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Date: Tue, 22 Jul 2008 14:48:26 +0400
From: Andrey Chernov <ache@nagual.pp.ru>
To: Poul-Henning Kamp <phk@phk.freebsd.dk>
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Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/lib/libc/gen arc4random.c
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On Tue, Jul 22, 2008 at 10:34:51AM +0000, Poul-Henning Kamp wrote:
> In message <200807221031.m6MAVe9I012301@repoman.freebsd.org>, "Andrey A. =
Cherno
> v" writes:
>=20
> >  Increase initially dropped bytes from 512 to 768 (768 is also
> >  suggested in the Ilya Mironov's article). 768 taken from another
> >  research where it treats as default for RC4-drop(768):
> >  http://www.users.zetnet.co.uk/hopwood/crypto/scan/cs.html#RC4-drop
>=20
> I've always wondered why the dropped number of bytes is constant,
> wouldn't it be smarter to drop a constant number, and then pull
> out the next byte and drop that many further bytes ?

=46rom math point of view, small pseudo-random dropping fraction added will=
=20
not increase distribution significantly. With good seeding from the kernel=
=20
PRNG even 256 bytes is enough (as OpenBSD currently does). It is just for=
=20
formal RC4-drop(768) implementation as it described and for rare corner=20
cases when /dev/urandom is unavailable.

--=20
http://ache.pp.ru/