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Electra Light Client -- Sync Protocol

Introduction

This upgrade updates light client data to include the Electra changes to the generalized indices of BeaconState. It extends the Deneb Light Client specifications. The fork document explains how to upgrade existing Deneb based deployments to Electra.

Additional documents describes the impact of the upgrade on certain roles:

Types

Name SSZ equivalent Description
FinalityBranch Vector[Bytes32, floorlog2(FINALIZED_ROOT_GINDEX_ELECTRA)] Merkle branch of finalized_checkpoint.root within BeaconState
CurrentSyncCommitteeBranch Vector[Bytes32, floorlog2(CURRENT_SYNC_COMMITTEE_GINDEX_ELECTRA)] Merkle branch of current_sync_committee within BeaconState
NextSyncCommitteeBranch Vector[Bytes32, floorlog2(NEXT_SYNC_COMMITTEE_GINDEX_ELECTRA)] Merkle branch of next_sync_committee within BeaconState

Constants

Frozen constants

Existing GeneralizedIndex constants are frozen at their Altair values.

Name Value
FINALIZED_ROOT_GINDEX get_generalized_index(altair.BeaconState, 'finalized_checkpoint', 'root') (= 105)
CURRENT_SYNC_COMMITTEE_GINDEX get_generalized_index(altair.BeaconState, 'current_sync_committee') (= 54)
NEXT_SYNC_COMMITTEE_GINDEX get_generalized_index(altair.BeaconState, 'next_sync_committee') (= 55)

New constants

Name Value
FINALIZED_ROOT_GINDEX_ELECTRA get_generalized_index(BeaconState, 'finalized_checkpoint', 'root') (= 169)
CURRENT_SYNC_COMMITTEE_GINDEX_ELECTRA get_generalized_index(BeaconState, 'current_sync_committee') (= 86)
NEXT_SYNC_COMMITTEE_GINDEX_ELECTRA get_generalized_index(BeaconState, 'next_sync_committee') (= 87)

Helpers

Modified finalized_root_gindex_at_slot

def finalized_root_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
    epoch = compute_epoch_at_slot(slot)

    # [Modified in Electra]
    if epoch >= ELECTRA_FORK_EPOCH:
        return FINALIZED_ROOT_GINDEX_ELECTRA
    return FINALIZED_ROOT_GINDEX

Modified current_sync_committee_gindex_at_slot

def current_sync_committee_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
    epoch = compute_epoch_at_slot(slot)

    # [Modified in Electra]
    if epoch >= ELECTRA_FORK_EPOCH:
        return CURRENT_SYNC_COMMITTEE_GINDEX_ELECTRA
    return CURRENT_SYNC_COMMITTEE_GINDEX

Modified next_sync_committee_gindex_at_slot

def next_sync_committee_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
    epoch = compute_epoch_at_slot(slot)

    # [Modified in Electra]
    if epoch >= ELECTRA_FORK_EPOCH:
        return NEXT_SYNC_COMMITTEE_GINDEX_ELECTRA
    return NEXT_SYNC_COMMITTEE_GINDEX