From owner-freebsd-questions@FreeBSD.ORG Wed Feb 18 18:54:48 2015 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id A8248ABF for ; Wed, 18 Feb 2015 18:54:48 +0000 (UTC) Received: from cosmo.uchicago.edu (cosmo.uchicago.edu [128.135.52.97]) by mx1.freebsd.org (Postfix) with ESMTP id 645A06DA for ; Wed, 18 Feb 2015 18:54:48 +0000 (UTC) Received: by cosmo.uchicago.edu (Postfix, from userid 48) id 1FC6DCB8C9C; Wed, 18 Feb 2015 12:54:47 -0600 (CST) Received: from 128.135.70.2 (SquirrelMail authenticated user valeri) by cosmo.uchicago.edu with HTTP; Wed, 18 Feb 2015 12:54:47 -0600 (CST) Message-ID: <52304.128.135.70.2.1424285687.squirrel@cosmo.uchicago.edu> Date: Wed, 18 Feb 2015 12:54:47 -0600 (CST) Subject: Re: What's in my hard drive? How can I get rid of it? From: "Valeri Galtsev" To: "Daniel Feenberg" , freebsd-questions@freebsd.org Reply-To: galtsev@kicp.uchicago.edu User-Agent: SquirrelMail/1.4.8-5.el5.centos.7 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal References: <54E39F83.70002@gmail.com> <51803.128.135.70.2.1424219858.squirrel@cosmo.uchicago.edu> <20150218180824.GB53030@slackbox.erewhon.home> In-Reply-To: <20150218180824.GB53030@slackbox.erewhon.home> 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 18:54:48 -0000 On Wed, February 18, 2015 12:08 pm, Roland Smith wrote: > On Tue, Feb 17, 2015 at 06:37:38PM -0600, Valeri Galtsev wrote: >> 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. >> > >> Interesting. I never saw this particular explanation. I have heard that overwiritten data can be recovered (to significant extent). > > From “Overwriting Hard Drive Data: The Great Wiping Controversy” 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 > that > 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 – there is a small chance of 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 > Thanks for the reference. Still, you reference has to do with another reference ("Gutman") which basically is about information that stays there due to track misalignment and similar. This, however has nothing to do with what I have described (which is deleted from the quote in this your e-mail; whoever is interested can get back to my original e-mail with lengthy description) which basically is about information that sat on the platter for years in the same physical locations and magnetic domain aging will leave some residual magnetization after it is uniformly magnetized (no matter what happened for short period of time in between). I hope to find that source... Valeri > A single wipe of a HDD is enough to destroy the data beyond hope of recovery. > > 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 location > X. > > > Roland > -- > 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) > ++++++++++++++++++++++++++++++++++++++++ Valeri Galtsev Sr System Administrator Department of Astronomy and Astrophysics Kavli Institute for Cosmological Physics University of Chicago Phone: 773-702-4247 ++++++++++++++++++++++++++++++++++++++++