CBC (Cipher Block Chaining) — Most common. Requires IV. Each block XORed with previous ciphertext. ECB (Electronic Codebook) — Simple but insecure. Same plaintext = same ciphertext. Avoid for sensitive data. CTR (Counter) — Stream cipher mode. Parallelizable. Good for large data. CFB (Cipher Feedback) — Self-synchronizing stream mode. OFB (Output Feedback) — Keystream independent of plaintext. GCM (Galois/Counter) — Authenticated encryption. Recommended for secure comms.
SECURITY LEVELS
128
bits — 2¹²⁸ combos
192
bits — 2¹⁹² combos
256
bits — Quantum safe
PBKDF2: Converts a password to a cryptographic key using salt + iterations. Prevents brute-force attacks. IV: Initialization Vector ensures identical plaintexts encrypt to different ciphertexts when reusing the same key. ⚠️ Never reuse the same IV with the same key!