RE: Slight Divergence16 Mar 2021 14:21
Satoshi Nakamoto set them. The starting block of the blockchain was the headline of The Times on 3 Jan 2009, and the SHA-256 algorithm is used to create a new block.
It is very easy to perform SHA-256 once, but for a given output, it is impossible to find the input except by trying every input. There are 2^256 possible outputs, so it takes a long time to find a corresponding input.
A new block is created by the first miner to find an output within a restricted range. The range is determined by the current mining power of the whole network.