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- Jun 20, 2001
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I reformatted my computer the other day, and it got me wondering if there's been any more information on the hard drive wiping front. A little Googling later provided something I hadn't seen before.
The most well-known resource regarding the wiping of hard drives is likely Peter Gutmann's "Secure Deletion of Data from Magnetic and Solid-State Memory". This paper, first published in 1996, looks at several ways that data could be recovered from a drive. The results of this paper inspired the writers of many wiping programs to even include a Gutmann-style 35-pass wipe. However, that was 1996. This is 2010. In the intervening time, drive densities have marched onward: the 1.5 GB drive of the day was just as much a marvel as a 1.5 TB drive is today. These increasing densities have chiefy come through the shrinking of magnetic domains, making the attacks outlined by Gutmann more difficult.
More recently (January 2009), Craig Wright et al. published "Overwriting Hard Drive Data: The Great Wiping Controversy" which aimed to unseat the notion that multiple erasure passes are required. Using techniques like Magnetic Force Microscopy (an attack vector specifically mentioned by Gutmann) they could only succeed 9 times in a million to recover just 4 bytes of data. Many news organizations wrote short articles about their results, leading many readers to believe that Gutmann's paper is out of date in today's high-density world.
Unfortunatly, few who have heard about the paper have actually read it. While this is in part due to simple lazyness, it's also due to the article being very difficult to get for free. In addition to the online version existing behind a paywall, few public libraries subscribe to the periodical.
Fortunately, Peter Gutmann has read this article and has posted a "Further Epilogue" to his paper (click on the link above and scroll to the very end) dealing specifically with this paper. He's found many glaring errors and talks breifly about each. One of the most glaring is their apparent confusion of magnetic force microscopes and electron microscopes (I don't see how anyone writing a paper on this topic could make that giant an error repeatedly). In short, because of the errors, Gutmann believes the results should be taken with a salt block or two.
EDIT: After more googling, I managed to find a "simplified" version of the paper. It doesn't go into as much detail as the actual paper, but provides a little info nonetheless.
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On an additional (but unrelated) note, Gutmann also has added an "Epilogue" section that you may not have read. This is directed to those who "[treat] the 35-pass overwrite technique . . . more as a kind of voodoo incantation to banish evil spirits"
JigPu
The most well-known resource regarding the wiping of hard drives is likely Peter Gutmann's "Secure Deletion of Data from Magnetic and Solid-State Memory". This paper, first published in 1996, looks at several ways that data could be recovered from a drive. The results of this paper inspired the writers of many wiping programs to even include a Gutmann-style 35-pass wipe. However, that was 1996. This is 2010. In the intervening time, drive densities have marched onward: the 1.5 GB drive of the day was just as much a marvel as a 1.5 TB drive is today. These increasing densities have chiefy come through the shrinking of magnetic domains, making the attacks outlined by Gutmann more difficult.
More recently (January 2009), Craig Wright et al. published "Overwriting Hard Drive Data: The Great Wiping Controversy" which aimed to unseat the notion that multiple erasure passes are required. Using techniques like Magnetic Force Microscopy (an attack vector specifically mentioned by Gutmann) they could only succeed 9 times in a million to recover just 4 bytes of data. Many news organizations wrote short articles about their results, leading many readers to believe that Gutmann's paper is out of date in today's high-density world.
Unfortunatly, few who have heard about the paper have actually read it. While this is in part due to simple lazyness, it's also due to the article being very difficult to get for free. In addition to the online version existing behind a paywall, few public libraries subscribe to the periodical.
Fortunately, Peter Gutmann has read this article and has posted a "Further Epilogue" to his paper (click on the link above and scroll to the very end) dealing specifically with this paper. He's found many glaring errors and talks breifly about each. One of the most glaring is their apparent confusion of magnetic force microscopes and electron microscopes (I don't see how anyone writing a paper on this topic could make that giant an error repeatedly). In short, because of the errors, Gutmann believes the results should be taken with a salt block or two.
EDIT: After more googling, I managed to find a "simplified" version of the paper. It doesn't go into as much detail as the actual paper, but provides a little info nonetheless.
~~~~
On an additional (but unrelated) note, Gutmann also has added an "Epilogue" section that you may not have read. This is directed to those who "[treat] the 35-pass overwrite technique . . . more as a kind of voodoo incantation to banish evil spirits"
Secure Deletion of Data from Magnetic and Solid-State Memory said:In fact performing the full 35-pass overwrite is pointless for any drive since it targets a blend of scenarios involving all types of (normally-used) encoding technology, which covers everything back to 30+-year-old MFM methods (if you don't understand that statement, re-read the paper). If you're using a drive which uses encoding technology X, you only need to perform the passes specific to X, and you never need to perform all 35 passes. For any modern PRML/EPRML drive, a few passes of random scrubbing is the best you can do.
JigPu
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