> -----Original Message----- > From: tclug-list-bounces at mn-linux.org > [mailto:tclug-list-bounces at mn-linux.org]On Behalf Of > Dean.Benjamin at mm.com > Sent: Friday, October 01, 2010 12:11 PM > To: TCLUG Mailing List > Subject: Re: [tclug-list] Hidden hard drive partitions > > > I had believed that a hard drive could be securely erased by > multiple over-writes with random bit patterns, such that not even > the NSA could salvage anything useful. > > Chuck, when you said "Not so", you made me sit up in surprise. I > am genuinely curious. Could you refer us to technical articles > that explain how experts can retrieve data from drives that have > been subjected to rigorous shredding (eg, with utilities such as > DBAN http://www.dban.org/)? (If indeed that is your claim.) Most such data is tightly guarded by manufacturers for mainly proprietary reasons, and it is only shared with customers by signatory releases. Several different means and head geometries are used to write tracks. Tracks are smeared in different ways, and are wider than the record head gaps. The data is recovered as an analog signal. Special heads can be used on platters to read centers versus edges of tracks, and do waveform reconstructions. The waveforms onto and from the platters are analog and not digital, and bits occupy more than just one atomic-level magnetic domain. Adjacent "ones" have "spillover" magnetism that greatly affects waveforms. PRML encoding and decryption deals with this to support/enable higher bit densities. With special heads and special analog signal handling, "fringe effects" become readable. Some people get PhDs in these topics. Hope that helps. Chuck > > At 10/1/2010 11:38 AM, T L wrote: > >It is logically impossible for Tony to prove a negative, but all > you'd have to do is one current reference to show that you're not > just blowing smoke. Care to do so? > > > >Thomas > > > >>On Oct 1, 2010 4:51 AM, "Chuck Cole" <<mailto:cncole at earthlink.net>cncole at earthlink.net> wrote: >> >>> -----Original Message----- >>> From: <mailto:tclug-list-bounces at mn-linux.org>tclug-list-bounces at mn-linux.org >>> [mailto:<mailto:tclug-list-bounces at mn.>tclug-list-bounces at mn... >> >>> Sent: Friday, October 01, 2010 2:59 AM >>> To: TCLUG Mailing List >>> Subject: Re: [tclug-list] Hidden... >> >>> Show me evidence that this can be done. All of that residual waveform >>> stuff is no longer detect... >>Too hard. You show evidence that it cannot, including all variants of >>platter imaging. Didn't say the drive "as delivered" could do it. I worked >>in the most advanced read/write end of the industry doing modeling, etc.. If >>you have, you probably wouldn't ask. If you haven't you might not have the >>PRML analysis, head design variant knowledge, knowledge of excess written >>space in data imaging on tracks, and spin stand background to follow the >>evidence. Didn't say it was easy or cheap. Did say it isn't trivial. >> >>Chuck _______________________________________________ TCLUG Mailing List - Minneapolis/St. Paul, Minnesota tclug-list at mn-linux.org http://mailman.mn-linux.org/mailman/listinfo/tclug-list