From owner-freebsd-questions@FreeBSD.ORG Wed Feb 18 18:09:38 2015 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 395D55BE for ; Wed, 18 Feb 2015 18:09:38 +0000 (UTC) Received: from lb2-smtp-cloud3.xs4all.net (lb2-smtp-cloud3.xs4all.net [194.109.24.26]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (Client CN "Bizanga Labs SMTP Client Certificate", Issuer "Bizanga Labs CA" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id B0CDEEB4 for ; Wed, 18 Feb 2015 18:09:37 +0000 (UTC) Received: from slackbox.erewhon.home ([83.162.243.5]) by smtp-cloud3.xs4all.net with ESMTP id tu8Q1p00407iGuj01u8R5o; Wed, 18 Feb 2015 19:08:25 +0100 Received: by slackbox.erewhon.home (Postfix, from userid 1001) id 4A43012381; Wed, 18 Feb 2015 19:08:24 +0100 (CET) Date: Wed, 18 Feb 2015 19:08:24 +0100 From: Roland Smith To: Valeri Galtsev Subject: Re: What's in my hard drive? How can I get rid of it? Message-ID: <20150218180824.GB53030@slackbox.erewhon.home> Mail-Followup-To: Valeri Galtsev , Daniel Feenberg , freebsd-questions@freebsd.org References: <54E39F83.70002@gmail.com> <51803.128.135.70.2.1424219858.squirrel@cosmo.uchicago.edu> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="9zSXsLTf0vkW971A" Content-Disposition: inline In-Reply-To: <51803.128.135.70.2.1424219858.squirrel@cosmo.uchicago.edu> X-GPG-Fingerprint: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 X-GPG-Key: http://www.xs4all.nl/~rsmith/pubkey.txt X-GPG-Notice: If this message is not signed, don't assume I sent it! User-Agent: Mutt/1.5.23 (2014-03-12) Cc: Daniel Feenberg , freebsd-questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 Feb 2015 18:09:38 -0000 --9zSXsLTf0vkW971A Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Feb 17, 2015 at 06:37:38PM -0600, Valeri Galtsev wrote: >=20 > On Tue, February 17, 2015 5:30 pm, Daniel Feenberg wrote: > > > > > > On Tue, 17 Feb 2015, Michael Powell wrote: > > > >> jd1008 wrote: > >> > >> [snip] > >> > >> Remove the cover. Remove the platters. Smash all platters with large > >> sledge > >> hammer until all pieces are fairly small. Melt material with > >> oxyacetylene > >> welders torch. Repeat smashing with hammer. Soak for few hours in > >> hydrofluoric acid. Rinse and allow to dry. Grind material into a fine > >> particulate dust. Dispose of out the back of airplane while flying or > >> drop > >> into convenient nearby volcano. That might be good enough. > >> > >> Send the electronic components to Kaspersky for analysis. > > > > I did once investigate claims that overwritten sectors could be read by > > sophisticated instruments and posted my results at: > > > > http://www.nber.org/sys-admin/overwritten-data-gutmann.html > > > > In short - that is pure science fiction. > > >=20 > Interesting. I never saw this particular explanation. I have heard that > overwiritten data can be recovered (to significant extent). =46rom =E2=80=9COverwriting Hard Drive Data: The Great Wiping Controversy= =E2=80=9D by Craig Wright, Dave Kleiman, and Shyaam Sundhar R.S; To start with; The acquisition time for 1 byte is about 4 minutes. At that speed, you can read 128 KiB in a year! Furthermore: Consequently, we can categorically state that there is a minimal (less than a 0.01% chance) of recovering any data on a NEW and unused drive t= hat has a single raw wipe pass (not even a low-level format). In the cases where a drive has been used (even being formatted for use) it is not possible to recover the information =E2=80=93 there is a small chance o= f bit recovery, but the odds of obtaining a whole word are small. Conclusion: Although there is a good chance of recovery for any individual bit from= a drive, the chances of recovery of any amount of data from a drive using= an electron microscope are negligible. You can get the paper from e.g. http://www.vidarholen.net/~vidar/overwriting_hard_drive_data.pdf A single wipe of a HDD is enough to destroy the data beyond hope of recover= y. For an SSD or other flash-based storage the picture is different. For one thing, because of the controller on those storage devices you cannot be sure that overwriting a block of data on location X actually is written to locat= ion X. Roland --=20 R.F.Smith http://rsmith.home.xs4all.nl/ [plain text _non-HTML_ PGP/GnuPG encrypted/signed email much appreciated] pgp: 5753 3324 1661 B0FE 8D93 FCED 40F6 D5DC A38A 33E0 (keyID: A38A33E0) --9zSXsLTf0vkW971A Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABAgAGBQJU5NUYAAoJEED21dyjijPg38AQAJYTTtO4mZDklzOhtD2pq8YF ty3/9fSUoFk/1NBE7dfRRHxntP475xirmN719oGT6OhuL+ea5bqI1RWJmbFUG/RC k4z0bjEqFOEbdMKmN7vl9e9HwcgXg4evzs2k1YIol6PS0YsG3xzTJYYeDcSBx2x7 TKiKhqmhRzjQFGXWogy9149PUUjFwBoYZa6ZKb70a10GhA4z47pARJgXtaW7pM98 ETM8QBtORIvUTraGZNyopvHVti9nABEAdWNqFV6H1tgyezwlG53bVJzo7L8FxoR0 ImcFRXtCav/iIMqVLeiokeuTU8/0LAoO+/c7T61s8c4/clF7qlXf7s0mkN1ynwZC AZMV6KjclMOPUw0DqlSiLo5a2IV3EWdCP+0v+TDev0t8AKW7kVxnf0TEN4MbydZv aoGmImht7cIcBBiJb6imA7hpVBVb3YQ1nl9bPBOtxAi4mh919QCLW+uQh1Nk8yx1 eKzEEnougsCB63Tw/xFc1xihmBnwbGcIg6n61mTIe9kTY/ucJIwhGVttZgDNO0Qh +y1hy9p9yHOZImJIaQtIk3LXTGFPtH4h+/6MnoaTgHndvYllr32Yg9cccdUyRlhj MSWrwa6jJ0gpW5Kxf8wP1WWr15mD4aIVtRepEU1n6XoTu5yRbvisriYKeWQGDMZj AnnDYI71guZwyItsW+rR =x5iq -----END PGP SIGNATURE----- --9zSXsLTf0vkW971A--