Some AMD CPU's RDRAND might not return random data after a suspend/resume

Re:Some AMD CPU's RDRAND might not return random data after ... by lvh on Tuesday May 07, 2019 @11:51AM (#19850615)

Do you mean if a PRNG is available? Because the answer is obvious if RDRAND is available: you don't do that because sometimes it fails, failure is almost always catastrophic but sublte, and CSRPNGs are not a bottleneck in almost all cases.

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Re:Some AMD CPU's RDRAND might not return random data after ... by amluto on Tuesday May 07, 2019 @12:11PM (#19850816)

RDRAND has major benefits over any CSPRNG: there is no software-visible state that could possibly leak. With attacks like Spectre, there’s always a concern that your CSPRNG secrets could be leaked.

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Re:Some AMD CPU's RDRAND might not return random data after ... by lvh on Tuesday May 07, 2019 @03:59PM (#19852913)

The scheme we’re discussing XORs the two at the end, so that flaw doesn’t apply. Also: empirically, “kernel leaks CSPRNG” state does not seem to be as much of a problem as “userspace is convinced it knows better than urandom/getrandom”.

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