Proof of Work

Proof of Work: 

To discourage wasteful or harmful uses of computer resources, such as sending spam emails or launching denial of service attacks, proof of work (PoW) specifies a system that needs a not small but practical amount of effort. By 2004, Hal Finney had applied the notion to the protection of digital currency through his “reusable proof of work” scheme based on the SHA-256 hashing algorithm.