# Cryptography

Cryptanalysis techniques, lattice attacks, padding oracles, weak-RNG exploitation...

- Repository: https://github.com/transilienceai/communitytools (600 stars)
- Category: Security
- License: MIT
- Last updated: 2026-07-29
- Runs scripts: no, instructions only

## Install

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

## Description

Cryptanalysis techniques, lattice attacks, padding oracles, weak-RNG exploitation, signature forgery, secret-sharing recovery.

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

# Cryptography

## Scope

Practical cryptanalysis for CTF and pentest engagements: identifying when a cryptographic primitive's structure (custom hash, partial leaks, related primes, bad RNG, weak modes) admits a faster-than-brute-force solver, then implementing that solver in pure Python where possible. Covers RSA-style algebraic factoring, lattice/AGCD recovery, GF(2) linear collapse of "complicated-looking" custom ciphers, smooth-order DLP, differential fault attacks, and Shamir-style secret-sharing recovery over non-prime moduli. Always read source first to detect linearity/algebraic structure before reaching for SageMath or symbolic solvers.

## When to use

- A challenge or target ships **custom crypto** (custom hash, custom block cipher, hand-rolled key derivation) and you need to look for affine / GF(2)-linear collapse.
- RSA-style primitives with **structured primes** (`p = a·r + b`, `phi(n)` perfect square, multi-prime hint files, common factors).
- A service exposes a **chosen-ciphertext / chosen-input oracle** and you suspect padding-oracle, smooth-order DLP, or Bleichenbacher-style recovery.
- AES with **fault injection** (correct + faulty ciphertext for the same key, Piret-Quisquater DFA).
- Shamir secret sharing or threshold schemes with non-prime moduli (2-adic recovery via Lagrange interpolation with valuation tracking).

## References

- [reference/lattice-attacks.md](reference/lattice-attacks.md), AGCD lattice, discriminant-square factoring, smooth-order DLP, Piret-Quisquater DFA.
- [reference/linear-secret-recovery.md](reference/linear-secret-recovery.md), GF(2) affine collapse of custom hashes/ciphers via column-by-column linear recovery.