salt n.

A tiny bit of near-random data inserted where too much regularity would be undesirable; a data frob (sense 1). For example, the Unix crypt(3) man page mentions that "the salt string is used to perturb the DES algorithm in one of 4096 different ways."

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.