_phases
@spec_state_test
@always_bls
 def test_get_slot_signature(spec, state):
    privkey = privkeys[0]
    pubkey = pubkeys[0]
    slot = spec.Slot(10)
    domain = spec.get_domain(state, spec.DOMAIN_SELECTION_PROOF, spec.compute_epoch_at_slot(slot))
    run_get_signature_test(
        spec=spec,
        state=state,
        obj=slot,
        domain=domain,
        get_signature_fn=spec.get_slot_signature,
        privkey=privkey,
        pubkey=pubkey,
    )
@with_all_phases
@spec_state_test
@always_bls
 def test_is_aggregator(spec, state):
    # TODO: we can test the probabilistic result against `TARGET_AGGREGATORS_PER_COMMITTEE`
    #  if we have more validators and larger committeee size
    slot = state.slot
    committee_index = 0
    has_aggregator = False
    beacon_committee = spec.get_beacon_committee(state, slot, committee_index)
    for validator_index in beacon_committee:
        privkey = privkeys[validator_index]
        slot_signature = spec.get_slot_signature(state, slot, privkey)
        if spec.is_aggregator(state, slot, committee_index, slot_signature):
            has_aggregator = True
            break
    assert has_aggregator
@with_all_phases
@spec_state_test
@always_bls
 def test_get_aggregate_signature(spec, state):
    attestations = []
    attesting_pubkeys = []
    slot = state.slot
    committee_index = 0
    attestation_data = build_attestation_data(spec, state, slot=slot, index=committee_index)
    beacon_committee = spec.get_beacon_committee(
        state,
        attestation_data.slot,
        attestation_data.index,
    )
    committee_size = len(beacon_committee)
    aggregation_bits = Bitlist[spec.MAX_VALIDATORS_PER_COMMITTEE](*([0] * committee_size))
    for i, validator_index in enumerate(beacon_committee):
        bits = aggregation_bits.copy()
        bits[i] = True
        attestations.append(
            spec.Attestation(
                data=attestation_data,
                aggregation_bits=bits,
                signature=spec.get_attestation_signature(state, attestation_data, privkeys[validator_index]),
            )
        )
        attesting_pubkeys.append(state.validators[validator_index].pubkey)
    assert len(attestations) > 0
    signature = spec.get_aggregate_signature(attestations)
    domain = spec.get_domain(state, spec.DOMAIN_BEACON_ATTESTER, attestation_data.target.epoch)
    signing_root = spec.compute_signing_root(attestation_data, domain)
    assert bls.FastAggregateVerify(attesting_pubkeys, signing_root, signature)
@with_all_phases
@spec_state_test
@always_bls
 def test_get_aggregate_and_proof(spec, state):
    privkey = privkeys[0]
    aggregator_index = spec.ValidatorIndex(10)
    aggregate = get_mock_aggregate(spec)
    aggregate_and_proof = spec.get_aggregate_and_proof(state, aggregator_index, aggregate, privkey)
    assert aggregate_and_proof.aggregator_index == aggregator_index
    assert aggregate_and_proof.aggregate == aggregate
    assert aggregate_and_proof.selection_proof == spec.get_slot_signature(state, aggregate.data.slot, privkey)
@with_all_phases
@spec_state_test
@always_bls
 def test_get_aggregate_and_proof_signature(spec, state):
    privkey = privkeys[0]
    pubkey = pubkeys[0]
    aggregate = get_mock_aggregate(spec)
    aggregate_and_proof = spec.get_aggregate_and_proof(state, spec.ValidatorIndex(1), aggregate, privkey)
    domain = spec.get_domain(state, spec.DOMAIN_AGGREGATE_AND_PROOF, spec.compute_epoch_at_slot(aggregate.data.slot))
    run_get_signature_test(
        spec=spec,
        state=state,
        obj=aggregate_and_proof,
        domain=domain,
        get_signature_fn=spec.get_aggregate_and_proof_signature,
        privkey=privkey,
        pubkey=pubkey,
    )
--- a/tests/core/pyspec/eth2spec/utils/bls.py
+++ b/tests/core/pyspec/eth2spec/utils/bls.py
@ -1,12 +1,17 @@
-from py_ecc.bls import G2ProofOfPossession as bls
+from py_ecc.bls import G2ProofOfPossession as py_ecc_bls
 from py_ecc.bls.g2_primatives import signature_to_G2 as _signature_to_G2
 import milagro_bls_binding as milagro_bls  # noqa: F401 for BLS switching option
 # Flag to make BLS active or not. Used for testing, do not ignore BLS in production unless you know what you are doing.
 bls_active = True
 # To change bls implementation, default to PyECC for correctness. Milagro is a good faster alternative.
 bls = py_ecc_bls
 STUB_SIGNATURE = b'\x11' * 96
 STUB_PUBKEY = b'\x22' * 48
-STUB_COORDINATES = _signature_to_G2(bls.Sign(0, b""))
+Z2_SIGNATURE = b'\xc0' + b'\x00' * 95
 STUB_COORDINATES = _signature_to_G2(Z2_SIGNATURE)
 def only_with_bls(alt_return=None):
@ -25,17 +30,32 @@ def only_with_bls(alt_return=None):
@only_with_bls(alt_return=True)
 def Verify(PK, message, signature):
-    return bls.Verify(PK, message, signature)
+    try:
        result = bls.Verify(PK, message, signature)
    except Exception:
        result = False
    finally:
        return result
@only_with_bls(alt_return=True)
-def AggregateVerify(pairs, signature):
+def AggregateVerify(pubkeys, messages, signature):
-    return bls.AggregateVerify(pairs, signature)
+    try:
        result = bls.AggregateVerify(list(pubkeys), list(messages), signature)
    except Exception:
        result = False
    finally:
        return result
@only_with_bls(alt_return=True)
-def FastAggregateVerify(PKs, message, signature):
+def FastAggregateVerify(pubkeys, message, signature):
-    return bls.FastAggregateVerify(PKs, message, signature)
+    try:
        result = bls.FastAggregateVerify(list(pubkeys), message, signature)
    except Exception:
        result = False
    finally:
        return result
@only_with_bls(alt_return=STUB_SIGNATURE)
@ -45,9 +65,22 @@ def Aggregate(signatures):
@only_with_bls(alt_return=STUB_SIGNATURE)
 def Sign(SK, message):
-    return bls.Sign(SK, message)
+    if bls == py_ecc_bls:
        return bls.Sign(SK, message)
    else:
        return bls.Sign(SK.to_bytes(32, 'big'), message)
@only_with_bls(alt_return=STUB_COORDINATES)
 def signature_to_G2(signature):
    return _signature_to_G2(signature)
@only_with_bls(alt_return=STUB_PUBKEY)
 def AggregatePKs(pubkeys):
    return bls._AggregatePKs(list(pubkeys))
@only_with_bls(alt_return=STUB_SIGNATURE)
 def SkToPk(SK):
    return bls.SkToPk(SK)
--- a/tests/core/pyspec/eth2spec/utils/hash_function.py
+++ b/tests/core/pyspec/eth2spec/utils/hash_function.py
@ -1,28 +1,17 @@
 from hashlib import sha256
 from typing import Dict, Union
 ZERO_BYTES32 = b'\x00' * 32
-def _hash(x):
+def _hash(x: Union[bytes, bytearray, memoryview]) -> bytes:
    return sha256(x).digest()
-# Minimal collection of (key, value) pairs, for fast hash-retrieval, to save on repetitive computation cost.
+hash_cache: Dict[bytes, bytes] = {}
 # Key = the hash input
 # Value = the hash output
 hash_cache = []
-def add_zero_hashes_to_cache():
+def hash(x: bytes) -> bytes:
-    zerohashes = [(None, ZERO_BYTES32)]
+    if x in hash_cache:
-    for layer in range(1, 32):
+        return hash_cache[x]
        k = zerohashes[layer - 1][1] + zerohashes[layer - 1][1]
        zerohashes.append((k, _hash(k)))
    hash_cache.extend(zerohashes[1:])
 def hash(x):
    for (k, h) in hash_cache:
        if x == k:
            return h
    return _hash(x)
--- a/tests/formats/bls/README.md
+++ b/tests/formats/bls/README.md
@ -5,11 +5,10 @@ We do not recommend rolling your own crypto or using an untested BLS library.
 The BLS test suite runner has the following handlers:
- [`aggregate_pubkeys`](./aggregate_pubkeys.md)
+- [`aggregate_verify`](./aggregate_verify.md)
- [`aggregate_sigs`](./aggregate_sigs.md)
+- [`aggregate`](./aggregate.md)
- [`msg_hash_g2_compressed`](./msg_hash_g2_compressed.md)
+- [`fast_aggregate_verify`](./fast_aggregate_verify.md)
- [`msg_hash_g2_uncompressed`](./msg_hash_g2_uncompressed.md)
+- [`sign`](./sign.md)
- [`priv_to_pub`](./priv_to_pub.md)
+- [`verify`](./verify.md)
 - [`sign_msg`](./sign_msg.md)
 *Note*: Signature-verification and aggregate-verify test cases are not yet supported.
--- a/tests/formats/bls/aggregate.md
+++ b/tests/formats/bls/aggregate.md
@ -0,0 +1,19 @@
 # Test format: BLS signature aggregation
 A BLS signature aggregation combines a series of signatures into a single signature.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input: List[BLS Signature] -- list of input BLS signatures
 output: BLS Signature -- expected output, single BLS signature or empty.
 ```
 - `BLS Signature` here is encoded as a string: hexadecimal encoding of 96 bytes (192 nibbles), prefixed with `0x`.
 - No output value if the input is invalid.
 ## Condition
 The `aggregate` handler should aggregate the signatures in the `input`, and the result should match the expected `output`.
--- a/tests/formats/bls/aggregate_pubkeys.md
+++ b/tests/formats/bls/aggregate_pubkeys.md
@ -1,19 +0,0 @@
 # Test format: BLS pubkey aggregation
 A BLS pubkey aggregation combines a series of pubkeys into a single pubkey.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input: List[BLS Pubkey] -- list of input BLS pubkeys
 output: BLS Pubkey -- expected output, single BLS pubkey
 ```
 `BLS Pubkey` here is encoded as a string: hexadecimal encoding of 48 bytes (96 nibbles), prefixed with `0x`.
 ## Condition
 The `aggregate_pubkeys` handler should aggregate the keys in the `input`, and the result should match the expected `output`.
--- a/tests/formats/bls/aggregate_sigs.md
+++ b/tests/formats/bls/aggregate_sigs.md
@ -1,19 +0,0 @@
 # Test format: BLS signature aggregation
 A BLS signature aggregation combines a series of signatures into a single signature.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input: List[BLS Signature] -- list of input BLS signatures
 output: BLS Signature -- expected output, single BLS signature
 ```
 `BLS Signature` here is encoded as a string: hexadecimal encoding of 96 bytes (192 nibbles), prefixed with `0x`.
 ## Condition
 The `aggregate_sigs` handler should aggregate the signatures in the `input`, and the result should match the expected `output`.
--- a/tests/formats/bls/aggregate_verify.md
+++ b/tests/formats/bls/aggregate_verify.md
@ -0,0 +1,17 @@
 # Test format: BLS sign message
 Verify the signature against the given pubkeys and one messages.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input:
  pubkeys: List[bytes48] -- the pubkeys
  messages: List[bytes32] -- the messages
  signature: bytes96 -- the signature to verify against pubkeys and messages
 output: bool  -- VALID or INVALID
 ```
 All byte(s) fields are encoded as strings, hexadecimal encoding, prefixed with `0x`.
--- a/tests/formats/bls/fast_aggregate_verify.md
+++ b/tests/formats/bls/fast_aggregate_verify.md
@ -0,0 +1,17 @@
 # Test format: BLS sign message
 Verify the signature against the given pubkeys and one message.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input:
  pubkeys: List[bytes48] -- the pubkey
  message: bytes32 -- the message
  signature: bytes96 -- the signature to verify against pubkeys and message
 output: bool  -- VALID or INVALID
 ```
 All byte(s) fields are encoded as strings, hexadecimal encoding, prefixed with `0x`.
--- a/tests/formats/bls/msg_hash_g2_compressed.md
+++ b/tests/formats/bls/msg_hash_g2_compressed.md
@ -1,21 +0,0 @@
 # Test format: BLS hash-compressed
 A BLS compressed-hash to G2.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input: 
  message: bytes32
  domain: bytes8   -- the BLS domain
 output: List[bytes48] -- length of two
 ```
 All byte(s) fields are encoded as strings, hexadecimal encoding, prefixed with `0x`.
 ## Condition
 The `msg_hash_g2_compressed` handler should hash the `message`, with the given `domain`, to G2 with compression, and the result should match the expected `output`.
--- a/tests/formats/bls/msg_hash_g2_uncompressed.md
+++ b/tests/formats/bls/msg_hash_g2_uncompressed.md
@ -1,21 +0,0 @@
 # Test format: BLS hash-uncompressed
 A BLS uncompressed-hash to G2.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input:
  message: bytes32
  domain: bytes8   -- the BLS domain
 output: List[List[bytes48]] -- 3 lists, each a length of two
 ```
 All byte(s) fields are encoded as strings, hexadecimal encoding, prefixed with `0x`.
 ## Condition
 The `msg_hash_g2_uncompressed` handler should hash the `message`, with the given `domain`, to G2, without compression, and the result should match the expected `output`.
--- a/tests/formats/bls/priv_to_pub.md
+++ b/tests/formats/bls/priv_to_pub.md
@ -1,19 +0,0 @@
 # Test format: BLS private key to pubkey
 A BLS private key to public key conversion.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input: bytes32 -- the private key
 output: bytes48 -- the public key
 ```
 All byte(s) fields are encoded as strings, hexadecimal encoding, prefixed with `0x`.
 ## Condition
 The `priv_to_pub` handler should compute the public key for the given private key `input`, and the result should match the expected `output`.
--- a/tests/formats/bls/sign_msg.md
+++ b/tests/formats/bls/sign_msg.md
@ -10,13 +10,7 @@ The test data is declared in a `data.yaml` file:
 input:
  privkey: bytes32 -- the private key used for signing
  message: bytes32 -- input message to sign (a hash)
  domain: bytes8   -- the BLS domain
 output: bytes96    -- expected signature
 ```
 All byte(s) fields are encoded as strings, hexadecimal encoding, prefixed with `0x`.
 ## Condition
 The `sign_msg` handler should sign the given `message`, with `domain`, using the given `privkey`, and the result should match the expected `output`.
--- a/tests/formats/bls/verify.md
+++ b/tests/formats/bls/verify.md
@ -0,0 +1,17 @@
 # Test format: BLS sign message
 Verify the signature against the given one pubkey and one message.
 ## Test case format
 The test data is declared in a `data.yaml` file:
 ```yaml
 input:
  pubkey: bytes48 -- the pubkey
  message: bytes32 -- the message
  signature: bytes96 -- the signature to verify against pubkey and message
 output: bool  -- VALID or INVALID
 ```
 All byte(s) fields are encoded as strings, hexadecimal encoding, prefixed with `0x`.
--- a/tests/formats/epoch_processing/README.md
+++ b/tests/formats/epoch_processing/README.md
@ -38,7 +38,7 @@ The provided pre-state is already transitioned to just before the specific sub-t
 Sub-transitions:
 - `justification_and_finalization`
- *`rewards_and_penalties` - planned testing extension*
+- `rewards_and_penalties` (limited to `minimal` config)
 - `registry_updates`
 - `slashings`
 - `final_updates`
--- a/tests/formats/rewards/README.md
+++ b/tests/formats/rewards/README.md
@ -0,0 +1,75 @@
 # Rewards tests
 All rewards deltas sub-functions are tested for each test case.
 There is no "change" factor, the rewards/penalties outputs are pure functions with just the pre-state as input.
 (See test condition documentation on how to run the tests.)
 `Deltas` is defined as:
 ```python
 class Deltas(Container):
    rewards: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
    penalties: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
 ```
 ## Test case format
 ### `meta.yaml`
 ```yaml
 description: string    -- Optional description of test case, purely for debugging purposes.
                          Tests should use the directory name of the test case as identifier, not the description.
 ```
 _Note_: No signature verification happens within rewards sub-functions. These
 tests can safely be run with or without BLS enabled.
 ### `pre.yaml`
 A YAML-encoded `BeaconState`, the state before running the rewards sub-function.
 Also available as `pre.ssz`.
 ### `source_deltas.yaml`
 A YAML-encoded `Deltas` representing the rewards and penalties returned by the rewards the `get_source_deltas` function
 Also available as `source_deltas.ssz`.
 ### `target_deltas.yaml`
 A YAML-encoded `Deltas` representing the rewards and penalties returned by the rewards the `get_target_deltas` function
 Also available as `target_deltas.ssz`.
 ### `head_deltas.yaml`
 A YAML-encoded `Deltas` representing the rewards and penalties returned by the rewards the `get_head_deltas` function
 Also available as `head_deltas.ssz`.
 ### `inclusion_delay_deltas.yaml`
 A YAML-encoded `Deltas` representing the rewards and penalties returned by the rewards the `get_inclusion_delay_deltas` function
 Also available as `inclusion_delay_deltas.ssz`.
 ### `inactivity_penalty_deltas.yaml`
 A YAML-encoded `Deltas` representing the rewards and penalties returned by the rewards the `get_inactivity_penalty_deltas` function
 Also available as `inactivity_penalty_deltas.ssz`.
 ## Condition
 A handler of the `rewards` test-runner should process these cases, 
 calling the corresponding rewards deltas function for each set of deltas.
 The provided pre-state is ready to be input into each rewards deltas function.
 The provided `deltas` should match the return values of the
 deltas function. Specifically the following must hold true for each set of deltas:
 ```python
    deltas.rewards == deltas_function(state)[0]
    deltas.penalties == deltas_function(state)[1]
 ```
--- a/tests/generators/README.md
+++ b/tests/generators/README.md
@ -184,7 +184,7 @@ def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typin
 if __name__ == "__main__":
    gen_runner.run_generator("epoch_processing", [
-        create_provider('crosslinks', test_process_crosslinks, 'minimal'),
+        create_provider('final_updates', test_process_final_updates, 'minimal'),
        ...
    ])
--- a/tests/generators/bls/README.md
+++ b/tests/generators/bls/README.md
@ -1,21 +1,11 @@
 # BLS Test Generator
-Explanation of BLS12-381 type hierarchy
+The [BLS Signature APIs](../../../specs/phase0/beacon-chain.md#bls-signatures)
 The base unit is bytes48 of which only 381 bits are used
- FQ: uint381 modulo field modulus
+Information on the format of the tests can be found in the [BLS test formats documentation](../../formats/bls/README.md).
 - FQ2: (FQ, FQ)
 - G2: (FQ2, FQ2, FQ2)
 ## Resources
- [Eth2 spec](../../../specs/phase0/beacon-chain.md#bls-signatures)
+- [IETF BLS Signature Scheme](https://datatracker.ietf.org/doc/draft-irtf-cfrg-bls-signature/)
 - [Finite Field Arithmetic](http://www.springeronline.com/sgw/cda/pageitems/document/cda_downloaddocument/0,11996,0-0-45-110359-0,00.pdf)
 - Chapter 2 of [Elliptic Curve Cryptography](http://cacr.uwaterloo.ca/ecc/). Darrel Hankerson, Alfred Menezes, and Scott Vanstone
 - [Zcash BLS parameters](https://github.com/zkcrypto/pairing/tree/master/src/bls12_381)
 - [Trinity implementation](https://github.com/ethereum/trinity/blob/master/eth2/_utils/bls.py)
 ## Comments
 Compared to Zcash, Ethereum specs always requires the compressed form (c_flag / most significant bit always set).
 Also note that pubkeys and privkeys are reversed.
--- a/tests/generators/bls/main.py
+++ b/tests/generators/bls/main.py
@ -2,27 +2,28 @@
 BLS test vectors generator
 """
 from hashlib import sha256
 from typing import Tuple, Iterable, Any, Callable, Dict
 from eth_utils import (
    encode_hex,
    int_to_big_endian,
 )
 import milagro_bls_binding as milagro_bls
 from eth2spec.utils import bls
 from eth2spec.test.context import PHASE0
 from gen_base import gen_runner, gen_typing
-from py_ecc import bls
+
-from hashlib import sha256
+def to_bytes(i):
    return i.to_bytes(32, "big")
 def hash(x):
    return sha256(x).digest()
 F2Q_COEFF_LEN = 48
 G2_COMPRESSED_Z_LEN = 48
 DST = bls.G2ProofOfPossession.DST
 def int_to_hex(n: int, byte_length: int = None) -> str:
    byte_value = int_to_big_endian(n)
    if byte_length:
@ -48,11 +49,15 @@ PRIVKEYS = [
    hex_to_int('0x00000000000000000000000000000000328388aff0d4a5b7dc9205abd374e7e98f3cd9f3418edb4eafda5fb16473d216'),
 ]
 Z1_PUBKEY = b'\xc0' + b'\x00' * 47
 NO_SIGNATURE = b'\x00' * 96
 Z2_SIGNATURE = b'\xc0' + b'\x00' * 95
 def case01_sign():
    for privkey in PRIVKEYS:
        for message in MESSAGES:
-            sig = bls.G2ProofOfPossession.Sign(privkey, message)
+            sig = bls.Sign(privkey, message)
            identifier = f'{int_to_hex(privkey)}_{encode_hex(message)}'
            yield f'sign_case_{(hash(bytes(identifier, "utf-8"))[:8]).hex()}', {
                'input': {
@ -67,9 +72,17 @@ def case02_verify():
    for i, privkey in enumerate(PRIVKEYS):
        for message in MESSAGES:
            # Valid signature
-            signature = bls.G2ProofOfPossession.Sign(privkey, message)
+            signature = bls.Sign(privkey, message)
-            pubkey = bls.G2ProofOfPossession.PrivToPub(privkey)
+            pubkey = bls.SkToPk(privkey)
            assert milagro_bls.SkToPk(to_bytes(privkey)) == pubkey
            assert milagro_bls.Sign(to_bytes(privkey), message) == signature
            identifier = f'{encode_hex(pubkey)}_{encode_hex(message)}'
            assert bls.Verify(pubkey, message, signature)
            assert milagro_bls.Verify(pubkey, message, signature)
            yield f'verify_valid_case_{(hash(bytes(identifier, "utf-8"))[:8]).hex()}', {
                'input': {
                    'pubkey': encode_hex(pubkey),
@ -80,8 +93,10 @@ def case02_verify():
            }
            # Invalid signatures -- wrong pubkey
-            wrong_pubkey = bls.G2ProofOfPossession.PrivToPub(PRIVKEYS[(i + 1) % len(PRIVKEYS)])
+            wrong_pubkey = bls.SkToPk(PRIVKEYS[(i + 1) % len(PRIVKEYS)])
            identifier = f'{encode_hex(wrong_pubkey)}_{encode_hex(message)}'
            assert not bls.Verify(wrong_pubkey, message, signature)
            assert not milagro_bls.Verify(wrong_pubkey, message, signature)
            yield f'verify_wrong_pubkey_case_{(hash(bytes(identifier, "utf-8"))[:8]).hex()}', {
                'input': {
                    'pubkey': encode_hex(wrong_pubkey),
@ -94,6 +109,8 @@ def case02_verify():
            # Invalid signature -- tampered with signature
            tampered_signature = signature[:-4] + b'\xFF\xFF\xFF\xFF'
            identifier = f'{encode_hex(pubkey)}_{encode_hex(message)}'
            assert not bls.Verify(pubkey, message, tampered_signature)
            assert not milagro_bls.Verify(pubkey, message, tampered_signature)
            yield f'verify_tampered_signature_case_{(hash(bytes(identifier, "utf-8"))[:8]).hex()}', {
                'input': {
                    'pubkey': encode_hex(pubkey),
@ -103,26 +120,53 @@ def case02_verify():
                'output': False,
            }
        # Valid pubkey and signature with the point at infinity
        assert bls.Verify(Z1_PUBKEY, message, Z2_SIGNATURE)
        assert milagro_bls.Verify(Z1_PUBKEY, message, Z2_SIGNATURE)
        yield f'verify_infinity_pubkey_and_infinity_signature', {
            'input': {
                'pubkey': encode_hex(Z1_PUBKEY),
                'message': encode_hex(message),
                'signature': encode_hex(Z2_SIGNATURE),
            },
            'output': True,
        }
 def case03_aggregate():
    for message in MESSAGES:
-        sigs = [bls.G2ProofOfPossession.Sign(privkey, message) for privkey in PRIVKEYS]
+        sigs = [bls.Sign(privkey, message) for privkey in PRIVKEYS]
        yield f'aggregate_{encode_hex(message)}', {
            'input': [encode_hex(sig) for sig in sigs],
-            'output': encode_hex(bls.G2ProofOfPossession.Aggregate(sigs)),
+            'output': encode_hex(bls.Aggregate(sigs)),
        }
    # Invalid pubkeys -- len(pubkeys) == 0
    try:
        bls.Aggregate([])
    except Exception:
        pass
    else:
        raise Exception("Should have been INVALID")
    yield f'aggregate_na_pubkeys', {
        'input': [],
        'output': None,
    }
 def case04_fast_aggregate_verify():
    for i, message in enumerate(MESSAGES):
        privkeys = PRIVKEYS[:i + 1]
-        sigs = [bls.G2ProofOfPossession.Sign(privkey, message) for privkey in privkeys]
+        sigs = [bls.Sign(privkey, message) for privkey in privkeys]
-        aggregate_signature = bls.G2ProofOfPossession.Aggregate(sigs)
+        aggregate_signature = bls.Aggregate(sigs)
-        pubkeys = [bls.G2ProofOfPossession.PrivToPub(privkey) for privkey in privkeys]
+        pubkeys = [bls.SkToPk(privkey) for privkey in privkeys]
        pubkeys_serial = [encode_hex(pubkey) for pubkey in pubkeys]
        # Valid signature
        identifier = f'{pubkeys_serial}_{encode_hex(message)}'
        assert bls.FastAggregateVerify(pubkeys, message, aggregate_signature)
        assert milagro_bls.FastAggregateVerify(pubkeys, message, aggregate_signature)
        yield f'fast_aggregate_verify_valid_{(hash(bytes(identifier, "utf-8"))[:8]).hex()}', {
            'input': {
                'pubkeys': pubkeys_serial,
@ -133,9 +177,11 @@ def case04_fast_aggregate_verify():
        }
        # Invalid signature -- extra pubkey
-        pubkeys_extra = pubkeys + [bls.G2ProofOfPossession.PrivToPub(PRIVKEYS[-1])]
+        pubkeys_extra = pubkeys + [bls.SkToPk(PRIVKEYS[-1])]
        pubkeys_extra_serial = [encode_hex(pubkey) for pubkey in pubkeys_extra]
        identifier = f'{pubkeys_extra_serial}_{encode_hex(message)}'
        assert not bls.FastAggregateVerify(pubkeys_extra, message, aggregate_signature)
        assert not milagro_bls.FastAggregateVerify(pubkeys_extra, message, aggregate_signature)
        yield f'fast_aggregate_verify_extra_pubkey_{(hash(bytes(identifier, "utf-8"))[:8]).hex()}', {
            'input': {
                'pubkeys': pubkeys_extra_serial,
@ -148,6 +194,8 @@ def case04_fast_aggregate_verify():
        # Invalid signature -- tampered with signature
        tampered_signature = aggregate_signature[:-4] + b'\xff\xff\xff\xff'
        identifier = f'{pubkeys_serial}_{encode_hex(message)}'
        assert not bls.FastAggregateVerify(pubkeys, message, tampered_signature)
        assert not milagro_bls.FastAggregateVerify(pubkeys, message, tampered_signature)
        yield f'fast_aggregate_verify_tampered_signature_{(hash(bytes(identifier, "utf-8"))[:8]).hex()}', {
            'input': {
                'pubkeys': pubkeys_serial,
@ -157,37 +205,94 @@ def case04_fast_aggregate_verify():
            'output': False,
        }
    # Invalid pubkeys and signature -- len(pubkeys) == 0 and signature == Z1_SIGNATURE
    assert not bls.FastAggregateVerify([], message, Z2_SIGNATURE)
    assert not milagro_bls.FastAggregateVerify([], message, Z2_SIGNATURE)
    yield f'fast_aggregate_verify_na_pubkeys_and_infinity_signature', {
        'input': {
            'pubkeys': [],
            'message': encode_hex(message),
            'signature': encode_hex(Z2_SIGNATURE),
        },
        'output': False,
    }
    # Invalid pubkeys and signature -- len(pubkeys) == 0 and signature == 0x00...
    assert not bls.FastAggregateVerify([], message, NO_SIGNATURE)
    assert not milagro_bls.FastAggregateVerify([], message, NO_SIGNATURE)
    yield f'fast_aggregate_verify_na_pubkeys_and_na_signature', {
        'input': {
            'pubkeys': [],
            'message': encode_hex(message),
            'signature': encode_hex(NO_SIGNATURE),
        },
        'output': False,
    }
 def case05_aggregate_verify():
-    pairs = []
+    pubkeys = []
    pubkeys_serial = []
    messages = []
    messages_serial = []
    sigs = []
    for privkey, message in zip(PRIVKEYS, MESSAGES):
-        sig = bls.G2ProofOfPossession.Sign(privkey, message)
+        sig = bls.Sign(privkey, message)
-        pubkey = bls.G2ProofOfPossession.PrivToPub(privkey)
+        pubkey = bls.SkToPk(privkey)
-        pairs.append({
+        pubkeys.append(pubkey)
-            'pubkey': encode_hex(pubkey),
+        pubkeys_serial.append(encode_hex(pubkey))
-            'message': encode_hex(message),
+        messages.append(message)
-        })
+        messages_serial.append(encode_hex(message))
        sigs.append(sig)
-    aggregate_signature = bls.G2ProofOfPossession.Aggregate(sigs)
+    aggregate_signature = bls.Aggregate(sigs)
    assert bls.AggregateVerify(pubkeys, messages, aggregate_signature)
    assert milagro_bls.AggregateVerify(pubkeys, messages, aggregate_signature)
    yield f'aggregate_verify_valid', {
        'input': {
-            'pairs': pairs,
+            'pubkeys': pubkeys_serial,
            'messages': messages_serial,
            'signature': encode_hex(aggregate_signature),
        },
        'output': True,
    }
    tampered_signature = aggregate_signature[:4] + b'\xff\xff\xff\xff'
    assert not bls.AggregateVerify(pubkey, messages, tampered_signature)
    assert not milagro_bls.AggregateVerify(pubkeys, messages, tampered_signature)
    yield f'aggregate_verify_tampered_signature', {
        'input': {
-            'pairs': pairs,
+            'pubkeys': pubkeys_serial,
            'messages': messages_serial,
            'signature': encode_hex(tampered_signature),
        },
        'output': False,
    }
    # Invalid pubkeys and signature -- len(pubkeys) == 0 and signature == Z1_SIGNATURE
    assert not bls.AggregateVerify([], [], Z2_SIGNATURE)
    assert not milagro_bls.AggregateVerify([], [], Z2_SIGNATURE)
    yield f'aggregate_verify_na_pubkeys_and_infinity_signature', {
        'input': {
            'pubkeys': [],
            'messages': [],
            'signature': encode_hex(Z2_SIGNATURE),
        },
        'output': False,
    }
    # Invalid pubkeys and signature -- len(pubkeys) == 0 and signature == 0x00...
    assert not bls.AggregateVerify([], [], NO_SIGNATURE)
    assert not milagro_bls.AggregateVerify([], [], NO_SIGNATURE)
    yield f'aggregate_verify_na_pubkeys_and_na_signature', {
        'input': {
            'pubkeys': [],
            'messages': [],
            'signature': encode_hex(NO_SIGNATURE),
        },
        'output': False,
    }
 def create_provider(handler_name: str,
                    test_case_fn: Callable[[], Iterable[Tuple[str, Dict[str, Any]]]]) -> gen_typing.TestProvider:
@ -202,7 +307,7 @@ def create_provider(handler_name: str,
            print(data)
            (case_name, case_content) = data
            yield gen_typing.TestCase(
-                fork_name='phase0',
+                fork_name=PHASE0,
                runner_name='bls',
                handler_name=handler_name,
                suite_name='small',
--- a/tests/generators/bls/requirements.txt
+++ b/tests/generators/bls/requirements.txt
@ -1,3 +1,4 @@
-py_ecc==2.0.0
+py_ecc==4.0.0
 eth-utils==1.6.0
 ../../core/gen_helpers
 ../../../
--- a/tests/generators/epoch_processing/main.py
+++ b/tests/generators/epoch_processing/main.py
@ -13,6 +13,7 @@ from gen_base import gen_runner, gen_typing
 from gen_from_tests.gen import generate_from_tests
 from importlib import reload
 from eth2spec.config import config_util
 from eth2spec.test.context import PHASE0
 def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typing.TestProvider:
@ -28,7 +29,7 @@ def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typin
            runner_name='epoch_processing',
            handler_name=handler_name,
            src=tests_src,
-            fork_name='phase0'
+            fork_name=PHASE0,
        )
    return gen_typing.TestProvider(prepare=prepare_fn, make_cases=cases_fn)
--- a/tests/generators/genesis/main.py
+++ b/tests/generators/genesis/main.py
@ -1,5 +1,6 @@
 from typing import Iterable
 from eth2spec.test.context import PHASE0
 from eth2spec.test.genesis import test_initialization, test_validity
 from gen_base import gen_runner, gen_typing
@ -21,7 +22,7 @@ def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typin
            runner_name='genesis',
            handler_name=handler_name,
            src=tests_src,
-            fork_name='phase0'
+            fork_name=PHASE0,
        )
    return gen_typing.TestProvider(prepare=prepare_fn, make_cases=cases_fn)
--- a/tests/generators/operations/main.py
+++ b/tests/generators/operations/main.py
@ -15,6 +15,7 @@ from importlib import reload
 from eth2spec.config import config_util
 from eth2spec.phase0 import spec as spec_phase0
 from eth2spec.phase1 import spec as spec_phase1
 from eth2spec.test.context import PHASE0
 def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typing.TestProvider:
@ -30,7 +31,7 @@ def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typin
            runner_name='operations',
            handler_name=handler_name,
            src=tests_src,
-            fork_name='phase0'
+            fork_name=PHASE0,
        )
    return gen_typing.TestProvider(prepare=prepare_fn, make_cases=cases_fn)
--- a/tests/generators/rewards/README.md
+++ b/tests/generators/rewards/README.md
@ -0,0 +1,8 @@
 # Rewards
 Rewards covers the sub-functions of `process_rewards_and_penalties` for granular testing of components of the rewards function.
 A rewards test-runner can consume these sub-transition test-suites,
 and handle different kinds of epoch sub-transitions by processing the cases using the specified test handler.
 Information on the format of the tests can be found in the [rewards test formats documentation](../../formats/rewards/README.md).
--- a/tests/generators/rewards/main.py
+++ b/tests/generators/rewards/main.py
@ -0,0 +1,44 @@
 from typing import Iterable
 from eth2spec.phase0 import spec as spec_phase0
 from eth2spec.phase1 import spec as spec_phase1
 from eth2spec.test.phase_0.rewards import (
    test_basic,
    test_leak,
    test_random,
 )
 from gen_base import gen_runner, gen_typing
 from gen_from_tests.gen import generate_from_tests
 from importlib import reload
 from eth2spec.config import config_util
 from eth2spec.test.context import PHASE0
 def create_provider(tests_src, config_name: str) -> gen_typing.TestProvider:
    def prepare_fn(configs_path: str) -> str:
        config_util.prepare_config(configs_path, config_name)
        reload(spec_phase0)
        reload(spec_phase1)
        return config_name
    def cases_fn() -> Iterable[gen_typing.TestCase]:
        return generate_from_tests(
            runner_name='rewards',
            handler_name='core',
            src=tests_src,
            fork_name=PHASE0,
        )
    return gen_typing.TestProvider(prepare=prepare_fn, make_cases=cases_fn)
 if __name__ == "__main__":
    gen_runner.run_generator("rewards", [
        create_provider(test_basic, 'minimal'),
        create_provider(test_basic, 'mainnet'),
        create_provider(test_leak, 'minimal'),
        create_provider(test_leak, 'mainnet'),
        create_provider(test_random, 'minimal'),
        create_provider(test_random, 'mainnet'),
    ])
--- a/tests/generators/rewards/requirements.txt
+++ b/tests/generators/rewards/requirements.txt
@ -0,0 +1,2 @@
 ../../core/gen_helpers
 ../../../
--- a/tests/generators/sanity/main.py
+++ b/tests/generators/sanity/main.py
@ -4,7 +4,8 @@ from importlib import reload
 from gen_base import gen_runner, gen_typing
 from gen_from_tests.gen import generate_from_tests
-from eth2spec.test.sanity import test_blocks, test_slots
+from eth2spec.test.context import PHASE0
 from eth2spec.test.phase_0.sanity import test_blocks, test_slots
 from eth2spec.config import config_util
 from eth2spec.phase0 import spec as spec_phase0
 from eth2spec.phase1 import spec as spec_phase1
@ -23,7 +24,7 @@ def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typin
            runner_name='sanity',
            handler_name=handler_name,
            src=tests_src,
-            fork_name='phase0'
+            fork_name=PHASE0,
        )
    return gen_typing.TestProvider(prepare=prepare_fn, make_cases=cases_fn)
--- a/tests/generators/shuffling/main.py
+++ b/tests/generators/shuffling/main.py
@ -6,6 +6,7 @@ from gen_base import gen_runner, gen_typing
 from eth2spec.config import config_util
 from eth2spec.phase0 import spec as spec
 from eth2spec.test.context import PHASE0
 def shuffling_case_fn(seed, count):
@ -37,7 +38,7 @@ def create_provider(config_name: str) -> gen_typing.TestProvider:
    def cases_fn() -> Iterable[gen_typing.TestCase]:
        for (case_name, case_fn) in shuffling_test_cases():
            yield gen_typing.TestCase(
-                fork_name='phase0',
+                fork_name=PHASE0,
                runner_name='shuffling',
                handler_name='core',
                suite_name='shuffle',
--- a/tests/generators/ssz_generic/main.py
+++ b/tests/generators/ssz_generic/main.py
@ -6,6 +6,7 @@ import ssz_bitvector
 import ssz_boolean
 import ssz_uints
 import ssz_container
 from eth2spec.test.context import PHASE0
 def create_provider(handler_name: str, suite_name: str, case_maker) -> gen_typing.TestProvider:
@ -16,7 +17,7 @@ def create_provider(handler_name: str, suite_name: str, case_maker) -> gen_typin
    def cases_fn() -> Iterable[gen_typing.TestCase]:
        for (case_name, case_fn) in case_maker():
            yield gen_typing.TestCase(
-                fork_name='phase0',
+                fork_name=PHASE0,
                runner_name='ssz_generic',
                handler_name=handler_name,
                suite_name=suite_name,
--- a/tests/generators/ssz_static/main.py
+++ b/tests/generators/ssz_static/main.py
@ -8,6 +8,7 @@ from gen_base import gen_runner, gen_typing
 from eth2spec.debug import random_value, encode
 from eth2spec.config import config_util
 from eth2spec.phase0 import spec
 from eth2spec.test.context import PHASE0
 from eth2spec.utils.ssz.ssz_typing import Container
 from eth2spec.utils.ssz.ssz_impl import (
    hash_tree_root,
@ -44,7 +45,7 @@ def ssz_static_cases(seed: int, name, ssz_type, mode: random_value.Randomization
    for i in range(count):
        yield gen_typing.TestCase(
-            fork_name='phase0',
+            fork_name=PHASE0,
            runner_name='ssz_static',
            handler_name=name,
            suite_name=f"ssz_{random_mode_name}{'_chaos' if chaos else ''}",