⚠️ Draft Standards Track: Core

EIP-6466: SSZ Receipts Root

Migration of receipts MPT commitment to SSZ

Authors	Etan Kissling (@etan-status), Vitalik Buterin (@vbuterin)
Created	2023-02-08
Discussion Link	https://ethereum-magicians.org/t/eip-6466-ssz-receipts-root/12884
Requires	EIP-6404, EIP-6493

Abstract
Motivation
Specification
Rationale
Backwards Compatibility
Test Cases
Reference Implementation
Security Considerations
Copyright

Abstract

This EIP defines a migration process of existing Merkle-Patricia Trie (MPT) commitments for receipts to Simple Serialize (SSZ)

Motivation

EIP-6404 introduces the more modern SSZ format to the transactions_root of the consensus ExecutionPayloadHeader and the execution block header. This EIP defines the equivalent transition for receipts_root to add support for EIP-6493 Receipt.

Note that in contrast to the transactions_root which refers to a Merkle Patricia Trie (MPT) root in execution but to an SSZ root in consensus, the receipts_root is already consistent and refers to the same MPT root. With this EIP, it will be changed to consistently refer to the same SSZ root.

Specification

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119 and RFC 8174.

Consensus `ExecutionPayload` changes

When building a consensus ExecutionPayload, the receipts_root is now based on the Receipt SSZ container. EIP-6493 defines how RLP receipts can be converted to SSZ.

This changes the type of receipts_root from an MPT Hash32 to an SSZ Root.

class ExecutionPayload(Container):
    ...
    receipts_root: Root
    ...

To compute the receipts_root, the list of individual Receipt containers is represented as an SSZ List.

Name	Value
`MAX_TRANSACTIONS_PER_PAYLOAD`	`uint64(2**20)` (= 1,048,576)

receipts = List[Receipt, MAX_TRANSACTIONS_PER_PAYLOAD](
    receipt_0, receipt_1, receipt_2, ...)

payload.receipts_root = receipts.hash_tree_root()

Consensus `ExecutionPayloadHeader` changes

The consensus ExecutionPayloadHeader is updated to match the new ExecutionPayload.receipts_root definition.

class ExecutionPayloadHeader(Container):
    ...
    receipts_root: Root
    ...

payload_header.receipts_root = payload.receipts_root

Execution block header changes

The execution block header’s receipts-root is updated to match the consensus ExecutionPayloadHeader.receipts_root.

Rationale

This change enables the use of SSZ transactions as defined in EIP-6493.

Backwards Compatibility

Applications that rely on the replaced MPT receipts_root in the block header require migration to the SSZ receipts_root.

Test Cases

TBD

Reference Implementation

TBD

Security Considerations

None

Copyright

Citation

Please cite this document as:

Etan Kissling (@etan-status), Vitalik Buterin (@vbuterin), "EIP-6466: SSZ Receipts Root [DRAFT]," Ethereum Improvement Proposals, no. 6466, February 2023. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-6466.