Date: Sun, 23 Sep 2012 02:37:48 +0200 From: Mariusz Gromada <mariusz.gromada@gmail.com> To: Pawel Jakub Dawidek <pjd@FreeBSD.org> Cc: Ben Laurie <benl@freebsd.org>, freebsd-security@freebsd.org, RW <rwmaillists@googlemail.com>, Jonathan Anderson <jonathan.anderson@cl.cam.ac.uk>, John Baldwin <jhb@freebsd.org> Subject: Re: Collecting entropy from device_attach() times. Message-ID: <505E59DC.7090505@gmail.com> In-Reply-To: <20120922195325.GH1454@garage.freebsd.pl> References: <20120918211422.GA1400@garage.freebsd.pl> <20120919231051.4bc5335b@gumby.homeunix.com> <20120920102104.GA1397@garage.freebsd.pl> <201209200758.51924.jhb@freebsd.org> <20120922080323.GA1454@garage.freebsd.pl> <20120922195325.GH1454@garage.freebsd.pl>
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W dniu 2012-09-22 21:53, Pawel Jakub Dawidek pisze: > Mariusz, can you confirm my findings? Pawel, Your conclusions can be easily confirmed by shape analysis of the EDF. Usually maximum quantile difference (called D-statistic) gives you a kind of overview, function shape gives you a strong feeling, p-value gives you a formal proof. D-statistic values (your data): 6bit: 0.33% 7bit: 0.29% 8bit: 0.27% 9bit: 0.21% 10bit: 6.34% 11bit: 19.07% 12bit: 54.80% What I would say: increasing the number of bits from 6 to 9 does not affect distribution "uniformity", reaching the tenth bit results in sudden increase in the difference measure - the more bits, the more difference is observed. Distribution shape analysis for the 10th bit shows non-linear function. Lack of "randomness" in the quntile difference curve - chart shows completely lack of noise (pure functional relation). These are very strong indicators that starting from 10th bit distribution was changed and is no longer uniform. To formally confirm above conclusion for i.e. 5% significance level, which means that confidence level is 95%, I need some extra data regarding sample sizes. Please pass to me number of collected observations in each 6-12 bit experiment. Regards, Mariusz
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