Messages in this thread | | | From | Stephan Mueller <> | Subject | Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and /dev/random | Date | Thu, 14 Nov 2013 19:34:04 +0100 |
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Am Donnerstag, 14. November 2013, 19:30:22 schrieb Clemens Ladisch:
Hi Clemens,
>Stephan Mueller wrote: >> Am Donnerstag, 14. November 2013, 11:51:03 schrieb Clemens Ladisch: >>> An attacker would not try to detect patterns; he would apply >>> knowledge >>> of the internals. >> >> I do not buy that argument, because if an attacker can detect or >> deduce the internals of the CPU, he surely can detect the state of >> the input_pool or the other entropy pools behind /dev/random. > >With "internals", I do not mean the actual state of the CPU, but the >behaviour of all the CPU's execution engines. > >An Intel engineer might know how to affect the CPU so that the CPU >jitter code measures a deterministic pattern, but he will not know the >contents of my memory.
Here I agree fully. > >>> Statistical tests are useful only for detecting the absence of >>> entropy, not for the opposite. >> >> Again, I fully agree. But it is equally important to understand that >> entropy is relative. > >In cryptography, we care about absolute entropy, i.e., _nobody_ must be >able to predict the RNG output, not even any CPU engineer.
With your clarification above, I agree here fully.
And now my task is to verify the root cause which I seem to have found.
Let me do my homework.
Ciao Stephan
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