Cryptographic nonce

Many nonces also include a timestamp to ensure exact timeliness, though this requires clock synchronisation between organisations.

The addition of a client nonce ("cnonce") helps to improve the security in some ways as implemented in digest access authentication.

The nonces are different each time the 401 authentication challenge response code is presented, thus making replay attacks virtually impossible.

In doing so, it becomes far more difficult to create a "desirable" hash than to verify it, shifting the burden of work onto one side of a transaction or system.

Similarly, the Bitcoin blockchain hashing algorithm can be tuned to an arbitrary difficulty by changing the required minimum/maximum value of the hash so that the number of bitcoins awarded for new blocks does not increase linearly with increased network computation power as new users join.