From owner-freebsd-rc@FreeBSD.ORG Tue Sep 11 21:13:41 2012 Return-Path: Delivered-To: freebsd-rc@FreeBSD.ORG Received: by hub.freebsd.org (Postfix, from userid 664) id 00F031065670; Tue, 11 Sep 2012 21:13:40 +0000 (UTC) Date: Tue, 11 Sep 2012 14:13:39 -0700 From: David O'Brien To: Ian Lepore Message-ID: <20120911211339.GA89188@dragon.NUXI.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1347397285.1110.15.camel@revolution.hippie.lan> X-Operating-System: FreeBSD 10.0-CURRENT X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.5.20 (2009-06-14) Cc: Arthur Mesh , Dag-Erling Sm?rgrav , RW , Doug Barton , freebsd-rc@FreeBSD.ORG Subject: Re: svn commit: r239569 - head/etc/rc.d X-BeenThere: freebsd-rc@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: obrien@freebsd.org List-Id: "Discussion related to /etc/rc.d design and implementation." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 11 Sep 2012 21:13:41 -0000 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)