The solution to this problem I've seen from actual cryptographers is Siphash: https://131002.net/siphash/ https://131002.net/siphash/ They address all of the p

The solution to this problem I've seen from actual cryptographers is Siphash: https://131002.net/siphash/ https://131002.net/siphash/ They address all of the problems of this sort by just designing a hash function that is good enough that collisions are difficult to find, I think even with the secret key.