Merge branch 'dev' into JustinDrake-patch-20

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Danny Ryan 2019-03-19 14:26:38 -06:00
commit ef0b3d2948
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23 changed files with 1677 additions and 112 deletions

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.circleci/config.yml Normal file
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@ -0,0 +1,41 @@
# Python CircleCI 2.0 configuration file
version: 2
jobs:
build:
docker:
- image: circleci/python:3.6
working_directory: ~/repo
steps:
- checkout
# Download and cache dependencies
- restore_cache:
keys:
- v1-dependencies-{{ checksum "requirements.txt" }}
# fallback to using the latest cache if no exact match is found
- v1-dependencies-
- run:
name: install dependencies
command: |
python3 -m venv venv
. venv/bin/activate
pip install -r requirements.txt
- run:
name: build phase0 spec
command: make build/phase0
- save_cache:
paths:
- ./venv
key: v1-dependencies-{{ checksum "requirements.txt" }}
- run:
name: run tests
command: |
. venv/bin/activate
pytest tests
- store_artifacts:
path: test-reports
destination: test-reports

6
.gitignore vendored Normal file
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@ -0,0 +1,6 @@
*.pyc
/__pycache__
/venv
/.pytest_cache
build/

29
Makefile Normal file
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@ -0,0 +1,29 @@
SPEC_DIR = ./specs
SCRIPT_DIR = ./scripts
BUILD_DIR = ./build
UTILS_DIR = ./utils
.PHONY: clean all test
all: $(BUILD_DIR)/phase0
clean:
rm -rf $(BUILD_DIR)
# runs a limited set of tests against a minimal config
# run pytest with `-m` option to full suite
test:
pytest -m "sanity and minimal_config" tests/
$(BUILD_DIR)/phase0:
mkdir -p $@
python3 $(SCRIPT_DIR)/phase0/build_spec.py $(SPEC_DIR)/core/0_beacon-chain.md $@/spec.py
mkdir -p $@/utils
cp $(UTILS_DIR)/phase0/* $@/utils
cp $(UTILS_DIR)/phase0/state_transition.py $@
touch $@/__init__.py $@/utils/__init__.py

6
requirements.txt Normal file
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@ -0,0 +1,6 @@
eth-utils>=1.3.0,<2
eth-typing>=2.1.0,<3.0.0
oyaml==0.7
pycryptodome==3.7.3
py_ecc>=1.6.0
pytest>=3.6,<3.7

0
scripts/__init__.py Normal file
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@ -0,0 +1,79 @@
import sys
import function_puller
def build_spec(sourcefile, outfile):
code_lines = []
code_lines.append("from build.phase0.utils.minimal_ssz import *")
code_lines.append("from build.phase0.utils.bls_stub import *")
for i in (1, 2, 3, 4, 8, 32, 48, 96):
code_lines.append("def int_to_bytes%d(x): return x.to_bytes(%d, 'little')" % (i, i))
code_lines.append("SLOTS_PER_EPOCH = 64") # stub, will get overwritten by real var
code_lines.append("def slot_to_epoch(x): return x // SLOTS_PER_EPOCH")
code_lines.append("""
from typing import (
Any,
Callable,
List,
NewType,
Tuple,
)
Slot = NewType('Slot', int) # uint64
Epoch = NewType('Epoch', int) # uint64
Shard = NewType('Shard', int) # uint64
ValidatorIndex = NewType('ValidatorIndex', int) # uint64
Gwei = NewType('Gwei', int) # uint64
Bytes32 = NewType('Bytes32', bytes) # bytes32
BLSPubkey = NewType('BLSPubkey', bytes) # bytes48
BLSSignature = NewType('BLSSignature', bytes) # bytes96
Any = None
Store = None
""")
code_lines += function_puller.get_lines(sourcefile)
code_lines.append("""
# Monkey patch validator get committee code
_compute_committee = compute_committee
committee_cache = {}
def compute_committee(validator_indices: List[ValidatorIndex],
seed: Bytes32,
index: int,
total_committees: int) -> List[ValidatorIndex]:
param_hash = (hash_tree_root(validator_indices), seed, index, total_committees)
if param_hash in committee_cache:
# print("Cache hit, epoch={0}".format(epoch))
return committee_cache[param_hash]
else:
# print("Cache miss, epoch={0}".format(epoch))
ret = _compute_committee(validator_indices, seed, index, total_committees)
committee_cache[param_hash] = ret
return ret
# Monkey patch hash cache
_hash = hash
hash_cache = {}
def hash(x):
if x in hash_cache:
return hash_cache[x]
else:
ret = _hash(x)
hash_cache[x] = ret
return ret
""")
with open(outfile, 'w') as out:
out.write("\n".join(code_lines))
if __name__ == '__main__':
if len(sys.argv) < 3:
print("Error: spec source and outfile must defined")
build_spec(sys.argv[1], sys.argv[2])

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@ -0,0 +1,46 @@
import sys
def get_lines(file_name):
code_lines = []
pulling_from = None
current_name = None
processing_typedef = False
for linenum, line in enumerate(open(sys.argv[1]).readlines()):
line = line.rstrip()
if pulling_from is None and len(line) > 0 and line[0] == '#' and line[-1] == '`':
current_name = line[line[:-1].rfind('`') + 1: -1]
if line[:9] == '```python':
assert pulling_from is None
pulling_from = linenum + 1
elif line[:3] == '```':
if pulling_from is None:
pulling_from = linenum
else:
if processing_typedef:
assert code_lines[-1] == '}'
code_lines[-1] = '})'
pulling_from = None
processing_typedef = False
else:
if pulling_from == linenum and line == '{':
code_lines.append('%s = SSZType({' % current_name)
processing_typedef = True
elif pulling_from is not None:
code_lines.append(line)
elif pulling_from is None and len(line) > 0 and line[0] == '|':
row = line[1:].split('|')
if len(row) >= 2:
for i in range(2):
row[i] = row[i].strip().strip('`')
if '`' in row[i]:
row[i] = row[i][:row[i].find('`')]
eligible = True
if row[0][0] not in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ_':
eligible = False
for c in row[0]:
if c not in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789':
eligible = False
if eligible:
code_lines.append(row[0] + ' = ' + (row[1].replace('**TBD**', '0x1234567890123567890123456789012357890')))
return code_lines

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@ -61,9 +61,9 @@
- [`is_active_validator`](#is_active_validator)
- [`get_active_validator_indices`](#get_active_validator_indices)
- [`get_permuted_index`](#get_permuted_index)
- [`split`](#split)
- [`get_split_offset`](#get_split_offset)
- [`get_epoch_committee_count`](#get_epoch_committee_count)
- [`get_shuffling`](#get_shuffling)
- [`compute_committee`](#compute_committee)
- [`get_previous_epoch_committee_count`](#get_previous_epoch_committee_count)
- [`get_current_epoch_committee_count`](#get_current_epoch_committee_count)
- [`get_next_epoch_committee_count`](#get_next_epoch_committee_count)
@ -773,18 +773,11 @@ def get_permuted_index(index: int, list_size: int, seed: Bytes32) -> int:
return index
```
### `split`
### `get_split_offset`
```python
def split(values: List[Any], split_count: int) -> List[List[Any]]:
"""
Splits ``values`` into ``split_count`` pieces.
"""
list_length = len(values)
return [
values[(list_length * i // split_count): (list_length * (i + 1) // split_count)]
for i in range(split_count)
]
def get_split_offset(list_length: int, split_count: int, index: int) -> int:
return (list_length * index) // split_count
```
### `get_epoch_committee_count`
@ -803,28 +796,26 @@ def get_epoch_committee_count(active_validator_count: int) -> int:
) * SLOTS_PER_EPOCH
```
### `get_shuffling`
### `compute_committee`
```python
def get_shuffling(seed: Bytes32,
validators: List[Validator],
epoch: Epoch) -> List[List[ValidatorIndex]]:
def compute_committee(validator_indices: List[ValidatorIndex],
seed: Bytes32,
index: int,
total_committees: int) -> List[ValidatorIndex]:
"""
Shuffle active validators and split into crosslink committees.
Return a list of committees (each a list of validator indices).
Return the ``index``'th shuffled committee out of a total ``total_committees``
using ``validator_indices`` and ``seed``.
"""
# Shuffle active validator indices
active_validator_indices = get_active_validator_indices(validators, epoch)
length = len(active_validator_indices)
shuffled_indices = [active_validator_indices[get_permuted_index(i, length, seed)] for i in range(length)]
# Split the shuffled active validator indices
return split(shuffled_indices, get_epoch_committee_count(length))
start_offset = get_split_offset(len(validator_indices), total_committees, index)
end_offset = get_split_offset(len(validator_indices), total_committees, index + 1)
return [
validator_indices[get_permuted_index(i, len(validator_indices), seed)]
for i in range(start_offset, end_offset)
]
```
**Invariant**: if `get_shuffling(seed, validators, epoch)` returns some value `x` for some `epoch <= get_current_epoch(state) + ACTIVATION_EXIT_DELAY`, it should return the same value `x` for the same `seed` and `epoch` and possible future modifications of `validators` forever in phase 0, and until the ~1 year deletion delay in phase 2 and in the future.
**Note**: this definition and the next few definitions make heavy use of repetitive computing. Production implementations are expected to appropriately use caching/memoization to avoid redoing work.
**Note**: this definition and the next few definitions are highly inefficient as algorithms as they re-calculate many sub-expressions. Production implementations are expected to appropriately use caching/memoization to avoid redoing work.
### `get_previous_epoch_committee_count`
@ -916,18 +907,14 @@ def get_crosslink_committees_at_slot(state: BeaconState,
shuffling_epoch = state.current_shuffling_epoch
shuffling_start_shard = state.current_shuffling_start_shard
shuffling = get_shuffling(
seed,
state.validator_registry,
shuffling_epoch,
)
offset = slot % SLOTS_PER_EPOCH
indices = get_active_validator_indices(state.validator_registry, shuffling_epoch)
committees_per_slot = committees_per_epoch // SLOTS_PER_EPOCH
offset = slot % SLOTS_PER_EPOCH
slot_start_shard = (shuffling_start_shard + committees_per_slot * offset) % SHARD_COUNT
return [
(
shuffling[committees_per_slot * offset + i],
compute_committee(indices, seed, committees_per_slot * offset + i, committees_per_epoch),
(slot_start_shard + i) % SHARD_COUNT,
)
for i in range(committees_per_slot)
@ -1377,17 +1364,14 @@ def initiate_validator_exit(state: BeaconState, index: ValidatorIndex) -> None:
```python
def exit_validator(state: BeaconState, index: ValidatorIndex) -> None:
"""
Exit the validator of the given ``index``.
Exit the validator with the given ``index``.
Note that this function mutates ``state``.
"""
validator = state.validator_registry[index]
delayed_activation_exit_epoch = get_delayed_activation_exit_epoch(get_current_epoch(state))
# The following updates only occur if not previous exited
if validator.exit_epoch <= delayed_activation_exit_epoch:
return
else:
validator.exit_epoch = delayed_activation_exit_epoch
# Update validator exit epoch if not previously exited
if validator.exit_epoch == FAR_FUTURE_EPOCH:
validator.exit_epoch = get_delayed_activation_exit_epoch(get_current_epoch(state))
```
#### `slash_validator`
@ -1531,7 +1515,7 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
latest_randao_mixes=Vector([ZERO_HASH for _ in range(LATEST_RANDAO_MIXES_LENGTH)]),
previous_shuffling_start_shard=GENESIS_START_SHARD,
current_shuffling_start_shard=GENESIS_START_SHARD,
previous_shuffling_epoch=GENESIS_EPOCH,
previous_shuffling_epoch=GENESIS_EPOCH - 1,
current_shuffling_epoch=GENESIS_EPOCH,
previous_shuffling_seed=ZERO_HASH,
current_shuffling_seed=ZERO_HASH,
@ -1539,7 +1523,7 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
# Finality
previous_epoch_attestations=[],
current_epoch_attestations=[],
previous_justified_epoch=GENESIS_EPOCH,
previous_justified_epoch=GENESIS_EPOCH - 1,
current_justified_epoch=GENESIS_EPOCH,
previous_justified_root=ZERO_HASH,
current_justified_root=ZERO_HASH,
@ -2050,7 +2034,7 @@ def process_ejections(state: BeaconState) -> None:
"""
for index in get_active_validator_indices(state.validator_registry, get_current_epoch(state)):
if state.validator_balances[index] < EJECTION_BALANCE:
exit_validator(state, index)
initiate_validator_exit(state, index)
```
#### Validator registry and shuffling seed data
@ -2102,16 +2086,21 @@ def update_validator_registry(state: BeaconState) -> None:
activate_validator(state, index, is_genesis=False)
# Exit validators within the allowable balance churn
balance_churn = 0
for index, validator in enumerate(state.validator_registry):
if validator.exit_epoch == FAR_FUTURE_EPOCH and validator.initiated_exit:
# Check the balance churn would be within the allowance
balance_churn += get_effective_balance(state, index)
if balance_churn > max_balance_churn:
break
if current_epoch < state.validator_registry_update_epoch + LATEST_SLASHED_EXIT_LENGTH:
balance_churn = (
state.latest_slashed_balances[state.validator_registry_update_epoch % LATEST_SLASHED_EXIT_LENGTH] -
state.latest_slashed_balances[current_epoch % LATEST_SLASHED_EXIT_LENGTH]
)
# Exit validator
exit_validator(state, index)
for index, validator in enumerate(state.validator_registry):
if validator.exit_epoch == FAR_FUTURE_EPOCH and validator.initiated_exit:
# Check the balance churn would be within the allowance
balance_churn += get_effective_balance(state, index)
if balance_churn > max_balance_churn:
break
# Exit validator
exit_validator(state, index)
state.validator_registry_update_epoch = current_epoch
```
@ -2375,74 +2364,49 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
Process ``Attestation`` transaction.
Note that this function mutates ``state``.
"""
# Can't submit attestations that are too far in history (or in prehistory)
assert attestation.data.slot >= GENESIS_SLOT
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 and root is correct
if slot_to_epoch(attestation.data.slot) >= get_current_epoch(state):
# Case 1: current epoch attestations
assert attestation.data.source_epoch == state.current_justified_epoch
assert attestation.data.source_root == state.current_justified_root
else:
# Case 2: previous epoch attestations
assert attestation.data.source_epoch == state.previous_justified_epoch
assert attestation.data.source_root == state.previous_justified_root
# Check that the crosslink data is valid
acceptable_crosslink_data = {
# Case 1: Latest crosslink matches the one in the state
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(
crosslink_data_root=attestation.data.crosslink_data_root,
epoch=slot_to_epoch(attestation.data.slot)
)
}
assert state.latest_crosslinks[attestation.data.shard] in acceptable_crosslink_data
# Attestation must be nonempty!
assert attestation.aggregation_bitfield != b'\x00' * len(attestation.aggregation_bitfield)
# Custody must be empty (to be removed in phase 1)
assert attestation.custody_bitfield == b'\x00' * len(attestation.custody_bitfield)
# Get the committee for the specific shard that this attestation is for
crosslink_committee = [
committee for committee, shard in get_crosslink_committees_at_slot(state, attestation.data.slot)
if shard == attestation.data.shard
][0]
# Custody bitfield must be a subset of the attestation bitfield
for i in range(len(crosslink_committee)):
if get_bitfield_bit(attestation.aggregation_bitfield, i) == 0b0:
assert get_bitfield_bit(attestation.custody_bitfield, i) == 0b0
# Verify aggregate signature
participants = get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield)
custody_bit_1_participants = get_attestation_participants(state, attestation.data, attestation.custody_bitfield)
custody_bit_0_participants = [i for i in participants if i not in custody_bit_1_participants]
assert max(GENESIS_SLOT, state.slot - SLOTS_PER_EPOCH) <= attestation.data.slot
assert attestation.data.slot <= state.slot - MIN_ATTESTATION_INCLUSION_DELAY
assert bls_verify_multiple(
pubkeys=[
bls_aggregate_pubkeys([state.validator_registry[i].pubkey for i in custody_bit_0_participants]),
bls_aggregate_pubkeys([state.validator_registry[i].pubkey for i in custody_bit_1_participants]),
],
message_hashes=[
hash_tree_root(AttestationDataAndCustodyBit(data=attestation.data, custody_bit=0b0)),
hash_tree_root(AttestationDataAndCustodyBit(data=attestation.data, custody_bit=0b1)),
],
# Check target epoch, source epoch, and source root
target_epoch = slot_to_epoch(attestation.data.slot)
assert (target_epoch, attestation.data.source_epoch, attestation.data.source_root) in {
(get_current_epoch(state), state.current_justified_epoch, state.current_justified_root),
(get_previous_epoch(state), state.previous_justified_epoch, state.previous_justified_root),
}
# Check crosslink data
assert attestation.data.crosslink_data_root == ZERO_HASH # [to be removed in phase 1]
assert state.latest_crosslinks[attestation.data.shard] in {
attestation.data.previous_crosslink, # Case 1: latest crosslink matches previous crosslink
Crosslink( # Case 2: latest crosslink matches current crosslink
crosslink_data_root=attestation.data.crosslink_data_root,
epoch=target_epoch,
),
}
# Check custody bits [to be generalised in phase 1]
assert attestation.custody_bitfield == b'\x00' * len(attestation.custody_bitfield)
# Check aggregate signature [to be generalised in phase 1]
participants = get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield)
assert len(participants) != 0
assert bls_verify(
pubkey=bls_aggregate_pubkeys([state.validator_registry[i].pubkey for i in participants]),
message_hash=hash_tree_root(AttestationDataAndCustodyBit(data=attestation.data, custody_bit=0b0)),
signature=attestation.aggregate_signature,
domain=get_domain(state.fork, slot_to_epoch(attestation.data.slot), DOMAIN_ATTESTATION),
domain=get_domain(state.fork, target_epoch, DOMAIN_ATTESTATION),
)
# Crosslink data root is zero (to be removed in phase 1)
assert attestation.data.crosslink_data_root == ZERO_HASH
# Apply the attestation
# Cache pending attestation
pending_attestation = PendingAttestation(
data=attestation.data,
aggregation_bitfield=attestation.aggregation_bitfield,
custody_bitfield=attestation.custody_bitfield,
inclusion_slot=state.slot
)
if slot_to_epoch(attestation.data.slot) == get_current_epoch(state):
if target_epoch == get_current_epoch(state):
state.current_epoch_attestations.append(pending_attestation)
elif slot_to_epoch(attestation.data.slot) == get_previous_epoch(state):
else:
state.previous_epoch_attestations.append(pending_attestation)
```

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@ -0,0 +1,134 @@
### Generalized Merkle tree index
In a binary Merkle tree, we define a "generalized index" of a node as `2**depth + index`. Visually, this looks as follows:
```
1
2 3
4 5 6 7
...
```
Note that the generalized index has the convenient property that the two children of node `k` are `2k` and `2k+1`, and also that it equals the position of a node in the linear representation of the Merkle tree that's computed by this function:
```python
def merkle_tree(leaves):
o = [0] * len(leaves) + leaves
for i in range(len(leaves)-1, 0, -1):
o[i] = hash(o[i*2] + o[i*2+1])
return o
```
We will define Merkle proofs in terms of generalized indices.
### SSZ object to index
We can describe the hash tree of any SSZ object, rooted in `hash_tree_root(object)`, as a binary Merkle tree whose depth may vary. For example, an object `{x: bytes32, y: List[uint64]}` would look as follows:
```
root
/ \
x y_root
/ \
y_data_root len(y)
/ \
/\ /\
.......
```
We can now define a concept of a "path", a way of describing a function that takes as input an SSZ object and outputs some specific (possibly deeply nested) member. For example, `foo -> foo.x` is a path, as are `foo -> len(foo.y)` and `foo -> foo[5]`. We'll describe paths as lists: in these three cases they are `["x"]`, `["y", "len"]` and `["y", 5]` respectively. We can now define a function `get_generalized_indices(object: Any, path: List[str OR int], root=1: int) -> int` that converts an object and a path to a set of generalized indices (note that for constant-sized objects, there is only one generalized index and it only depends on the path, but for dynamically sized objects the indices may depend on the object itself too). For dynamically-sized objects, the set of indices will have more than one member because of the need to access an array's length to determine the correct generalized index for some array access.
```python
def get_generalized_indices(obj: Any, path: List[str or int], root=1) -> List[int]:
if len(path) == 0:
return [root]
elif isinstance(obj, StaticList):
items_per_chunk = (32 // len(serialize(x))) if isinstance(x, int) else 1
new_root = root * next_power_of_2(len(obj) // items_per_chunk) + path[0] // items_per_chunk
return get_generalized_indices(obj[path[0]], path[1:], new_root)
elif isinstance(obj, DynamicList) and path[0] == "len":
return [root * 2 + 1]
elif isinstance(obj, DynamicList) and isinstance(path[0], int):
assert path[0] < len(obj)
items_per_chunk = (32 // len(serialize(x))) if isinstance(x, int) else 1
new_root = root * 2 * next_power_of_2(len(obj) // items_per_chunk) + path[0] // items_per_chunk
return [root *2 + 1] + get_generalized_indices(obj[path[0]], path[1:], new_root)
elif hasattr(obj, "fields"):
index = list(fields.keys()).index(path[0])
new_root = root * next_power_of_2(len(fields)) + index
return get_generalized_indices(getattr(obj, path[0]), path[1:], new_root)
else:
raise Exception("Unknown type / path")
```
### Merkle multiproofs
We define a Merkle multiproof as a minimal subset of nodes in a Merkle tree needed to fully authenticate that a set of nodes actually are part of a Merkle tree with some specified root, at a particular set of generalized indices. For example, here is the Merkle multiproof for positions 0, 1, 6 in an 8-node Merkle tree (ie. generalized indices 8, 9, 14):
```
.
. .
. * * .
x x . . . . x *
```
. are unused nodes, * are used nodes, x are the values we are trying to prove. Notice how despite being a multiproof for 3 values, it requires only 3 auxiliary nodes, only one node more than would be required to prove a single value. Normally the efficiency gains are not quite that extreme, but the savings relative to individual Merkle proofs are still significant. As a rule of thumb, a multiproof for k nodes at the same level of an n-node tree has size `k * (n/k + log(n/k))`.
Here is code for creating and verifying a multiproof. First a helper:
```python
def log2(x):
return 0 if x == 1 else 1 + log2(x//2)
```
First, a method for computing the generalized indices of the auxiliary tree nodes that a proof of a given set of generalized indices will require:
```python
def get_proof_indices(tree_indices: List[int]) -> List[int]:
# Get all indices touched by the proof
maximal_indices = set({})
for i in tree_indices:
x = i
while x > 1:
maximal_indices.add(x ^ 1)
x //= 2
maximal_indices = tree_indices + sorted(list(maximal_indices))[::-1]
# Get indices that cannot be recalculated from earlier indices
redundant_indices = set({})
proof = []
for index in maximal_indices:
if index not in redundant_indices:
proof.append(index)
while index > 1:
redundant_indices.add(index)
if (index ^ 1) not in redundant_indices:
break
index //= 2
return [i for i in proof if i not in tree_indices]
````
Generating a proof is simply a matter of taking the node of the SSZ hash tree with the union of the given generalized indices for each index given by `get_proof_indices`, and outputting the list of nodes in the same order.
```python
def verify_multi_proof(root, indices, leaves, proof):
tree = {}
for index, leaf in zip(indices, leaves):
tree[index] = leaf
for index, proofitem in zip(get_proof_indices(indices), proof):
tree[index] = proofitem
indexqueue = sorted(tree.keys())[:-1]
i = 0
while i < len(indexqueue):
index = indexqueue[i]
if index >= 2 and index^1 in tree:
tree[index//2] = hash(tree[index - index%2] + tree[index - index%2 + 1])
indexqueue.append(index//2)
i += 1
return (indices == []) or (1 in tree and tree[1] == root)
```
#### Proofs for execution
We define `MerklePartial(f, arg1, arg2...)` as being a list of Merkle multiproofs of the sets of nodes in the hash trees of the SSZ objects that are needed to authenticate the values needed to compute some function `f(arg1, arg2...)`. An individual Merkle multiproof is given as a dynamic sized list of `bytes32` values, a `MerklePartial` is a fixed-size list of objects `{proof: ["bytes32"], value: "bytes32"}`, one for each `arg` to `f` (if some `arg` is a base type, then the multiproof is empty).
Ideally, any function which accepts an SSZ object should also be able to accept a `MerklePartial` object as a substitute.

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# Beacon chain light client syncing
One of the design goals of the eth2 beacon chain is light-client friendlines, both to allow low-resource clients (mobile phones, IoT, etc) to maintain access to the blockchain in a reasonably safe way, but also to facilitate the development of "bridges" between the eth2 beacon chain and other chains.
### Preliminaries
We define an "expansion" of an object as an object where a field in an object that is meant to represent the `hash_tree_root` of another object is replaced by the object. Note that defining expansions is not a consensus-layer-change; it is merely a "re-interpretation" of the object. Particularly, the `hash_tree_root` of an expansion of an object is identical to that of the original object, and we can define expansions where, given a complete history, it is always possible to compute the expansion of any object in the history. The opposite of an expansion is a "summary" (eg. `BeaconBlockHeader` is a summary of `BeaconBlock`).
We define two expansions:
* `ExtendedBeaconBlock`, which is identical to a `BeaconBlock` except `state_root` is replaced with the corresponding `state: ExtendedBeaconState`
* `ExtendedBeaconState`, which is identical to a `BeaconState` except `latest_active_index_roots: List[Bytes32]` is replaced by `latest_active_indices: List[List[ValidatorIndex]]`, where `BeaconState.latest_active_index_roots[i] = hash_tree_root(ExtendedBeaconState.latest_active_indices[i])`
Note that there is now a new way to compute `get_active_validator_indices`:
```python
def get_active_validator_indices(state: BeaconState, epoch: Epoch) -> List[ValidatorIndex]:
return state.latest_active_indices[epoch % LATEST_ACTIVE_INDEX_ROOTS_LENGTH]
```
Note that it takes `state` instead of `state.validator_registry` as an argument. This does not affect its use in `get_shuffled_committee`, because `get_shuffled_committee` has access to the full `state` as one of its arguments.
A `MerklePartial(f, *args)` is an object that contains a minimal Merkle proof needed to compute `f(*args)`. A `MerklePartial` can be used in place of a regular SSZ object, though a computation would return an error if it attempts to access part of the object that is not contained in the proof.
We add a data type `PeriodData` and four helpers:
```python
{
'validator_count': 'uint64',
'seed': 'bytes32',
'committee': [Validator]
}
```
```python
def get_earlier_start_epoch(slot: Slot) -> int:
return slot - slot % PERSISTENT_COMMITTEE_PERIOD - PERSISTENT_COMMITTEE_PERIOD * 2
def get_later_start_epoch(slot: Slot) -> int:
return slot - slot % PERSISTENT_COMMITTEE_PERIOD - PERSISTENT_COMMITTEE_PERIOD
def get_earlier_period_data(block: ExtendedBeaconBlock, shard_id: Shard) -> PeriodData:
period_start = get_earlier_start_epoch(header.slot)
validator_count = len(get_active_validator_indices(state, period_start))
committee_count = validator_count // (SHARD_COUNT * TARGET_COMMITTEE_SIZE) + 1
indices = get_shuffled_committee(block.state, shard_id, period_start, 0, committee_count)
return PeriodData(
validator_count,
generate_seed(block.state, period_start),
[block.state.validator_registry[i] for i in indices]
)
def get_later_period_data(block: ExtendedBeaconBlock, shard_id: Shard) -> PeriodData:
period_start = get_later_start_epoch(header.slot)
validator_count = len(get_active_validator_indices(state, period_start))
committee_count = validator_count // (SHARD_COUNT * TARGET_COMMITTEE_SIZE) + 1
indices = get_shuffled_committee(block.state, shard_id, period_start, 0, committee_count)
return PeriodData(
validator_count,
generate_seed(block.state, period_start),
[block.state.validator_registry[i] for i in indices]
)
```
### Light client state
A light client will keep track of:
* A random `shard_id` in `[0...SHARD_COUNT-1]` (selected once and retained forever)
* A block header that they consider to be finalized (`finalized_header`) and do not expect to revert.
* `later_period_data = get_maximal_later_committee(finalized_header, shard_id)`
* `earlier_period_data = get_maximal_earlier_committee(finalized_header, shard_id)`
We use the struct `validator_memory` to keep track of these variables.
### Updating the shuffled committee
If a client's `validator_memory.finalized_header` changes so that `header.slot // PERSISTENT_COMMITTEE_PERIOD` increases, then the client can ask the network for a `new_committee_proof = MerklePartial(get_maximal_later_committee, validator_memory.finalized_header, shard_id)`. It can then compute:
```python
earlier_period_data = later_period_data
later_period_data = get_later_period_data(new_committee_proof, finalized_header, shard_id)
```
The maximum size of a proof is `128 * ((22-7) * 32 + 110) = 75520` bytes for validator records and `(22-7) * 32 + 128 * 8 = 1504` for the active index proof (much smaller because the relevant active indices are all beside each other in the Merkle tree). This needs to be done once per `PERSISTENT_COMMITTEE_PERIOD` epochs (2048 epochs / 9 days), or ~38 bytes per epoch.
### Computing the current committee
Here is a helper to compute the committee at a slot given the maximal earlier and later committees:
```python
def compute_committee(header: BeaconBlockHeader,
validator_memory: ValidatorMemory):
earlier_validator_count = validator_memory.earlier_period_data.validator_count
later_validator_count = validator_memory.later_period_data.validator_count
earlier_committee = validator_memory.earlier_period_data.committee
later_committee = validator_memory.later_period_data.committee
earlier_start_epoch = get_earlier_start_epoch(header.slot)
later_start_epoch = get_later_start_epoch(header.slot)
epoch = slot_to_epoch(header.slot)
actual_committee_count = max(
earlier_validator_count // (SHARD_COUNT * TARGET_COMMITTEE_SIZE),
later_validator_count // (SHARD_COUNT * TARGET_COMMITTEE_SIZE),
) + 1
def get_offset(count, end:bool):
return get_split_offset(count,
SHARD_COUNT * committee_count,
validator_memory.shard_id * committee_count + (1 if end else 0))
actual_earlier_committee = maximal_earlier_committee[
0:get_offset(earlier_validator_count, True) - get_offset(earlier_validator_count, False)
]
actual_later_committee = maximal_later_committee[
0:get_offset(later_validator_count, True) - get_offset(later_validator_count, False)
]
def get_switchover_epoch(index):
return (
bytes_to_int(hash(validator_memory.earlier_period_data.seed + bytes3(index))[0:8]) %
PERSISTENT_COMMITTEE_PERIOD
)
# Take not-yet-cycled-out validators from earlier committee and already-cycled-in validators from
# later committee; return a sorted list of the union of the two, deduplicated
return sorted(list(set(
[i for i in earlier_committee if epoch % PERSISTENT_COMMITTEE_PERIOD < get_switchover_epoch(i)] +
[i for i in later_committee if epoch % PERSISTENT_COMMITTEE_PERIOD >= get_switchover_epoch(i)]
)))
```
Note that this method makes use of the fact that the committee for any given shard always starts and ends at the same validator index independently of the committee count (this is because the validator set is split into `SHARD_COUNT * committee_count` slices but the first slice of a shard is a multiple `committee_count * i`, so the start of the slice is `n * committee_count * i // (SHARD_COUNT * committee_count) = n * i // SHARD_COUNT`, using the slightly nontrivial algebraic identity `(x * a) // ab == x // b`).
### Verifying blocks
If a client wants to update its `finalized_header` it asks the network for a `BlockValidityProof`, which is simply:
```python
{
'header': BlockHeader,
'shard_aggregate_signature': 'bytes96',
'shard_bitfield': 'bytes',
'shard_parent_block': ShardBlock
}
```
The verification procedure is as follows:
```python
def verify_block_validity_proof(proof: BlockValidityProof, validator_memory: ValidatorMemory) -> bool:
assert proof.shard_parent_block.beacon_chain_ref == hash_tree_root(proof.header)
committee = compute_committee(proof.header, validator_memory)
# Verify that we have >=50% support
support_balance = sum([c.high_balance for i, c in enumerate(committee) if get_bitfield_bit(proof.shard_bitfield, i) is True])
total_balance = sum([c.high_balance for i, c in enumerate(committee)]
assert support_balance * 2 > total_balance
# Verify shard attestations
group_public_key = bls_aggregate_pubkeys([
v.pubkey for v, index in enumerate(committee) if
get_bitfield_bit(proof.shard_bitfield, i) is True
])
assert bls_verify(
pubkey=group_public_key,
message_hash=hash_tree_root(shard_parent_block),
signature=shard_aggregate_signature,
domain=get_domain(state, slot_to_epoch(shard_block.slot), DOMAIN_SHARD_ATTESTER)
)
```
The size of this proof is only 200 (header) + 96 (signature) + 16 (bitfield) + 352 (shard block) = 664 bytes. It can be reduced further by replacing `ShardBlock` with `MerklePartial(lambda x: x.beacon_chain_ref, ShardBlock)`, which would cut off ~220 bytes.

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import pytest
from build.phase0 import spec
from tests.phase0.helpers import (
privkeys_list,
pubkeys_list,
create_genesis_state,
)
DEFAULT_CONFIG = {} # no change
MINIMAL_CONFIG = {
"SHARD_COUNT": 8,
"MIN_ATTESTATION_INCLUSION_DELAY": 2,
"TARGET_COMMITTEE_SIZE": 4,
"SLOTS_PER_EPOCH": 8,
"GENESIS_EPOCH": spec.GENESIS_SLOT // 8,
"SLOTS_PER_HISTORICAL_ROOT": 64,
"LATEST_RANDAO_MIXES_LENGTH": 64,
"LATEST_ACTIVE_INDEX_ROOTS_LENGTH": 64,
"LATEST_SLASHED_EXIT_LENGTH": 64,
}
@pytest.fixture
def privkeys():
return privkeys_list
@pytest.fixture
def pubkeys():
return pubkeys_list
def overwrite_spec_config(config):
for field in config:
setattr(spec, field, config[field])
if field == "LATEST_RANDAO_MIXES_LENGTH":
spec.BeaconState.fields['latest_randao_mixes'][1] = config[field]
elif field == "SHARD_COUNT":
spec.BeaconState.fields['latest_crosslinks'][1] = config[field]
elif field == "SLOTS_PER_HISTORICAL_ROOT":
spec.BeaconState.fields['latest_block_roots'][1] = config[field]
spec.BeaconState.fields['latest_state_roots'][1] = config[field]
spec.HistoricalBatch.fields['block_roots'][1] = config[field]
spec.HistoricalBatch.fields['state_roots'][1] = config[field]
elif field == "LATEST_ACTIVE_INDEX_ROOTS_LENGTH":
spec.BeaconState.fields['latest_active_index_roots'][1] = config[field]
elif field == "LATEST_SLASHED_EXIT_LENGTH":
spec.BeaconState.fields['latest_slashed_balances'][1] = config[field]
@pytest.fixture(
params=[
pytest.param(MINIMAL_CONFIG, marks=pytest.mark.minimal_config),
DEFAULT_CONFIG,
]
)
def config(request):
return request.param
@pytest.fixture(autouse=True)
def overwrite_config(config):
overwrite_spec_config(config)
@pytest.fixture
def num_validators():
return 100
@pytest.fixture
def deposit_data_leaves():
return list()
@pytest.fixture
def state(num_validators, deposit_data_leaves):
return create_genesis_state(num_validators, deposit_data_leaves)

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from copy import deepcopy
from py_ecc import bls
import build.phase0.spec as spec
from build.phase0.utils.minimal_ssz import signed_root
from build.phase0.spec import (
# constants
EMPTY_SIGNATURE,
# SSZ
AttestationData,
Deposit,
DepositInput,
DepositData,
Eth1Data,
# functions
get_block_root,
get_current_epoch,
get_domain,
get_empty_block,
get_epoch_start_slot,
get_genesis_beacon_state,
verify_merkle_branch,
hash,
)
from build.phase0.utils.merkle_minimal import (
calc_merkle_tree_from_leaves,
get_merkle_proof,
get_merkle_root,
)
privkeys_list = [i + 1 for i in range(1000)]
pubkeys_list = [bls.privtopub(privkey) for privkey in privkeys_list]
pubkey_to_privkey = {pubkey: privkey for privkey, pubkey in zip(privkeys_list, pubkeys_list)}
def create_mock_genesis_validator_deposits(num_validators, deposit_data_leaves):
deposit_timestamp = 0
proof_of_possession = b'\x33' * 96
deposit_data_list = []
for i in range(num_validators):
pubkey = pubkeys_list[i]
deposit_data = DepositData(
amount=spec.MAX_DEPOSIT_AMOUNT,
timestamp=deposit_timestamp,
deposit_input=DepositInput(
pubkey=pubkey,
# insecurely use pubkey as withdrawal key as well
withdrawal_credentials=spec.BLS_WITHDRAWAL_PREFIX_BYTE + hash(pubkey)[1:],
proof_of_possession=proof_of_possession,
),
)
item = hash(deposit_data.serialize())
deposit_data_leaves.append(item)
tree = calc_merkle_tree_from_leaves(tuple(deposit_data_leaves))
root = get_merkle_root((tuple(deposit_data_leaves)))
proof = list(get_merkle_proof(tree, item_index=i))
assert verify_merkle_branch(item, proof, spec.DEPOSIT_CONTRACT_TREE_DEPTH, i, root)
deposit_data_list.append(deposit_data)
genesis_validator_deposits = []
for i in range(num_validators):
genesis_validator_deposits.append(Deposit(
proof=list(get_merkle_proof(tree, item_index=i)),
index=i,
deposit_data=deposit_data_list[i]
))
return genesis_validator_deposits, root
def create_genesis_state(num_validators, deposit_data_leaves):
initial_deposits, deposit_root = create_mock_genesis_validator_deposits(num_validators, deposit_data_leaves)
return get_genesis_beacon_state(
initial_deposits,
genesis_time=0,
genesis_eth1_data=Eth1Data(
deposit_root=deposit_root,
block_hash=spec.ZERO_HASH,
),
)
def build_empty_block_for_next_slot(state):
empty_block = get_empty_block()
empty_block.slot = state.slot + 1
previous_block_header = deepcopy(state.latest_block_header)
if previous_block_header.state_root == spec.ZERO_HASH:
previous_block_header.state_root = state.hash_tree_root()
empty_block.previous_block_root = previous_block_header.hash_tree_root()
return empty_block
def build_deposit_data(state, pubkey, privkey, amount):
deposit_input = DepositInput(
pubkey=pubkey,
# insecurely use pubkey as withdrawal key as well
withdrawal_credentials=spec.BLS_WITHDRAWAL_PREFIX_BYTE + hash(pubkey)[1:],
proof_of_possession=EMPTY_SIGNATURE,
)
proof_of_possession = bls.sign(
message_hash=signed_root(deposit_input),
privkey=privkey,
domain=get_domain(
state.fork,
get_current_epoch(state),
spec.DOMAIN_DEPOSIT,
)
)
deposit_input.proof_of_possession = proof_of_possession
deposit_data = DepositData(
amount=amount,
timestamp=0,
deposit_input=deposit_input,
)
return deposit_data
def build_attestation_data(state, slot, shard):
assert state.slot >= slot
block_root = build_empty_block_for_next_slot(state).previous_block_root
epoch_start_slot = get_epoch_start_slot(get_current_epoch(state))
if epoch_start_slot == slot:
epoch_boundary_root = block_root
else:
get_block_root(state, epoch_start_slot)
if slot < epoch_start_slot:
justified_block_root = state.previous_justified_root
else:
justified_block_root = state.current_justified_root
return AttestationData(
slot=slot,
shard=shard,
beacon_block_root=block_root,
source_epoch=state.current_justified_epoch,
source_root=justified_block_root,
target_root=epoch_boundary_root,
crosslink_data_root=spec.ZERO_HASH,
previous_crosslink=deepcopy(state.latest_crosslinks[shard]),
)

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from copy import deepcopy
import pytest
from py_ecc import bls
import build.phase0.spec as spec
from build.phase0.utils.minimal_ssz import signed_root
from build.phase0.spec import (
# constants
EMPTY_SIGNATURE,
ZERO_HASH,
# SSZ
Attestation,
AttestationDataAndCustodyBit,
BeaconBlockHeader,
Deposit,
Transfer,
ProposerSlashing,
VoluntaryExit,
# functions
get_active_validator_indices,
get_attestation_participants,
get_block_root,
get_crosslink_committees_at_slot,
get_current_epoch,
get_domain,
get_state_root,
advance_slot,
cache_state,
verify_merkle_branch,
hash,
)
from build.phase0.state_transition import (
state_transition,
)
from build.phase0.utils.merkle_minimal import (
calc_merkle_tree_from_leaves,
get_merkle_proof,
get_merkle_root,
)
from tests.phase0.helpers import (
build_attestation_data,
build_deposit_data,
build_empty_block_for_next_slot,
)
# mark entire file as 'sanity'
pytestmark = pytest.mark.sanity
def test_slot_transition(state):
test_state = deepcopy(state)
cache_state(test_state)
advance_slot(test_state)
assert test_state.slot == state.slot + 1
assert get_state_root(test_state, state.slot) == state.hash_tree_root()
return test_state
def test_empty_block_transition(state):
test_state = deepcopy(state)
block = build_empty_block_for_next_slot(test_state)
state_transition(test_state, block)
assert len(test_state.eth1_data_votes) == len(state.eth1_data_votes) + 1
assert get_block_root(test_state, state.slot) == block.previous_block_root
return state, [block], test_state
def test_skipped_slots(state):
test_state = deepcopy(state)
block = build_empty_block_for_next_slot(test_state)
block.slot += 3
state_transition(test_state, block)
assert test_state.slot == block.slot
for slot in range(state.slot, test_state.slot):
assert get_block_root(test_state, slot) == block.previous_block_root
return state, [block], test_state
def test_empty_epoch_transition(state):
test_state = deepcopy(state)
block = build_empty_block_for_next_slot(test_state)
block.slot += spec.SLOTS_PER_EPOCH
state_transition(test_state, block)
assert test_state.slot == block.slot
for slot in range(state.slot, test_state.slot):
assert get_block_root(test_state, slot) == block.previous_block_root
return state, [block], test_state
def test_empty_epoch_transition_not_finalizing(state):
test_state = deepcopy(state)
block = build_empty_block_for_next_slot(test_state)
block.slot += spec.SLOTS_PER_EPOCH * 5
state_transition(test_state, block)
assert test_state.slot == block.slot
assert test_state.finalized_epoch < get_current_epoch(test_state) - 4
return state, [block], test_state
def test_proposer_slashing(state, pubkeys, privkeys):
test_state = deepcopy(state)
current_epoch = get_current_epoch(test_state)
validator_index = get_active_validator_indices(test_state.validator_registry, current_epoch)[-1]
privkey = privkeys[validator_index]
slot = spec.GENESIS_SLOT
header_1 = BeaconBlockHeader(
slot=slot,
previous_block_root=ZERO_HASH,
state_root=ZERO_HASH,
block_body_root=ZERO_HASH,
signature=EMPTY_SIGNATURE,
)
header_2 = deepcopy(header_1)
header_2.previous_block_root = b'\x02' * 32
header_2.slot = slot + 1
domain = get_domain(
fork=test_state.fork,
epoch=get_current_epoch(test_state),
domain_type=spec.DOMAIN_BEACON_BLOCK,
)
header_1.signature = bls.sign(
message_hash=signed_root(header_1),
privkey=privkey,
domain=domain,
)
header_2.signature = bls.sign(
message_hash=signed_root(header_2),
privkey=privkey,
domain=domain,
)
proposer_slashing = ProposerSlashing(
proposer_index=validator_index,
header_1=header_1,
header_2=header_2,
)
#
# Add to state via block transition
#
block = build_empty_block_for_next_slot(test_state)
block.body.proposer_slashings.append(proposer_slashing)
state_transition(test_state, block)
assert not state.validator_registry[validator_index].initiated_exit
assert not state.validator_registry[validator_index].slashed
slashed_validator = test_state.validator_registry[validator_index]
assert not slashed_validator.initiated_exit
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 test_state.validator_balances[validator_index] < state.validator_balances[validator_index]
return state, [block], test_state
def test_deposit_in_block(state, deposit_data_leaves, pubkeys, privkeys):
pre_state = deepcopy(state)
test_deposit_data_leaves = deepcopy(deposit_data_leaves)
index = len(test_deposit_data_leaves)
pubkey = pubkeys[index]
privkey = privkeys[index]
deposit_data = build_deposit_data(pre_state, pubkey, privkey, spec.MAX_DEPOSIT_AMOUNT)
item = hash(deposit_data.serialize())
test_deposit_data_leaves.append(item)
tree = calc_merkle_tree_from_leaves(tuple(test_deposit_data_leaves))
root = get_merkle_root((tuple(test_deposit_data_leaves)))
proof = list(get_merkle_proof(tree, item_index=index))
assert verify_merkle_branch(item, proof, spec.DEPOSIT_CONTRACT_TREE_DEPTH, index, root)
deposit = Deposit(
proof=list(proof),
index=index,
deposit_data=deposit_data,
)
pre_state.latest_eth1_data.deposit_root = root
post_state = deepcopy(pre_state)
block = build_empty_block_for_next_slot(post_state)
block.body.deposits.append(deposit)
state_transition(post_state, block)
assert len(post_state.validator_registry) == len(state.validator_registry) + 1
assert len(post_state.validator_balances) == len(state.validator_balances) + 1
assert post_state.validator_registry[index].pubkey == pubkeys[index]
return pre_state, [block], post_state
def test_deposit_top_up(state, pubkeys, privkeys, deposit_data_leaves):
pre_state = deepcopy(state)
test_deposit_data_leaves = deepcopy(deposit_data_leaves)
validator_index = 0
amount = spec.MAX_DEPOSIT_AMOUNT // 4
pubkey = pubkeys[validator_index]
privkey = privkeys[validator_index]
deposit_data = build_deposit_data(pre_state, pubkey, privkey, amount)
merkle_index = len(test_deposit_data_leaves)
item = hash(deposit_data.serialize())
test_deposit_data_leaves.append(item)
tree = calc_merkle_tree_from_leaves(tuple(test_deposit_data_leaves))
root = get_merkle_root((tuple(test_deposit_data_leaves)))
proof = list(get_merkle_proof(tree, item_index=merkle_index))
assert verify_merkle_branch(item, proof, spec.DEPOSIT_CONTRACT_TREE_DEPTH, merkle_index, root)
deposit = Deposit(
proof=list(proof),
index=merkle_index,
deposit_data=deposit_data,
)
pre_state.latest_eth1_data.deposit_root = root
block = build_empty_block_for_next_slot(pre_state)
block.body.deposits.append(deposit)
pre_balance = pre_state.validator_balances[validator_index]
post_state = deepcopy(pre_state)
state_transition(post_state, block)
assert len(post_state.validator_registry) == len(pre_state.validator_registry)
assert len(post_state.validator_balances) == len(pre_state.validator_balances)
assert post_state.validator_balances[validator_index] == pre_balance + amount
return pre_state, [block], post_state
def test_attestation(state, pubkeys, privkeys):
test_state = deepcopy(state)
slot = state.slot
shard = state.current_shuffling_start_shard
attestation_data = build_attestation_data(state, slot, shard)
crosslink_committees = get_crosslink_committees_at_slot(state, slot)
crosslink_committee = [committee for committee, _shard in crosslink_committees if _shard == attestation_data.shard][0]
committee_size = len(crosslink_committee)
bitfield_length = (committee_size + 7) // 8
aggregation_bitfield = b'\x01' + b'\x00' * (bitfield_length - 1)
custody_bitfield = b'\x00' * bitfield_length
attestation = Attestation(
aggregation_bitfield=aggregation_bitfield,
data=attestation_data,
custody_bitfield=custody_bitfield,
aggregate_signature=EMPTY_SIGNATURE,
)
participants = get_attestation_participants(
test_state,
attestation.data,
attestation.aggregation_bitfield,
)
assert len(participants) == 1
validator_index = participants[0]
privkey = privkeys[validator_index]
message_hash = AttestationDataAndCustodyBit(
data=attestation.data,
custody_bit=0b0,
).hash_tree_root()
attestation.aggregation_signature = bls.sign(
message_hash=message_hash,
privkey=privkey,
domain=get_domain(
fork=test_state.fork,
epoch=get_current_epoch(test_state),
domain_type=spec.DOMAIN_ATTESTATION,
)
)
#
# Add to state via block transition
#
attestation_block = build_empty_block_for_next_slot(test_state)
attestation_block.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
attestation_block.body.attestations.append(attestation)
state_transition(test_state, attestation_block)
assert len(test_state.current_epoch_attestations) == len(state.current_epoch_attestations) + 1
#
# Epoch transition should move to previous_epoch_attestations
#
pre_current_epoch_attestations = deepcopy(test_state.current_epoch_attestations)
epoch_block = build_empty_block_for_next_slot(test_state)
epoch_block.slot += spec.SLOTS_PER_EPOCH
state_transition(test_state, epoch_block)
assert len(test_state.current_epoch_attestations) == 0
assert test_state.previous_epoch_attestations == pre_current_epoch_attestations
return state, [attestation_block, epoch_block], test_state
def test_voluntary_exit(state, pubkeys, privkeys):
pre_state = deepcopy(state)
validator_index = get_active_validator_indices(
pre_state.validator_registry,
get_current_epoch(pre_state)
)[-1]
# move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
pre_state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
# artificially trigger registry update at next epoch transition
pre_state.finalized_epoch = get_current_epoch(pre_state) - 1
for crosslink in pre_state.latest_crosslinks:
crosslink.epoch = pre_state.finalized_epoch
pre_state.validator_registry_update_epoch = pre_state.finalized_epoch - 1
post_state = deepcopy(pre_state)
voluntary_exit = VoluntaryExit(
epoch=get_current_epoch(pre_state),
validator_index=validator_index,
signature=EMPTY_SIGNATURE,
)
voluntary_exit.signature = bls.sign(
message_hash=signed_root(voluntary_exit),
privkey=privkeys[validator_index],
domain=get_domain(
fork=pre_state.fork,
epoch=get_current_epoch(pre_state),
domain_type=spec.DOMAIN_VOLUNTARY_EXIT,
)
)
#
# Add to state via block transition
#
initiate_exit_block = build_empty_block_for_next_slot(post_state)
initiate_exit_block.body.voluntary_exits.append(voluntary_exit)
state_transition(post_state, initiate_exit_block)
assert not pre_state.validator_registry[validator_index].initiated_exit
assert post_state.validator_registry[validator_index].initiated_exit
assert post_state.validator_registry[validator_index].exit_epoch == spec.FAR_FUTURE_EPOCH
#
# Process within epoch transition
#
exit_block = build_empty_block_for_next_slot(post_state)
exit_block.slot += spec.SLOTS_PER_EPOCH
state_transition(post_state, exit_block)
assert post_state.validator_registry[validator_index].exit_epoch < spec.FAR_FUTURE_EPOCH
return pre_state, [initiate_exit_block, exit_block], post_state
def test_no_exit_too_long_since_change(state):
pre_state = deepcopy(state)
validator_index = get_active_validator_indices(
pre_state.validator_registry,
get_current_epoch(pre_state)
)[-1]
#
# setup pre_state
#
# move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
pre_state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
# artificially trigger registry update at next epoch transition
pre_state.finalized_epoch = get_current_epoch(pre_state) - 1
for crosslink in pre_state.latest_crosslinks:
crosslink.epoch = pre_state.finalized_epoch
# make epochs since registry update greater than LATEST_SLASHED_EXIT_LENGTH
pre_state.validator_registry_update_epoch = (
get_current_epoch(pre_state) - spec.LATEST_SLASHED_EXIT_LENGTH
)
# set validator to have previously initiated exit
pre_state.validator_registry[validator_index].initiated_exit = True
post_state = deepcopy(pre_state)
#
# Process registry change but ensure no exit
#
block = build_empty_block_for_next_slot(post_state)
block.slot += spec.SLOTS_PER_EPOCH
state_transition(post_state, block)
assert post_state.validator_registry_update_epoch == get_current_epoch(post_state) - 1
assert post_state.validator_registry[validator_index].exit_epoch == spec.FAR_FUTURE_EPOCH
return pre_state, [block], post_state
def test_transfer(state, pubkeys, privkeys):
pre_state = deepcopy(state)
current_epoch = get_current_epoch(pre_state)
sender_index = get_active_validator_indices(pre_state.validator_registry, current_epoch)[-1]
recipient_index = get_active_validator_indices(pre_state.validator_registry, current_epoch)[0]
transfer_pubkey = pubkeys[-1]
transfer_privkey = privkeys[-1]
amount = pre_state.validator_balances[sender_index]
pre_transfer_recipient_balance = pre_state.validator_balances[recipient_index]
transfer = Transfer(
sender=sender_index,
recipient=recipient_index,
amount=amount,
fee=0,
slot=pre_state.slot + 1,
pubkey=transfer_pubkey,
signature=EMPTY_SIGNATURE,
)
transfer.signature = bls.sign(
message_hash=signed_root(transfer),
privkey=transfer_privkey,
domain=get_domain(
fork=pre_state.fork,
epoch=get_current_epoch(pre_state),
domain_type=spec.DOMAIN_TRANSFER,
)
)
# ensure withdrawal_credentials reproducable
pre_state.validator_registry[sender_index].withdrawal_credentials = (
spec.BLS_WITHDRAWAL_PREFIX_BYTE + hash(transfer_pubkey)[1:]
)
# un-activate so validator can transfer
pre_state.validator_registry[sender_index].activation_epoch = spec.FAR_FUTURE_EPOCH
post_state = deepcopy(pre_state)
#
# Add to state via block transition
#
block = build_empty_block_for_next_slot(post_state)
block.body.transfers.append(transfer)
state_transition(post_state, block)
sender_balance = post_state.validator_balances[sender_index]
recipient_balance = post_state.validator_balances[recipient_index]
assert sender_balance == 0
assert recipient_balance == pre_transfer_recipient_balance + amount
return pre_state, [block], post_state
def test_ejection(state):
pre_state = deepcopy(state)
current_epoch = get_current_epoch(pre_state)
validator_index = get_active_validator_indices(pre_state.validator_registry, current_epoch)[-1]
assert pre_state.validator_registry[validator_index].exit_epoch == spec.FAR_FUTURE_EPOCH
# set validator balance to below ejection threshold
pre_state.validator_balances[validator_index] = spec.EJECTION_BALANCE - 1
post_state = deepcopy(pre_state)
#
# trigger epoch transition
#
block = build_empty_block_for_next_slot(post_state)
block.slot += spec.SLOTS_PER_EPOCH
state_transition(post_state, block)
assert post_state.validator_registry[validator_index].initiated_exit == True
return pre_state, [block], post_state
def test_historical_batch(state):
pre_state = deepcopy(state)
pre_state.slot += spec.SLOTS_PER_HISTORICAL_ROOT - (pre_state.slot % spec.SLOTS_PER_HISTORICAL_ROOT) - 1
post_state = deepcopy(pre_state)
block = build_empty_block_for_next_slot(post_state)
state_transition(post_state, block)
assert post_state.slot == block.slot
assert get_current_epoch(post_state) % (spec.SLOTS_PER_HISTORICAL_ROOT // spec.SLOTS_PER_EPOCH) == 0
assert len(post_state.historical_roots) == len(pre_state.historical_roots) + 1
return pre_state, [block], post_state

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utils/__init__.py Normal file
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0
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12
utils/phase0/bls_stub.py Normal file
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def bls_verify(pubkey, message_hash, signature, domain):
return True
def bls_verify_multiple(pubkeys, message_hashes, signature, domain):
return True
def bls_aggregate_pubkeys(pubkeys):
return b'\x42' * 96

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# from hashlib import sha256
from eth_utils import keccak
# def hash(x): return sha256(x).digest()
def hash(x):
return keccak(x)

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from .hash_function import hash
zerohashes = [b'\x00' * 32]
for layer in range(1, 32):
zerohashes.append(hash(zerohashes[layer - 1] + zerohashes[layer - 1]))
# Compute a Merkle root of a right-zerobyte-padded 2**32 sized tree
def calc_merkle_tree_from_leaves(values):
values = list(values)
tree = [values[::]]
for h in range(32):
if len(values) % 2 == 1:
values.append(zerohashes[h])
values = [hash(values[i] + values[i + 1]) for i in range(0, len(values), 2)]
tree.append(values[::])
return tree
def get_merkle_root(values):
return calc_merkle_tree_from_leaves(values)[-1][0]
def get_merkle_proof(tree, item_index):
proof = []
for i in range(32):
subindex = (item_index // 2**i) ^ 1
proof.append(tree[i][subindex] if subindex < len(tree[i]) else zerohashes[i])
return proof

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utils/phase0/minimal_ssz.py Normal file
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from .hash_function import hash
BYTES_PER_CHUNK = 32
BYTES_PER_LENGTH_PREFIX = 4
ZERO_CHUNK = b'\x00' * BYTES_PER_CHUNK
def SSZType(fields):
class SSZObject():
def __init__(self, **kwargs):
for f in fields:
if f not in kwargs:
raise Exception("Missing constructor argument: %s" % f)
setattr(self, f, kwargs[f])
def __eq__(self, other):
return (
self.fields == other.fields and
self.serialize() == other.serialize()
)
def __hash__(self):
return int.from_bytes(self.hash_tree_root(), byteorder="little")
def __str__(self):
output = []
for field in self.fields:
output.append(f'{field}: {getattr(self, field)}')
return "\n".join(output)
def serialize(self):
return serialize_value(self, self.__class__)
def hash_tree_root(self):
return hash_tree_root(self, self.__class__)
SSZObject.fields = fields
return SSZObject
class Vector():
def __init__(self, items):
self.items = items
self.length = len(items)
def __getitem__(self, key):
return self.items[key]
def __setitem__(self, key, value):
self.items[key] = value
def __iter__(self):
return iter(self.items)
def __len__(self):
return self.length
def is_basic(typ):
return isinstance(typ, str) and (typ[:4] in ('uint', 'bool') or typ == 'byte')
def is_constant_sized(typ):
if is_basic(typ):
return True
elif isinstance(typ, list) and len(typ) == 1:
return is_constant_sized(typ[0])
elif isinstance(typ, list) and len(typ) == 2:
return False
elif isinstance(typ, str) and typ[:5] == 'bytes':
return len(typ) > 5
elif hasattr(typ, 'fields'):
for subtype in typ.fields.values():
if not is_constant_sized(subtype):
return False
return True
else:
raise Exception("Type not recognized")
def coerce_to_bytes(x):
if isinstance(x, str):
o = x.encode('utf-8')
assert len(o) == len(x)
return o
elif isinstance(x, bytes):
return x
else:
raise Exception("Expecting bytes")
def serialize_value(value, typ=None):
if typ is None:
typ = infer_type(value)
if isinstance(typ, str) and typ[:4] == 'uint':
length = int(typ[4:])
assert length in (8, 16, 32, 64, 128, 256)
return value.to_bytes(length // 8, 'little')
elif typ == 'bool':
assert value in (True, False)
return b'\x01' if value is True else b'\x00'
elif (isinstance(typ, list) and len(typ) == 1) or typ == 'bytes':
serialized_bytes = coerce_to_bytes(value) if typ == 'bytes' else b''.join([serialize_value(element, typ[0]) for element in value])
assert len(serialized_bytes) < 2**(8 * BYTES_PER_LENGTH_PREFIX)
serialized_length = len(serialized_bytes).to_bytes(BYTES_PER_LENGTH_PREFIX, 'little')
return serialized_length + serialized_bytes
elif isinstance(typ, list) and len(typ) == 2:
assert len(value) == typ[1]
return b''.join([serialize_value(element, typ[0]) for element in value])
elif isinstance(typ, str) and len(typ) > 5 and typ[:5] == 'bytes':
assert len(value) == int(typ[5:]), (value, int(typ[5:]))
return coerce_to_bytes(value)
elif hasattr(typ, 'fields'):
serialized_bytes = b''.join([serialize_value(getattr(value, field), subtype) for field, subtype in typ.fields.items()])
if is_constant_sized(typ):
return serialized_bytes
else:
assert len(serialized_bytes) < 2**(8 * BYTES_PER_LENGTH_PREFIX)
serialized_length = len(serialized_bytes).to_bytes(BYTES_PER_LENGTH_PREFIX, 'little')
return serialized_length + serialized_bytes
else:
print(value, typ)
raise Exception("Type not recognized")
def chunkify(bytez):
bytez += b'\x00' * (-len(bytez) % BYTES_PER_CHUNK)
return [bytez[i:i + 32] for i in range(0, len(bytez), 32)]
def pack(values, subtype):
return chunkify(b''.join([serialize_value(value, subtype) for value in values]))
def is_power_of_two(x):
return x > 0 and x & (x - 1) == 0
def merkleize(chunks):
tree = chunks[::]
while not is_power_of_two(len(tree)):
tree.append(ZERO_CHUNK)
tree = [ZERO_CHUNK] * len(tree) + tree
for i in range(len(tree) // 2 - 1, 0, -1):
tree[i] = hash(tree[i * 2] + tree[i * 2 + 1])
return tree[1]
def mix_in_length(root, length):
return hash(root + length.to_bytes(32, 'little'))
def infer_type(value):
if hasattr(value.__class__, 'fields'):
return value.__class__
elif isinstance(value, Vector):
return [infer_type(value[0]) if len(value) > 0 else 'uint64', len(value)]
elif isinstance(value, list):
return [infer_type(value[0])] if len(value) > 0 else ['uint64']
elif isinstance(value, (bytes, str)):
return 'bytes'
elif isinstance(value, int):
return 'uint64'
else:
raise Exception("Failed to infer type")
def hash_tree_root(value, typ=None):
if typ is None:
typ = infer_type(value)
if is_basic(typ):
return merkleize(pack([value], typ))
elif isinstance(typ, list) and len(typ) == 1 and is_basic(typ[0]):
return mix_in_length(merkleize(pack(value, typ[0])), len(value))
elif isinstance(typ, list) and len(typ) == 1 and not is_basic(typ[0]):
return mix_in_length(merkleize([hash_tree_root(element, typ[0]) for element in value]), len(value))
elif isinstance(typ, list) and len(typ) == 2 and is_basic(typ[0]):
assert len(value) == typ[1]
return merkleize(pack(value, typ[0]))
elif typ == 'bytes':
return mix_in_length(merkleize(chunkify(coerce_to_bytes(value))), len(value))
elif isinstance(typ, str) and typ[:5] == 'bytes' and len(typ) > 5:
assert len(value) == int(typ[5:])
return merkleize(chunkify(coerce_to_bytes(value)))
elif isinstance(typ, list) and len(typ) == 2 and not is_basic(typ[0]):
return merkleize([hash_tree_root(element, typ[0]) for element in value])
elif hasattr(typ, 'fields'):
return merkleize([hash_tree_root(getattr(value, field), subtype) for field, subtype in typ.fields.items()])
else:
raise Exception("Type not recognized")
def truncate(container):
field_keys = list(container.fields.keys())
truncated_fields = {
key: container.fields[key]
for key in field_keys[:-1]
}
truncated_class = SSZType(truncated_fields)
kwargs = {
field: getattr(container, field)
for field in field_keys[:-1]
}
return truncated_class(**kwargs)
def signed_root(container):
return hash_tree_root(truncate(container))
def serialize(ssz_object):
return getattr(ssz_object, 'serialize')()

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from . import spec
from typing import ( # noqa: F401
Any,
Callable,
List,
NewType,
Tuple,
)
from .spec import (
BeaconState,
BeaconBlock,
)
def process_transaction_type(state: BeaconState,
transactions: List[Any],
max_transactions: int,
tx_fn: Callable[[BeaconState, Any], None]) -> None:
assert len(transactions) <= max_transactions
for transaction in transactions:
tx_fn(state, transaction)
def process_transactions(state: BeaconState, block: BeaconBlock) -> None:
process_transaction_type(
state,
block.body.proposer_slashings,
spec.MAX_PROPOSER_SLASHINGS,
spec.process_proposer_slashing,
)
process_transaction_type(
state,
block.body.attester_slashings,
spec.MAX_ATTESTER_SLASHINGS,
spec.process_attester_slashing,
)
process_transaction_type(
state,
block.body.attestations,
spec.MAX_ATTESTATIONS,
spec.process_attestation,
)
process_transaction_type(
state,
block.body.deposits,
spec.MAX_DEPOSITS,
spec.process_deposit,
)
process_transaction_type(
state,
block.body.voluntary_exits,
spec.MAX_VOLUNTARY_EXITS,
spec.process_voluntary_exit,
)
assert len(block.body.transfers) == len(set(block.body.transfers))
process_transaction_type(
state,
block.body.transfers,
spec.MAX_TRANSFERS,
spec.process_transfer,
)
def process_block(state: BeaconState,
block: BeaconBlock,
verify_state_root: bool=False) -> None:
spec.process_block_header(state, block)
spec.process_randao(state, block)
spec.process_eth1_data(state, block)
process_transactions(state, block)
if verify_state_root:
spec.verify_block_state_root(state, block)
def process_epoch_transition(state: BeaconState) -> None:
spec.update_justification_and_finalization(state)
spec.process_crosslinks(state)
spec.maybe_reset_eth1_period(state)
spec.apply_rewards(state)
spec.process_ejections(state)
spec.update_registry_and_shuffling_data(state)
spec.process_slashings(state)
spec.process_exit_queue(state)
spec.finish_epoch_update(state)
def state_transition(state: BeaconState,
block: BeaconBlock,
verify_state_root: bool=False) -> BeaconState:
while state.slot < block.slot:
spec.cache_state(state)
if (state.slot + 1) % spec.SLOTS_PER_EPOCH == 0:
process_epoch_transition(state)
spec.advance_slot(state)
if block.slot == state.slot:
process_block(state, block, verify_state_root)