bshepp/

round-reduced-sha256-learnability

	Round-Reduced SHA-256 Learnability: A Controls-Gated Negative Result




	
	TL;DR

A small CNN learns to distinguish round-reduced SHA-256 outputs from random with ~100% accuracy through 3 rounds, then collapses to chance at round 4 and stays there through the full 64 rounds — a sharp learnability cliff, replicated across 5 seeds and 2 dataset sizes. Full SHA-256 is statistically indistinguishable from random to these probes at this budget (a bounded null, not a proof). An… See the full description on the dataset page: https://huggingface.co/datasets/bshepp/round-reduced-sha256-learnability.