why hash the output then? this is introducing a dependence in the PRNG that you seem not to need (nor want). if you're going to generate another 80 bits of ent

why hash the output then? this is introducing a dependence in the PRNG that you seem not to need (nor want). if you're going to generate another 80 bits of entropy, then simply use this as the seed for another PRNG. this, sure, i agree, will get you more entropy, because you're adding more entropy to the system from an external source (such as the advertised device).