Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752399AbXLHRqq (ORCPT ); Sat, 8 Dec 2007 12:46:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750843AbXLHRqi (ORCPT ); Sat, 8 Dec 2007 12:46:38 -0500 Received: from dallas.jonmasters.org ([72.29.103.172]:33968 "EHLO dallas.jonmasters.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750789AbXLHRqh (ORCPT ); Sat, 8 Dec 2007 12:46:37 -0500 Subject: Re: Why does reading from /dev/urandom deplete entropy so much? From: Jon Masters To: Theodore Tso Cc: Mike McGrath , Matt Mackall , Alan Cox , Ray Lee , Adrian Bunk , Marc Haber , linux-kernel@vger.kernel.org In-Reply-To: <20071208173204.GI17037@thunk.org> References: <20071204195021.GB7259@thunk.org> <20071204204036.484f11ac@the-village.bc.nu> <20071204210827.GE19691@waste.org> <4755C423.60907@redhat.com> <20071204221525.GG19691@waste.org> <4755D350.1080801@redhat.com> <20071204223345.GJ19691@waste.org> <4756B50B.3060100@redhat.com> <20071205144934.GL7259@thunk.org> <1197099477.20786.149.camel@perihelion> <20071208173204.GI17037@thunk.org> Content-Type: text/plain Organization: World Organi[sz]ation Of Broken Dreams Date: Sat, 08 Dec 2007 12:45:27 -0500 Message-Id: <1197135927.6899.13.camel@perihelion> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 (2.12.0-3.fc8) Content-Transfer-Encoding: 7bit X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 74.92.29.237 X-SA-Exim-Mail-From: jonathan@jonmasters.org X-SA-Exim-Scanned: No (on dallas.jonmasters.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1367 Lines: 29 On Sat, 2007-12-08 at 12:32 -0500, Theodore Tso wrote: > On Sat, Dec 08, 2007 at 02:37:57AM -0500, Jon Masters wrote: > > > BTW, You may be better off using "uuidgen -t" to generate the UUID in > > > the smolt RPM, since that will use 12 bits of randomness from > > > /dev/random, plus the MAC, address and timestamp. So even if there is > > > zero randomness in /dev/random, and the time is January 1, 1970, at > > > least the MAC will contribute some uniqueness to the UUID. > > > > I haven't checked how uuidgen uses the MAC, but I would suggest that > > that is not something Fedora should jump at doing - although it would > > help ensure unique UUIDs, it also contributes to the tinfoil hat > > responses that usually come up with things like smolt. > > Huh? What's the concern? All you are submitting is a list of > hardware devices in your system. That's hardly anything sensitive.... Right, but the MAC is globally unique (well, that's normally true) so it is an identifiable user characteristic, moreso than just a list of PCI device IDs sitting on a particular bus. It's silly, but there it is. Jon. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/