Nonce
Nonce means 'for the present time' or 'for a single occasion or purpose', although the word is not often found in general use. A dictionary may note nonce words, those for which there is only a single textual instance.
In security engineering, a nonce is a 'number used once'. It is often a random or pseudo-random number issued in an authentication protocol to ensure that old communications cannot be reused in 'repeat attacks'.
Nonce is used in HTTP Digest Authentication to calculate MD5 Digest of the password. The Nonce is different each time the 401 authentication challenge is presented, thus making the replay attack virtually impossible.
In the UK, the term nonce is a slang word used to refer to a paedophile.
