annatchijova·annatchijova/SKILLS/crypto-misuse-reasoning/SKILL.md

crypto-misuse-reasoning

Skill9 starsChanged 4 months agoLicence not identifiedView on GitHub

Judge a cryptographic system by how it is used, not by which primitive it names — because "we use AES-256" says nothing, and almost every real-world break is a misuse (reused nonce, ECB, unauthenticated ciphertext, a padding oracle, a homemade KDF, an accepted downgrade) sitting on top of a perfectly good algorithm. Use whenever crypto is being designed, reviewed, or trusted: "is this encryption secure", "we roll our own", "AES/RSA/we're fine", "how should I encrypt this", "sign then encrypt or encrypt then sign", "why is a nonce/IV a problem", "is ECB ok here", "verify this token/JWT", "compare passwords", "our TLS config". Sibling of secure-by-construction (build it hostile-first) and validate-at-the-boundary (a decrypted blob is still untrusted input); it reasons about misuse, not primitive selection. It does not implement primitives, does not hand out attack recipes, and never certifies a scheme secure from the algorithm name alone.