Date: Tue, 11 Sep 2012 14:13:39 -0700 From: David O'Brien <obrien@FreeBSD.org> To: Ian Lepore <freebsd@damnhippie.dyndns.org> Cc: Arthur Mesh <arthurmesh@gmail.com>, Dag-Erling Sm?rgrav <des@des.no>, RW <rwmaillists@googlemail.com>, Doug Barton <dougb@FreeBSD.ORG>, freebsd-rc@FreeBSD.ORG Subject: Re: svn commit: r239569 - head/etc/rc.d Message-ID: <20120911211339.GA89188@dragon.NUXI.org> In-Reply-To: <1347397285.1110.15.camel@revolution.hippie.lan> References: <20120906174247.GB13179@dragon.NUXI.org> <20120906230157.5307a21f@gumby.homeunix.com> <20120906224703.GD89120@x96.org> <50493480.8060307@FreeBSD.org> <20120911061530.GA77399@dragon.NUXI.org> <504EDC67.9070700@FreeBSD.org> <86sjao7q8c.fsf@ds4.des.no> <20120911205302.27484fd6@gumby.homeunix.com> <20120911200925.GA88456@dragon.NUXI.org> <1347397285.1110.15.camel@revolution.hippie.lan>
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On Tue, Sep 11, 2012 at 03:01:25PM -0600, Ian Lepore wrote: > On Tue, 2012-09-11 at 13:09 -0700, David O'Brien wrote: > > Good to see someone have thoughts on this. I've only seen it stated > > that entropy passes thru mostly "untouched" thru a cryptographic hash > > in the literature. ... > Whether the same might be true of a hash is an interesting question, > since it discards information rather than just changing the way it's > encoded. Ian, This is a key point of Yarrow's design. See http://www.schneier.com/paper-yarrow.ps.gz in 5 'The Generic Yarrow Design an Yarrow-160' The reason is if you take an 'm' bit random value and apply a hash function that produces 'm' bits of output, the result has less than 'm' bits of entropy due to the collisions that occur. This is a very minor effect, and overall results in the loss of at most a few bits of entropy. -- -- David (obrien@FreeBSD.org)
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