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EIP-7732 -- Networking

This document contains the consensus-layer networking specification for EIP7732.

Modification in EIP-7732

Preset

[Modified in EIP-7732]

Name Value Description
KZG_COMMITMENT_INCLUSION_PROOF_DEPTH_EIP7732 13 # TODO: Compute it when the spec stabilizes Merkle proof depth for the blob_kzg_commitments list item

Configuration

[New in EIP-7732]

Name Value Description
MAX_REQUEST_PAYLOADS 2**7 (= 128) Maximum number of execution payload envelopes in a single request

Containers

BlobSidecar

The BlobSidecar container is modified indirectly because the constant KZG_COMMITMENT_INCLUSION_PROOF_DEPTH is modified.

class BlobSidecar(Container):
    index: BlobIndex  # Index of blob in block
    blob: Blob
    kzg_commitment: KZGCommitment
    kzg_proof: KZGProof  # Allows for quick verification of kzg_commitment
    signed_block_header: SignedBeaconBlockHeader
    kzg_commitment_inclusion_proof: Vector[Bytes32, KZG_COMMITMENT_INCLUSION_PROOF_DEPTH_EIP7732]

Helpers

Modified verify_blob_sidecar_inclusion_proof

verify_blob_sidecar_inclusion_proof is modified in EIP-7732 to account for the fact that the KZG commitments are included in the ExecutionPayloadEnvelope and no longer in the beacon block body.

def verify_blob_sidecar_inclusion_proof(blob_sidecar: BlobSidecar) -> bool:
    inner_gindex = get_generalized_index(
        List[KZGCommitment, MAX_BLOB_COMMITMENTS_PER_BLOCK],
        blob_sidecar.index
    )
    outer_gindex = get_generalized_index(
        BeaconBlockBody,
        "signed_execution_payload_header",
        "message",
        "blob_kzg_commitments_root",
    )
    gindex = get_subtree_index(concat_generalized_indices(outer_gindex, inner_gindex))

    return is_valid_merkle_branch(
        leaf=blob_sidecar.kzg_commitment.hash_tree_root(),
        branch=blob_sidecar.kzg_commitment_inclusion_proof,
        depth=KZG_COMMITMENT_INCLUSION_PROOF_DEPTH_EIP7732,
        index=gindex,
        root=blob_sidecar.signed_block_header.message.body_root,
    )

The gossip domain: gossipsub

Some gossip meshes are upgraded in the fork of EIP-7732 to support upgraded types.

Topics and messages

Topics follow the same specification as in prior upgrades.

The beacon_block topic is updated to support the modified type

Name Message Type
beacon_block SignedBeaconBlock [modified in EIP-7732]

The new topics along with the type of the data field of a gossipsub message are given in this table:

Name Message Type
execution_payload_header SignedExecutionPayloadHeader [New in EIP-7732]
execution_payload SignedExecutionPayloadEnvelope [New in EIP-7732]
payload_attestation_message PayloadAttestationMessage [New in EIP-7732]
Global topics

EIP-7732 introduces new global topics for execution header, execution payload and payload attestation.

beacon_block

[Modified in EIP-7732]

The type of the payload of this topic changes to the (modified) SignedBeaconBlock found in the Beacon Chain changes.

There are no new validations for this topic. However, all validations with regards to the ExecutionPayload are removed:

  • [REJECT] The length of KZG commitments is less than or equal to the limitation defined in Consensus Layer -- i.e. validate that len(body.signed_beacon_block.message.blob_kzg_commitments) <= MAX_BLOBS_PER_BLOCK
  • [REJECT] The block's execution payload timestamp is correct with respect to the slot -- i.e. execution_payload.timestamp == compute_timestamp_at_slot(state, block.slot).
  • If execution_payload verification of block's parent by an execution node is not complete:
    • [REJECT] The block's parent (defined by block.parent_root) passes all validation (excluding execution node verification of the block.body.execution_payload).
  • otherwise:
    • [IGNORE] The block's parent (defined by block.parent_root) passes all validation (including execution node verification of the block.body.execution_payload).
  • [REJECT] The block's parent (defined by block.parent_root) passes validation.

And instead the following validations are set in place with the alias header = signed_execution_payload_header.message:

  • If execution_payload verification of block's execution payload parent by an execution node is complete:
    • [REJECT] The block's execution payload parent (defined by header.parent_block_hash) passes all validation.
  • [REJECT] The block's parent (defined by block.parent_root) passes validation.
execution_payload

This topic is used to propagate execution payload messages as SignedExecutionPayloadEnvelope.

The following validations MUST pass before forwarding the signed_execution_payload_envelope on the network, assuming the alias envelope = signed_execution_payload_envelope.message, payload = payload_envelope.payload:

  • [IGNORE] The envelope's block root envelope.block_root has been seen (via both gossip and non-gossip sources) (a client MAY queue payload for processing once the block is retrieved).
  • [IGNORE] The node has not seen another valid SignedExecutionPayloadEnvelope for this block root from this builder.

Let block be the block with envelope.beacon_block_root. Let header alias block.body.signed_execution_payload_header.message (notice that this can be obtained from the state.signed_execution_payload_header)

  • [REJECT] block passes validation.
  • [REJECT] envelope.builder_index == header.builder_index
  • if envelope.payload_withheld == False then
    • [REJECT] payload.block_hash == header.block_hash
  • [REJECT] The builder signature, signed_execution_payload_envelope.signature, is valid with respect to the builder's public key.
payload_attestation_message

This topic is used to propagate signed payload attestation message.

The following validations MUST pass before forwarding the payload_attestation_message on the network, assuming the alias data = payload_attestation_message.data:

  • [IGNORE] The message's slot is for the current slot (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance), i.e. data.slot == current_slot.
  • [REJECT] The message's payload status is a valid status, i.e. data.payload_status < PAYLOAD_INVALID_STATUS.
  • [IGNORE] The payload_attestation_message is the first valid message received from the validator with index payload_attestation_message.validate_index.
  • [IGNORE] The message's block data.beacon_block_root has been seen (via both gossip and non-gossip sources) (a client MAY queue attestation for processing once the block is retrieved. Note a client might want to request payload after).
  • [REJECT] The message's block data.beacon_block_root passes validation.
  • [REJECT] The message's validator index is within the payload committee in get_ptc(state, data.slot). The state is the head state corresponding to processing the block up to the current slot as determined by the fork choice.
  • [REJECT] The message's signature of payload_attestation_message.signature is valid with respect to the validator index.
execution_payload_header

This topic is used to propagate signed bids as SignedExecutionPayloadHeader.

The following validations MUST pass before forwarding the signed_execution_payload_header on the network, assuming the alias header = signed_execution_payload_header.message:

  • [IGNORE] this is the first signed bid seen with a valid signature from the given builder for this slot.
  • [IGNORE] this bid is the highest value bid seen for the pair of the corresponding slot and the given parent block hash.
  • [REJECT] The signed builder bid, header.builder_index is a valid and non-slashed builder index in state.
  • [IGNORE] The signed builder bid value, header.value, is less or equal than the builder's balance in state. i.e. MIN_BUILDER_BALANCE + header.value < state.builder_balances[header.builder_index].
  • [IGNORE] header.parent_block_hash is the block hash of a known execution payload in fork choice.
  • [IGNORE] header.slot is the current slot or the next slot.
  • [REJECT] The builder signature, signed_execution_payload_header_envelope.signature, is valid with respect to the header_envelope.builder_index.

The Req/Resp domain

Messages

BeaconBlocksByRange v3

Protocol ID: /eth2/beacon_chain/req/beacon_blocks_by_range/3/

fork_version Chunk SSZ type
GENESIS_FORK_VERSION phase0.SignedBeaconBlock
ALTAIR_FORK_VERSION altair.SignedBeaconBlock
BELLATRIX_FORK_VERSION bellatrix.SignedBeaconBlock
CAPELLA_FORK_VERSION capella.SignedBeaconBlock
DENEB_FORK_VERSION deneb.SignedBeaconBlock
EIP7732_FORK_VERSION eip7732.SignedBeaconBlock
BeaconBlocksByRoot v3

Protocol ID: /eth2/beacon_chain/req/beacon_blocks_by_root/3/

Per context = compute_fork_digest(fork_version, genesis_validators_root):

fork_version Chunk SSZ type
GENESIS_FORK_VERSION phase0.SignedBeaconBlock
ALTAIR_FORK_VERSION altair.SignedBeaconBlock
BELLATRIX_FORK_VERSION bellatrix.SignedBeaconBlock
CAPELLA_FORK_VERSION capella.SignedBeaconBlock
DENEB_FORK_VERSION deneb.SignedBeaconBlock
EIP7732_FORK_VERSION eip7732.SignedBeaconBlock
BlobSidecarsByRoot v2

Protocol ID: /eth2/beacon_chain/req/blob_sidecars_by_root/2/

fork_version Chunk SSZ type
DENEB_FORK_VERSION deneb.BlobSidecar
EIP7732_FORK_VERSION eip7732.BlobSidecar
ExecutionPayloadEnvelopesByRoot v1

Protocol ID: /eth2/beacon_chain/req/execution_payload_envelopes_by_root/1/

The <context-bytes> field is calculated as context = compute_fork_digest(fork_version, genesis_validators_root):

fork_version Chunk SSZ type
EIP7732_FORK_VERSION eip7732.SignedExecutionPayloadEnvelope

Request Content:

(
  List[Root, MAX_REQUEST_PAYLOADS]
)

Response Content:

(
  List[SignedExecutionPayloadEnvelope, MAX_REQUEST_PAYLOADS]
)

Requests execution payload envelopes by signed_execution_payload_envelope.message.block_root. The response is a list of SignedExecutionPayloadEnvelope whose length is less than or equal to the number of requested execution payload envelopes. It may be less in the case that the responding peer is missing payload envelopes.

No more than MAX_REQUEST_PAYLOADS may be requested at a time.

ExecutionPayloadEnvelopesByRoot is primarily used to recover recent execution payload envelopes (e.g. when receiving a payload attestation with revealed status as true but never received a payload).

The request MUST be encoded as an SSZ-field.

The response MUST consist of zero or more response_chunk. Each successful response_chunk MUST contain a single SignedExecutionPayloadEnvelope payload.

Clients MUST support requesting payload envelopes since the latest finalized epoch.

Clients MUST respond with at least one payload envelope, if they have it. Clients MAY limit the number of payload envelopes in the response.