Nonces are random or pseudo-random numbers that authentication protocols attach to communications. Sometimes these numbers include a timestamp to intensity the fleeting nature of these communications.
If subsequent requests to a server, for example during digest access authentication via username and password, contain the wrong nonce and/or timestamp, they are rejected.
When used in this way, nonces prevent replay attacks that rely on impersonating prior communications in order to gain access.
Cryptographic nonces are used in proof-of-work systems
Proof of work (PoW) is a decentralized consensus mechanism that requires members of a network to expend effort solving an arbitrary mathematical puzzle to prevent anybody from gaming the system.Learn more to vary the input to a cryptographic hash function
A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size to a bit array of a fixed size (the "hash).Learn more so as to obtain a hash for a certain input that fulfils certain arbitrary conditions.
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 BitcoinBitcoin1$67,714.930.18%-6.01%-15.89%details 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.
