ConceptProof of work (PoW) is a form of cryptographic zero-knowledge proof in which one party (the prover) proves to others (the verifiers) that a certain amount of computational effort has been expended for some purpose.There are two classes of proof-of-work protocolsChallenge“responseSolution“verificationIn Proof of Work, other nodes verify the validity of the block by checking that the hash of the data of the block is less than a preset number.Additional InformationProof of WorkThe concept was invented by Cynthia Dwork and Moni Naor in 1993 as a way to deter denial-of-service attacks and other service abuses such as spam on a network by requiring some work from a service requester, usually meaning processing time by a computer.The term "proof of work" was first coined and formalized in a 1999 paper by Markus Jakobsson and Ari JuelsProof of work was later popularized by Bitcoin as a foundation for consensus in permissionless blockchains and cryptocurrencies, in which miners compete to append blocks and mint new currency, each miner experiencing a success probability proportional to the amount of computational effort they have provably expended.