# Nonce 1. This is an arbitrary number that can only be used once and is often used with [[Cryptography|cryptographic]] systems in co-ordination with random number generators to improve security. They are also be used in co-ordination with [[Blockchain|blockcahin]] mining specifications to allow for variation in the [[Mining Difficulty|difficulty]] of successfully [[Mining|mining]] a [[Block(s)|block]]. 2. A number only used once in a cryptographic communication (often includes a [[Timestamp|timestamp]]). 3. The [[Nonce|nonce]] in a [[Bitcoin (blockchain)]] [[Block(s)|block]] is a 32-bit (4-byte) field whose value is set so that the [[Hash|hash]] of the block will contain a run of leading zeros. The rest of the fields may not be changed, as they have a defined meaning. 4. A single-use arbitrary number generated for verification purposes to prevent replaying past nonce[[Transaction(s)|nonce]]. ![[Bitcoin-mining-process.png]]