110 lines
4.4 KiB
Markdown
110 lines
4.4 KiB
Markdown
# The Merge -- Honest Validator
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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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- [Prerequisites](#prerequisites)
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- [Protocols](#protocols)
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- [`ExecutionEngine`](#executionengine)
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- [`assemble_block`](#assemble_block)
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- [Beacon chain responsibilities](#beacon-chain-responsibilities)
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- [Block proposal](#block-proposal)
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- [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
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- [Execution Payload](#execution-payload)
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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 document represents the changes to be made in the code of an "honest validator" to implement executable beacon chain proposal.
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## Prerequisites
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This document is an extension of the [Altair -- Honest Validator](../altair/validator.md) guide.
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All behaviors and definitions defined in this document, and documents it extends, carry over unless explicitly noted or overridden.
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All terminology, constants, functions, and protocol mechanics defined in the updated Beacon Chain doc of [The Merge](./beacon-chain.md) are requisite for this document and used throughout.
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Please see related Beacon Chain doc before continuing and use them as a reference throughout.
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## Protocols
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### `ExecutionEngine`
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The following methods are added to the `ExecutionEngine` protocol for use as a validator:
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#### `assemble_block`
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Produces a new instance of an execution payload, with the specified `timestamp`,
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on top of the execution payload chain tip identified by `block_hash`.
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The body of this function is implementation dependent.
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The Consensus API may be used to implement this with an external execution engine.
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```python
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def assemble_block(self: ExecutionEngine, block_hash: Hash32, timestamp: uint64, random: Bytes32) -> ExecutionPayload:
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...
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```
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## Beacon chain responsibilities
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All validator responsibilities remain unchanged other than those noted below. Namely, the transition block handling and the addition of `ExecutionPayload`.
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### Block proposal
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#### Constructing the `BeaconBlockBody`
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##### Execution Payload
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* Set `block.body.execution_payload = get_execution_payload(state, transition_store, execution_engine, pow_chain)` where:
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```python
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def get_pow_block_at_total_difficulty(total_difficulty: uint256, pow_chain: Sequence[PowBlock]) -> Optional[PowBlock]:
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# `pow_chain` abstractly represents all blocks in the PoW chain
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for block in pow_chain:
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parent = get_pow_block(block.parent_hash)
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if block.total_difficulty >= total_difficulty and parent.total_difficulty < total_difficulty:
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return block
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return None
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def compute_randao_mix(state: BeaconState, randao_reveal: BLSSignature) -> Bytes32:
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epoch = get_current_epoch(state)
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return xor(get_randao_mix(state, epoch), hash(randao_reveal))
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def produce_execution_payload(state: BeaconState,
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parent_hash: Hash32,
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randao_reveal: BLSSignature,
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execution_engine: ExecutionEngine) -> ExecutionPayload:
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timestamp = compute_timestamp_at_slot(state, state.slot)
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randao_mix = compute_randao_mix(state, randao_reveal)
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return execution_engine.assemble_block(parent_hash, timestamp, randao_mix)
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def get_execution_payload(state: BeaconState,
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transition_store: TransitionStore,
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randao_reveal: BLSSignature,
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execution_engine: ExecutionEngine,
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pow_chain: Sequence[PowBlock]) -> ExecutionPayload:
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if not is_merge_complete(state):
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terminal_pow_block = get_pow_block_at_total_difficulty(transition_store.terminal_total_difficulty, pow_chain)
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if terminal_pow_block is None:
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# Pre-merge, empty payload
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return ExecutionPayload()
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else:
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# Signify merge via producing on top of the last PoW block
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return produce_execution_payload(state, terminal_pow_block.block_hash, randao_reveal, execution_engine)
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# Post-merge, normal payload
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parent_hash = state.latest_execution_payload_header.block_hash
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return produce_execution_payload(state, parent_hash, randao_reveal, execution_engine)
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```
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