The proof-of-work system/protocol, was first used in the mid-1990's for fighting spam emails. The idea never found a truly useful cause until 2009 when bitcoin was created. Bitcoin itself utilizes this protocol in its transaction blockchain and thanks to this we can witness the growth in bitcoin mining. The base idea of this lies in a challenge and proof (or response). The challenge is a transaction, which is a specific cryptographic puzzle. The proof is that a miners computer cracks the puzzle, so the transaction goes through. And that is proof of the miners' work and him providing his hardware for the validation of transactions. The more hash power a miner can provide for validating transactions, the bigger his cryptocurrency coin reward for the service is. The problem with PoW is that mining has become so large that miners are investing into giant A.S.I.C. hardware which is highly energy consuming. Many mining farms are built around the globe as bitcoin has risen in value.
143 coins using PoW
