eth2.0-specs/specs/_features/eip7594/p2p-interface.md

EIP-7594 -- Networking

Notice: This document is a work-in-progress for researchers and implementers.

Table of contents

• Modifications in EIP-7594
  • Preset
  • Containers
    • DataColumnIdentifier
  • Helpers
    • verify_data_column_sidecar_kzg_proofs
    • verify_data_column_sidecar_inclusion_proof
    • compute_subnet_for_data_column_sidecar
  • The gossip domain: gossipsub
    • Topics and messages
      • Samples subnets
        • data_column_sidecar_{subnet_id}
  • The Req/Resp domain
    • Messages
      • DataColumnSidecarByRoot v1

Modifications in EIP-7594

Preset

Name	Value	Description
KZG_COMMITMENTS_INCLUSION_PROOF_DEPTH	uint64(floorlog2(get_generalized_index(BeaconBlockBody, 'blob_kzg_commitments'))) (= 4)	Merkle proof index for blob_kzg_commitments

Containers

DataColumnIdentifier

class DataColumnIdentifier(Container):
    block_root: Root
    index: ColumnIndex

Helpers

verify_data_column_sidecar_kzg_proofs

def verify_data_column_sidecar_kzg_proofs(sidecar: DataColumnSidecar) -> bool:
    """
    Verify if the proofs are correct
    """
    assert sidecar.index < NUMBER_OF_COLUMNS
    assert len(sidecar.column) == len(sidecar.kzg_commitments) == len(sidecar.kzg_proofs)
    row_ids = [RowIndex(i) for i in range(len(sidecar.column))]

    # KZG batch verifies that the cells match the corresponding commitments and proofs
    return verify_cell_proof_batch(
        row_commitments=sidecar.kzg_commitments,
        row_indices=row_ids,  # all rows
        column_indices=[sidecar.index],
        cells=sidecar.column,
        proofs=sidecar.kzg_proofs,
    )

verify_data_column_sidecar_inclusion_proof

def verify_data_column_sidecar_inclusion_proof(sidecar: DataColumnSidecar) -> bool:
    """
    Verify if the given KZG commitments included in the given beacon block.
    """
    gindex = get_subtree_index(get_generalized_index(BeaconBlockBody, 'blob_kzg_commitments'))
    return is_valid_merkle_branch(
        leaf=hash_tree_root(sidecar.kzg_commitments),
        branch=sidecar.kzg_commitments_inclusion_proof,
        depth=KZG_COMMITMENTS_INCLUSION_PROOF_DEPTH,
        index=gindex,
        root=sidecar.signed_block_header.message.body_root,
    )

compute_subnet_for_data_column_sidecar

def compute_subnet_for_data_column_sidecar(column_index: ColumnIndex) -> SubnetID:
    return SubnetID(column_index % DATA_COLUMN_SIDECAR_SUBNET_COUNT)

The gossip domain: gossipsub

Some gossip meshes are upgraded in the EIP-7594 fork to support upgraded types.

Topics and messages

Samples subnets

data_column_sidecar_{subnet_id}

This topic is used to propagate column sidecars, where each column maps to some subnet_id.

The type of the payload of this topic is DataColumnSidecar.

The following validations MUST pass before forwarding the sidecar: DataColumnSidecar on the network, assuming the alias block_header = sidecar.signed_block_header.message:

• [REJECT] The sidecar's index is consistent with NUMBER_OF_COLUMNS -- i.e. sidecar.index < NUMBER_OF_COLUMNS.
• [REJECT] The sidecar is for the correct subnet -- i.e. compute_subnet_for_data_column_sidecar(sidecar.index) == subnet_id.
• [IGNORE] The sidecar is not from a future slot (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance) -- i.e. validate that block_header.slot <= current_slot (a client MAY queue future sidecars for processing at the appropriate slot).
• [IGNORE] The sidecar is from a slot greater than the latest finalized slot -- i.e. validate that block_header.slot > compute_start_slot_at_epoch(state.finalized_checkpoint.epoch)
• [REJECT] The proposer signature of sidecar.signed_block_header, is valid with respect to the block_header.proposer_index pubkey.
• [IGNORE] The sidecar's block's parent (defined by block_header.parent_root) has been seen (via both gossip and non-gossip sources) (a client MAY queue sidecars for processing once the parent block is retrieved).
• [REJECT] The sidecar's block's parent (defined by block_header.parent_root) passes validation.
• [REJECT] The sidecar is from a higher slot than the sidecar's block's parent (defined by block_header.parent_root).
• [REJECT] The current finalized_checkpoint is an ancestor of the sidecar's block -- i.e. get_checkpoint_block(store, block_header.parent_root, store.finalized_checkpoint.epoch) == store.finalized_checkpoint.root.
• [REJECT] The sidecar's kzg_commitments field inclusion proof is valid as verified by verify_data_column_sidecar_inclusion_proof(sidecar).
• [REJECT] The sidecar's column data is valid as verified by verify_data_column_sidecar_kzg_proofs(sidecar).
• [IGNORE] The sidecar is the first sidecar for the tuple (block_header.slot, block_header.proposer_index, sidecar.index) with valid header signature, sidecar inclusion proof, and kzg proof.
• [REJECT] The sidecar is proposed by the expected proposer_index for the block's slot in the context of the current shuffling (defined by block_header.parent_root/block_header.slot). If the proposer_index cannot immediately be verified against the expected shuffling, the sidecar MAY be queued for later processing while proposers for the block's branch are calculated -- in such a case do not REJECT, instead IGNORE this message.

Note: In the verify_data_column_sidecar_inclusion_proof(sidecar) check, for all the sidecars of the same block, it verifies against the same set of kzg_commitments of the given beacon beacon. Client can choose to cache the result of the arguments tuple (sidecar.kzg_commitments, sidecar.kzg_commitments_inclusion_proof, sidecar.signed_block_header).

The Req/Resp domain

Messages

DataColumnSidecarByRoot v1

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

[New in Deneb:EIP4844]

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

fork_version	Chunk SSZ type
EIP7594_FORK_VERSION	eip7594.DataColumnSidecar

Request Content:

(
  DataColumnIdentifier
)

Response Content:

(
  DataColumnSidecar
)