mining BTC

Mining is a record-keeping service.[note 6] Miners keep the blockchain consistent, complete, and unalterable by repeatedly verifying and collecting newly broadcast transactions into a new group of transactions called a block.[44] Each block contains a cryptographic hash of the previous block,[44] using the SHA-256 hashing algorithm,[7]:ch. 7 which links it to the previous block[44] thus giving the blockchain its name.

In order to be accepted by the rest of the network, a new block must contain a so-called proof-of-work.[44] The proof-of-work requires miners to find a number called a nonce, such that when the block content is hashed along with the nonce, the result is numerically smaller than the network's difficulty target.[7]:ch. 8 This proof is easy for any node in the network to verify, but extremely time-consuming to generate, as for a secure cryptographic hash, miners must try many different nonce values (usually the sequence of tested values is 0, 1, 2, 3, …[7]:ch. 8) before meeting the difficulty target.