Today is PoW.



Proof-of-Work — the first implementation of the blockchain network. On client side, a complex computational task is performed, and a simple verification task is performed on server side. Due to the fact that the computation time on client and on server is asymmetric, the algorithm can bring a stable solution for the blockchain network.Those with more computing power, have a greater chance of creating the next block.

Disadvantages of PoW:

The more computing power you have — the more chances there are to create a block.

Huge electricity consumption.

Some vulnerabilities that can be exploited in PoW: