Salt (cryptography)

In cryptography, salt consists of random bits (typically 12 or more) used as one of the inputs to a key derivation function, which is often used to derive a key for use in a cryptographic algorithm.

In the case of password attacks, this additional data makes it more difficult to conduct a dictionary attack to discover a password. It is also effective against such attacks using pre encryption of dictionary entries, as each bit of salt used doubles the required computation.

In some protocols, salt is sometimes non-secret data and is often transmitted with the encrypted data along with the number of iterations used in generating the key.