Crypto mining

Mining is the process by which proof-of-work blockchains such as Bitcoin add new blocks. Miners bundle pending transactions into a candidate block and repeatedly run a hash function with different inputs until they find a result below a target set by the network. The first miner to find a valid block broadcasts it and earns the block reward: newly issued coins plus the fees paid by the transactions inside.

The difficulty of the puzzle adjusts automatically (every 2,016 blocks on Bitcoin) so that blocks keep arriving roughly every ten minutes no matter how much computing power joins. Today Bitcoin mining uses specialised chips called ASICs, and most miners join pools that share rewards.

Mining consumes significant electricity; that cost is what makes rewriting the chain expensive for an attacker.