status-im
/
eth2.0-specs
mirror of https://github.com/status-im/eth2.0-specs.git
2
0
Fork 0
Code Issues Projects Releases Wiki Activity
eth2.0-specs/specs/merge/beacon-chain.md

9.5 KiB
Raw Blame History

Ethereum 2.0 The Merge

Warning: This document is currently based on Phase 0 and will be rebased on Altair.

Notice: This document is a work-in-progress for researchers and implementers.

Table of contents

Introduction

This patch adds transaction execution to the beacon chain as part of the Merge fork.

Custom types

Note: The Transaction type is a stub which is not final.

Name SSZ equivalent Description
OpaqueTransaction ByteList[MAX_BYTES_PER_OPAQUE_TRANSACTION] a typed transaction envelope structured as TransactionType || TransactionPayload
Transaction Union[OpaqueTransaction] a transaction

Constants

Execution

Name Value
MAX_BYTES_PER_OPAQUE_TRANSACTION uint64(2**20) (= 1,048,576)
MAX_TRANSACTIONS_PER_PAYLOAD uint64(2**14) (= 16,384)
BYTES_PER_LOGS_BLOOM uint64(2**8) (= 256)

Containers

Extended containers

BeaconBlockBody

class BeaconBlockBody(phase0.BeaconBlockBody):
    # Execution
    execution_payload: ExecutionPayload  # [New in Merge]

BeaconState

class BeaconState(phase0.BeaconState):
    # Execution
    latest_execution_payload_header: ExecutionPayloadHeader  # [New in Merge]

New containers

ExecutionPayload

class ExecutionPayload(Container):
    # Execution block header fields
    parent_hash: Hash32
    coinbase: Bytes20  # 'beneficiary' in the yellow paper
    state_root: Bytes32
    receipt_root: Bytes32  # 'receipts root' in the yellow paper
    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
    random: Bytes32  # 'difficulty' in the yellow paper
    block_number: uint64  # 'number' in the yellow paper
    gas_limit: uint64
    gas_used: uint64
    timestamp: uint64
    # Extra payload fields
    block_hash: Hash32  # Hash of execution block
    transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]

ExecutionPayloadHeader

class ExecutionPayloadHeader(Container):
    # Execution block header fields
    parent_hash: Hash32
    coinbase: Bytes20
    state_root: Bytes32
    receipt_root: Bytes32
    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
    random: Bytes32
    block_number: uint64
    gas_limit: uint64
    gas_used: uint64
    timestamp: uint64
    # Extra payload fields
    block_hash: Hash32  # Hash of execution block
    transactions_root: Root

Helper functions

Predicates

is_merge_complete

def is_merge_complete(state: BeaconState) -> bool:
    return state.latest_execution_payload_header != ExecutionPayloadHeader()

is_merge_block

def is_merge_block(state: BeaconState, body: BeaconBlockBody) -> bool:
    return not is_merge_complete(state) and body.execution_payload != ExecutionPayload()

is_execution_enabled

def is_execution_enabled(state: BeaconState, body: BeaconBlockBody) -> bool:
    return is_merge_block(state, body) or is_merge_complete(state)

Misc

compute_timestamp_at_slot

Note: This function is unsafe with respect to overflows and underflows.

def compute_timestamp_at_slot(state: BeaconState, slot: Slot) -> uint64:
    slots_since_genesis = slot - GENESIS_SLOT
    return uint64(state.genesis_time + slots_since_genesis * SECONDS_PER_SLOT)

Beacon chain state transition function

Execution engine

The implementation-dependent ExecutionEngine protocol encapsulates the execution sub-system logic via:

  • a state object self.execution_state of type ExecutionState
  • a state transition function self.on_payload which mutates self.execution_state

on_payload

def on_payload(self: ExecutionEngine, execution_payload: ExecutionPayload) -> bool:
    """
    Returns ``True`` iff ``execution_payload`` is valid with respect to ``self.execution_state``.
    """
    ...

The above function is accessed through the EXECUTION_ENGINE module which instantiates the ExecutionEngine protocol.

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)
    process_operations(state, block.body)
    if is_execution_enabled(state, block.body):
        # [New in Merge]
        randao_mix = get_randao_mix(state, get_current_epoch(state))
        process_execution_payload(state, block.body.execution_payload, randao_mix, EXECUTION_ENGINE)

Execution payload processing

process_execution_payload

def process_execution_payload(state: BeaconState,
                              payload: ExecutionPayload,
                              randao_mix: Bytes32,
                              execution_engine: ExecutionEngine) -> None:
    # Verify consistency of the parent hash, block number and random
    if is_merge_complete(state):
        assert payload.parent_hash == state.latest_execution_payload_header.block_hash
        assert payload.block_number == state.latest_execution_payload_header.block_number + uint64(1)
        assert payload.random == randao_mix
    # Verify timestamp
    assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)
    # Verify the execution payload is valid
    assert execution_engine.on_payload(payload)
    # Cache execution payload
    state.latest_execution_payload_header = ExecutionPayloadHeader(
        parent_hash=payload.parent_hash,
        coinbase=payload.coinbase,
        state_root=payload.state_root,
        receipt_root=payload.receipt_root,
        logs_bloom=payload.logs_bloom,
        random=payload.random,
        block_number=payload.block_number,
        gas_limit=payload.gas_limit,
        gas_used=payload.gas_used,
        timestamp=payload.timestamp,
        block_hash=payload.block_hash,
        transactions_root=hash_tree_root(payload.transactions),
    )

Testing

Note: The function initialize_beacon_state_from_eth1 is modified for pure Merge testing only.

Note: The function initialize_beacon_state_from_eth1 is modified to use MERGE_FORK_VERSION and initialize latest_execution_payload_header.

def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
                                      eth1_timestamp: uint64,
                                      deposits: Sequence[Deposit]) -> BeaconState:
    randao_seed = eth1_block_hash
    fork = Fork(
        previous_version=GENESIS_FORK_VERSION,
        current_version=MERGE_FORK_VERSION,  # [Modified in Merge]
        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=[randao_seed] * 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)

    # [New in Merge] Initialize the execution payload header (with block number set to 0)
    state.latest_execution_payload_header.block_hash = eth1_block_hash
    state.latest_execution_payload_header.timestamp = eth1_timestamp
    state.latest_execution_payload_header.random = randao_seed

    return state