eth2.0-specs/specs/merge/validator.md

Ethereum 2.0 The Merge

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

Table of contents

• Introduction
• Prerequisites
• Beacon chain responsibilities
  • Block proposal
    • Constructing the BeaconBlockBody
      • Eth1 data
        • get_eth1_data
      • Application Payload
        • produce_application_payload

Introduction

This document represents the changes to be made in the code of an "honest validator" to implement executable beacon chain proposal.

Prerequisites

This document is an extension of the Phase 0 -- Validator. All behaviors and definitions defined in the Phase 0 doc carry over unless explicitly noted or overridden.

All terminology, constants, functions, and protocol mechanics defined in the updated Beacon Chain doc of The Merge are requisite for this document and used throughout. Please see related Beacon Chain doc before continuing and use them as a reference throughout.

Beacon chain responsibilities

All validator responsibilities remain unchanged other than those noted below. Namely, the modification of Eth1Data and the addition of ApplicationPayload.

Block proposal

Constructing the BeaconBlockBody

Eth1 data

The block.body.eth1_data field is for block proposers to publish recent Eth1 data. This recent data contains deposit root (as calculated by the get_deposit_root() method of the deposit contract) and deposit count after processing of the parent block. The fork choice verifies Eth1 data of a block, then state.eth1_data updates immediately allowing new deposits to be processed. Each deposit in block.body.deposits must verify against state.eth1_data.deposit_root.

get_eth1_data

Let get_eth1_data(state: BeaconState) -> Eth1Data be the function that returns the Eth1Data obtained from the beacon state.

Note: This is mostly a function of the state of the beacon chain deposit contract. It can be read from the application state and/or logs. The block_hash value of Eth1Data must be set to state.application_block_hash.

Set block.body.eth1_data = get_eth1_data(state).

Application Payload

produce_application_payload

Let produce_application_payload(parent_hash: Bytes32, beacon_chain_data: BeaconChainData) -> ApplicationPayload be the function that produces new instance of application payload. The body of this function is implementation dependant.

• Let randao_reveal be block.body.randao_reveal of the block that is being produced
• Set block.body.application_payload = get_application_payload(state, randao_reveal) where:

def get_application_payload(state: BeaconState, randao_reveal: BLSSignature) -> ApplicationPayload:   
    application_parent_hash = state.application_block_hash
    beacon_chain_data = BeaconChainData(
        slot=state.slot,
        randao_mix=compute_randao_mix(state, randao_reveal),
        timestamp=compute_time_at_slot(state.genesis_time, state.slot),
        recent_block_roots=get_evm_beacon_block_roots(state) 
    )
    
    return produce_application_payload(application_parent_hash, beacon_chain_data)