Instruction file imported from alexCOsp/secretKitty (.github/instructions/crypto-security.instructions.md). Copyright stays with the author.

Cryptography & Security Rules

Library

• Use the cryptography library exclusively for all crypto operations
• NEVER roll custom crypto ??no hand-written AES, no XOR "encryption"
• Prefer high-level APIs (Fernet) unless low-level is explicitly needed

Key Derivation

• PBKDF2: minimum 600,000 iterations (OWASP 2024 recommendation)
• Argon2id: preferred if available (argon2-cffi package)
• Salt: minimum 16 bytes from os.urandom(), unique per derivation
• NEVER reuse salts across different passwords/keys

Encryption

• Use authenticated encryption only: AES-GCM or Fernet
• AES-GCM nonces: 12 bytes from os.urandom(), NEVER reuse with same key
• Fernet handles nonce/IV internally ??prefer for simplicity
• NEVER use ECB mode or unauthenticated CBC

Random Generation

• Use secrets module for tokens, passwords, IDs
• Use os.urandom() for cryptographic bytes
• NEVER use random module for anything security-related
• random is a PRNG seeded predictably ??not cryptographically secure

Sensitive Data

• Zeroize byte arrays after use: sensitive_bytes[:] = b'\x00' * len(sensitive_bytes)
• NEVER log passwords, keys, or plaintext secrets
• NEVER hardcode keys, passwords, or salts in source code
• Use getpass.getpass() for interactive password input

Storage

• Store encrypted data + salt + nonce together (but never the key)
• Use SQLite parameterized queries to prevent SQL injection
• Database file permissions: owner-only read/write

Common Mistakes to Flag

• Using hashlib alone for password storage (no salt, no iterations)
• Comparing hashes with == instead of hmac.compare_digest() (timing attack)
• Encrypting without authenticating (bit-flipping attacks)
• Storing base64-encoded data thinking it's "encrypted"

Mandatory Task Confirmation

• ALWAYS use the vscode_askQuestions tool during the task to ask the user for confirmation.
• NEVER end the task without explicit user confirmation.