What Is Proof of Work (PoW)?

Proof of work (PoW) describes a system that requires a not-insignificant but feasible amount of effort in order to deter frivolous or malicious uses of computing power, such as sending spam emails or launching denial of service attacks. The concept was subsequently adapted to securing digital money by Hal Finney in 2004 through the idea of "reusable proof of work" using the SHA-256 hashing algorithm