Most block cipher modes require a unique binary sequence, often called an initialization vector (IV), for each encryption operation.
same as salt ?
An initialization vector (IV) is a data block that some modes of operation require as an additional initial input.
The initialization vector is used to ensure distinct ciphertexts are produced even when the same plaintext is encrypted multiple times independently with the same key
An initialization vector (IV) or starting variable (SV) is a block of bits that is used by several modes to randomize the encryption and hence to produce distinct ciphertexts even if the same plaintext is encrypted multiple times, without the need for a slower re-keying process.
- the IV does not need to be secret.
- for the OFB mode, unique IVs must be used for each execution of the encryption process.