mailing list archives
Re: Gutmann's research paper today
From: Valdis.Kletnieks () vt edu
Date: Tue, 07 Feb 2006 10:07:38 -0500
On Tue, 07 Feb 2006 15:44:37 +0100, gimeshell () web 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... ;)
Full-Disclosure - We believe in it.
Hosted and sponsored by Secunia - http://secunia.com/