A nonce is a one-time-only use number that is required for some cryptographic procedures. The term is an acronym for "number only used once." Nonces are used in the Proof of Work (PoW) consensus method on blockchains. A nonce is entered into a hash function, including any new transaction data and the preceding block's hash, to construct a block on a blockchain. A new hash code, known as a "header hash," is generated. As miners, nodes use computational power to identify a nonce that generates a hash that is numerically less than or equal to a target hash. A "golden nonce" is a number that generates a hash result with a sufficiently low value to allow the block to be mined and added to the network, Cryptographic hash problems are hard to solve because identical inputs produce the same hash. Because of the avalanche effect in hashing, even little changes to input data can result in drastically different hash outputs. Miners on a blockchain must discover the nonce value in order to demonstrate that they have expended sufficient power to validate the block. Blockchain miners are rewarded with local cryptocurrency.
