311 lines
11 KiB
Markdown
311 lines
11 KiB
Markdown
# Deneb -- The Beacon Chain
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**Notice**: This document is a work-in-progress for researchers and implementers.
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## Table of contents
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<!-- TOC -->
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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- [Introduction](#introduction)
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- [Custom types](#custom-types)
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- [Constants](#constants)
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- [Domain types](#domain-types)
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- [Blob](#blob)
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- [Preset](#preset)
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- [Execution](#execution)
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- [Configuration](#configuration)
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- [Containers](#containers)
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- [Extended containers](#extended-containers)
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- [`BeaconBlockBody`](#beaconblockbody)
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- [`ExecutionPayload`](#executionpayload)
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- [`ExecutionPayloadHeader`](#executionpayloadheader)
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- [Helper functions](#helper-functions)
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- [Misc](#misc)
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- [`kzg_commitment_to_versioned_hash`](#kzg_commitment_to_versioned_hash)
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- [`tx_peek_blob_versioned_hashes`](#tx_peek_blob_versioned_hashes)
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- [`verify_kzg_commitments_against_transactions`](#verify_kzg_commitments_against_transactions)
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- [Beacon chain state transition function](#beacon-chain-state-transition-function)
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- [Block processing](#block-processing)
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- [Execution payload](#execution-payload)
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- [`process_execution_payload`](#process_execution_payload)
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- [Blob KZG commitments](#blob-kzg-commitments)
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- [Testing](#testing)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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<!-- /TOC -->
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## Introduction
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This upgrade adds blobs to the beacon chain as part of Deneb. This is an extension of the Capella upgrade.
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## Custom types
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| Name | SSZ equivalent | Description |
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| - | - | - |
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| `VersionedHash` | `Bytes32` | |
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| `BlobIndex` | `uint64` | |
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## Constants
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### Domain types
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| Name | Value |
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| - | - |
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| `DOMAIN_BLOB_SIDECAR` | `DomainType('0x0B000000')` |
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### Blob
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| Name | Value |
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| - | - |
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| `BLOB_TX_TYPE` | `uint8(0x05)` |
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| `VERSIONED_HASH_VERSION_KZG` | `Bytes1('0x01')` |
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## Preset
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### Execution
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| Name | Value |
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| - | - |
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| `MAX_BLOBS_PER_BLOCK` | `uint64(2**2)` (= 4) |
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## Configuration
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## Containers
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### Extended containers
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#### `BeaconBlockBody`
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Note: `BeaconBlock` and `SignedBeaconBlock` types are updated indirectly.
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```python
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class BeaconBlockBody(Container):
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randao_reveal: BLSSignature
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eth1_data: Eth1Data # Eth1 data vote
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graffiti: Bytes32 # Arbitrary data
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# Operations
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proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
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attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS]
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attestations: List[Attestation, MAX_ATTESTATIONS]
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deposits: List[Deposit, MAX_DEPOSITS]
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voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
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sync_aggregate: SyncAggregate
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# Execution
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execution_payload: ExecutionPayload # [Modified in Deneb]
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bls_to_execution_changes: List[SignedBLSToExecutionChange, MAX_BLS_TO_EXECUTION_CHANGES]
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blob_kzg_commitments: List[KZGCommitment, MAX_BLOBS_PER_BLOCK] # [New in Deneb]
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```
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#### `ExecutionPayload`
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```python
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class ExecutionPayload(Container):
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# Execution block header fields
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parent_hash: Hash32
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fee_recipient: ExecutionAddress # 'beneficiary' in the yellow paper
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state_root: Bytes32
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receipts_root: Bytes32
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logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
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prev_randao: Bytes32 # 'difficulty' in the yellow paper
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block_number: uint64 # 'number' in the yellow paper
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gas_limit: uint64
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gas_used: uint64
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timestamp: uint64
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extra_data: ByteList[MAX_EXTRA_DATA_BYTES]
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base_fee_per_gas: uint256
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excess_data_gas: uint256 # [New in Deneb]
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# Extra payload fields
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block_hash: Hash32 # Hash of execution block
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transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]
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withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
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```
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#### `ExecutionPayloadHeader`
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```python
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class ExecutionPayloadHeader(Container):
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# Execution block header fields
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parent_hash: Hash32
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fee_recipient: ExecutionAddress
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state_root: Bytes32
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receipts_root: Bytes32
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logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
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prev_randao: Bytes32
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block_number: uint64
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gas_limit: uint64
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gas_used: uint64
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timestamp: uint64
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extra_data: ByteList[MAX_EXTRA_DATA_BYTES]
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base_fee_per_gas: uint256
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excess_data_gas: uint256 # [New in Deneb]
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# Extra payload fields
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block_hash: Hash32 # Hash of execution block
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transactions_root: Root
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withdrawals_root: Root
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```
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## Helper functions
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### Misc
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#### `kzg_commitment_to_versioned_hash`
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```python
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def kzg_commitment_to_versioned_hash(kzg_commitment: KZGCommitment) -> VersionedHash:
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return VERSIONED_HASH_VERSION_KZG + hash(kzg_commitment)[1:]
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```
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#### `tx_peek_blob_versioned_hashes`
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This function retrieves the hashes from the `SignedBlobTransaction` as defined in Deneb, using SSZ offsets.
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Offsets are little-endian `uint32` values, as defined in the [SSZ specification](../../ssz/simple-serialize.md).
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See [the full details of `blob_versioned_hashes` offset calculation](https://gist.github.com/protolambda/23bd106b66f6d4bb854ce46044aa3ca3).
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```python
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def tx_peek_blob_versioned_hashes(opaque_tx: Transaction) -> Sequence[VersionedHash]:
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assert opaque_tx[0] == BLOB_TX_TYPE
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message_offset = 1 + uint32.decode_bytes(opaque_tx[1:5])
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# field offset: 32 + 8 + 32 + 32 + 8 + 4 + 32 + 4 + 4 + 32 = 188
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blob_versioned_hashes_offset = (
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message_offset
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+ uint32.decode_bytes(opaque_tx[(message_offset + 188):(message_offset + 192)])
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)
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return [
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VersionedHash(opaque_tx[x:(x + 32)])
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for x in range(blob_versioned_hashes_offset, len(opaque_tx), 32)
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]
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```
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#### `verify_kzg_commitments_against_transactions`
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```python
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def verify_kzg_commitments_against_transactions(transactions: Sequence[Transaction],
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kzg_commitments: Sequence[KZGCommitment]) -> bool:
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all_versioned_hashes: List[VersionedHash] = []
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for tx in transactions:
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if tx[0] == BLOB_TX_TYPE:
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all_versioned_hashes += tx_peek_blob_versioned_hashes(tx)
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return all_versioned_hashes == [kzg_commitment_to_versioned_hash(commitment) for commitment in kzg_commitments]
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```
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## Beacon chain state transition function
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### Block processing
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```python
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def process_block(state: BeaconState, block: BeaconBlock) -> None:
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process_block_header(state, block)
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if is_execution_enabled(state, block.body):
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process_withdrawals(state, block.body.execution_payload)
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process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE) # [Modified in Deneb]
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process_randao(state, block.body)
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process_eth1_data(state, block.body)
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process_operations(state, block.body)
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process_sync_aggregate(state, block.body.sync_aggregate)
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process_blob_kzg_commitments(state, block.body) # [New in Deneb]
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```
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#### Execution payload
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##### `process_execution_payload`
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```python
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def process_execution_payload(state: BeaconState, payload: ExecutionPayload, execution_engine: ExecutionEngine) -> None:
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# Verify consistency of the parent hash with respect to the previous execution payload header
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if is_merge_transition_complete(state):
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assert payload.parent_hash == state.latest_execution_payload_header.block_hash
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# Verify prev_randao
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assert payload.prev_randao == get_randao_mix(state, get_current_epoch(state))
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# Verify timestamp
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assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)
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# Verify the execution payload is valid
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assert execution_engine.notify_new_payload(payload)
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# Cache execution payload header
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state.latest_execution_payload_header = ExecutionPayloadHeader(
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parent_hash=payload.parent_hash,
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fee_recipient=payload.fee_recipient,
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state_root=payload.state_root,
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receipts_root=payload.receipts_root,
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logs_bloom=payload.logs_bloom,
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prev_randao=payload.prev_randao,
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block_number=payload.block_number,
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gas_limit=payload.gas_limit,
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gas_used=payload.gas_used,
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timestamp=payload.timestamp,
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extra_data=payload.extra_data,
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base_fee_per_gas=payload.base_fee_per_gas,
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excess_data_gas=payload.excess_data_gas, # [New in Deneb]
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block_hash=payload.block_hash,
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transactions_root=hash_tree_root(payload.transactions),
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withdrawals_root=hash_tree_root(payload.withdrawals),
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)
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```
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#### Blob KZG commitments
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```python
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def process_blob_kzg_commitments(state: BeaconState, body: BeaconBlockBody) -> None:
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# pylint: disable=unused-argument
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assert verify_kzg_commitments_against_transactions(body.execution_payload.transactions, body.blob_kzg_commitments)
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```
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## Testing
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*Note*: The function `initialize_beacon_state_from_eth1` is modified for pure Deneb testing only.
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The `BeaconState` initialization is unchanged, except for the use of the updated `deneb.BeaconBlockBody` type
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when initializing the first body-root.
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```python
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def initialize_beacon_state_from_eth1(eth1_block_hash: Hash32,
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eth1_timestamp: uint64,
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deposits: Sequence[Deposit],
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execution_payload_header: ExecutionPayloadHeader=ExecutionPayloadHeader()
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) -> BeaconState:
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fork = Fork(
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previous_version=DENEB_FORK_VERSION, # [Modified in Deneb] for testing only
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current_version=DENEB_FORK_VERSION, # [Modified in Deneb]
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epoch=GENESIS_EPOCH,
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)
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state = BeaconState(
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genesis_time=eth1_timestamp + GENESIS_DELAY,
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fork=fork,
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eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=uint64(len(deposits))),
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latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
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randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR, # Seed RANDAO with Eth1 entropy
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)
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# Process deposits
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leaves = list(map(lambda deposit: deposit.data, deposits))
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for index, deposit in enumerate(deposits):
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deposit_data_list = List[DepositData, 2**DEPOSIT_CONTRACT_TREE_DEPTH](*leaves[:index + 1])
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state.eth1_data.deposit_root = hash_tree_root(deposit_data_list)
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process_deposit(state, deposit)
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# Process activations
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for index, validator in enumerate(state.validators):
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balance = state.balances[index]
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validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
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if validator.effective_balance == MAX_EFFECTIVE_BALANCE:
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validator.activation_eligibility_epoch = GENESIS_EPOCH
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validator.activation_epoch = GENESIS_EPOCH
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# Set genesis validators root for domain separation and chain versioning
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state.genesis_validators_root = hash_tree_root(state.validators)
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# Fill in sync committees
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# Note: A duplicate committee is assigned for the current and next committee at genesis
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state.current_sync_committee = get_next_sync_committee(state)
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state.next_sync_committee = get_next_sync_committee(state)
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# Initialize the execution payload header
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# If empty, will initialize a chain that has not yet gone through the Merge transition
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state.latest_execution_payload_header = execution_payload_header
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return state
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```
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