Ctf Crypto

A comprehensive attack reference for crypto CTF challenges, covering everything from Vigenère to lattice reduction. The skill organizes techniques across a dozen markdown files, from classical ciphers and padding oracles to LWE/CVP, ECDSA nonce reuse, and exotic stuff like braid group crypto. Each attack gets a one-liner in the main file plus full code in supporting docs. Setup requires Python crypto libraries, optionally SageMath and RsaCtfTool for automated RSA attacks. The breadth is impressive, classical to post-quantum, but you'll need to know when to reach for it versus a reverse engineering skill. Best used when you've identified the crypto primitive and need the specific exploit technique.

skills.sh installs: 9.8K
GitHub stars: 3.7K
last updated: Aug 21, 2026

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Install

$ npx -y skills add ljagiello/ctf-skills --skill ctf-crypto --agent claude-code

Installs into .claude/skills of the current project.

Files

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):

pip install pycryptodome z3-solver sympy gmpy2 hashpumpy fpylll py_ecc
# Coppersmith (optional): pip install coppersmith
# Alternative Coppersmith lib: git clone https://github.com/jvdsn/crypto-attacks ~/.ctf-tools/crypto-attacks && pip install -r ~/.ctf-tools/crypto-attacks/requirements.txt

Linux (apt):

apt install hashcat

macOS (Homebrew):

brew install hashcat

Manual install:

SageMath (optional — only for legacy Sage fallback snippets (collapsed sections)) — Linux: apt install sagemath, macOS: brew install --cask sage
RsaCtfTool — git clone https://github.com/RsaCtfTool/RsaCtfTool (automated RSA attacks)
crypto-attacks (Coppersmith) — git clone https://github.com/jvdsn/crypto-attacks ~/.ctf-tools/crypto-attacks + pip install -r ~/.ctf-tools/crypto-attacks/requirements.txt (alternative to pip install coppersmith)