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Date: Tue Feb 7 15:07:46 2006 From: Valdis.Kletnieks at vt.edu (Valdis.Kletnieks@...edu) Subject: Gutmann's research paper today On Tue, 07 Feb 2006 15:44:37 +0100, gimeshell@....de said: > Am i misunderstanding something or you can really say, if you're > writing to a modern disk, forget all special scrubbing technologies, > don't use Gutmann, don't use DoS 5220.22M or other pattern writing > technologies, only a few passes of random scrubbing will do the job? DoD 5220.22M only requires 3 passes and verify of each pass - all zeros, all ones, and all "the same character" (for instance, 'AAAAAAA..' or similar). That's good for sanitizing disks up to Secret. For anything higher, physical destruction is mandated. A "few passes of random scrubbing" is probably equivalent to 5220.22M for any realistic usage. One place where "random scrubbing" falls down is the requirement to *verify* that the blocks were written. If you wrote a disk full of zeros, it's a trivial matter to read it back and verify that all the bytes are zeros. If you wrote a whole disk of pseudo-random, then you have to regenerate the entire pseudo-random data stream in order to compare it.... And yes, the verify step is important - I've had more than one disk drive that was still perfectly readable, but suffered hardware damage to the write hardware. Writing 3 passes of anything and failing to verify on such a disk would result in a disclosure of the entire disk's contents. Yes Virginia, there *are* disk drive failures that will report a successful write but not actually work... ;) -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 226 bytes Desc: not available Url : http://lists.grok.org.uk/pipermail/full-disclosure/attachments/20060207/4da0c5b5/attachment.bin
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