[ronyfadel]

For someone uninitiated: what if you had high computing power? Instead of scanning your HDD, can’t you generate these hashes on the spot?

[insulanus]

Yes, you can. That's called a grinding attack. There is mitigation in the proof-of-space construction for exactly that. That is also the reason that they will have to move to more expensive proofs as time goes on, and hardware improves.