> Though it's hard to imagine anything with 4kib of state being very fast! is it just a precomputed power table or something where the whole thing isn't even ac

> Though it's hard to imagine anything with 4kib of state being very fast! is it just a precomputed power table or something where the whole thing isn't even accessed for short inputs? Correct, it's a pregenerated table of random bits that, in essence, gets multiplied with the input. If the input is small, only a small portion gets accessed. > That mix at the end is just an addition with a secret constant, right? I'd expect then the least significant bits to not be improved much by it. No, the mix at the end is as follows: x ^= x >> 32; x *= 0xe9846af9b1a615dULL; x ^= x >> 32; x *= 0xe9846af9b1a615dULL; x ^= x >> 28; x += secret; The addition of secret at the end ensures that the permutation is not trivially invertible by an adversary. The rest is a Murmur-style permutation, which PolymurHash gets part of its name from.