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initialisation vector (IV)
An initialisation vector is a per-message random or unique value that makes encryption of the same data look different each time.
Encrypting identical plaintext with the same key would otherwise produce identical ciphertext, leaking information. An IV — a nonce paired with the key for each record — perturbs the process so outputs differ and patterns are hidden. It generally need not be secret, but for many schemes it must be unique (and sometimes unpredictable) per encryption, or the security guarantees break.
See also
- handshakeA handshake is the opening negotiation of a secure connection where both sides agree on keys before any data flows.
- HKDFHKDF is a standard method for turning one shared secret into several strong, purpose-specific keys.
- HMACHMAC is a way to attach a secret-keyed tag to a message so the receiver can verify it was not altered or forged.