You need to prep your surface. Sand it so smooth you want to rub your face all over it, and that's how you get a finish that goes down proper and gleams like a mirror to blind everyone who comes upon it after.
Madness string 105929
Cryptographically secure hashes are Hard to get right, and harder to evaluate with any amount of certainty. History is littered with the dessicated failed corpses of roll-your-own crypto.