Iv

What's an IV, and why does it matter?

An IV (Initialization Vector), often called a nonce, is per-operation input to an encryption scheme. Its requirements depend on that scheme: it may need to be random, unique, or both. It normally travels alongside the ciphertext in the clear because it is not secret. With the usual randomized or nonce-based schemes, encrypting the same value twice produces different ciphertext, so you cannot search by re-encrypting a term and comparing ciphertext. See What Is ALE, and Why Do We Still Need It? and Structured Ciphertext.