Proof of Work

Proof of Work (PoW) is the original blockchain consensus mechanism introduced by Satoshi Nakamoto with Bitcoin. Miners use specialized hardware (ASIC machines) to solve complex mathematical problems — the first to solve it creates the next block and receives the reward.

PoW ensures security through massive energy expenditure — to rewrite the blockchain, someone would need to control more than 50% of the network's total computing power (51% attack).

Downside: extreme energy consumption. The Bitcoin network consumes more electricity than some countries.