Detecting Weak Cryptography

What it does

When your agent uses it

• : pre-merge gate on crypto-touching code
• Audit before SOC2 / PCI assessment
• Post-incident review when we found a weakness in our token signing. Threshold: any call to a known-weak algorithm with non-test context
• Cert verification explicitly disabled

Example prompts

• “we found a weakness in our token signing.”
• “scan weak crypto”
• “find MD5 usage”
• “/detecting-weak-cryptography”

Requirements

• Python 3
• Compatibility (from SKILL.md): Designed for Claude Code
• Pre-approved tools (allowed-tools): Read, Bash(python3:*), Glob, Grep

What it can do on your machine

Read from SKILL.md and the folder at commit cfae287. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Bash(python3:*)
  • Glob
  • Grep

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 1 file in scripts/ (Python), which the agent can run.

  Shell commands in SKILL.md call:

  • python3
  • git

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md. Its commands use git, which can reach the network depending on how they are called.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

• Compatibility

  Designed for Claude Code

  From compatibility in the SKILL.md frontmatter.

Context cost

Detecting Weak Cryptography loads about 1.3k tokens when it runs, and up to ~5.8k if it reads all its reference files. Until then it costs about 195 tokens; SKILL.md has 400 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~195

When it runs · the whole SKILL.md, loaded when a task matches

~1.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~5.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit cfae287, republished under its MIT licence (© jeremylongshore). 400 words, ~1,314 tokens.

name

detecting-weak-cryptography

description

Scan a source tree for weak cryptographic primitives: MD5 / SHA-1 used for security purposes, DES / 3DES / RC4 ciphers, ECB block mode, custom-built crypto (XOR loops, hand-rolled HMAC), hardcoded IVs, predictable random (Math.random / java.util.Random for crypto seeds), missing certificate verification (verify=False, rejectUnauthorized: false). Use when: pre-merge gate on crypto-touching code, audit before SOC2 / PCI assessment, post-incident review when "we found a weakness in our token signing." Threshold: any call to a known-weak algorithm with non-test context, OR cert verification explicitly disabled, OR a custom crypto loop pattern. Trigger with: "scan weak crypto", "find MD5 usage", "check ECB mode", "audit ssl verify", "weak random".

allowed-tools

Read, Bash(python3:*), Glob, Grep

compatibility

Designed for Claude Code

disallowed-tools

Bash(rm:*), Bash(curl:*)

version

3.30.0

author

Jeremy Longshore <jeremy@intentsolutions.io>

license

MIT

tags

security, static-analysis, cryptography, pentest

python3 ${CLAUDE_PLUGIN_ROOT}/skills/detecting-weak-cryptography/scripts/scan_weak_crypto.py /path/to/repo

python3 ${CLAUDE_PLUGIN_ROOT}/skills/detecting-weak-cryptography/scripts/scan_weak_crypto.py \
    --min-severity high $(git diff --name-only main...HEAD | tr '\n' ' ')

- name: Weak-crypto scan
  run: |
    python3 plugins/security/penetration-tester/skills/detecting-weak-cryptography/scripts/scan_weak_crypto.py \
        . --min-severity high

© jeremylongshore, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 3 other files (scripts, references) in skills/.curated/detecting-weak-cryptography of jeremylongshore/tons-of-skills-marketplace.

• SKILL.md
• references/PLAYBOOK.md
• references/THEORY.md
• scripts/scan_weak_crypto.py

Open the folder on GitHubat commit cfae287