From owner-freebsd-fs@FreeBSD.ORG Fri Jul 15 10:14:29 2005 Return-Path: X-Original-To: freebsd-fs@freebsd.org Delivered-To: freebsd-fs@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2E30016A41C; Fri, 15 Jul 2005 10:14:29 +0000 (GMT) (envelope-from kreil@ebi.ac.uk) Received: from maui.ebi.ac.uk (maui.ebi.ac.uk [193.62.196.100]) by mx1.FreeBSD.org (Postfix) with ESMTP id D0CD343D67; Fri, 15 Jul 2005 10:14:20 +0000 (GMT) (envelope-from kreil@ebi.ac.uk) Received: from parrot.ebi.ac.uk (parrot.ebi.ac.uk [193.62.196.69]) by maui.ebi.ac.uk (8.11.7+Sun/8.11.7) with ESMTP id j6FAEDQ21657; Fri, 15 Jul 2005 11:14:13 +0100 (BST) Received: from parrot.ebi.ac.uk (kreil@localhost) by parrot.ebi.ac.uk (8.11.6/8.11.6) with ESMTP id j6FAEDt02003; Fri, 15 Jul 2005 11:14:13 +0100 Message-Id: <200507151014.j6FAEDt02003@parrot.ebi.ac.uk> X-Mailer: exmh version 2.4 06/23/2000 with nmh-1.0.4 To: "Poul-Henning Kamp" In-Reply-To: Your message of "Fri, 15 Jul 2005 11:24:18 +0200." <9297.1121419458@phk.freebsd.dk> X-Habeas-SWE-1: winter into spring X-Habeas-SWE-2: brightly anticipated X-Habeas-SWE-3: like Habeas SWE (tm) X-Habeas-SWE-4: Copyright 2002 Habeas (tm) X-Habeas-SWE-5: Sender Warranted Email (SWE) (tm). The sender of this X-Habeas-SWE-6: email in exchange for a license for this Habeas X-Habeas-SWE-7: warrant mark warrants that this is a Habeas Compliant X-Habeas-SWE-8: Message (HCM) and not spam. Please report use of this X-Habeas-SWE-9: mark in spam to . Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Date: Fri, 15 Jul 2005 11:14:13 +0100 From: David Kreil X-EBI-Information: This email is scanned using www.mailscanner.info. X-EBI: Found to be clean X-EBI-SpamCheck: not spam, SpamAssassin (score=-8, required 5, HABEAS_SWE -8.00) Cc: freebsd-fs@freebsd.org, David Kreil , freebsd-questions@freebsd.org Subject: Re: gbde blackening feature - how can on disk keys be "destroyed" thoroughly? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Jul 2005 10:14:29 -0000 Dear Poul-Henning, Thank you for your fast and friendly reply! > In FreeBSD you need to study the cvs logs to see what happened. > = > http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/geom/bde/?hideattic=3D0> Ah, thanks! > >You have been most helpful in our discussion last year. I have now, in= = > >particular, been wondering whether you have since at all had a chance = of = > >revisiting the issue of blackening keys with multiple physical random = > >overwrite before resetting them to zero to avoid key recovery by metho= ds = > >as available from companies like www.dataclinic.co.uk. > = > I have talked with some people from various disk manufactureres who > know what they talk about and their unanimous advice is: "forget it". > The geometry of modern disk R/W heads does not allow you to do anything= > which will be really efficient. This, however, would not matter due to the beauty of the gbde design! The= = areas that one would need to "wipe" are very small. All we need to thorou= ghly = destroy are the keys, then the rest can safely stay in place. So, even if one doesn't know how to disable device caching, if a typical = disk = cash is 8MB, I suppose one could flush it through by writing 20MB. so, if= one = has |key|20MB bla| on disk and one wrote |random|20MB bla| that should ge= the = "random" bits overwriting the key on disk (but for hardware level sector = remapping but that is a rare event). One would have to bypass the operati= ng = system cache though but I guess you would know how to do that, right? This should take less than 1s on a modern disk, i.e., less than half a mi= nute = for the entire procedure, x4 =3D 1-2 minutes, which should be fast enough= for a = final destruction. Would it be a lot of work for someone knowledgable to implement that? I'd= be = happy to help but my knowledge of FreeBSD internals is sketchy to say the= = least. What do you think? I much look forward to hearing from you. With best regards, David. -------------------------------------------------------------------------= -- Dr David Philip Kreil = Research Fellow, Darwin College, | WWTF Vienna Science Chair of University of Cambridge | Bioinformatics, Dept of Biotechnology, ++44 1223 764107, fax 7092 810040 | c/o IAM / BOKU, A-1190 Muthgasse 18 www.inference.phy.cam.ac.uk/dpk20 | ++43 1 360066830