7.2 KiB

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Ethereum 2.0 The Merge

Warning: This document is currently based on Phase 0 but will be rebased to Altair once the latter is shipped.

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

Introduction
Custom types
Constants
- Transition
- Execution
Containers
Helper functions
- Misc
- Block processing
  - Execution payload processing
    - verify_execution_state_transition
    - process_execution_payload

Introduction

This is a patch implementing the executable beacon chain proposal. It enshrines transaction execution and validity as a first class citizen at the core of the beacon chain.

Custom types

We define the following Python custom types for type hinting and readability:

Name	SSZ equivalent	Description
`OpaqueTransaction`	`ByteList[MAX_BYTES_PER_OPAQUE_TRANSACTION]`	a byte-list containing a single typed transaction envelope structured as `TransactionType \|\| TransactionPayload`
`Hash32`	`Bytes32`	a 256-bit hash

Constants

Transition

Name	Value
`TRANSITION_TOTAL_DIFFICULTY`	TBD

Execution

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

Containers

Modified containers

`Eth1Data`

Note: The only modification is the type of block_hash field that is changed to Hash32.

class Eth1Data(Container):
    deposit_root: Root
    deposit_count: uint64
    block_hash: Hash32  # [Modified in Merge]

Extended containers

Note: Extended SSZ containers inherit all fields from the parent in the original order and append any additional fields to the end.

`BeaconBlockBody`

Note: BeaconBlockBody fields remain unchanged other than the addition of execution_payload.

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

`BeaconState`

Note: BeaconState fields remain unchanged other than addition of latest_execution_payload_header.

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

New containers

`ExecutionPayload`

The execution payload included in a BeaconBlockBody.

class ExecutionPayload(Container):
    block_hash: Hash32  # Hash of execution block
    parent_hash: Hash32
    coinbase: Bytes20
    state_root: Bytes32
    number: uint64
    gas_limit: uint64
    gas_used: uint64
    timestamp: uint64
    receipt_root: Bytes32
    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
    transactions: List[OpaqueTransaction, MAX_APPLICATION_TRANSACTIONS]

`ExecutionPayloadHeader`

The execution payload header included in a BeaconState.

Note: Holds execution payload data without transaction bodies.

class ExecutionPayloadHeader(Container):
    block_hash: Hash32  # Hash of execution block
    parent_hash: Hash32
    coinbase: Bytes20
    state_root: Bytes32
    number: uint64
    gas_limit: uint64
    gas_used: uint64
    timestamp: uint64
    receipt_root: Bytes32
    logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
    transactions_root: Root

Helper functions

Misc

`is_transition_completed`

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

`is_transition_block`

def is_transition_block(state: BeaconState, block_body: BeaconBlockBody) -> bool:
    return not is_transition_completed(state) and block_body.execution_payload != ExecutionPayload()

`compute_time_at_slot`

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

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

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)
    process_execution_payload(state, block.body)  # [New in Merge]

Execution payload processing

`verify_execution_state_transition`

Let verify_execution_state_transition(execution_payload: ExecutionPayload) -> bool be the function that verifies given ExecutionPayload with respect to execution state transition. The body of the function is implementation dependent.

`process_execution_payload`

def process_execution_payload(state: BeaconState, body: BeaconBlockBody) -> None:
    """
    Note: This function is designed to be able to be run in parallel with the other `process_block` sub-functions
    """
    # Pre-merge, skip processing
    if not is_transition_completed(state) and not is_transition_block(state, body):
        return

    execution_payload = body.execution_payload

    if is_transition_completed(state):
        assert execution_payload.parent_hash == state.latest_execution_payload_header.block_hash
        assert execution_payload.number == state.latest_execution_payload_header.number + 1

    assert execution_payload.timestamp == compute_time_at_slot(state, state.slot)

    assert verify_execution_state_transition(execution_payload)

    state.latest_execution_payload_header = ExecutionPayloadHeader(
        block_hash=execution_payload.block_hash,
        parent_hash=execution_payload.parent_hash,
        coinbase=execution_payload.coinbase,
        state_root=execution_payload.state_root,
        number=execution_payload.number,
        gas_limit=execution_payload.gas_limit,
        gas_used=execution_payload.gas_used,
        timestamp=execution_payload.timestamp,
        receipt_root=execution_payload.receipt_root,
        logs_bloom=execution_payload.logs_bloom,
        transactions_root=hash_tree_root(execution_payload.transactions),
    )

7.2 KiB Raw Blame History

Ethereum 2.0 The Merge

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