consensus-specs/fork_choice/safe-block.md

Fork Choice -- Safe Block

Table of contents

• Introduction
• get_safe_beacon_block_root
• get_safe_execution_payload_hash

Introduction

Under honest majority and certain network synchronicity assumptions there exists a block that is safe from re-orgs. Normally this block is pretty close to the head of canonical chain which makes it valuable to expose a safe block to users.

This section describes an algorithm to find a safe block.

get_safe_beacon_block_root

def get_safe_beacon_block_root(store: Store) -> Root:
    # Use most recent justified block as a stopgap
    return store.justified_checkpoint.root

Note: Currently safe block algorithm simply returns store.justified_checkpoint.root and is meant to be improved in the future.

get_safe_execution_payload_hash

def get_safe_execution_payload_hash(store: Store) -> Hash32:
    safe_block_root = get_safe_beacon_block_root(store)
    safe_block = store.blocks[safe_block_root]

    # Return Hash32() if no payload is yet justified
    if compute_epoch_at_slot(safe_block.slot) >= BELLATRIX_FORK_EPOCH:
        return safe_block.body.execution_payload.block_hash
    else:
        return Hash32()

Note: This helper uses beacon block container extended in Bellatrix.