Which value is specialized to be unique per encryption session and helps prevent replay and pattern analysis?

• A. Nonces
• B. Pass-the-Hash
• C. Initialization Vector (IV)
• D. Replay Attack

Answer: (C)

Initialization Vector is designed to be unique for each encryption session. In common block cipher modes, the IV is combined with the first plaintext block so that the same message encrypted with the same key yields different ciphertext on different occasions. This randomness prevents observers from noticing repeated patterns and makes replaying previously captured ciphertext ineffective, because the same plaintext will no longer map to the same ciphertext unless the IV repeats. The IV doesn’t have to be secret, but it should be unpredictable and unique per session to maintain security; reusing it with the same key undermines the protection. Nonces are values used once to guarantee freshness, but the mechanism described here specifically relies on the IV to break determinism in encryption. Pass-the-Hash is a credential theft technique, and a replay attack is the type of attack, not a value used in encryption.