I'm trying to apply the hash function combination method described in https://eprint.iacr.org/2013/210.pdf to a HKDF PRNG construction. Thing is it needs 4 uniformly random parameters/keys chosen by the signer during the combination step, but that's what I was already using the PRNG for so it feels like I'm running into some chicken-egg problem.
What would be the recommended way to generate these keys? Is it at all possible to strengthen PRNGs with this trick?