Hash functions are supposed to be fast, though. (If you need something slow like a keystretching function, you iterate a hash function, and you pick the number of iterations based on wall clock time on a representative machine.) BLAKE2 is competitive with MD5 and way, way more secure, for instance: <a href="https:&#x2F;&#x2F;blake2.net&#x2F;" rel="nofollow">https:&#x2F;&#x2F;blake2.net&#x2F;</a>