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Yue-Zhou1 (@yue-zhou1) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Threshold Ecdsa Auditor by yue-zhou1

Name: Threshold Ecdsa Auditor
Author: Yue-Zhou1

Threshold Ecdsa Auditor

Audit threshold ECDSA implementations (GG18, GG20, CGGMP21, Lindell-style) for Paillier modulus validity, MtA/MtAwc range-proof gaps, share-conversion soundness, resharing and concurrent-session isolation, and identifiable-abort leakage. Use when reviewing multi-party ECDSA keygen, signing, or resharing.

Yue-Zhou1 Updated Sep 17, 2026

File contents

threshold-ecdsa-auditor

Domain auditor for multi-party ECDSA: protocols that split an ECDSA key across parties and sign via Paillier-based or OT-based share conversion (GG18, GG20, CGGMP21, Lindell 2P-ECDSA and descendants).

When to Use

Auditing GG18/GG20/CGGMP21/Lindell-style keygen, signing, or resharing
Reviewing Paillier modulus generation and validity (square-free, no-small-factor) proofs
Reviewing MtA/MtAwc range and consistency proofs and share conversions
Reviewing presignature handling, concurrent signing sessions, and identifiable-abort behavior

When NOT to Use

FROST, MuSig2, threshold Schnorr, or generic DKG/VSS review -> dkg-threshold-auditor
Generic OT, garbled circuits, or share-MAC (SPDZ-style) review -> mpc-auditor
Single-party ECDSA signing in an Ethereum application (ecrecover, EIP-712, alloy/ethers-rs) -> ethereum-crypto-auditor
Generic single-party signature scheme review (verification equations, malleability, encodings) -> signature-scheme-auditor
Nonce/CSPRNG generation mechanics -> randomness-auditor
Timing/cache leakage of share arithmetic -> side-channel-auditor

Core Review Areas

Paillier modulus N: generation, biprimality/square-free proof, and no-small-factor proof actually verified by every counterparty
MtA/MtAwc: range proofs present AND verified on both directions of the conversion; missing range proofs enable the classic key-extraction attacks (Alpha-Rays class)
Share conversion algebra: additive/multiplicative conversion consistency, Lagrange coefficient handling, and modulus mixing (mod N vs mod q)
Key generation: commitment-then-reveal ordering, feldman VSS checks, rogue-key resistance
Signing sessions: presignature single-use, concurrent-session state isolation, nonce contribution binding (k-share vs gamma-share)
Resharing: old-committee/new-committee authorization and share zeroization
Identifiable abort: blame paths must not leak share or nonce information (GG20 identifiable abort vs CGGMP21 accountability)

Workflow

Phase 1: Protocol and version mapping

Read references/threshold-ecdsa-checklist.md
Identify the exact construction and paper version (GG18 vs GG20 vs CGGMP21 revision) — checks differ per construction
Map rounds to code: keygen, presign/sign, reshare entry points

Phase 2: Paillier and MtA review

Execute workflows/mta-review.md
Verify modulus validity proofs and both MtA directions' range proofs

Phase 3: Pattern hunt

Read references/finding-patterns.md
Prioritize missing range-proof verification, presignature reuse, concurrent-session nonce leakage, and abort-path oracles

Phase 4: Handoff

Send surviving findings to crypto-fp-check
Cross-route generic MPC building blocks to mpc-auditor, RNG concerns to randomness-auditor, and leakage concerns to side-channel-auditor

Output Contract

Produce a threshold-ECDSA handoff that includes:

protocol_round
proof_or_range_check
invariant_at_risk
evidence
disposition (one of verified, false_positive, unverified, observation, residual_risk)
next_route

Reference Index

references/threshold-ecdsa-checklist.md
references/finding-patterns.md
references/spec-sources.md
workflows/mta-review.md

---name: threshold-ecdsa-auditor-2description: Audit threshold ECDSA implementations (GG18, GG20, CGGMP21, Lindell-style) for Paillier modulus validity, MtA/MtAwc range-proof gaps, share-conversion soundness, resharing and concurrent-session isolation, and identifiable-abort leakage. Use when reviewing multi-party ECDSA keygen, signing, or resharing.---# threshold-ecdsa-auditorDomain auditor for multi-party ECDSA: protocols that split an ECDSA keyacross parties and sign via Paillier-based or OT-based share conversion(GG18, GG20, CGGMP21, Lindell 2P-ECDSA and descendants).## When to Use- Auditing GG18/GG20/CGGMP21/Lindell-style keygen, signing, or resharing- Reviewing Paillier modulus generation and validity (square-free, no-small-factor) proofs- Reviewing MtA/MtAwc range and consistency proofs and share conversions- Reviewing presignature handling, concurrent signing sessions, and identifiable-abort behavior## When NOT to Use- FROST, MuSig2, threshold Schnorr, or generic DKG/VSS review -> `dkg-threshold-auditor`- Generic OT, garbled circuits, or share-MAC (SPDZ-style) review -> `mpc-auditor`- Single-party ECDSA signing in an Ethereum application (ecrecover, EIP-712, alloy/ethers-rs) -> `ethereum-crypto-auditor`- Generic single-party signature scheme review (verification equations, malleability, encodings) -> `signature-scheme-auditor`- Nonce/CSPRNG generation mechanics -> `randomness-auditor`- Timing/cache leakage of share arithmetic -> `side-channel-auditor`## Core Review Areas1. Paillier modulus N: generation, biprimality/square-free proof, and no-small-factor proof actually verified by every counterparty2. MtA/MtAwc: range proofs present AND verified on both directions of the conversion; missing range proofs enable the classic key-extraction attacks (Alpha-Rays class)3. Share conversion algebra: additive/multiplicative conversion consistency, Lagrange coefficient handling, and modulus mixing (mod N vs mod q)4. Key generation: commitment-then-reveal ordering, feldman VSS checks, rogue-key resistance5. Signing sessions: presignature single-use, concurrent-session state isolation, nonce contribution binding (k-share vs gamma-share)6. Resharing: old-committee/new-committee authorization and share zeroization7. Identifiable abort: blame paths must not leak share or nonce information (GG20 identifiable abort vs CGGMP21 accountability)## Workflow### Phase 1: Protocol and version mapping- Read `references/threshold-ecdsa-checklist.md`- Identify the exact construction and paper version (GG18 vs GG20 vs CGGMP21 revision) — checks differ per construction- Map rounds to code: keygen, presign/sign, reshare entry points### Phase 2: Paillier and MtA review- Execute `workflows/mta-review.md`- Verify modulus validity proofs and both MtA directions' range proofs### Phase 3: Pattern hunt- Read `references/finding-patterns.md`- Prioritize missing range-proof verification, presignature reuse, concurrent-session nonce leakage, and abort-path oracles### Phase 4: Handoff- Send surviving findings to `crypto-fp-check`- Cross-route generic MPC building blocks to `mpc-auditor`, RNG concerns to `randomness-auditor`, and leakage concerns to `side-channel-auditor`## Output ContractProduce a threshold-ECDSA handoff that includes:- `protocol_round`- `proof_or_range_check`- `invariant_at_risk`- `evidence`- `disposition` (one of `verified`, `false_positive`, `unverified`, `observation`, `residual_risk`)- `next_route`## Reference Index- [references/threshold-ecdsa-checklist.md](references/threshold-ecdsa-checklist.md)- [references/finding-patterns.md](references/finding-patterns.md)- [references/spec-sources.md](references/spec-sources.md)- [workflows/mta-review.md](workflows/mta-review.md)

Frequently asked questions