4.8 KiB
EIP-4844 -- Honest Validator
Notice: This document is a work-in-progress for researchers and implementers.
Table of contents
Introduction
This document represents the changes to be made in the code of an "honest validator" to implement EIP-4844.
Prerequisites
This document is an extension of the Capella -- 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-4844 are requisite for this document and used throughout. Please see related Beacon Chain doc before continuing and use them as a reference throughout.
Helpers
get_blobs_and_kzg_commitments
The interface to retrieve blobs and corresponding kzg commitments.
Note: This API is unstable. get_blobs_and_kzg_commitments
and get_payload
may be unified.
Implementers may also retrieve blobs individually per transaction.
def get_blobs_and_kzg_commitments(payload_id: PayloadId) -> Tuple[Sequence[BLSFieldElement], Sequence[KZGCommitment]]:
# pylint: disable=unused-argument
...
Beacon chain responsibilities
All validator responsibilities remain unchanged other than those noted below.
Namely, the blob handling and the addition of SignedBeaconBlockAndBlobsSidecar
.
Block and sidecar proposal
Constructing the BeaconBlockBody
Blob KZG commitments
- After retrieving the execution payload from the execution engine as specified in Capella,
use the
payload_id
to retrieveblobs
andblob_kzg_commitments
viaget_blobs_and_kzg_commitments(payload_id)
. - Validate
blobs
andblob_kzg_commitments
:
def validate_blobs_and_kzg_commitments(execution_payload: ExecutionPayload,
blobs: Sequence[Blob],
blob_kzg_commitments: Sequence[KZGCommitment]) -> None:
# Optionally sanity-check that the KZG commitments match the versioned hashes in the transactions
assert verify_kzg_commitments_against_transactions(execution_payload.transactions, blob_kzg_commitments)
# Optionally sanity-check that the KZG commitments match the blobs (as produced by the execution engine)
assert len(blob_kzg_commitments) == len(blobs)
assert [blob_to_kzg_commitment(blob) == commitment for blob, commitment in zip(blobs, blob_kzg_commitments)]
- If valid, set
block.body.blob_kzg_commitments = blob_kzg_commitments
.
Constructing the SignedBeaconBlockAndBlobsSidecar
To construct a SignedBeaconBlockAndBlobsSidecar
, a signed_beacon_block_and_blobs_sidecar
is defined with the necessary context for block and sidecar proposal.
Block
Set signed_beacon_block_and_blobs_sidecar.beacon_block = block
where block
is obtained above.
Sidecar
Coupled with block, the corresponding blobs are packaged into a sidecar object for distribution to the network.
Set signed_beacon_block_and_blobs_sidecar.blobs_sidecar = sidecar
where sidecar
is obtained from:
def get_blobs_sidecar(block: BeaconBlock, blobs: Sequence[Blob]) -> BlobsSidecar:
return BlobsSidecar(
beacon_block_root=hash_tree_root(block),
beacon_block_slot=block.slot,
blobs=blobs,
# Disabled because not available before switch to single blob sidecars
kzg_aggregated_proof=KZGProof(), # compute_aggregate_kzg_proof(blobs),
)
This signed_beacon_block_and_blobs_sidecar
is then published to the global beacon_block_and_blobs_sidecar
topic.
After publishing the peers on the network may request the sidecar through sync-requests, or a local user may be interested.
The validator MUST hold on to sidecars for MIN_EPOCHS_FOR_BLOBS_SIDECARS_REQUESTS
epochs and serve when capable,
to ensure the data-availability of these blobs throughout the network.
After MIN_EPOCHS_FOR_BLOBS_SIDECARS_REQUESTS
nodes MAY prune the sidecars and/or stop serving them.