What you describe is just one particular (although by far the most common) Proof-of-Work algorithm called HashCash. There are several others, such as Cuckoo Cyc

What you describe is just one particular (although by far the most common) Proof-of-Work algorithm called HashCash. There are several others, such as Cuckoo Cycle, in which one must find a fixed length cycle in a huge random graph, an obvious mathematical (graph theory) problem [1]. [1] https://cryptorials.io/beyond-hashcash-proof-work-theres-mining-hashing/ https://cryptorials.io/beyond-hashcash-proof-work-theres-min...