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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
- Extended containers
  - BeaconBlockBody
  - BeaconState
- New containers
  - ApplicationPayload
  - ApplicationBlockHeader
Helper functions
- Misc
  - is_transition_completed
  - is_transition_block
- Block processing
  - Application payload processing

Introduction

This is a patch implementing the executable beacon chain proposal. It enshrines application-layer 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`

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

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 application_payload.

class BeaconBlockBody(phase0.BeaconBlockBody):
    application_payload: ApplicationPayload  # [New in Merge] application payload

`BeaconState`

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

class BeaconState(phase0.BeaconState):
    # Application-layer
    latest_application_block_header: ApplicationBlockHeader  # [New in Merge]

New containers

`ApplicationPayload`

The application payload included in a BeaconBlockBody.

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

`ApplicationBlockHeader`

The application block header included in a BeaconState.

Note: Holds application payload data without transaction list.

class ApplicationBlockHeader(Container):
    block_hash: Bytes32  # Hash of application block
    parent_hash: Bytes32
    coinbase: Bytes20
    state_root: Bytes32
    number: uint64
    gas_limit: uint64
    gas_used: 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) -> boolean:
    return state.latest_application_block_header.block_hash != Bytes32()

`is_transition_block`

def is_transition_block(state: BeaconState, block_body: BeaconBlockBody) -> boolean:
    is_empty_latest_application_block_header = state.latest_application_block_header.block_hash == Bytes32()
    is_empty_application_payload_block_hash = block_body.application_payload.block_hash == Bytes32()
    return is_empty_latest_application_block_header and not is_empty_application_payload_block_hash

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

Application payload processing

`get_application_state`

Note: ApplicationState class is an abstract class representing ethereum application state.

Let get_application_state(application_state_root: Bytes32) -> ApplicationState be the function that given the root hash returns a copy of ethereum application state. The body of the function is implementation dependent.

`application_state_transition`

Let application_state_transition(application_state: ApplicationState, application_payload: ApplicationPayload) -> None be the transition function of ethereum application state. The body of the function is implementation dependent.

Note: application_state_transition must throw AssertionError if either the transition itself or one of the post-transition verifications has failed.

`process_application_payload`

def process_application_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
    """
    application_payload = body.application_payload

    if not is_transition_completed(state):
        assert application_payload == ApplicationPayload()
        return

    if not is_transition_block(state, body):
        assert application_payload.parent_hash == state.latest_application_block_header.block_hash
        assert application_payload.number == state.latest_application_block_header.number + 1

    application_state = get_application_state(state.latest_application_block_header.state_root)
    application_state_transition(application_state, body.application_payload)

    state.latest_application_block_header = ApplicationBlockHeader(
        block_hash=application_payload.block_hash,
        parent_hash=application_payload.parent_hash,
        coinbase=application_payload.coinbase,
        state_root=application_payload.state_root,
        number=application_payload.number,
        gas_limit=application_payload.gas_limit,
        gas_used=application_payload.gas_used,
        receipt_root=application_payload.receipt_root,
        logs_bloom=application_payload.logs_bloom,
        transactions_root=hash_tree_root(application_payload.transactions),
    )

7.2 KiB Raw Blame History

Ethereum 2.0 The Merge

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