16 KiB
16 KiB
EIP-6110 -- The Beacon Chain
Table of contents
Introduction
This is the beacon chain specification of in-protocol deposits processing mechanism. This mechanism relies on the changes proposed by EIP-6110.
Note: This specification is under development and should be used with care.
Constants
The following values are (non-configurable) constants used throughout the specification.
Misc
| Name | Value |
|---|---|
NOT_SET_DEPOSIT_RECEIPT_START_INDEX |
2**64 - 1 |
Preset
State list lengths
| Name | Value |
|---|---|
PENDING_DEPOSITS_LIMIT |
2**32 (= 4,294,967,296) |
Execution
| Name | Value | Description |
|---|---|---|
MAX_DEPOSIT_RECEIPTS_PER_PAYLOAD |
uint64(2**13) (= 8,192) |
Maximum number of deposit receipts allowed in each payload |
Containers
New containers
DepositReceipt
class DepositReceipt(Container):
pubkey: BLSPubkey
withdrawal_credentials: Bytes32
amount: Gwei
signature: BLSSignature
index: uint64
IndexedDepositData
class IndexedDepositData(Container):
pubkey: BLSPubkey
withdrawal_credentials: Bytes32
amount: Gwei
index: uint64
epoch: Epoch
Extended Containers
ExecutionPayload
class ExecutionPayload(Container):
# Execution block header fields
parent_hash: Hash32
fee_recipient: ExecutionAddress
state_root: Bytes32
receipts_root: Bytes32
logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
prev_randao: Bytes32
block_number: uint64
gas_limit: uint64
gas_used: uint64
timestamp: uint64
extra_data: ByteList[MAX_EXTRA_DATA_BYTES]
base_fee_per_gas: uint256
# Extra payload fields
block_hash: Hash32
transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]
withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
deposit_receipts: List[DepositReceipt, MAX_DEPOSIT_RECEIPTS_PER_PAYLOAD] # [New in EIP-6110]
ExecutionPayloadHeader
class ExecutionPayloadHeader(Container):
# Execution block header fields
parent_hash: Hash32
fee_recipient: ExecutionAddress
state_root: Bytes32
receipts_root: Bytes32
logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
prev_randao: Bytes32
block_number: uint64
gas_limit: uint64
gas_used: uint64
timestamp: uint64
extra_data: ByteList[MAX_EXTRA_DATA_BYTES]
base_fee_per_gas: uint256
# Extra payload fields
block_hash: Hash32
transactions_root: Root
withdrawals_root: Root
deposit_receipts_root: Root # [New in EIP-6110]
BeaconState
class BeaconState(Container):
# Versioning
genesis_time: uint64
genesis_validators_root: Root
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, EPOCHS_PER_ETH1_VOTING_PERIOD * SLOTS_PER_EPOCH]
eth1_deposit_index: uint64
# Registry
validators: List[Validator, VALIDATOR_REGISTRY_LIMIT]
balances: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
# Randomness
randao_mixes: Vector[Bytes32, EPOCHS_PER_HISTORICAL_VECTOR]
# Slashings
slashings: Vector[Gwei, EPOCHS_PER_SLASHINGS_VECTOR] # Per-epoch sums of slashed effective balances
# Participation
previous_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT]
current_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT]
# Finality
justification_bits: Bitvector[JUSTIFICATION_BITS_LENGTH] # Bit set for every recent justified epoch
previous_justified_checkpoint: Checkpoint
current_justified_checkpoint: Checkpoint
finalized_checkpoint: Checkpoint
# Inactivity
inactivity_scores: List[uint64, VALIDATOR_REGISTRY_LIMIT]
# Sync
current_sync_committee: SyncCommittee
next_sync_committee: SyncCommittee
# Execution
latest_execution_payload_header: ExecutionPayloadHeader
# Withdrawals
next_withdrawal_index: WithdrawalIndex
next_withdrawal_validator_index: ValidatorIndex
# EIP-6110
deposit_receipt_start_index: uint64
deposit_receipt_next_index: uint64
Beacon chain state transition function
Block processing
def process_block(state: BeaconState, block: BeaconBlock) -> None:
process_block_header(state, block)
if is_execution_enabled(state, block.body):
process_withdrawals(state, block.body.execution_payload)
process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE) # [Modified in EIP-6110]
process_randao(state, block.body)
process_eth1_data(state, block.body)
process_operations(state, block.body) # [Modified in EIP-6110]
process_sync_aggregate(state, block.body.sync_aggregate)
Modified process_operations
Note: The function process_operations is modified to process DepositReceipt operations included in the payload.
def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
# Prevent potential underflow introduced by mixing two deposit processing flows
unprocessed_deposits_count = max(0, state.eth1_data.deposit_count - state.eth1_deposit_index) # [New in EIP-6110]
# Verify that outstanding deposits are processed up to the maximum number of deposits
assert len(body.deposits) == min(MAX_DEPOSITS, unprocessed_deposits_count) # [Modified in EIP-6110]
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)
for_ops(body.attestations, process_attestation)
for_ops(body.deposits, process_deposit) # [Modified in EIP-6110]
for_ops(body.voluntary_exits, process_voluntary_exit)
for_ops(body.bls_to_execution_changes, process_bls_to_execution_change)
# [New in EIP-6110]
if is_execution_enabled(state, body):
for_ops(body.execution_payload.deposit_receipts, process_deposit_receipt)
# Signify the end of transition to in-protocol deposits logic
if state.eth1_deposit_index >= state.deposit_receipt_start_index
state.eth1_deposit_index = state.deposit_receipt_next_index
New get_validator_from_deposit_receipt
def get_validator_from_deposit_receipt(deposit_receipt: DepositReceipt) -> Validator:
amount = deposit_receipt.amount
effective_balance = min(amount - amount % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
return Validator(
pubkey=deposit_receipt.pubkey,
withdrawal_credentials=deposit_receipt.withdrawal_credentials,
activation_eligibility_epoch=FAR_FUTURE_EPOCH,
activation_epoch=FAR_FUTURE_EPOCH,
exit_epoch=FAR_FUTURE_EPOCH,
withdrawable_epoch=FAR_FUTURE_EPOCH,
effective_balance=effective_balance,
)
New process_deposit_receipt
def process_deposit_receipt(state: BeaconState, deposit_receipt: DepositReceipt) -> None:
# Set deposit receipt start index
if state.deposit_receipt_start_index == NOT_SET_DEPOSIT_RECEIPT_START_INDEX:
state.deposit_receipt_start_index = deposit_receipt.index
state.deposit_receipt_next_index = deposit_receipt.index + 1
pubkey = deposit_receipt.pubkey
amount = deposit_receipt.amount
validator_pubkeys = [validator.pubkey for validator in state.validators]
if pubkey not in validator_pubkeys:
# Verify the deposit signature (proof of possession) which is not checked by the deposit contract
deposit_message = DepositMessage(
pubkey=deposit.data.pubkey,
withdrawal_credentials=deposit.data.withdrawal_credentials,
amount=deposit.data.amount,
)
domain = compute_domain(DOMAIN_DEPOSIT) # Fork-agnostic domain since deposits are valid across forks
signing_root = compute_signing_root(deposit_message, domain)
# Initialize validator if the deposit signature is valid
if bls.Verify(pubkey, signing_root, deposit.data.signature):
state.validators.append(get_validator_from_deposit_receipt(deposit))
state.balances.append(amount)
state.previous_epoch_participation.append(ParticipationFlags(0b0000_0000))
state.current_epoch_participation.append(ParticipationFlags(0b0000_0000))
state.inactivity_scores.append(uint64(0))
else:
# Increase balance by deposit amount
index = ValidatorIndex(validator_pubkeys.index(pubkey))
increase_balance(state, index, amount)
Modified process_deposit
Note: The function process_deposit is modified to prevent deposits from being processed in the second time (due to process_deposit_receipt).
def process_deposit(state: BeaconState, deposit: Deposit) -> None:
# Skip already processed deposits
if state.eth1_deposit_index >= state.deposit_receipt_start_index:
return
# Verify the Merkle branch
assert is_valid_merkle_branch(
leaf=hash_tree_root(deposit.data),
branch=deposit.proof,
depth=DEPOSIT_CONTRACT_TREE_DEPTH + 1, # Add 1 for the List length mix-in
index=state.eth1_deposit_index,
root=state.eth1_data.deposit_root,
)
# Deposits must be processed in order
state.eth1_deposit_index += 1
pubkey = deposit.data.pubkey
amount = deposit.data.amount
validator_pubkeys = [validator.pubkey for validator in state.validators]
if pubkey not in validator_pubkeys:
# Verify the deposit signature (proof of possession) which is not checked by the deposit contract
deposit_message = DepositMessage(
pubkey=deposit.data.pubkey,
withdrawal_credentials=deposit.data.withdrawal_credentials,
amount=deposit.data.amount,
)
domain = compute_domain(DOMAIN_DEPOSIT) # Fork-agnostic domain since deposits are valid across forks
signing_root = compute_signing_root(deposit_message, domain)
# Initialize validator if the deposit signature is valid
if bls.Verify(pubkey, signing_root, deposit.data.signature):
state.validators.append(get_validator_from_deposit(deposit))
state.balances.append(amount)
# [New in Altair]
state.previous_epoch_participation.append(ParticipationFlags(0b0000_0000))
state.current_epoch_participation.append(ParticipationFlags(0b0000_0000))
state.inactivity_scores.append(uint64(0))
else:
# Increase balance by deposit amount
index = ValidatorIndex(validator_pubkeys.index(pubkey))
increase_balance(state, index, amount)
Modified process_execution_payload
Note: The function process_execution_payload is modified to use the new ExecutionPayloadHeader type.
def process_execution_payload(state: BeaconState, payload: ExecutionPayload, execution_engine: ExecutionEngine) -> None:
# Verify consistency of the parent hash with respect to the previous execution payload header
if is_merge_transition_complete(state):
assert payload.parent_hash == state.latest_execution_payload_header.block_hash
# Verify prev_randao
assert payload.prev_randao == get_randao_mix(state, get_current_epoch(state))
# Verify timestamp
assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)
# Verify the execution payload is valid
assert execution_engine.notify_new_payload(payload)
# Cache execution payload header
state.latest_execution_payload_header = ExecutionPayloadHeader(
parent_hash=payload.parent_hash,
fee_recipient=payload.fee_recipient,
state_root=payload.state_root,
receipts_root=payload.receipts_root,
logs_bloom=payload.logs_bloom,
prev_randao=payload.prev_randao,
block_number=payload.block_number,
gas_limit=payload.gas_limit,
gas_used=payload.gas_used,
timestamp=payload.timestamp,
extra_data=payload.extra_data,
base_fee_per_gas=payload.base_fee_per_gas,
block_hash=payload.block_hash,
transactions_root=hash_tree_root(payload.transactions),
withdrawals_root=hash_tree_root(payload.withdrawals),
deposit_receipts_root=hash_tree_root(payload.deposit_receipts), # [New in EIP-6110]
)
Testing
Note: The function initialize_beacon_state_from_eth1 is modified for pure EIP-6110 testing only.
Modifications include:
- Use
DEPOSITS_EIP_FORK_VERSIONas the previous and current fork version. - Utilize the EIP-6110
BeaconBlockBodywhen constructing the initiallatest_block_header.
def initialize_beacon_state_from_eth1(eth1_block_hash: Hash32,
eth1_timestamp: uint64,
deposits: Sequence[Deposit],
execution_payload_header: ExecutionPayloadHeader=ExecutionPayloadHeader()
) -> BeaconState:
fork = Fork(
previous_version=CAPELLA_FORK_VERSION, # [Modified in Capella] for testing only
current_version=CAPELLA_FORK_VERSION, # [Modified in Capella]
epoch=GENESIS_EPOCH,
)
state = BeaconState(
genesis_time=eth1_timestamp + GENESIS_DELAY,
fork=fork,
eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=uint64(len(deposits))),
latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR, # Seed RANDAO with Eth1 entropy
deposit_receipt_start_index = NOT_SET_DEPOSIT_RECEIPT_START_INDEX,
)
# Process deposits
leaves = list(map(lambda deposit: deposit.data, deposits))
for index, deposit in enumerate(deposits):
deposit_data_list = List[DepositData, 2**DEPOSIT_CONTRACT_TREE_DEPTH](*leaves[:index + 1])
state.eth1_data.deposit_root = hash_tree_root(deposit_data_list)
process_deposit(state, deposit)
# Process activations
for index, validator in enumerate(state.validators):
balance = state.balances[index]
validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
if validator.effective_balance == MAX_EFFECTIVE_BALANCE:
validator.activation_eligibility_epoch = GENESIS_EPOCH
validator.activation_epoch = GENESIS_EPOCH
# Set genesis validators root for domain separation and chain versioning
state.genesis_validators_root = hash_tree_root(state.validators)
# Fill in sync committees
# Note: A duplicate committee is assigned for the current and next committee at genesis
state.current_sync_committee = get_next_sync_committee(state)
state.next_sync_committee = get_next_sync_committee(state)
# Initialize the execution payload header
state.latest_execution_payload_header = execution_payload_header
return state