# Wycheproof

Validates cryptographic implementations against Project Wycheproof's test vectors...

- Repository: https://github.com/trailofbits/skills (7935 stars)
- Category: Testing
- License: CC-BY-SA-4.0
- Last updated: 2026-10-28
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add trailofbits/skills --skill wycheproof -g -a claude-code -y`
Codex: `npx skills add trailofbits/skills --skill wycheproof -g -a codex -y`
Cursor: `npx skills add trailofbits/skills --skill wycheproof -g -a cursor -y`
Gemini CLI: `npx skills add trailofbits/skills --skill wycheproof -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add trailofbits/skills`

## Description

Validates cryptographic implementations against Project Wycheproof's test vectors, which encode known attacks and edge cases across AES, RSA, ECDSA, ECDH, and more. Covers loading test vectors, mapping result flags onto pass and fail expectations, and reading a failure. Use when testing a crypto implementation against known attacks, checking a library against standard test vectors, or investigating why two implementations disagree on the same input.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Wycheproof

Wycheproof is an extensive collection of test vectors designed to verify the correctness of cryptographic implementations and test against known attacks. Originally developed by Google, it is now a community-managed project where contributors can add test vectors for specific cryptographic constructions.

## Background

### Key Concepts

| Concept | Description |
|---------|-------------|
| Test vector | Input/output pair for validating crypto implementation correctness |
| Test group | Collection of test vectors sharing attributes (key size, IV size, curve) |
| Result flag | Indicates if test should pass (valid), fail (invalid), or is acceptable |
| Edge case testing | Testing for known vulnerabilities and attack patterns |

### Why This Matters

Cryptographic implementations are notoriously difficult to get right. Even small bugs can:
- Expose private keys
- Allow signature forgery
- Enable message decryption
- Create consensus problems when different implementations accept/reject the same inputs

Wycheproof has found vulnerabilities in major libraries including OpenJDK's SHA1withDSA, Bouncy Castle's ECDHC, and the elliptic npm package.

## When to Use

**Apply Wycheproof when:**
- Testing cryptographic implementations (AES-GCM, ECDSA, ECDH, RSA, etc.)
- Validating that crypto code handles edge cases correctly
- Verifying implementations against known attack vectors
- Setting up CI/CD for cryptographic libraries
- Auditing third-party crypto code for correctness

**Consider alternatives when:**
- Testing for timing side-channels (use constant-time testing tools instead)
- Finding new unknown bugs (use fuzzing instead)
- Testing custom/experimental cryptographic algorithms (Wycheproof only covers established algorithms)

## Quick Reference

The rest: https://github.com/trailofbits/skills/blob/HEAD/plugins/testing-handbook-skills/skills/wycheproof/SKILL.md