The idea of the proof of work algorithm, which is the first consensus mechanism, was introduced in 1993 to tackle spam emails. However, it had not been used effectively until Satoshi Nakamoto introduced it as the consensus mechanism for Bitcoin in 2009. Proof of work algorithms works by having all the nodes solve a cryptographic puzzle, the first one to find a solution gets the rewards. Proof of work gives more rewards to people with better and more equipment, to increase their chances, miners come together to form a mining pool and distribute rewards evenly. As a result, mining becomes centralised and uses huge amounts of electricity. This has come under heavy criticism for being bad for the environment.