> On Jan 9, 2020, at 12:02 PM, Kurt Roeckx <kurt@xxxxxxxxx> wrote: > > > If the kernel provides a good RNG, the only reason I can see why > you would like to have direct access to a hwrng is to verify that > it's working correctly. That might mean that you put it in some > special mode where it returns raw unprocessed values. If the device > is in such a mode, it's output will not provide the same entropy > per bit, and so I would expect the kernel to stop using it directly. I disagree. If I buy a ChaosKey or a fancy EAL4FIPSOMG key, I presumably have it for a reason and I want to actually use the thing for real. Maybe it’s for some certification reason and maybe it’s just because it’s really cool. As for “direct” access, I think AMD provides an interface to read raw output from the on-die entropy source. Exposing this to user space is potentially quite useful for anyone who wants to try to characterize it. I don’t really think people should use a raw sample interface as a source of production random numbers, though.
