A nonce is a random number or string that is used once and only once for cryptography and information security. They are typically generated with a random number generator or algorithms that generate reproducible results based on factors such as a timestamp and a key. The following are illustrative examples.
Authentication
Authentication protocols may use a nonce to prevent replay attacks. A nouce that can only be used once prevents an old message being resent to authenticate.
Cryptographic Salt
Cryptographic salt is a type of nouce that is added to a string before it is hashed to make the hash more difficult to reverse.
One-time Passwords
A nouce may be generated and then communicated to a user as a one time password. For example, a customer that calls customer support to reset their password may be given a nouce that enables them to perform the reset.
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