Merge 5672cd9 into 686bc3c

Author: mkalinin

EIPS/eip-6987.md

@@ -0,0 +1,59 @@
+---
+eip: 6988
+title: Elected block proposer is not slashed
+description: Prevents a slashed validator from being elected as a block proposer
+author: Mikhail Kalinin (@mkalinin)
+discussions-to: <URL>
+status: Draft
+type: Standards Track
+category: Core
+created: 2023-05-04
+---
+
+## 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`](https://github.com/ethereum/consensus-specs/blob/3115d1140b23dd4c9c23fbd9e2428186cf816bde/specs/phase0/beacon-chain.md#block-header) function as defined in the consensus layer specification.
+
+At the same time the definition of the [`phase0/compute_proposer_index`](https://github.com/ethereum/consensus-specs/blob/3115d1140b23dd4c9c23fbd9e2428186cf816bde/specs/phase0/beacon-chain.md#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`](https://github.com/ethereum/consensus-specs/blob/0ad3972725e7c22e8edf3bab2dd7730acbe3c272/specs/_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:
+* [`test_slashed_proposer_rewarded_for_sync_aggregate_inclusion`](https://github.com/ethereum/consensus-specs/blob/0ad3972725e7c22e8edf3bab2dd7730acbe3c272/tests/core/pyspec/eth2spec/test/altair/block_processing/sync_aggregate/test_process_sync_aggregate.py#L712)
+* [`test_slashed_proposer_rewarded_for_attestation_inclusion`](https://github.com/ethereum/consensus-specs/blob/0ad3972725e7c22e8edf3bab2dd7730acbe3c272/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_attestation.py#L17)
+* [`test_slashed_validator_not_elected_for_proposal`](https://github.com/ethereum/consensus-specs/blob/0ad3972725e7c22e8edf3bab2dd7730acbe3c272/tests/core/pyspec/eth2spec/test/eip6988/unittests/validator/test_validator.py#L9)
+* [`test_slashed_validator_elected_for_proposal`](https://github.com/ethereum/consensus-specs/blob/0ad3972725e7c22e8edf3bab2dd7730acbe3c272/tests/core/pyspec/eth2spec/test/phase0/unittests/validator/test_validator_unittest.py#L520)
+
+## Reference Implementation
+
+Reference implementation is in the same place as [Specification](#specification).
+
+## Security Considerations
+
+There are no observed security issues introduced by the proposed change.
+
+## Copyright
+
+Copyright and related rights waived via [CC0](../LICENSE.md).