Our hash randomization will always leak some information about the randomization keys. The only way to properly secure our secrets is a cryptographic secure algorithms, for example a crypto hashing function in combination with a message authentication code like HMAC. I don't have to explain how that is going to hurt performance ...

We can try to make it harder to guess the secret parts with a slightly modified algorithm like e.g. V8's hash but that's never going to be 100% secure. But might be secure enough to make an attack too hard.