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2a91b43eaf
Only store a 32 byte root for every shard block Rationale: originally, I added shard block chunking (store 4 chunks for every shard block instead of one root) to facilitate construction of data availability roots. However, it turns out that there is an easier technique. Set the width of the data availability rectangle's rows to be 1/4 the max size of a shard block, so each block would fill multiple rows. Then, non-full blocks will generally create lots of zero rows. For example if the block bodies are `31415926535` and `897932` with a max size of 24 bytes, the rows might look like this: ``` 31415926 53500000 00000000 89793200 00000000 00000000 ``` Zero rows would extend rightward to complete zero rows, and when extending downward we can count the number of zero rows, and reduce the number of extra rows that we make, so we only make a new row for every nonzero row in the original data. This way we get only a close-to-optimal ~4-5x blowup in the data even if the data has zero rows in the middle.
34 KiB
34 KiB
Ethereum 2.0 Phase 1 -- The Beacon Chain for Shards
Notice: This document is a work-in-progress for researchers and implementers.
Table of contents
Table of Contents
- Introduction
- Custom types
- Configuration
- Updated containers
- New containers
- Helper functions
Introduction
This document describes the extensions made to the Phase 0 design of The Beacon Chain to facilitate the new shards as part of Phase 1 of Eth2.
Custom types
We define the following Python custom types for type hinting and readability:
| Name | SSZ equivalent | Description |
|---|---|---|
Shard |
uint64 |
a shard number |
OnlineEpochs |
uint8 |
online countdown epochs |
Configuration
Configuration is not namespaced. Instead it is strictly an extension; no constants of phase 0 change, but new constants are adopted for changing behaviors.
Misc
| Name | Value | Unit | Duration |
|---|---|---|---|
MAX_SHARDS |
2**10 (= 1024) |
||
ONLINE_PERIOD |
OnlineEpochs(2**3) (= 8) |
online epochs | ~51 min |
LIGHT_CLIENT_COMMITTEE_SIZE |
2**7 (= 128) |
||
LIGHT_CLIENT_COMMITTEE_PERIOD |
Epoch(2**8) (= 256) |
epochs | ~27 hours |
SHARD_COMMITTEE_PERIOD |
Epoch(2**8) (= 256) |
epochs | ~27 hours |
MAX_SHARD_BLOCK_SIZE |
2**20 (= 1,048,576) |
||
TARGET_SHARD_BLOCK_SIZE |
2**18 (= 262,144) |
||
SHARD_BLOCK_OFFSETS |
[1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233] |
||
MAX_SHARD_BLOCKS_PER_ATTESTATION |
len(SHARD_BLOCK_OFFSETS) |
||
MAX_GASPRICE |
Gwei(2**14) (= 16,384) |
Gwei | |
MIN_GASPRICE |
Gwei(2**5) (= 32) |
Gwei | |
GASPRICE_ADJUSTMENT_COEFFICIENT |
2**3 (= 8) |
||
DOMAIN_SHARD_PROPOSAL |
DomainType('0x80000000') |
||
DOMAIN_SHARD_COMMITTEE |
DomainType('0x81000000') |
||
DOMAIN_LIGHT_CLIENT |
DomainType('0x82000000') |
Updated containers
The following containers have updated definitions in Phase 1.
Extended AttestationData
class AttestationData(Container):
slot: Slot
index: CommitteeIndex
# LMD GHOST vote
beacon_block_root: Root
# FFG vote
source: Checkpoint
target: Checkpoint
# Current-slot shard block root
head_shard_root: Root
# Shard transition root
shard_transition_root: Root
Extended Attestation
class Attestation(Container):
aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
data: AttestationData
custody_bits_blocks: List[Bitlist[MAX_VALIDATORS_PER_COMMITTEE], MAX_SHARD_BLOCKS_PER_ATTESTATION]
signature: BLSSignature
Extended PendingAttestation
class PendingAttestation(Container):
aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
data: AttestationData
inclusion_delay: Slot
proposer_index: ValidatorIndex
crosslink_success: boolean
IndexedAttestation
class IndexedAttestation(Container):
committee: List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE]
attestation: Attestation
Extended AttesterSlashing
Note that the attestation_1 and attestation_2 have a new IndexedAttestation definition.
class AttesterSlashing(Container):
attestation_1: IndexedAttestation
attestation_2: IndexedAttestation
Extended Validator
class Validator(Container):
pubkey: BLSPubkey
withdrawal_credentials: Bytes32 # Commitment to pubkey for withdrawals
effective_balance: Gwei # Balance at stake
slashed: boolean
# Status epochs
activation_eligibility_epoch: Epoch # When criteria for activation were met
activation_epoch: Epoch
exit_epoch: Epoch
withdrawable_epoch: Epoch # When validator can withdraw funds
# Custody game
# next_custody_secret_to_reveal is initialised to the custody period
# (of the particular validator) in which the validator is activated
# = get_custody_period_for_validator(...)
next_custody_secret_to_reveal: uint64
max_reveal_lateness: Epoch
Extended BeaconBlockBody
class BeaconBlockBody(Container):
randao_reveal: BLSSignature
eth1_data: Eth1Data # Eth1 data vote
graffiti: Bytes32 # Arbitrary data
# Slashings
proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS]
# Attesting
attestations: List[Attestation, MAX_ATTESTATIONS]
# Entry & exit
deposits: List[Deposit, MAX_DEPOSITS]
voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
# Custody game
custody_slashings: List[SignedCustodySlashing, MAX_CUSTODY_SLASHINGS]
custody_key_reveals: List[CustodyKeyReveal, MAX_CUSTODY_KEY_REVEALS]
early_derived_secret_reveals: List[EarlyDerivedSecretReveal, MAX_EARLY_DERIVED_SECRET_REVEALS]
# Shards
shard_transitions: Vector[ShardTransition, MAX_SHARDS]
# Light clients
light_client_signature_bitfield: Bitvector[LIGHT_CLIENT_COMMITTEE_SIZE]
light_client_signature: BLSSignature
Extended BeaconBlock
Note that the body has a new BeaconBlockBody definition.
class BeaconBlock(Container):
slot: Slot
parent_root: Root
state_root: Root
body: BeaconBlockBody
Extended SignedBeaconBlock
Note that the message has a new BeaconBlock definition.
class SignedBeaconBlock(Container):
message: BeaconBlock
signature: BLSSignature
Extended BeaconState
Note that aside from the new additions, Validator and PendingAttestation have new definitions.
class BeaconState(Container):
# Versioning
genesis_time: uint64
slot: Slot
fork: Fork
# History
latest_block_header: BeaconBlockHeader
block_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
state_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
historical_roots: List[Root, HISTORICAL_ROOTS_LIMIT]
# Eth1
eth1_data: Eth1Data
eth1_data_votes: List[Eth1Data, SLOTS_PER_ETH1_VOTING_PERIOD]
eth1_deposit_index: uint64
# Registry
validators: List[Validator, VALIDATOR_REGISTRY_LIMIT]
balances: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
# Randomness
randao_mixes: Vector[Root, EPOCHS_PER_HISTORICAL_VECTOR]
# Slashings
slashings: Vector[Gwei, EPOCHS_PER_SLASHINGS_VECTOR] # Per-epoch sums of slashed effective balances
# Attestations
previous_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
current_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
# Finality
justification_bits: Bitvector[JUSTIFICATION_BITS_LENGTH] # Bit set for every recent justified epoch
previous_justified_checkpoint: Checkpoint # Previous epoch snapshot
current_justified_checkpoint: Checkpoint
finalized_checkpoint: Checkpoint
# Phase 1
shard_states: List[ShardState, MAX_SHARDS]
online_countdown: List[OnlineEpochs, VALIDATOR_REGISTRY_LIMIT] # not a raw byte array, considered its large size.
current_light_committee: CompactCommittee
next_light_committee: CompactCommittee
# Custody game
# Future derived secrets already exposed; contains the indices of the exposed validator
# at RANDAO reveal period % EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS
exposed_derived_secrets: Vector[List[ValidatorIndex, MAX_EARLY_DERIVED_SECRET_REVEALS * SLOTS_PER_EPOCH],
EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS]
New containers
The following containers are new in Phase 1.
ShardBlockWrapper
Wrapper for being broadcasted over the network.
class ShardBlockWrapper(Container):
shard_parent_root: Root
beacon_parent_root: Root
slot: Slot
body: ByteList[MAX_SHARD_BLOCK_SIZE]
signature: BLSSignature
ShardSignableHeader
class ShardSignableHeader(Container):
shard_parent_root: Root
beacon_parent_root: Root
slot: Slot
body_root: Root
ShardState
class ShardState(Container):
slot: Slot
gasprice: Gwei
data: Bytes32
latest_block_root: Root
ShardTransition
class ShardTransition(Container):
# Starting from slot
start_slot: Slot
# Shard block lengths
shard_block_lengths: List[uint64, MAX_SHARD_BLOCKS_PER_ATTESTATION]
# Shard data roots
shard_data_roots: List[Bytes32, MAX_SHARD_BLOCKS_PER_ATTESTATION]
# Intermediate shard states
shard_states: List[ShardState, MAX_SHARD_BLOCKS_PER_ATTESTATION]
# Proposer signature aggregate
proposer_signature_aggregate: BLSSignature
CompactCommittee
class CompactCommittee(Container):
pubkeys: List[BLSPubkey, MAX_VALIDATORS_PER_COMMITTEE]
compact_validators: List[uint64, MAX_VALIDATORS_PER_COMMITTEE]
AttestationCustodyBitWrapper
class AttestationCustodyBitWrapper(Container):
attestation_data_root: Root
block_index: uint64
bit: boolean
Helper functions
Misc
get_previous_slot
def get_previous_slot(slot: Slot) -> Slot:
if slot > 0:
return Slot(slot - 1)
else:
return Slot(0)
pack_compact_validator
def pack_compact_validator(index: int, slashed: bool, balance_in_increments: int) -> int:
"""
Creates a compact validator object representing index, slashed status, and compressed balance.
Takes as input balance-in-increments (// EFFECTIVE_BALANCE_INCREMENT) to preserve symmetry with
the unpacking function.
"""
return (index << 16) + (slashed << 15) + balance_in_increments
committee_to_compact_committee
def committee_to_compact_committee(state: BeaconState, committee: Sequence[ValidatorIndex]) -> CompactCommittee:
"""
Given a state and a list of validator indices, outputs the CompactCommittee representing them.
"""
validators = [state.validators[i] for i in committee]
compact_validators = [
pack_compact_validator(i, v.slashed, v.effective_balance // EFFECTIVE_BALANCE_INCREMENT)
for i, v in zip(committee, validators)
]
pubkeys = [v.pubkey for v in validators]
return CompactCommittee(pubkeys=pubkeys, compact_validators=compact_validators)
compute_shard_from_committee_index
def compute_shard_from_committee_index(state: BeaconState, index: CommitteeIndex, slot: Slot) -> Shard:
active_shards = get_active_shard_count(state)
return Shard((index + get_start_shard(state, slot)) % active_shards)
Beacon state accessors
get_active_shard_count
def get_active_shard_count(state: BeaconState) -> uint64:
return len(state.shard_states) # May adapt in the future, or change over time.
get_online_validator_indices
def get_online_validator_indices(state: BeaconState) -> Set[ValidatorIndex]:
active_validators = get_active_validator_indices(state, get_current_epoch(state))
return set([i for i in active_validators if state.online_countdown[i] != 0])
get_shard_committee
def get_shard_committee(beacon_state: BeaconState, epoch: Epoch, shard: Shard) -> Sequence[ValidatorIndex]:
source_epoch = epoch - epoch % SHARD_COMMITTEE_PERIOD
if source_epoch > 0:
source_epoch -= SHARD_COMMITTEE_PERIOD
active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
seed = get_seed(beacon_state, source_epoch, DOMAIN_SHARD_COMMITTEE)
return compute_committee(active_validator_indices, seed, shard, get_active_shard_count(beacon_state))
get_shard_proposer_index
def get_shard_proposer_index(beacon_state: BeaconState, slot: Slot, shard: Shard) -> ValidatorIndex:
committee = get_shard_committee(beacon_state, compute_epoch_at_slot(slot), shard)
r = bytes_to_int(get_seed(beacon_state, get_current_epoch(beacon_state), DOMAIN_SHARD_COMMITTEE)[:8])
return committee[r % len(committee)]
get_light_client_committee
def get_light_client_committee(beacon_state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
source_epoch = epoch - epoch % LIGHT_CLIENT_COMMITTEE_PERIOD
if source_epoch > 0:
source_epoch -= LIGHT_CLIENT_COMMITTEE_PERIOD
active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
seed = get_seed(beacon_state, source_epoch, DOMAIN_LIGHT_CLIENT)
active_shards = get_active_shard_count(beacon_state)
return compute_committee(active_validator_indices, seed, 0, active_shards)[:TARGET_COMMITTEE_SIZE]
get_indexed_attestation
def get_indexed_attestation(beacon_state: BeaconState, attestation: Attestation) -> IndexedAttestation:
committee = get_beacon_committee(beacon_state, attestation.data.slot, attestation.data.index)
return IndexedAttestation(
committee=committee,
attestation=attestation,
)
get_updated_gasprice
def get_updated_gasprice(prev_gasprice: Gwei, length: uint8) -> Gwei:
if length > TARGET_SHARD_BLOCK_SIZE:
delta = (prev_gasprice * (length - TARGET_SHARD_BLOCK_SIZE)
// TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
return min(prev_gasprice + delta, MAX_GASPRICE)
else:
delta = (prev_gasprice * (TARGET_SHARD_BLOCK_SIZE - length)
// TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
return max(prev_gasprice, MIN_GASPRICE + delta) - delta
get_start_shard
def get_start_shard(state: BeaconState, slot: Slot) -> Shard:
# TODO: implement start shard logic
return Shard(0)
get_shard
def get_shard(state: BeaconState, attestation: Attestation) -> Shard:
return compute_shard_from_committee_index(state, attestation.data.index, attestation.data.slot)
get_next_slot_for_shard
def get_next_slot_for_shard(state: BeaconState, shard: Shard) -> Slot:
return Slot(state.shard_states[shard].slot + 1)
get_offset_slots
def get_offset_slots(state: BeaconState, start_slot: Slot) -> Sequence[Slot]:
return [Slot(start_slot + x) for x in SHARD_BLOCK_OFFSETS if start_slot + x < state.slot]
Predicates
Updated is_valid_indexed_attestation
Note that this replaces the Phase 0 is_valid_indexed_attestation.
def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: IndexedAttestation) -> bool:
"""
Check if ``indexed_attestation`` has valid indices and signature.
"""
# Verify aggregate signature
all_pubkeys = []
all_signing_roots = []
attestation = indexed_attestation.attestation
domain = get_domain(state, DOMAIN_BEACON_ATTESTER, attestation.data.target.epoch)
aggregation_bits = attestation.aggregation_bits
assert len(aggregation_bits) == len(indexed_attestation.committee)
if len(attestation.custody_bits_blocks) == 0:
# fall back on phase0 behavior if there is no shard data.
for participant, abit in zip(indexed_attestation.committee, aggregation_bits):
if abit:
all_pubkeys.append(state.validators[participant].pubkey)
signing_root = compute_signing_root(indexed_attestation.attestation.data, domain)
return bls.FastAggregateVerify(all_pubkeys, signing_root, signature=attestation.signature)
else:
for i, custody_bits in enumerate(attestation.custody_bits_blocks):
assert len(custody_bits) == len(indexed_attestation.committee)
for participant, abit, cbit in zip(indexed_attestation.committee, aggregation_bits, custody_bits):
if abit:
all_pubkeys.append(state.validators[participant].pubkey)
# Note: only 2N distinct message hashes
all_signing_roots.append(compute_signing_root(
AttestationCustodyBitWrapper(hash_tree_root(attestation.data), i, cbit), domain))
else:
assert not cbit
return bls.AggregateVerify(zip(all_pubkeys, all_signing_roots), signature=attestation.signature)
Block processing
def process_block(state: BeaconState, block: BeaconBlock) -> None:
process_block_header(state, block)
process_randao(state, block.body)
process_eth1_data(state, block.body)
verify_shard_transition_false_positives(state, block.body)
process_light_client_signatures(state, block.body)
process_operations(state, block.body)
Operations
def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
# Verify that outstanding deposits are processed up to the maximum number of deposits
assert len(body.deposits) == min(MAX_DEPOSITS, state.eth1_data.deposit_count - state.eth1_deposit_index)
def for_ops(operations: Sequence[Any], fn: Callable[[BeaconState, Any], None]) -> None:
for operation in operations:
fn(state, operation)
for_ops(body.proposer_slashings, process_proposer_slashing)
for_ops(body.attester_slashings, process_attester_slashing)
# New attestation processing
process_attestations(state, body, body.attestations)
for_ops(body.deposits, process_deposit)
for_ops(body.voluntary_exits, process_voluntary_exit)
# See custody game spec.
process_custody_game_operations(state, body)
# TODO process_operations(body.shard_receipt_proofs, process_shard_receipt_proofs)
New Attestation processing
validate_attestation
def validate_attestation(state: BeaconState, attestation: Attestation) -> None:
data = attestation.data
assert data.index < get_committee_count_at_slot(state, data.slot)
assert data.index < get_active_shard_count(state)
assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot <= data.slot + SLOTS_PER_EPOCH
committee = get_beacon_committee(state, data.slot, data.index)
assert len(attestation.aggregation_bits) == len(committee)
if attestation.data.target.epoch == get_current_epoch(state):
assert attestation.data.source == state.current_justified_checkpoint
else:
assert attestation.data.source == state.previous_justified_checkpoint
shard = get_shard(state, attestation)
shard_start_slot = get_next_slot_for_shard(state, shard)
# Signature check
assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
# Type 1: on-time attestations
if attestation.custody_bits_blocks != []:
# Correct slot
assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY == state.slot
# Correct data root count
assert len(attestation.custody_bits_blocks) == len(get_offset_slots(state, shard_start_slot))
# Correct parent block root
assert data.beacon_block_root == get_block_root_at_slot(state, get_previous_slot(state.slot))
# Type 2: no shard transition, no custody bits # TODO: could only allow for older attestations.
else:
# assert state.slot - compute_start_slot_at_epoch(compute_epoch_at_slot(data.slot)) < SLOTS_PER_EPOCH
assert data.shard_transition_root == Root()
apply_shard_transition
def apply_shard_transition(state: BeaconState, shard: Shard, transition: ShardTransition) -> None:
# Slot the attestation starts counting from
start_slot = get_next_slot_for_shard(state, shard)
# Correct data root count
offset_slots = get_offset_slots(state, start_slot)
assert (
len(transition.shard_data_roots)
== len(transition.shard_states)
== len(transition.shard_block_lengths)
== len(offset_slots)
)
assert transition.start_slot == start_slot
# Reconstruct shard headers
headers = []
proposers = []
shard_parent_root = state.shard_states[shard].latest_block_root
for i in range(len(offset_slots)):
if any(transition.shard_data_roots):
headers.append(ShardSignableHeader(
shard_parent_root=shard_parent_root,
parent_hash=get_block_root_at_slot(state, get_previous_slot(state.slot)),
slot=offset_slots[i],
body_root=transition.shard_data_roots[i]
))
proposers.append(get_shard_proposer_index(state, shard, offset_slots[i]))
shard_parent_root = hash_tree_root(headers[-1])
# Verify correct calculation of gas prices and slots
prev_gasprice = state.shard_states[shard].gasprice
for i in range(len(offset_slots)):
shard_state = transition.shard_states[i]
block_length = transition.shard_block_lengths[i]
assert shard_state.gasprice == get_updated_gasprice(prev_gasprice, block_length)
assert shard_state.slot == offset_slots[i]
prev_gasprice = shard_state.gasprice
pubkeys = [state.validators[proposer].pubkey for proposer in proposers]
signing_roots = [
compute_signing_root(header, get_domain(state, DOMAIN_SHARD_PROPOSAL, compute_epoch_at_slot(header.slot)))
for header in headers
]
# Verify combined proposer signature
assert bls.AggregateVerify(zip(pubkeys, signing_roots), signature=transition.proposer_signature_aggregate)
# Save updated state
state.shard_states[shard] = transition.shard_states[-1]
state.shard_states[shard].slot = state.slot - 1
process_crosslink_for_shard
def process_crosslink_for_shard(state: BeaconState,
shard: Shard,
shard_transition: ShardTransition,
attestations: Sequence[Attestation]) -> Root:
committee = get_beacon_committee(state, get_current_epoch(state), shard)
online_indices = get_online_validator_indices(state)
# Loop over all shard transition roots
shard_transition_roots = set([a.data.shard_transition_root for a in attestations])
for shard_transition_root in sorted(shard_transition_roots):
transition_attestations = [a for a in attestations if a.data.shard_transition_root == shard_transition_root]
transition_participants: Set[ValidatorIndex] = set()
for attestation in transition_attestations:
participants = get_attesting_indices(state, attestation.data, attestation.aggregation_bits)
transition_participants = transition_participants.union(participants)
enough_online_stake = (
get_total_balance(state, online_indices.intersection(transition_participants)) * 3 >=
get_total_balance(state, online_indices.intersection(committee)) * 2
)
# If not enough stake, try next transition root
if not enough_online_stake:
continue
# Attestation <-> shard transition consistency
assert shard_transition_root == hash_tree_root(shard_transition)
assert attestation.data.head_shard_root == shard_transition.shard_data_roots[-1]
# Apply transition
apply_shard_transition(state, shard, shard_transition)
# Apply proposer reward and cost
beacon_proposer_index = get_beacon_proposer_index(state)
estimated_attester_reward = sum([get_base_reward(state, attester) for attester in transition_participants])
proposer_reward = Gwei(estimated_attester_reward // PROPOSER_REWARD_QUOTIENT)
increase_balance(state, beacon_proposer_index, proposer_reward)
states_slots_lengths = zip(
shard_transition.shard_states,
get_offset_slots(state, get_next_slot_for_shard(state, shard)),
shard_transition.shard_block_lengths
)
for shard_state, slot, length in states_slots_lengths:
proposer_index = get_shard_proposer_index(state, shard, slot)
decrease_balance(state, proposer_index, shard_state.gasprice * length)
# Return winning transition root
return shard_transition_root
# No winning transition root, ensure empty and return empty root
assert shard_transition == ShardTransition()
return Root()
process_crosslinks
def process_crosslinks(state: BeaconState,
block_body: BeaconBlockBody,
attestations: Sequence[Attestation]) -> Set[Tuple[Shard, Root]]:
winners: Set[Tuple[Shard, Root]] = set()
committee_count = get_committee_count_at_slot(state, state.slot)
for committee_index in map(CommitteeIndex, range(committee_count)):
shard = compute_shard_from_committee_index(state, committee_index, state.slot)
# All attestations in the block for this shard
shard_attestations = [
attestation for attestation in attestations
if get_shard(state, attestation) == shard and attestation.data.slot == state.slot
]
shard_transition = block_body.shard_transitions[shard]
winning_root = process_crosslink_for_shard(state, shard, shard_transition, shard_attestations)
if winning_root != Root():
winners.add((shard, winning_root))
return winners
process_attestations
def process_attestations(state: BeaconState, block_body: BeaconBlockBody, attestations: Sequence[Attestation]) -> None:
# Basic validation
for attestation in attestations:
validate_attestation(state, attestation)
# Process crosslinks
winners = process_crosslinks(state, block_body, attestations)
# Store pending attestations for epoch processing
for attestation in attestations:
is_winning_transition = (get_shard(state, attestation), attestation.data.shard_transition_root) in winners
pending_attestation = PendingAttestation(
aggregation_bits=attestation.aggregation_bits,
data=attestation.data,
inclusion_delay=state.slot - attestation.data.slot,
crosslink_success=is_winning_transition and attestation.data.slot == state.slot,
proposer_index=get_beacon_proposer_index(state),
)
if attestation.data.target.epoch == get_current_epoch(state):
state.current_epoch_attestations.append(pending_attestation)
else:
state.previous_epoch_attestations.append(pending_attestation)
New Attester slashing processing
def get_indices_from_committee(
committee: List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE],
bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]) -> List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE]:
assert len(bits) == len(committee)
return List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE](
[validator_index for i, validator_index in enumerate(committee) if bits[i]]
)
def process_attester_slashing(state: BeaconState, attester_slashing: AttesterSlashing) -> None:
indexed_attestation_1 = attester_slashing.attestation_1
indexed_attestation_2 = attester_slashing.attestation_2
assert is_slashable_attestation_data(
indexed_attestation_1.attestation.data,
indexed_attestation_2.attestation.data,
)
assert is_valid_indexed_attestation(state, indexed_attestation_1)
assert is_valid_indexed_attestation(state, indexed_attestation_2)
indices_1 = get_indices_from_committee(
indexed_attestation_1.committee,
indexed_attestation_1.attestation.aggregation_bits,
)
indices_2 = get_indices_from_committee(
indexed_attestation_2.committee,
indexed_attestation_2.attestation.aggregation_bits,
)
slashed_any = False
indices = set(indices_1).intersection(indices_2)
for index in sorted(indices):
if is_slashable_validator(state.validators[index], get_current_epoch(state)):
slash_validator(state, index)
slashed_any = True
assert slashed_any
Shard transition false positives
def verify_shard_transition_false_positives(state: BeaconState, block_body: BeaconBlockBody) -> None:
# Verify that a `shard_transition` in a block is empty if an attestation was not processed for it
for shard in range(get_active_shard_count(state)):
if state.shard_states[shard].slot != state.slot - 1:
assert block_body.shard_transitions[shard] == ShardTransition()
Light client processing
def process_light_client_signatures(state: BeaconState, block_body: BeaconBlockBody) -> None:
committee = get_light_client_committee(state, get_current_epoch(state))
total_reward = Gwei(0)
signer_pubkeys = []
for bit_index, participant_index in enumerate(committee):
if block_body.light_client_signature_bitfield[bit_index]:
signer_pubkeys.append(state.validators[participant_index].pubkey)
increase_balance(state, participant_index, get_base_reward(state, participant_index))
total_reward += get_base_reward(state, participant_index)
increase_balance(state, get_beacon_proposer_index(state), Gwei(total_reward // PROPOSER_REWARD_QUOTIENT))
slot = get_previous_slot(state.slot)
signing_root = compute_signing_root(get_block_root_at_slot(state, slot),
get_domain(state, DOMAIN_LIGHT_CLIENT, compute_epoch_at_slot(slot)))
return bls.FastAggregateVerify(signer_pubkeys, signing_root, signature=block_body.light_client_signature)
Epoch transition
This epoch transition overrides the phase0 epoch transition:
def process_epoch(state: BeaconState) -> None:
process_justification_and_finalization(state)
process_rewards_and_penalties(state)
process_registry_updates(state)
process_reveal_deadlines(state)
process_slashings(state)
process_final_updates(state)
process_custody_final_updates(state)
process_online_tracking(state)
process_light_client_committee_updates(state)
Custody game updates
process_reveal_deadlines and process_custody_final_updates are defined in the Custody Game spec,
Online-tracking
def process_online_tracking(state: BeaconState) -> None:
# Slowly remove validators from the "online" set if they do not show up
for index in range(len(state.validators)):
if state.online_countdown[index] != 0:
state.online_countdown[index] = state.online_countdown[index] - 1
# Process pending attestations
for pending_attestation in state.current_epoch_attestations + state.previous_epoch_attestations:
for index in get_attesting_indices(state, pending_attestation.data, pending_attestation.aggregation_bits):
state.online_countdown[index] = ONLINE_PERIOD
Light client committee updates
def process_light_client_committee_updates(state: BeaconState) -> None:
# Update light client committees
if get_current_epoch(state) % LIGHT_CLIENT_COMMITTEE_PERIOD == 0:
state.current_light_committee = state.next_light_committee
new_committee = get_light_client_committee(state, get_current_epoch(state) + LIGHT_CLIENT_COMMITTEE_PERIOD)
state.next_light_committee = committee_to_compact_committee(state, new_committee)