Proof of Work

The most famous way is Proof of Work (PoW), which is used by Bitcoin. The PoW requires the nodes to compete to be a first candidate to get the hash value with a certain amount of 0.

In this competition, each users are attempting in millions of trials for generating the hash value with a certain amount of 0 by changing the random string (Nonce) or the combination.

The more computing power you have, the highest chance you can become the next leader on writing the transaction in the chain. The weak lose and the strong win.

During the process, each user has to consume the computing power to generate the hash value, leading to high level of waste.