ctf-crypto

# CTF Cryptography Quick reference for crypto CTF challenges. Each technique has a one-liner here; see supporting files for full details with code. ## Prerequisites **Python packages (all platforms):** ```bash pip install pycryptodome z3-solver sympy gmpy2 hashpumpy fpylll py_ecc ``` **Linux (apt):** ```bash apt install hashcat sagemath ``` **macOS (Homebrew):** ```bash brew install hashcat ``` **Manual install:** - SageMath — Linux: `apt install sagemath`, macOS: `brew install --cask sage` - RsaCtfTool — `git clone https://github.com/RsaCtfTool/RsaCtfTool` (automated RSA attacks) > **Note:** `gmpy2` requires libgmp — Linux: `apt install libgmp-dev`, macOS: `brew install gmp`. ## Additional Resources - [classic-ciphers.md](classic-ciphers.md) - Classic ciphers: Vigenere (+ Kasiski examination), Atbash, substitution wheels, XOR variants (+ multi-byte frequency analysis), deterministic OTP, cascade XOR, book cipher, OTP key reuse / many-time pad, variable-length homophonic substitution, grid permutation cipher keyspace reduction, image-based Caesar shift ciphers, XOR key recovery via file format headers - [modern-ciphers.md](modern-ciphers.md) - Modern cipher attacks: AES (CFB-8, ECB leakage), CBC-MAC/OFB-MAC, padding oracle, S-box collisions, GF(2) elimination, LCG partial output recovery, affine cipher over composite modulus, AES-GCM with derived keys, AES-GCM nonce reuse (forbidden attack), Ascon-like reduced-round differential cryptanalysis, custom linear MAC forge...