(
Number
ONCE) An arbitrary number that is generated to provide a unique identification or for security purposes such as when logging in to a network (see
initialization vector). A nonce is also used in cryptography (see
cryptographic hash function). Pronounced like the "nons" in "
nonsense," nonce is actually an English word that means "for the present occasion or time."
The nonce is used one time and not repeated. Although random and pseudo-random numbers theoretically produce unique numbers, there is the possibility that the same number can be generated more than once. However, if a very large, true random number is used, the chances are extremely small. A perfect nonce is the time of day; for example, 12.53 seconds past 5:13pm on 1/1/2020 can only occur once.