看板FB_security
标 题Re: Collecting entropy from device_attach() times.
发信站NCTU CS FreeBSD Server (Mon Sep 24 01:17:06 2012)
转信站ptt!csnews.cs.nctu!news.cs.nctu!FreeBSD.cs.nctu!freebsd.org!owner-free
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On Sun, Sep 23, 2012 at 02:37:48AM +0200, Mariusz Gromada wrote:
> W dniu 2012-09-22 21:53, Pawel Jakub Dawidek pisze:
> > Mariusz, can you confirm my findings?=20
>=20
> Pawel,
>=20
> Your conclusions can be easily confirmed by shape analysis of the EDF.=20
> Usually maximum quantile difference (called D-statistic) gives you a=20
> kind of overview, function shape gives you a strong feeling, p-value=20
> gives you a formal proof.
> D-statistic values (your data):
>=20
> 6bit: 0.33%
> 7bit: 0.29%
> 8bit: 0.27%
> 9bit: 0.21%
> 10bit: 6.34%
> 11bit: 19.07%
> 12bit: 54.80%
>=20
> What I would say: increasing the number of bits from 6 to 9 does not=20
> affect distribution "uniformity", reaching the tenth bit results in=20
> sudden increase in the difference measure - the more bits, the more=20
> difference is observed. Distribution shape analysis for the 10th bit=20
> shows non-linear function. Lack of "randomness" in the quntile=20
> difference curve - chart shows completely lack of noise (pure=20
> functional relation). These are very strong indicators that starting=20
> from 10th bit distribution was changed and is no longer uniform.
>=20
> To formally confirm above conclusion for i.e. 5% significance level,=20
> which means that confidence level is 95%, I need some extra data=20
> regarding sample sizes. Please pass to me number of collected=20
> observations in each 6-12 bit experiment.
Total number of observations was 162833.
--=20
Pawel Jakub Dawidek
http://www.wheelsystems.com
FreeBSD committer
http://www.FreeBSD.org
Am I Evil? Yes, I Am!
http://tupytaj.pl
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