2024-06-21 08:59:13 +00:00
# Electra Light Client -- Sync Protocol
**Notice**: This document is a work-in-progress for researchers and implementers.
## Table of contents
<!-- TOC -->
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE - RUN doctoc TO UPDATE -->
- [Introduction ](#introduction )
2024-07-09 18:23:27 +00:00
- [Custom types ](#custom-types )
2024-06-21 08:59:13 +00:00
- [Constants ](#constants )
2024-07-09 18:23:27 +00:00
- [Frozen constants ](#frozen-constants )
- [New constants ](#new-constants )
2024-06-21 08:59:13 +00:00
- [Helper functions ](#helper-functions )
- [Modified `finalized_root_gindex_at_slot` ](#modified-finalized_root_gindex_at_slot )
- [Modified `current_sync_committee_gindex_at_slot` ](#modified-current_sync_committee_gindex_at_slot )
- [Modified `next_sync_committee_gindex_at_slot` ](#modified-next_sync_committee_gindex_at_slot )
- [Modified `get_lc_execution_root` ](#modified-get_lc_execution_root )
- [Modified `is_valid_light_client_header` ](#modified-is_valid_light_client_header )
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
<!-- /TOC -->
## Introduction
This upgrade updates light client data to include the Electra changes to the [`ExecutionPayload` ](../beacon-chain.md ) structure and to the generalized indices of surrounding containers. It extends the [Deneb Light Client specifications ](../../deneb/light-client/sync-protocol.md ). The [fork document ](./fork.md ) explains how to upgrade existing Deneb based deployments to Electra.
Additional documents describes the impact of the upgrade on certain roles:
- [Full node ](./full-node.md )
- [Networking ](./p2p-interface.md )
2024-07-09 18:15:31 +00:00
## Custom 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` |
2024-06-21 08:59:13 +00:00
## Constants
2024-07-09 18:23:27 +00:00
### Frozen constants
Existing `GeneralizedIndex` constants are frozen at their [Altair ](../../altair/light-client/sync-protocol#constants ) 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
2024-06-21 08:59:13 +00:00
| Name | Value |
| - | - |
2024-07-09 18:15:31 +00:00
| `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) |
2024-06-21 08:59:13 +00:00
## Helper functions
### Modified `finalized_root_gindex_at_slot`
```python
def finalized_root_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
epoch = compute_epoch_at_slot(slot)
# [Modified in Electra]
if epoch >= ELECTRA_FORK_EPOCH:
2024-07-09 18:15:31 +00:00
return FINALIZED_ROOT_GINDEX_ELECTRA
return GeneralizedIndex(FINALIZED_ROOT_GINDEX)
2024-06-21 08:59:13 +00:00
```
### Modified `current_sync_committee_gindex_at_slot`
```python
def current_sync_committee_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
epoch = compute_epoch_at_slot(slot)
# [Modified in Electra]
if epoch >= ELECTRA_FORK_EPOCH:
2024-07-09 18:15:31 +00:00
return CURRENT_SYNC_COMMITTEE_GINDEX_ELECTRA
return GeneralizedIndex(CURRENT_SYNC_COMMITTEE_GINDEX)
2024-06-21 08:59:13 +00:00
```
### Modified `next_sync_committee_gindex_at_slot`
```python
def next_sync_committee_gindex_at_slot(slot: Slot) -> GeneralizedIndex:
epoch = compute_epoch_at_slot(slot)
# [Modified in Electra]
if epoch >= ELECTRA_FORK_EPOCH:
2024-07-09 18:15:31 +00:00
return NEXT_SYNC_COMMITTEE_GINDEX_ELECTRA
return GeneralizedIndex(NEXT_SYNC_COMMITTEE_GINDEX)
2024-06-21 08:59:13 +00:00
```
### Modified `get_lc_execution_root`
```python
def get_lc_execution_root(header: LightClientHeader) -> Root:
epoch = compute_epoch_at_slot(header.beacon.slot)
# [New in Electra]
if epoch >= ELECTRA_FORK_EPOCH:
return hash_tree_root(header.execution)
# [Modified in Electra]
if epoch >= DENEB_FORK_EPOCH:
execution_header = deneb.ExecutionPayloadHeader(
parent_hash=header.execution.parent_hash,
fee_recipient=header.execution.fee_recipient,
state_root=header.execution.state_root,
receipts_root=header.execution.receipts_root,
logs_bloom=header.execution.logs_bloom,
prev_randao=header.execution.prev_randao,
block_number=header.execution.block_number,
gas_limit=header.execution.gas_limit,
gas_used=header.execution.gas_used,
timestamp=header.execution.timestamp,
extra_data=header.execution.extra_data,
base_fee_per_gas=header.execution.base_fee_per_gas,
block_hash=header.execution.block_hash,
transactions_root=header.execution.transactions_root,
withdrawals_root=header.execution.withdrawals_root,
blob_gas_used=header.execution.blob_gas_used,
excess_blob_gas=header.execution.excess_blob_gas,
)
return hash_tree_root(execution_header)
if epoch >= CAPELLA_FORK_EPOCH:
execution_header = capella.ExecutionPayloadHeader(
parent_hash=header.execution.parent_hash,
fee_recipient=header.execution.fee_recipient,
state_root=header.execution.state_root,
receipts_root=header.execution.receipts_root,
logs_bloom=header.execution.logs_bloom,
prev_randao=header.execution.prev_randao,
block_number=header.execution.block_number,
gas_limit=header.execution.gas_limit,
gas_used=header.execution.gas_used,
timestamp=header.execution.timestamp,
extra_data=header.execution.extra_data,
base_fee_per_gas=header.execution.base_fee_per_gas,
block_hash=header.execution.block_hash,
transactions_root=header.execution.transactions_root,
withdrawals_root=header.execution.withdrawals_root,
)
return hash_tree_root(execution_header)
return Root()
```
### Modified `is_valid_light_client_header`
```python
def is_valid_light_client_header(header: LightClientHeader) -> bool:
epoch = compute_epoch_at_slot(header.beacon.slot)
# [New in Electra:EIP6110:EIP7002:EIP7251]
if epoch < ELECTRA_FORK_EPOCH:
if (
header.execution.deposit_requests_root != Root()
or header.execution.withdrawal_requests_root != Root()
or header.execution.consolidation_requests_root != Root()
):
return False
if epoch < DENEB_FORK_EPOCH:
if header.execution.blob_gas_used != uint64(0) or header.execution.excess_blob_gas != uint64(0):
return False
if epoch < CAPELLA_FORK_EPOCH:
return (
header.execution == ExecutionPayloadHeader()
and header.execution_branch == ExecutionBranch()
)
return is_valid_merkle_branch(
leaf=get_lc_execution_root(header),
branch=header.execution_branch,
depth=floorlog2(EXECUTION_PAYLOAD_GINDEX),
index=get_subtree_index(EXECUTION_PAYLOAD_GINDEX),
root=header.beacon.body_root,
)
```