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 -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
