Off-chain C2→C4 check blames a dealer only when it matches no recipient

[hmzakhalid]

Summary

The off-chain C2→C4 commitment check blames a dealer only when its commitments match no recipient.

Evidence

• crates/slashing/src/commitment_consistency/workflow.rs:372-449 (LinkScope::SourceMustExistInTargets): for each C2a/C2b source, found = all_targets.iter().any(|tgt| link.check_consistency(…)). A mismatch is recorded only when found is false.
• check_consistency compares the source row for that specific recipient (c2_to_c4/mod.rs:196-230, exact match of all L values).
• So a dealer with correct commitments for one recipient and wrong commitments for the others is not accused off-chain.
• The module docs say that fault is attributed when the commitments "for the C4 recipient do not exactly match". The aggregation circuit still checks every pair, so a bad dealer makes the DKG proof fail instead of causing an accusation.

Question

Is the any rule intended (for example, to tolerate missing C4 targets)? If not, the check can require a match for every recipient on the roster.

[hmzakhalid]

Rechecked against main at 6b47f39ba on 2026-10-02. The code is unchanged (crates/slashing/src/commitment_consistency/workflow.rs:371-449), and the question is still open.