Crypto Core Education

What is a nonce in cryptography and blockchain?

A nonce is a number used once, a value introduced into a cryptographic process to make each operation unique and prevent reuse or replay. In blockchain it appears in two main roles: in proof-of-work mining, the nonce is the number miners change repeatedly until a block's hash meets the target difficulty; in accounts like Ethereum, the nonce is a counter that orders each transaction and stops the same one being processed twice. For example, a miner may try billions of nonces to find a valid block hash. The shared idea is freshness: a nonce makes a result single-use.