Skip to content

EIP-7805 -- Honest Validator

Introduction

This document represents the changes to be made in the code of an "honest validator" to implement EIP-7805.

Prerequisites

This document is an extension of the Fulu -- Honest Validator guide. All behaviors and definitions defined in this document, and documents it extends, carry over unless explicitly noted or overridden.

All terminology, constants, functions, and protocol mechanics defined in the updated Beacon Chain doc of EIP-7805 are requisite for this document and used throughout. Please see related Beacon Chain doc before continuing and use them as a reference throughout.

Configuration

Time parameters

Name Value Unit Duration
INCLUSION_LIST_SUBMISSION_DUE_BPS uint64(6667) basis points ~67% of SLOT_DURATION_MS
PROPOSER_INCLUSION_LIST_CUTOFF_BPS uint64(9167) basis points ~92% of SLOT_DURATION_MS

Helpers

New GetInclusionListResponse

1
2
3
@dataclass
class GetInclusionListResponse(object):
    inclusion_list_transactions: Sequence[Transaction]

Protocols

ExecutionEngine

Note: get_inclusion_list function is added to the ExecutionEngine protocol for use as an inclusion list committee member.

The body of this function is implementation dependent. The Engine API may be used to implement it with an external execution engine.

New get_inclusion_list

get_inclusion_list returns GetInclusionListResponse with the most recent inclusion list transactions that has been built based on the latest view of the public mempool.

1
2
3
4
5
def get_inclusion_list(self: ExecutionEngine) -> GetInclusionListResponse:
    """
    Return ``GetInclusionListResponse`` object.
    """
    ...

Beacon chain responsibilities

All validator responsibilities remain unchanged other than those noted below.

Validator assignments

Inclusion list committee

A validator may be a member of the new inclusion list committee for a given slot. To determine inclusion list committee assignments, the validator can run the following function: get_inclusion_committee_assignment(state, epoch, validator_index) where epoch <= next_epoch.

Inclusion list committee selection is only stable within the context of the current and next epoch.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
def get_inclusion_committee_assignment(
    state: BeaconState, epoch: Epoch, validator_index: ValidatorIndex
) -> Optional[Slot]:
    """
    Returns the slot during the requested epoch in which the validator with index ``validator_index``
    is a member of the inclusion list committee. Returns None if no assignment is found.
    """
    next_epoch = Epoch(get_current_epoch(state) + 1)
    assert epoch <= next_epoch

    start_slot = compute_start_slot_at_epoch(epoch)
    for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH):
        if validator_index in get_inclusion_list_committee(state, Slot(slot)):
            return Slot(slot)
    return None

Lookahead

get_inclusion_committee_assignment should be called at the start of each epoch to get the assignment for the next epoch (current_epoch + 1). A validator should plan for future assignments by noting their assigned inclusion list committee slot.

Block and sidecar proposal

Constructing the BeaconBlockBody

ExecutionPayload

Note: In this section, state is the state of the slot for the block proposal without the block yet applied. That is, state is the previous_state processed through any empty slots up to the assigned slot using process_slots(previous_state, slot).

Note: The only change to prepare_execution_payload is to call get_inclusion_list_store and get_inclusion_list_transactions to set the new inclusion_list_transactions field of PayloadAttributes.

Note: A proposer should produce an execution payload that satisfies the inclusion list constraints with respect to the inclusion lists gathered up to get_proposer_inclusion_list_cutoff_ms(epoch) milliseconds into the slot.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
def prepare_execution_payload(
    state: BeaconState,
    safe_block_hash: Hash32,
    finalized_block_hash: Hash32,
    suggested_fee_recipient: ExecutionAddress,
    execution_engine: ExecutionEngine,
) -> Optional[PayloadId]:
    # Verify consistency of the parent hash with respect to the previous execution payload header
    parent_hash = state.latest_execution_payload_header.block_hash

    # Set the forkchoice head and initiate the payload build process
    withdrawals, _ = get_expected_withdrawals(state)

    # [New in EIP7805]
    # Get the inclusion list store
    inclusion_list_store = get_inclusion_list_store()

    payload_attributes = PayloadAttributes(
        timestamp=compute_time_at_slot(state, state.slot),
        prev_randao=get_randao_mix(state, get_current_epoch(state)),
        suggested_fee_recipient=suggested_fee_recipient,
        withdrawals=withdrawals,
        parent_beacon_block_root=hash_tree_root(state.latest_block_header),
        # [New in EIP7805]
        inclusion_list_transactions=get_inclusion_list_transactions(
            inclusion_list_store, state, Slot(state.slot - 1)
        ),
    )
    return execution_engine.notify_forkchoice_updated(
        head_block_hash=parent_hash,
        safe_block_hash=safe_block_hash,
        finalized_block_hash=finalized_block_hash,
        payload_attributes=payload_attributes,
    )

Inclusion list proposal

A validator is expected to propose a SignedInclusionList at the beginning of any slot for which get_inclusion_committee_assignment(state, epoch, validator_index) returns.

If a validator is in the current inclusion list committee, the validator should create and broadcast the signed_inclusion_list to the global inclusion_list subnet by get_inclusion_list_submission_due_ms(epoch) milliseconds into the slot after processing the block for the current slot and confirming it as the head. If no block is received by get_inclusion_list_submission_due_ms(epoch) - 1000 milliseconds into the slot, the validator should run get_head to determine the local head and construct and broadcast the inclusion list based on this local head by get_inclusion_list_submission_due_ms(epoch) milliseconds into the slot.

Constructing the SignedInclusionList

The validator creates the signed_inclusion_list as follows:

  • First, the validator creates the inclusion_list.
  • Set inclusion_list.slot to the assigned slot returned by get_inclusion_committee_assignment.
  • Set inclusion_list.validator_index to the validator's index.
  • Set inclusion_list.inclusion_list_committee_root to the hash tree root of the committee that the validator is a member of.
  • Set inclusion_list.transactions using the response from ExecutionEngine via get_inclusion_list.
  • Sign the inclusion_list using the helper get_inclusion_list_signature and obtain the signature.
  • Set signed_inclusion_list.message to inclusion_list.
  • Set signed_inclusion_list.signature to signature.
1
2
3
4
5
6
7
8
def get_inclusion_list_signature(
    state: BeaconState, inclusion_list: InclusionList, privkey: int
) -> BLSSignature:
    domain = get_domain(
        state, DOMAIN_INCLUSION_LIST_COMMITTEE, compute_epoch_at_slot(inclusion_list.slot)
    )
    signing_root = compute_signing_root(inclusion_list, domain)
    return bls.Sign(privkey, signing_root)

Attesting

Attestation data

Note: The only change to attestation_data is to call get_attester_head(store, head_root) to set the beacon_block_root field of attestation_data.

Modified LMD GHOST vote

Set attestation_data.beacon_block_root = get_attester_head(store, head_root).

Sync committee

Note: The only change to get_sync_committee_message is to call get_attester_head(store, head_root) to set the beacon_block_root parameter of get_sync_committee_message.

get_sync_committee_message

Modified beacon_block_root

The beacon_block_root parameter MUST be set to return value of get_attester_head(store: Store, head_root: Root) function.