Merge branch 'dev' into vbuterin-patch-3

LICENSE

@@ -0,0 +1,116 @@
+CC0 1.0 Universal
+
+Statement of Purpose
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specs/core/0_beacon-chain.md

@@ -61,9 +61,9 @@
         - [`is_active_validator`](#is_active_validator)
         - [`get_active_validator_indices`](#get_active_validator_indices)
         - [`get_balance`](#get_balance)
-        - [`set_balance`](#set_balance)
+            - [`set_balance`](#set_balance)
-        - [`increase_balance`](#increase_balance)
+            - [`increase_balance`](#increase_balance)
-        - [`decrease_balance`](#decrease_balance)
+            - [`decrease_balance`](#decrease_balance)
         - [`get_permuted_index`](#get_permuted_index)
         - [`split`](#split)
         - [`get_epoch_committee_count`](#get_epoch_committee_count)
@@ -119,7 +119,7 @@
             - [Helper functions](#helper-functions-1)
             - [Justification](#justification)
             - [Crosslinks](#crosslinks)
-            - [Eth1 data](#eth1-data-1)
+            - [Eth1 data](#eth1-data)
             - [Rewards and penalties](#rewards-and-penalties)
                 - [Justification and finalization](#justification-and-finalization)
                 - [Crosslinks](#crosslinks-1)
@@ -132,7 +132,7 @@
         - [Per-block processing](#per-block-processing)
             - [Block header](#block-header)
             - [RANDAO](#randao)
-            - [Eth1 data](#eth1-data)
+            - [Eth1 data](#eth1-data-1)
             - [Transactions](#transactions)
                 - [Proposer slashings](#proposer-slashings)
                 - [Attester slashings](#attester-slashings)
@@ -294,9 +294,9 @@ The types are defined topologically to aid in facilitating an executable version
 ```python
 {
     # Previous fork version
-    'previous_version': 'uint64',
+    'previous_version': 'bytes4',
     # Current fork version
-    'current_version': 'uint64',
+    'current_version': 'bytes4',
     # Fork epoch number
     'epoch': 'uint64',
 }
@@ -339,22 +339,19 @@ The types are defined topologically to aid in facilitating an executable version
 
 ```python
 {
-    # Slot number
+    # LMD GHOST vote
     'slot': 'uint64',
-    # Shard number
-    'shard': 'uint64',
-    # Root of the signed beacon block
     'beacon_block_root': 'bytes32',
-    # Root of the ancestor at the epoch boundary
+
-    'epoch_boundary_root': 'bytes32',
+    # FFG vote
-    # Data from the shard since the last attestation
+    'source_epoch': 'uint64',
+    'source_root': 'bytes32',
+    'target_root': 'bytes32',
+
+    # Crosslink vote
+    'shard': 'uint64',
+    'previous_crosslink': Crosslink,
     'crosslink_data_root': 'bytes32',
-    # Last crosslink
-    'latest_crosslink': Crosslink,
-    # Last justified epoch in the beacon state
-    'justified_epoch': 'uint64',
-    # Hash of the last justified beacon block
-    'justified_block_root': 'bytes32',
 }
 ```
 
@@ -617,9 +614,12 @@ The types are defined topologically to aid in facilitating an executable version
     'previous_epoch_attestations': [PendingAttestation],
     'current_epoch_attestations': [PendingAttestation],
     'previous_justified_epoch': 'uint64',
-    'justified_epoch': 'uint64',
+    'current_justified_epoch': 'uint64',
+    'previous_justified_root': 'bytes32',
+    'current_justified_root': 'bytes32',
     'justification_bitfield': 'uint64',
     'finalized_epoch': 'uint64',
+    'finalized_root': 'bytes32',
 
     # Recent state
     'latest_crosslinks': [Crosslink, SHARD_COUNT],
@@ -1052,7 +1052,7 @@ def get_beacon_proposer_index(state: BeaconState,
     assert previous_epoch <= epoch <= next_epoch
 
     first_committee, _ = get_crosslink_committees_at_slot(state, slot, registry_change)[0]
-    return first_committee[slot % len(first_committee)]
+    return first_committee[epoch % len(first_committee)]
 ```
 
 ### `verify_merkle_branch`
@@ -1143,7 +1143,7 @@ def get_total_balance(state: BeaconState, validators: List[ValidatorIndex]) -> G
 
 ```python
 def get_fork_version(fork: Fork,
-                     epoch: Epoch) -> int:
+                     epoch: Epoch) -> bytes:
     """
     Return the fork version of the given ``epoch``.
     """
@@ -1162,8 +1162,7 @@ def get_domain(fork: Fork,
     """
     Get the domain number that represents the fork meta and signature domain.
     """
-    fork_version = get_fork_version(fork, epoch)
+    return bytes_to_int(get_fork_version(fork, epoch) + int_to_bytes4(domain_type))
-    return fork_version * 2**32 + domain_type
 ```
 
 ### `get_bitfield_bit`
@@ -1260,8 +1259,8 @@ def is_surround_vote(attestation_data_1: AttestationData,
     """
     Check if ``attestation_data_1`` surrounds ``attestation_data_2``.
     """
-    source_epoch_1 = attestation_data_1.justified_epoch
+    source_epoch_1 = attestation_data_1.source_epoch
-    source_epoch_2 = attestation_data_2.justified_epoch
+    source_epoch_2 = attestation_data_2.source_epoch
     target_epoch_1 = slot_to_epoch(attestation_data_1.slot)
     target_epoch_2 = slot_to_epoch(attestation_data_2.slot)
 
@@ -1342,27 +1341,26 @@ def process_deposit(state: BeaconState, deposit: Deposit) -> None:
     # object, and we need to be able to skip over it
     state.deposit_index += 1
 
-    # Verify the proof of possession
-    proof_is_valid = bls_verify(
-        pubkey=deposit_input.pubkey,
-        message_hash=signed_root(deposit_input),
-        signature=deposit_input.proof_of_possession,
-        domain=get_domain(
-            state.fork,
-            get_current_epoch(state),
-            DOMAIN_DEPOSIT,
-        )
-    )
-    
-    if not proof_is_valid:
-        return
-
     validator_pubkeys = [v.pubkey for v in state.validator_registry]
     pubkey = deposit_input.pubkey
     amount = deposit.deposit_data.amount
     withdrawal_credentials = deposit_input.withdrawal_credentials
 
     if pubkey not in validator_pubkeys:
+        # Verify the proof of possession
+        proof_is_valid = bls_verify(
+            pubkey=deposit_input.pubkey,
+            message_hash=signed_root(deposit_input),
+            signature=deposit_input.proof_of_possession,
+            domain=get_domain(
+                state.fork,
+                get_current_epoch(state),
+                DOMAIN_DEPOSIT,
+            )
+        )
+        if not proof_is_valid:
+            return
+
         # Add new validator
         validator = Validator(
             pubkey=pubkey,
@@ -1382,7 +1380,6 @@ def process_deposit(state: BeaconState, deposit: Deposit) -> None:
     else:
         # Increase balance by deposit amount
         index = validator_pubkeys.index(pubkey)
-        assert state.validator_registry[index].withdrawal_credentials == withdrawal_credentials
         increase_balance(state, index, amount)
 ```
 
@@ -1560,8 +1557,8 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
         slot=GENESIS_SLOT,
         genesis_time=genesis_time,
         fork=Fork(
-            previous_version=GENESIS_FORK_VERSION,
+            previous_version=int_to_bytes4(GENESIS_FORK_VERSION),
-            current_version=GENESIS_FORK_VERSION,
+            current_version=int_to_bytes4(GENESIS_FORK_VERSION),
             epoch=GENESIS_EPOCH,
         ),
 
@@ -1583,9 +1580,12 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
         previous_epoch_attestations=[],
         current_epoch_attestations=[],
         previous_justified_epoch=GENESIS_EPOCH,
-        justified_epoch=GENESIS_EPOCH,
+        current_justified_epoch=GENESIS_EPOCH,
+        previous_justified_root=ZERO_HASH,
+        current_justified_root=ZERO_HASH,
         justification_bitfield=0,
         finalized_epoch=GENESIS_EPOCH,
+        finalized_root=ZERO_HASH,
 
         # Recent state
         latest_crosslinks=[Crosslink(epoch=GENESIS_EPOCH, crosslink_data_root=ZERO_HASH) for _ in range(SHARD_COUNT)],
@@ -1762,7 +1762,7 @@ def get_attesting_indices(state: BeaconState, attestations: List[PendingAttestat
 ```
 
 ```python
-def get_attesting_balance(state: BeaconState, attestations: List[PendingAttestation]) -> List[ValidatorIndex]:
+def get_attesting_balance(state: BeaconState, attestations: List[PendingAttestation]) -> Gwei:
     return get_total_balance(state, get_attesting_indices(state, attestations))
 ```
 
@@ -1770,7 +1770,7 @@ def get_attesting_balance(state: BeaconState, attestations: List[PendingAttestat
 def get_current_epoch_boundary_attestations(state: BeaconState) -> List[PendingAttestation]:
     return [
         a for a in state.current_epoch_attestations
-        if a.data.epoch_boundary_root == get_block_root(state, get_epoch_start_slot(get_current_epoch(state)))
+        if a.data.target_root == get_block_root(state, get_epoch_start_slot(get_current_epoch(state)))
     ]
 ```
 
@@ -1778,7 +1778,7 @@ def get_current_epoch_boundary_attestations(state: BeaconState) -> List[PendingA
 def get_previous_epoch_boundary_attestations(state: BeaconState) -> List[PendingAttestation]:
     return [
         a for a in state.previous_epoch_attestations
-        if a.data.epoch_boundary_root == get_block_root(state, get_epoch_start_slot(get_previous_epoch(state)))
+        if a.data.target_root == get_block_root(state, get_epoch_start_slot(get_previous_epoch(state)))
     ]
 ```
 
@@ -1796,7 +1796,7 @@ def get_previous_epoch_matching_head_attestations(state: BeaconState) -> List[Pe
 def get_winning_root_and_participants(state: BeaconState, shard: Shard) -> Tuple[Bytes32, List[ValidatorIndex]]:
     all_attestations = state.current_epoch_attestations + state.previous_epoch_attestations
     valid_attestations = [
-        a for a in all_attestations if a.data.latest_crosslink == state.latest_crosslinks[shard]
+        a for a in all_attestations if a.data.previous_crosslink == state.latest_crosslinks[shard]
     ]
     all_roots = [a.data.crosslink_data_root for a in valid_attestations]
 
@@ -1839,7 +1839,9 @@ Run the following function:
 
 ```python
 def update_justification_and_finalization(state: BeaconState) -> None:
-    new_justified_epoch = state.justified_epoch
+    new_justified_epoch = state.current_justified_epoch
+    new_finalized_epoch = state.finalized_epoch
+
     # Rotate the justification bitfield up one epoch to make room for the current epoch
     state.justification_bitfield <<= 1
     # If the previous epoch gets justified, fill the second last bit
@@ -1858,20 +1860,26 @@ def update_justification_and_finalization(state: BeaconState) -> None:
     current_epoch = get_current_epoch(state)
     # The 2nd/3rd/4th most recent epochs are all justified, the 2nd using the 4th as source
     if (bitfield >> 1) % 8 == 0b111 and state.previous_justified_epoch == current_epoch - 3:
-        state.finalized_epoch = state.previous_justified_epoch
+        new_finalized_epoch = state.previous_justified_epoch
     # The 2nd/3rd most recent epochs are both justified, the 2nd using the 3rd as source
     if (bitfield >> 1) % 4 == 0b11 and state.previous_justified_epoch == current_epoch - 2:
-        state.finalized_epoch = state.previous_justified_epoch
+        new_finalized_epoch = state.previous_justified_epoch
     # The 1st/2nd/3rd most recent epochs are all justified, the 1st using the 3rd as source
-    if (bitfield >> 0) % 8 == 0b111 and state.justified_epoch == current_epoch - 2:
+    if (bitfield >> 0) % 8 == 0b111 and state.current_justified_epoch == current_epoch - 2:
-        state.finalized_epoch = state.justified_epoch
+        new_finalized_epoch = state.current_justified_epoch
     # The 1st/2nd most recent epochs are both justified, the 1st using the 2nd as source
-    if (bitfield >> 0) % 4 == 0b11 and state.justified_epoch == current_epoch - 1:
+    if (bitfield >> 0) % 4 == 0b11 and state.current_justified_epoch == current_epoch - 1:
-        state.finalized_epoch = state.justified_epoch
+        new_finalized_epoch = state.current_justified_epoch
 
-    # Rotate justified epochs
+    # Update state jusification/finality fields
-    state.previous_justified_epoch = state.justified_epoch
+    state.previous_justified_epoch = state.current_justified_epoch
-    state.justified_epoch = new_justified_epoch
+    state.previous_justified_root = state.current_justified_root
+    if new_justified_epoch != state.current_justified_epoch:
+        state.current_justified_epoch = new_justified_epoch
+        state.current_justified_root = get_block_root(state, get_epoch_start_slot(new_justified_epoch))
+    if new_finalized_epoch != state.finalized_epoch:
+        state.finalized_epoch = new_finalized_epoch
+        state.finalized_root = get_block_root(state, get_epoch_start_slot(new_finalized_epoch))
 ```
 
 #### Crosslinks
@@ -2346,8 +2354,8 @@ def process_proposer_slashing(state: BeaconState,
     Note that this function mutates ``state``.
     """
     proposer = state.validator_registry[proposer_slashing.proposer_index]
-    # Verify that the slot is the same
+    # Verify that the epoch is the same
-    assert proposer_slashing.header_1.slot == proposer_slashing.header_2.slot
+    assert slot_to_epoch(proposer_slashing.header_1.slot) == slot_to_epoch(proposer_slashing.header_2.slot)
     # But the headers are different
     assert proposer_slashing.header_1 != proposer_slashing.header_2
     # Proposer is not yet slashed
@@ -2415,20 +2423,19 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     assert state.slot <= attestation.data.slot + SLOTS_PER_EPOCH
     # Can't submit attestations too quickly
     assert attestation.data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot
-    # Verify that the justified epoch is correct, case 1: current epoch attestations
+    # Verify that the justified epoch and root is correct
     if slot_to_epoch(attestation.data.slot) >= get_current_epoch(state):
-        assert attestation.data.justified_epoch == state.justified_epoch
+        # Case 1: current epoch attestations
-    # Case 2: previous epoch attestations
+        assert attestation.data.source_epoch == state.current_justified_epoch
+        assert attestation.data.source_root == state.current_justified_root
     else:
-        assert attestation.data.justified_epoch == state.previous_justified_epoch
+        # Case 2: previous epoch attestations
-    # Check that the justified block root is correct
+        assert attestation.data.source_epoch == state.previous_justified_epoch
-    assert attestation.data.justified_block_root == get_block_root(
+        assert attestation.data.source_root == state.previous_justified_root
-        state, get_epoch_start_slot(attestation.data.justified_epoch)
-    )
     # Check that the crosslink data is valid
     acceptable_crosslink_data = {
         # Case 1: Latest crosslink matches the one in the state
-        attestation.data.latest_crosslink,
+        attestation.data.previous_crosslink,
         # Case 2: State has already been updated, state's latest crosslink matches the crosslink
         # the attestation is trying to create
         Crosslink(

specs/core/1_shard-data-chains.md

@@ -556,7 +556,7 @@ def verify_custody_subkey_reveal(pubkey: bytes48,
 ```python
 def verify_signed_challenge_message(message: Any, pubkey: bytes48) -> bool:
     return bls_verify(
-        message_hash=signed_root(message, 'signature'),
+        message_hash=signed_root(message),
         pubkey=pubkey,
         signature=message.signature,
         domain=get_domain(state, get_current_epoch(state), DOMAIN_CUSTODY_INTERACTIVE)
@@ -607,8 +607,8 @@ Verify that `len(block.body.branch_challenges) <= MAX_BRANCH_CHALLENGES`.
 For each `challenge` in `block.body.branch_challenges`, run:
 
 ```python
-def process_branch_challenge(challenge: BranchChallenge,
+def process_branch_challenge(state: BeaconState,
-                             state: BeaconState):
+                             challenge: BranchChallenge) -> None:
     # Check that it's not too late to challenge
     assert slot_to_epoch(challenge.attestation.data.slot) >= get_current_epoch(state) - MAX_BRANCH_CHALLENGE_DELAY
     assert state.validator_registry[responder_index].exit_epoch >= get_current_epoch(state) - MAX_BRANCH_CHALLENGE_DELAY
@@ -643,8 +643,8 @@ Verify that `len(block.body.branch_responses) <= MAX_BRANCH_RESPONSES`.
 For each `response` in `block.body.branch_responses`, if `response.responding_to_custody_challenge == False`, run:
 
 ```python
-def process_branch_exploration_response(response: BranchResponse,
+def process_branch_exploration_response(state: BeaconState,
-                                        state: BeaconState):
+                                        response: BranchResponse) -> None:
     challenge = get_branch_challenge_record_by_id(response.challenge_id)
     assert verify_merkle_branch(
         leaf=response.data,
@@ -664,8 +664,8 @@ def process_branch_exploration_response(response: BranchResponse,
 If `response.responding_to_custody_challenge == True`, run:
 
 ```python
-def process_branch_custody_response(response: BranchResponse,
+def process_branch_custody_response(state: BeaconState,
-                                    state: BeaconState):
+                                    response: BranchResponse) -> None:
     challenge = get_custody_challenge_record_by_id(response.challenge_id)
     responder = state.validator_registry[challenge.responder_index]
     # Verify we're not too late
@@ -718,8 +718,8 @@ Verify that `len(block.body.interactive_custody_challenge_initiations) <= MAX_IN
 For each `initiation` in `block.body.interactive_custody_challenge_initiations`, use the following function to process it:
 
 ```python
-def process_initiation(initiation: InteractiveCustodyChallengeInitiation,
+def process_initiation(state: BeaconState,
-                       state: BeaconState):
+                       initiation: InteractiveCustodyChallengeInitiation) -> None:
     challenger = state.validator_registry[initiation.challenger_index]
     responder = state.validator_registry[initiation.responder_index]
     # Verify the signature
@@ -771,8 +771,8 @@ Verify that `len(block.body.interactive_custody_challenge_responses) <= MAX_INTE
 For each `response` in `block.body.interactive_custody_challenge_responses`, use the following function to process it:
 
 ```python
-def process_response(response: InteractiveCustodyChallengeResponse,
+def process_response(state: BeaconState,
-                     state: State):
+                     response: InteractiveCustodyChallengeResponse) -> None:
     challenge = get_custody_challenge_record_by_id(state, response.challenge_id)
     responder = state.validator_registry[challenge.responder_index]
     # Check that the right number of hashes was provided
@@ -804,8 +804,8 @@ Verify that `len(block.body.interactive_custody_challenge_continuations) <= MAX_
 For each `continuation` in `block.body.interactive_custody_challenge_continuations`, use the following function to process it:
 
 ```python
-def process_continuation(continuation: InteractiveCustodyChallengeContinuation,
+def process_continuation(state: BeaconState,
-                         state: State):
+                         continuation: InteractiveCustodyChallengeContinuation) -> None:
     challenge = get_custody_challenge_record_by_id(state, continuation.challenge_id)
     challenger = state.validator_registry[challenge.challenger_index]
     responder = state.validator_registry[challenge.responder_index]

specs/validator/0_beacon-chain-validator.md

@@ -40,11 +40,11 @@ __NOTICE__: This document is a work-in-progress for researchers and implementers
                 - [Slot](#slot-1)
                 - [Shard](#shard)
                 - [Beacon block root](#beacon-block-root)
-                - [Epoch boundary root](#epoch-boundary-root)
+                - [Target root](#target-root)
                 - [Crosslink data root](#crosslink-data-root)
                 - [Latest crosslink](#latest-crosslink)
-                - [Justified epoch](#justified-epoch)
+                - [Source epoch](#source-epoch)
-                - [Justified block root](#justified-block-root)
+                - [Source root](#source-root)
             - [Construct attestation](#construct-attestation)
                 - [Data](#data)
                 - [Aggregation bitfield](#aggregation-bitfield)
@@ -101,8 +101,7 @@ In phase 0, all incoming validator deposits originate from the Ethereum 1.0 PoW
 To submit a deposit:
 
 * Pack the validator's [initialization parameters](#initialization) into `deposit_input`, a [`DepositInput`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#depositinput) SSZ object.
-* Set `deposit_input.proof_of_possession = EMPTY_SIGNATURE`.
+* Let `proof_of_possession` be the result of `bls_sign` of the `signed_root(deposit_input)` with `domain=DOMAIN_DEPOSIT`.
-* Let `proof_of_possession` be the result of `bls_sign` of the `hash_tree_root(deposit_input)` with `domain=DOMAIN_DEPOSIT`.
 * Set `deposit_input.proof_of_possession = proof_of_possession`.
 * Let `amount` be the amount in Gwei to be deposited by the validator where `MIN_DEPOSIT_AMOUNT <= amount <= MAX_DEPOSIT_AMOUNT`.
 * Send a transaction on the Ethereum 1.0 chain to `DEPOSIT_CONTRACT_ADDRESS` executing `deposit` along with `serialize(deposit_input)` as the singular `bytes` input along with a deposit `amount` in Gwei.
@@ -121,11 +120,12 @@ Once a validator has been processed and added to the beacon state's `validator_r
 
 In normal operation, the validator is quickly activated at which point the validator is added to the shuffling and begins validation after an additional `ACTIVATION_EXIT_DELAY` epochs (25.6 minutes).
 
-The function [`is_active_validator`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#is_active_validator) can be used to check if a validator is active during a given epoch. Usage is as follows:
+The function [`is_active_validator`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#is_active_validator) can be used to check if a validator is active during a given shuffling epoch. Note that the `BeaconState` contains a field `current_shuffling_epoch` which dictates from which epoch the current active validators are taken. Usage is as follows:
 
 ```python
+shuffling_epoch = state.current_shuffling_epoch
 validator = state.validator_registry[validator_index]
-is_active = is_active_validator(validator, epoch)
+is_active = is_active_validator(validator, shuffling_epoch)
 ```
 
 Once a validator is activated, the validator is assigned [responsibilities](#beacon-chain-responsibilities) until exited.
@@ -138,7 +138,7 @@ A validator has two primary responsibilities to the beacon chain -- [proposing b
 
 ### Block proposal
 
-A validator is expected to propose a [`BeaconBlock`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#beaconblock) at the beginning of any slot during which `get_beacon_proposer_index(state, slot)` returns the validator's `validator_index`. To propose, the validator selects the `BeaconBlock`, `parent`, that in their view of the fork choice is the head of the chain during `slot`. The validator is to create, sign, and broadcast a `block` that is a child of `parent` and that executes a valid [beacon chain state transition](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#beacon-chain-state-transition-function).
+A validator is expected to propose a [`BeaconBlock`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#beaconblock) at the beginning of any slot during which `get_beacon_proposer_index(state, slot)` returns the validator's `validator_index`. To propose, the validator selects the `BeaconBlock`, `parent`, that in their view of the fork choice is the head of the chain during `slot - 1`. The validator is to create, sign, and broadcast a `block` that is a child of `parent` and that executes a valid [beacon chain state transition](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#beacon-chain-state-transition-function).
 
 There is one proposer per slot, so if there are N active validators any individual validator will on average be assigned to propose once per N slots (eg. at 312500 validators = 10 million ETH, that's once per ~3 weeks).
 
@@ -152,13 +152,13 @@ _Note:_ there might be "skipped" slots between the `parent` and `block`. These s
 
 ##### Parent root
 
-Set `block.parent_root = hash_tree_root(parent)`.
+Set `block.previous_block_root = hash_tree_root(parent)`.
 
 ##### State root
 
 Set `block.state_root = hash_tree_root(state)` of the resulting `state` of the `parent -> block` state transition.
 
-_Note_: To calculate `state_root`, the validator should first run the state transition function on an unsigned `block` containing a stub for the `state_root`. It is useful to be able to run a state transition function that does _not_ validate signatures for this purpose.
+_Note_: To calculate `state_root`, the validator should first run the state transition function on an unsigned `block` containing a stub for the `state_root`. It is useful to be able to run a state transition function that does _not_ validate signatures or state root for this purpose.
 
 ##### Randao reveal
 
@@ -166,8 +166,8 @@ Set `block.randao_reveal = epoch_signature` where `epoch_signature` is defined a
 
 ```python
 epoch_signature = bls_sign(
-    privkey=validator.privkey,  # privkey store locally, not in state
+    privkey=validator.privkey,  # privkey stored locally, not in state
-    message_hash=int_to_bytes32(slot_to_epoch(block.slot)),
+    message_hash=hash_tree_root(slot_to_epoch(block.slot)),
     domain=get_domain(
         fork=fork,  # `fork` is the fork object at the slot `block.slot`
         epoch=slot_to_epoch(block.slot),
@@ -194,23 +194,16 @@ epoch_signature = bls_sign(
 
 ##### Signature
 
-Set `block.signature = signed_proposal_data` where `signed_proposal_data` is defined as:
+Set `block.signature = block_signature` where `block_signature` is defined as:
 
 ```python
-proposal_data = ProposalSignedData(
+block_signature = bls_sign(
-    slot=slot,
-    shard=BEACON_CHAIN_SHARD_NUMBER,
-    block_root=hash_tree_root(block),  # where `block.sigature == EMPTY_SIGNATURE
-)
-proposal_root = hash_tree_root(proposal_data)
-
-signed_proposal_data = bls_sign(
     privkey=validator.privkey,  # privkey store locally, not in state
-    message_hash=proposal_root,
+    message_hash=signed_root(block),
     domain=get_domain(
         fork=fork,  # `fork` is the fork object at the slot `block.slot`
         epoch=slot_to_epoch(block.slot),
-        domain_type=DOMAIN_PROPOSAL,
+        domain_type=DOMAIN_BEACON_BLOCK,
     )
 )
 ```
@@ -227,12 +220,14 @@ Up to `MAX_ATTESTER_SLASHINGS` [`AttesterSlashing`](https://github.com/ethereum/
 
 ##### Attestations
 
-Up to `MAX_ATTESTATIONS` aggregate attestations can be included in the `block`. The attestations added must satisfy the verification conditions found in [attestation processing](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#attestations-1). To maximize profit, the validator should attempt to create aggregate attestations that include singular attestations from the largest number of validators whose signatures from the same epoch have not previously been added on chain.
+Up to `MAX_ATTESTATIONS` aggregate attestations can be included in the `block`. The attestations added must satisfy the verification conditions found in [attestation processing](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#attestations-1). To maximize profit, the validator should attempt to gather aggregate attestations that include singular attestations from the largest number of validators whose signatures from the same epoch have not previously been added on chain.
 
 ##### Deposits
 
 Up to `MAX_DEPOSITS` [`Deposit`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#deposit) objects can be included in the `block`. These deposits are constructed from the `Deposit` logs from the [Eth1.0 deposit contract](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#ethereum-10-deposit-contract) and must be processed in sequential order. The deposits included in the `block` must satisfy the verification conditions found in [deposits processing](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#deposits-1).
 
+The `proof` for each deposit must be constructed against the deposit root contained in `state.latest_eth1_data` rather than the deposit root at the time the deposit was initially logged from the 1.0 chain. This entails storing a full deposit merkle tree locally and computing updated proofs against the `latest_eth1_data.deposit_root` as needed. See [`minimal_merkle.py`](https://github.com/ethereum/research/blob/master/spec_pythonizer/utils/merkle_minimal.py) for a sample implementation.
+
 ##### Voluntary exits
 
 Up to `MAX_VOLUNTARY_EXITS` [`VoluntaryExit`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#voluntaryexit) objects can be included in the `block`. The exits must satisfy the verification conditions found in [exits processing](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#exits-1).
@@ -247,9 +242,12 @@ A validator should create and broadcast the attestation halfway through the `slo
 
 First the validator should construct `attestation_data`, an [`AttestationData`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#attestationdata) object based upon the state at the assigned slot.
 
+* Let `head_block` be the result of running the fork choice during the assigned slot.
+* Let `head_state` be the state of `head_block` processed through any empty slots up to the assigned slot.
+
 ##### Slot
 
-Set `attestation_data.slot = slot` where `slot` is the current slot of which the validator is a member of a committee.
+Set `attestation_data.slot = head_state.slot`.
 
 ##### Shard
 
@@ -257,15 +255,15 @@ Set `attestation_data.shard = shard` where `shard` is the shard associated with
 
 ##### Beacon block root
 
-Set `attestation_data.beacon_block_root = hash_tree_root(head)` where `head` is the validator's view of the `head` block of the beacon chain during `slot`.
+Set `attestation_data.beacon_block_root = hash_tree_root(head_block)`.
 
-##### Epoch boundary root
+##### Target root
 
-Set `attestation_data.epoch_boundary_root = hash_tree_root(epoch_boundary)` where `epoch_boundary` is the block at the most recent epoch boundary in the chain defined by `head` -- i.e. the `BeaconBlock` where `block.slot == get_epoch_start_slot(slot_to_epoch(head.slot))`.
+Set `attestation_data.target_root = hash_tree_root(epoch_boundary)` where `epoch_boundary` is the block at the most recent epoch boundary.
 
 _Note:_ This can be looked up in the state using:
-* Let `epoch_start_slot = get_epoch_start_slot(slot_to_epoch(head.slot))`.
+* Let `epoch_start_slot = get_epoch_start_slot(get_current_epoch(head_state))`.
-* Set `epoch_boundary_root = hash_tree_root(head) if epoch_start_slot == head.slot else get_block_root(state, epoch_start_slot)`.
+* Set `epoch_boundary = head if epoch_start_slot == head_state.slot else get_block_root(state, epoch_start_slot)`.
 
 ##### Crosslink data root
 
@@ -275,17 +273,15 @@ _Note:_ This is a stub for phase 0.
 
 ##### Latest crosslink
 
-Set `attestation_data.latest_crosslink = state.latest_crosslinks[shard]` where `state` is the beacon state at `head` and `shard` is the validator's assigned shard.
+Set `attestation_data.previous_crosslink = head_state.latest_crosslinks[shard]`.
 
-##### Justified epoch
+##### Source epoch
 
-Set `attestation_data.justified_epoch = state.justified_epoch` where `state` is the beacon state at `head`.
+Set `attestation_data.source_epoch = head_state.justified_epoch`.
 
-##### Justified block root
+##### Source root
 
-Set `attestation_data.justified_block_root = hash_tree_root(justified_block)` where `justified_block` is the block at the slot `get_epoch_start_slot(state.justified_epoch)` in the chain defined by `head`.
+Set `attestation_data.source_root = head_state.current_justified_root`.
-
-_Note:_ This can be looked up in the state using `get_block_root(state, get_epoch_start_slot(state.justified_epoch))`.
 
 #### Construct attestation
 
@@ -320,11 +316,11 @@ attestation_data_and_custody_bit = AttestationDataAndCustodyBit(
     data=attestation.data,
     custody_bit=0b0,
 )
-attestation_message_to_sign = hash_tree_root(attestation_data_and_custody_bit)
+attestation_message = hash_tree_root(attestation_data_and_custody_bit)
 
 signed_attestation_data = bls_sign(
-    privkey=validator.privkey,  # privkey store locally, not in state
+    privkey=validator.privkey,  # privkey stored locally, not in state
-    message_hash=attestation_message_to_sign,
+    message_hash=attestation_message,
     domain=get_domain(
         fork=fork,  # `fork` is the fork object at the slot, `attestation_data.slot`
         epoch=slot_to_epoch(attestation_data.slot),
@@ -402,12 +398,12 @@ _Note_: Signed data must be within a sequential `Fork` context to conflict. Mess
 
 ### Proposer slashing
 
-To avoid "proposer slashings", a validator must not sign two conflicting [`ProposalSignedData`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#proposalsigneddata) where conflicting is defined as having the same `slot` and `shard` but a different `block_root`. In phase 0, proposals are only made for the beacon chain (`shard == BEACON_CHAIN_SHARD_NUMBER`).
+To avoid "proposer slashings", a validator must not sign two conflicting [`BeaconBlock`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#proposalsigneddata) where conflicting is defined as two distinct blocks within the same epoch.
 
-_In phase 0, as long as the validator does not sign two different beacon chain proposals for the same slot, the validator is safe against proposer slashings._
+_In phase 0, as long as the validator does not sign two different beacon blocks for the same epoch, the validator is safe against proposer slashings._
 
 Specifically, when signing an `BeaconBlock`, a validator should perform the following steps in the following order:
-1. Save a record to hard disk that an beacon block has been signed for the `slot=slot` and `shard=BEACON_CHAIN_SHARD_NUMBER`.
+1. Save a record to hard disk that an beacon block has been signed for the `epoch=slot_to_epoch(block.slot)`.
 2. Generate and broadcast the block.
 
 If the software crashes at some point within this routine, then when the validator comes back online the hard disk has the record of the _potentially_ signed/broadcast block and can effectively avoid slashing.
@@ -417,7 +413,7 @@ If the software crashes at some point within this routine, then when the validat
 To avoid "attester slashings", a validator must not sign two conflicting [`AttestationData`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#attestationdata) objects where conflicting is defined as a set of two attestations that satisfy either [`is_double_vote`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#is_double_vote) or [`is_surround_vote`](https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#is_surround_vote).
 
 Specifically, when signing an `Attestation`, a validator should perform the following steps in the following order:
-1. Save a record to hard disk that an attestation has been signed for source -- `attestation_data.justified_epoch` -- and target -- `slot_to_epoch(attestation_data.slot)`.
+1. Save a record to hard disk that an attestation has been signed for source -- `attestation_data.source_epoch` -- and target -- `slot_to_epoch(attestation_data.slot)`.
 2. Generate and broadcast attestation.
 
 If the software crashes at some point within this routine, then when the validator comes back online the hard disk has the record of the _potentially_ signed/broadcast attestation and can effectively avoid slashing.