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Date:      Sun, 23 Sep 2012 17:17:06 +0200
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        Mariusz Gromada <mariusz.gromada@gmail.com>
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:  <20120923151706.GN1454@garage.freebsd.pl>
In-Reply-To: <505E59DC.7090505@gmail.com>
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> <505E59DC.7090505@gmail.com>

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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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