Nonce

A nonce is an arbitrary number usable just once in a cryptographic communication and is commonly used in blockchains. One such use is in Proof of Work systems for varying the input of cryptographic hash functions; in certain Proof of Work systems, miners compete to find a nonce that produces a hash with a sufficient level of difficulty. Nonces can also be used as a value to keep track of the number of transactions sent by an account, ordering the execution of a set of transactions and preventing replay attacks.