EIP-6988: Elected block proposer has not been slashed

Prevents a slashed validator from being elected as a block proposer

Metadata

Status: StagnantStandards Track: CoreCreated: 2023-05-04

Authors

Mikhail Kalinin (@mkalinin)

Links

GitHub page Discussion on Ethereum Magicians

Abstract

Introduces a modification to the consensus layer specification which ensures that slashed validator cannot be elected as block proposer.

Motivation

A block proposed by a slashed validator is rejected by the corresponding validity check in the phase0/process_block_header function as defined in the consensus layer specification.

At the same time the definition of the phase0/compute_proposer_index allows for a slashed validator to be elected as a proposer. This contradiction effectively leads to a missed proposal if it is supposed to be made by a slashed validator.

The impact of the proposed fix in the case of a single slashing on Ethereum Mainnet is negligible but it becomes significant in the case of correlated slashings. For instance, a correlated slashing of 1/10th of a validator set can lead to 1/10th of missed proposals in a number of epochs after the slashing.

Specification

Specification of the proposed change can be found in /_features/eip6988/beacon-chain.md.

Rationale

Modifying `get_beacon_proposer_index`

This function is modified to read a proposer index from a beacon state if a slot of a latest block header is the same as the state.slot.

This modification is done to make the function return correct proposer index in the case when the proposer of a given block is being slashed during processing of the block.

Backwards Compatibility

This fix changes proposer election mechanism in a backwards incompatible way and requires a hard fork to be deployed.

Test Cases

The following test cases were added to cover this change:

Reference Implementation

Reference implementation is in the same place as Specification.

Security Considerations

There are no observed security issues introduced by the proposed change.