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.
git clone --depth 1 https://github.com/briiirussell/cybersecurity-skillsWrote 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.
[](https://agentmods.dev/rules/briiirussell/cybersecurity-skills/crypto-audit)<a href="https://agentmods.dev/rules/briiirussell/cybersecurity-skills/crypto-audit"><img src="https://agentmods.dev/badge/rules/briiirussell/cybersecurity-skills/crypto-audit/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/rules/briiirussell/cybersecurity-skills/crypto-audit"><img src="https://agentmods.dev/badge/rules/briiirussell/cybersecurity-skills/crypto-audit.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00135 | $0.02888 |
| Opus 5.5 | $0.00054 | $0.01155 |
| Sonnet 5.5 | $0.00027 | $0.00578 |
| Haiku 4.5 | $0.00014 | $0.00289 |
Grade A, and why
crypto-audit scanned grade A with 1 finding 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 today.
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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
- For TLS changes: verify with `testssl.sh` and `curl --tlsv1.3 --tls-max 1.3 https://target` (lower-bound TLS version enforcement) How it starts
The opening of the file, as written. The whole thing — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Crypto Audit — Cryptography Implementation Review
Audit how cryptography is implemented in an application — algorithm choices, parameters, modes, and the implementation patterns that turn good primitives into broken systems. Deeper than owasp-audit A04 Cryptographic Failures (which catches the obvious "MD5 password" and "VERIFY_NONE" cases). This skill is for the subtler implementation review.
Most crypto failures are not "they used MD5." Most failures are: right primitive, wrong mode (ECB instead of GCM), right algorithm, wrong parameter (PBKDF2 with 1,000 iterations in 2026), right library, wrong call order (init the cipher after the data was loaded).
Cross-references: owasp-audit A04 (baseline) + A07 (timing-safe comparison), secrets-audit (key storage), iam-audit (KMS / HSM patterns).
Authorization
Review code, configuration and key-management setup the user owns or is authorized to audit. TLS probing (testssl.sh, openssl s_client) is a live check: run it only against endpoints the user is authorized to test; it isn't pre-approved, so it prompts every time. Never try to recover keys, crack hashes or decrypt data you weren't given access to.
Don't roll your own
The default audit verdict for any custom encryption scheme is "use libsodium / Tink / WebCrypto instead." There are < 50 people on Earth who can design new crypto safely, and they don't work at your company. Unless an explicit threat model says otherwise, custom crypto is a finding.
Audit Checklist
Algorithm and mode
- Symmetric: AES-256-GCM or ChaCha20-Poly1305 (authenticated encryption — confidentiality + integrity in one primitive)
- Reject: AES-ECB (block-pattern leak — identical plaintext → identical ciphertext), AES-CBC without HMAC (unauthenticated; padding oracle attacks), AES-CTR without HMAC (malleable; bit-flip = plaintext-flip), DES / 3DES, RC4, Blowfish (use Twofish or skip altogether)
- Asymmetric: Ed25519 / X25519 for signatures and key exchange; RSA-OAEP / RSA-PSS at 3072+ bits if compatibility forces RSA; never RSA with PKCS#1 v1.5 padding for encryption (Bleichenbacher); never raw RSA
- Hashing (general purpose): SHA-256, SHA-3, BLAKE2 / BLAKE3
- Hashing (passwords) — categorically different problem: Argon2id, scrypt, bcrypt (with cost ≥ 12 for bcrypt; OWASP 2024 floor)
- MAC: HMAC-SHA256 minimum; never CBC-MAC; never homemade
hash(key + message) - Grep for:
MD5,SHA1(outside of HMAC-SHA1 in legacy compat),DES,RC4,Blowfish,AES.*ECB,pkcs1_v1_5(Python),RSA.encryptwithout OAEP
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.
- today Changed · +4 lines a3ae35d91b68
- 1mo ago First seen · 157 lines · 135 tokens per session scan A 6d122b12daf5
crypto-audit is a cursor rule published in the GitHub repository briiirussell/cybersecurity-skills (435 stars, last pushed today), licensed MIT. It adds 135 tokens to every session and 2,888 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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