| name | differential-test-harness-gen |
| description | Generate cross-implementation differential test harnesses for cryptographic code: official test-vector and Wycheproof replay, normalization of error/result semantics, deterministic corpus capture, and evidence handoff to crypto-fp-check. User-triggered only — never auto-invoked by the audit flow.
|
| allowed-tools | ["Read","Grep","Glob","Bash","Write"] |
differential-test-harness-gen
Evidence-tooling skill that builds differential test harnesses: run the
target implementation and a reference (or a second implementation) over the
same inputs, normalize their result/error semantics, and capture every
divergence as reproducible evidence. User-triggered only; the router never
selects it automatically.
When to Use
- A reviewer explicitly requests a differential/cross-implementation test
harness for a crypto primitive
- Replaying official test vectors (NIST CAVP/ACVP, RFC vectors) or Project
Wycheproof cases against the target
- Producing deterministic crash/divergence corpora as evidence for
crypto-fp-check
When NOT to Use
- Automatic domain routing (this skill is
user_triggered_only and is
excluded from all router rules and phase defaults)
- Finding the vulnerability in the first place -> the domain auditors
- Property-based crash fuzzing of Rust code ->
fuzz-harness-gen
- Bounded formal proofs ->
kani-harness-gen
Core Review Areas
- Implementations compared: the target and a well-chosen reference (or
two references), with versions pinned
- Vector/corpus source: official vectors (CAVP/ACVP, RFC), Wycheproof
where the primitive is covered, or a generated boundary corpus
- Normalization: mapping each implementation's accept/reject/error
representation onto a common verdict so a real divergence is not masked
by cosmetic API differences
- Determinism: fixed seeds, pinned versions, and captured inputs so every
divergence reproduces
- Evidence handoff: a corpus of diverging inputs plus a reproduction
command per divergence, formatted for
crypto-fp-check
Workflow
Phase 1: Scope the harness
- Read
references/differential-test-checklist.md
- Identify the primitive, the target entry point, the reference
implementation(s), and the applicable vector sources
Phase 2: Build and replay
- Execute
workflows/wycheproof-replay.md
- Generate the harness, replay vectors, and record divergences
Phase 3: Normalize and capture
- Read
references/finding-patterns.md
- Apply result/error normalization and capture a deterministic corpus
Phase 4: Handoff
- Package divergences with reproduction commands and route to
crypto-fp-check
Output Contract
Produce a differential-testing evidence handoff that includes:
implementations_comparedvector_or_corpus_sourcenormalization_rulesreproduction_commandevidence_artifactsnext_route
Reference Index
