ctf-crypto

ctf-crypto is a skill for Claude Code, Codex from Unclecheng-li/DeepSec. It costs 67 tokens per session (752 once invoked), scanned A, a copy of ctf-crypto, MIT.

A reference library for attacking cryptography challenges in CTFs, or capture-the-flag security competitions. It covers attack patterns for RSA, AES, elliptic-curve cryptography, random-number generators, classic ciphers, and lattice-based systems.

In plain words
What is it for?
Solving challenges involving small-exponent or shared-modulus RSA, padding oracles, AES mode mistakes, elliptic-curve weaknesses, predictable random generators, classical ciphers, and lattice attacks.
Why use it?
It helps identify the likely weakness in a challenge and provides the relevant formulas, parameters, and code patterns to investigate it.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/unclecheng-li/deepsec/ctf-crypto
Any agent
npx skills add Unclecheng-li/DeepSec --skill ctf-crypto
Clone the repo
git clone --depth 1 https://github.com/Unclecheng-li/DeepSec

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for ctf-crypto

README.md
[![agentmods](https://agentmods.dev/badge/skills/unclecheng-li/deepsec/ctf-crypto.svg)](https://agentmods.dev/skills/unclecheng-li/deepsec/ctf-crypto)
Your own site
<a href="https://agentmods.dev/skills/unclecheng-li/deepsec/ctf-crypto"><img src="https://agentmods.dev/badge/skills/unclecheng-li/deepsec/ctf-crypto.svg" alt="Measured on agentmods" height="20"></a>
Per session 67 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 752 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00067 $0.00752
Opus 5 $0.00034 $0.00376
Sonnet 5 $0.00013 $0.00150
Haiku 4.5 $0.00007 $0.00075

Measured 5d ago against content hash 0f642e55d735, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

ctf-crypto scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to ctf-crypto — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

deepsec/spear/skills/specialized/ctf-crypto/SKILL.md · 48 lines

What it actually says

CTF 密码学攻击知识库

针对 CTF Crypto 题目的实战攻击知识库,提供具体攻击参数、数学公式、Python 代码片段

crypto-toolkit 的区别

  • crypto-toolkit → 编解码操作工具(base64 解码、MD5 哈希、AES 加解密)
  • ctf-crypto → 密码学攻击知识(RSA 小指数攻击怎么做、Padding Oracle 怎么利用)

核心原则

  1. 先识别加密体系 — 看密钥长度、加密模式、已知量,确定攻击方向
  2. 工具验证 — 使用 python_execute 执行攻击代码,用 crypto_decode 做辅助编解码
  3. 参数敏感 — 密码学攻击对参数极其敏感,必须精确计算

场景路由

场景 参考文档 核心攻击
RSA 攻击 rsa-attacks-cheatsheet.md 小e/共模/Wiener/Pollard/Fermat/Coppersmith
AES/分组密码攻击 aes-and-block-cipher-attacks.md ECB翻转/Padding Oracle/GCM nonce重用
ECC 攻击 ecc-attacks-cheatsheet.md 小子群/invalid curve/Smart/Pohlig-Hellman
PRNG/流密码攻击 prng-and-stream-cipher-attacks.md MT19937/LCG/LFSR/RC4
古典密码 classic-cipher-attacks.md Vigenere/XOR频率分析/OTP重用
格攻击 lattice-and-lwe-attacks.md LLL/BKZ/HNP/LWE embedding

快速判题指南

题目特征 可能攻击 推荐参考
给了 n, e, c RSA rsa-attacks-cheatsheet.md
e=3 或 e 很小 RSA 小指数攻击 rsa-attacks-cheatsheet.md
多组 (n, e, c) 且 n 相同 RSA 共模攻击 rsa-attacks-cheatsheet.md
n 很大但 e 很大 Wiener 攻击 rsa-attacks-cheatsheet.md
AES-CBC + 解密 oracle Padding Oracle aes-and-block-cipher-attacks.md
AES-ECB + 可控明文 ECB 字节翻转 aes-and-block-cipher-attacks.md
椭圆曲线参数 ECC 攻击 ecc-attacks-cheatsheet.md
给了随机数序列 PRNG 预测 prng-and-stream-cipher-attacks.md
给了密文和部分明文 XOR/流密码 classic-cipher-attacks.md
矩阵/向量运算 格攻击 lattice-and-lwe-attacks.md
Files

What ships with it

6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 48 lines · 67 tokens per session scan A 0f642e55d735

Subscribe to this mod's changes

ctf-crypto is a skill published in the GitHub repository Unclecheng-li/DeepSec (386 stars, last pushed 11d ago), licensed MIT. It adds 67 tokens to every session and 752 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to ctf-crypto, differing in 0 lines, and is treated as a copy.