Slashing Condition Evidence Expiration Window Inconsistency Between Slot and Epoch Units

[JamesEjembi]

Problem Statement / Feature Objective

Slashing evidence (double-vote, surround-vote) carries an expiration window measured in epochs from the time of the infraction. The slashing engine checks evidence.Slot + MAX_SLASHING_WINDOW > current_slot, but the window constant is defined in slots while evidence timestamps use a mix of slot and epoch units. A surround-vote evidence spanning an epoch boundary can be incorrectly expired or accepted.

Technical Invariants & Bounds

• MAX_SLASHING_WINDOW = 8192 slots (~36 hours).
• WHISTLEBLOWER_REWARD_QUOTIENT = 512 (reward fraction).
• Evidence must include both source and target epochs (surround vote).
• Slot-to-epoch conversion: epoch = slot / 32.
• Window check uses slot comparison; source/target are epochs.
• Off-by-SLOTS_PER_EPOCH can extend/reduce window by 32 slots.

Codebase Navigation Guide

• src/slashing/evidence-verifier.rs - verify_evidence_expiry() and verify_surround_vote().
• src/slashing/types.rs - SlashingEvidence struct with slot, source_epoch, target_epoch.
• src/slashing/condition-engine.rs - process_slashing() entry point.
• tests/slashing/evidence_expiry_test.rs - expiry edge case tests.

Implementation Blueprint

1. In src/slashing/evidence-verifier.rs, normalize all expiry checks to a single unit (slots). Convert source_epoch and target_epoch to their equivalent slot ranges (source_slot_start = source_epoch * 32, etc.).
2. Update verify_evidence_expiry() to use slot_start of the earliest infraction for the window check.
3. Add a helper fn evidence_infraction_slot_range(ev: &SlashingEvidence) -> (Slot, Slot) that returns the inclusive slot range of the violation.
4. Write tests for surround-vote evidence exactly at the window boundary and one slot past it.
5. Add a property test that randomly generates evidence timestamps and verifies the window rule is symmetric.

[Mona-i]

Hello. Thank you

[grantfox-oss]

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