192 lines
7.0 KiB
Markdown
192 lines
7.0 KiB
Markdown
# Deneb -- Honest Validator
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**Notice**: This document is a work-in-progress for researchers and implementers.
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## Table of contents
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<!-- TOC -->
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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- [Introduction](#introduction)
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- [Prerequisites](#prerequisites)
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- [Helpers](#helpers)
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- [`BlobsBundle`](#blobsbundle)
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- [Modified `GetPayloadResponse`](#modified-getpayloadresponse)
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- [Protocol](#protocol)
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- [`ExecutionEngine`](#executionengine)
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- [Modified `get_payload`](#modified-get_payload)
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- [Beacon chain responsibilities](#beacon-chain-responsibilities)
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- [Block and sidecar proposal](#block-and-sidecar-proposal)
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- [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
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- [ExecutionPayload](#executionpayload)
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- [Blob KZG commitments](#blob-kzg-commitments)
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- [Constructing the `SignedBlobSidecar`s](#constructing-the-signedblobsidecars)
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- [Sidecar](#sidecar)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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<!-- /TOC -->
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## Introduction
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This document represents the changes to be made in the code of an "honest validator" to implement Deneb.
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## Prerequisites
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This document is an extension of the [Capella -- Honest Validator](../capella/validator.md) guide.
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All behaviors and definitions defined in this document, and documents it extends, carry over unless explicitly noted or overridden.
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All terminology, constants, functions, and protocol mechanics defined in the updated [Beacon Chain doc of Deneb](./beacon-chain.md) are requisite for this document and used throughout.
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Please see related Beacon Chain doc before continuing and use them as a reference throughout.
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## Helpers
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### `BlobsBundle`
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*[New in Deneb:EIP4844]*
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```python
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@dataclass
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class BlobsBundle(object):
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commitments: Sequence[KZGCommitment]
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proofs: Sequence[KZGProof]
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blobs: Sequence[Blob]
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```
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### Modified `GetPayloadResponse`
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```python
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@dataclass
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class GetPayloadResponse(object):
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execution_payload: ExecutionPayload
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block_value: uint256
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blobs_bundle: BlobsBundle # [New in Deneb:EIP4844]
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```
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## Protocol
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### `ExecutionEngine`
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#### Modified `get_payload`
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Given the `payload_id`, `get_payload` returns the most recent version of the execution payload that
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has been built since the corresponding call to `notify_forkchoice_updated` method.
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```python
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def get_payload(self: ExecutionEngine, payload_id: PayloadId) -> GetPayloadResponse:
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"""
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Return ExecutionPayload, uint256, BlobsBundle objects.
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"""
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# pylint: disable=unused-argument
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...
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```
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## Beacon chain responsibilities
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All validator responsibilities remain unchanged other than those noted below.
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### Block and sidecar proposal
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#### Constructing the `BeaconBlockBody`
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##### ExecutionPayload
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`prepare_execution_payload` is updated from the Capella specs to provide the parent beacon block root.
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*Note*: In this section, `state` is the state of the slot for the block proposal _without_ the block yet applied.
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That is, `state` is the `previous_state` processed through any empty slots up to the assigned slot using `process_slots(previous_state, slot)`.
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*Note*: The only change made to `prepare_execution_payload` is to add the parent beacon block root as an additional
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parameter to the `PayloadAttributes`.
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```python
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def prepare_execution_payload(state: BeaconState,
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safe_block_hash: Hash32,
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finalized_block_hash: Hash32,
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suggested_fee_recipient: ExecutionAddress,
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execution_engine: ExecutionEngine) -> Optional[PayloadId]:
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# Verify consistency of the parent hash with respect to the previous execution payload header
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parent_hash = state.latest_execution_payload_header.block_hash
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# Set the forkchoice head and initiate the payload build process
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payload_attributes = PayloadAttributes(
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timestamp=compute_timestamp_at_slot(state, state.slot),
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prev_randao=get_randao_mix(state, get_current_epoch(state)),
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suggested_fee_recipient=suggested_fee_recipient,
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withdrawals=get_expected_withdrawals(state),
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parent_beacon_block_root=hash_tree_root(state.latest_block_header), # [New in Deneb:EIP4788]
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)
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return execution_engine.notify_forkchoice_updated(
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head_block_hash=parent_hash,
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safe_block_hash=safe_block_hash,
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finalized_block_hash=finalized_block_hash,
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payload_attributes=payload_attributes,
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)
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```
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##### Blob KZG commitments
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*[New in Deneb:EIP4844]*
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1. The execution payload is obtained from the execution engine as defined above using `payload_id`. The response also includes a `blobs_bundle` entry containing the corresponding `blobs`, `commitments`, and `proofs`.
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2. Set `block.body.blob_kzg_commitments = commitments`.
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#### Constructing the `SignedBlobSidecar`s
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*[New in Deneb:EIP4844]*
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To construct a `SignedBlobSidecar`, a `signed_blob_sidecar` is defined with the necessary context for block and sidecar proposal.
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##### Sidecar
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Blobs associated with a block are packaged into sidecar objects for distribution to the network.
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Each `sidecar` is obtained from:
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```python
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def get_blob_sidecars(block: BeaconBlock,
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blobs: Sequence[Blob],
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blob_kzg_proofs: Sequence[KZGProof]) -> Sequence[BlobSidecar]:
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return [
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BlobSidecar(
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block_root=hash_tree_root(block),
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index=index,
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slot=block.slot,
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block_parent_root=block.parent_root,
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blob=blob,
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kzg_commitment=block.body.blob_kzg_commitments[index],
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kzg_proof=blob_kzg_proofs[index],
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)
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for index, blob in enumerate(blobs)
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]
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```
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Then for each sidecar, `signed_sidecar = SignedBlobSidecar(message=sidecar, signature=signature)` is constructed and published to the associated sidecar topic, the `blob_sidecar_{subnet_id}` pubsub topic.
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`signature` is obtained from:
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```python
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def get_blob_sidecar_signature(state: BeaconState,
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sidecar: BlobSidecar,
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privkey: int) -> BLSSignature:
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domain = get_domain(state, DOMAIN_BLOB_SIDECAR, compute_epoch_at_slot(sidecar.slot))
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signing_root = compute_signing_root(sidecar, domain)
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return bls.Sign(privkey, signing_root)
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```
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The `subnet_id` for the `signed_sidecar` is calculated with:
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- Let `blob_index = signed_sidecar.message.index`.
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- Let `subnet_id = compute_subnet_for_blob_sidecar(blob_index)`.
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```python
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def compute_subnet_for_blob_sidecar(blob_index: BlobIndex) -> SubnetID:
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return SubnetID(blob_index % BLOB_SIDECAR_SUBNET_COUNT)
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```
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After publishing the peers on the network may request the sidecar through sync-requests, or a local user may be interested.
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The validator MUST hold on to sidecars for `MIN_EPOCHS_FOR_BLOB_SIDECARS_REQUESTS` epochs and serve when capable,
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to ensure the data-availability of these blobs throughout the network.
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After `MIN_EPOCHS_FOR_BLOB_SIDECARS_REQUESTS` nodes MAY prune the sidecars and/or stop serving them.
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