# DepositEIP -- The Beacon Chain ## Table of contents - [Introduction](#introduction) - [Preset](#preset) - [State list lengths](#state-list-lengths) - [Execution](#execution) - [Containers](#containers) - [New containers](#new-containers) - [`DepositReceipt`](#depositreceipt) - [`IndexedDepositData`](#indexeddepositdata) - [Extended Containers](#extended-containers) - [`ExecutionPayload`](#executionpayload) - [`ExecutionPayloadHeader`](#executionpayloadheader) - [`BeaconState`](#beaconstate) - [Beacon chain state transition function](#beacon-chain-state-transition-function) - [Epoch processing](#epoch-processing) - [Helper functions](#helper-functions) - [New `get_validator_from_indexed_deposit_data`](#new-get_validator_from_indexed_deposit_data) - [New `apply_indexed_deposit_data`](#new-apply_indexed_deposit_data) - [New `process_pending_deposits`](#new-process_pending_deposits) - [Block processing](#block-processing) - [New `process_deposit_receipts`](#new-process_deposit_receipts) - [Modified `process_execution_payload`](#modified-process_execution_payload) - [Modified `process_operations`](#modified-process_operations) - [Testing](#testing) ## Introduction This is the beacon chain specification of in-protocol deposits processing mechanism. This mechanism relies on the changes proposed by the corresponding EIP. *Note:* This specification is under development and should be used with care. ## 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**10)` (= 1,024) | Maximum number of deposit receipts allowed in each payload | ## Containers ### New containers #### `DepositReceipt` ```python class DepositReceipt(Container): pubkey: BLSPubkey withdrawal_credentials: Bytes32 amount: Gwei signature: BLSSignature index: uint64 ``` #### `IndexedDepositData` ```python class IndexedDepositData(Container): pubkey: BLSPubkey withdrawal_credentials: Bytes32 amount: Gwei index: uint64 epoch: Epoch ``` ### Extended Containers #### `ExecutionPayload` ```python 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 DepositEIP] ``` #### `ExecutionPayloadHeader` ```python 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 DepositEIP] ``` #### `BeaconState` ```python 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 # DepositsEIP pending_deposits: List[IndexedDepositData, PENDING_DEPOSITS_LIMIT] ``` ## Beacon chain state transition function ### Epoch processing ```python def process_epoch(state: BeaconState) -> None: process_justification_and_finalization(state) process_inactivity_updates(state) process_rewards_and_penalties(state) # Run before registry and after finality updates process_pending_deposits(state) # [New in DepositsEIP] process_registry_updates(state) process_slashings(state) process_eth1_data_reset(state) process_effective_balance_updates(state) process_slashings_reset(state) process_randao_mixes_reset(state) process_historical_roots_update(state) process_participation_flag_updates(state) process_sync_committee_updates(state) ``` #### Helper functions ##### New `get_validator_from_indexed_deposit_data` ```python def get_validator_from_indexed_deposit_data(indexed_deposit_data: IndexedDepositData) -> Validator: amount = indexed_deposit_data.amount effective_balance = min(amount - amount % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE) return Validator( pubkey=indexed_deposit_data.pubkey, withdrawal_credentials=indexed_deposit_data.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 `apply_indexed_deposit_data` ```python def apply_indexed_deposit_data(state: BeaconState, indexed_deposit_data: IndexedDepositData) -> None: pubkey = indexed_deposit_data.pubkey amount = indexed_deposit_data.amount validator_pubkeys = [v.pubkey for v in state.validators] if pubkey not in validator_pubkeys: # Add validator and balance entries state.validators.append(get_validator_from_indexed_deposit_data(indexed_deposit_data)) state.balances.append(amount) else: # Increase balance by deposit amount index = ValidatorIndex(validator_pubkeys.index(pubkey)) increase_balance(state, index, amount) ``` #### New `process_pending_deposits` ```python def process_pending_deposits(state: BeaconState) -> None: finalized_epoch = state.finalized_checkpoint.epoch next_pending_deposit_index = 0 for pending_deposit in state.pending_deposits: # Preserve deposits per epoch boundary if next_pending_deposit_index >= MAX_DEPOSITS * SLOTS_PER_EPOCH: break # Apply only finalized deposits if pending_deposit.epoch > finalized_epoch: break # Skip already applied deposits if pending_deposit.index >= state.eth1_deposit_index: apply_indexed_deposit_data(state, pending_deposit) state.eth1_deposit_index += 1 next_pending_deposit_index += 1 state.pending_deposit = state.pending_deposit[next_pending_deposit_index:] ``` ### Block processing ```python 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 DepositsEIP] process_deposit_receipts(state, block.body.execution_payload) # [New in DepositsEIP] process_randao(state, block.body) process_eth1_data(state, block.body) process_operations(state, block.body) # [Modified in DepositsEIP] process_sync_aggregate(state, block.body.sync_aggregate) ``` #### New `process_deposit_receipts` ```python def process_deposit_receipts(state: BeaconState, payload: ExecutionPayload) -> None: current_epoch = get_current_epoch(state) for deposit_receipt in payload.deposit_receipts: 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_receipt.pubkey, withdrawal_credentials=deposit_receipt.withdrawal_credentials, amount=deposit_receipt.amount, ) domain = compute_domain(DOMAIN_DEPOSIT) # Fork-agnostic domain since deposits are valid across forks signing_root = compute_signing_root(deposit_message, domain) if not bls.Verify(pubkey, signing_root, deposit.data.signature): continue pending_deposit = IndexedDepositData( pubkey=deposit_receipt.pubkey, withdrawal_credentials=deposit_receipt.withdrawal_credentials, amount=deposit_receipt.amount, index=deposit_receipt.index, epoch=current_epoch, ) state.pending_deposits.append(pending_deposit) ``` #### Modified `process_execution_payload` *Note*: The function `process_execution_payload` is modified to use the new `ExecutionPayloadHeader` type. ```python 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 DepositsEIP] ) ``` #### Modified `process_operations` *Note*: The function `process_operations` is modified to process `BLSToExecutionChange` operations included in the block. ```python def process_operations(state: BeaconState, body: BeaconBlockBody) -> None: # Prevent potential underflow that is introduced by the mix of two deposit processing flows unprocessed_deposits_count = max(0, state.eth1_data.deposit_count - state.eth1_deposit_index) # [New in DepositsEIP] # 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 DepositsEIP] 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) for_ops(body.voluntary_exits, process_voluntary_exit) for_ops(body.bls_to_execution_changes, process_bls_to_execution_change) # [New in Capella] ``` ## Testing *Note*: The function `initialize_beacon_state_from_eth1` is modified for pure DepositsEIP testing only. Modifications include: 1. Use `DEPOSITS_EIP_FORK_VERSION` as the previous and current fork version. 2. Utilize the DepositsEIP `BeaconBlockBody` when constructing the initial `latest_block_header`. ```python 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 ) # 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 ```