Re: Wanted: Secure-delete utility for Linux

Steffen Grunewald (steffen@gfz-potsdam.de)
Tue, 22 Dec 1998 10:36:19 +0100 (MET)

Dave Cinege wrote:
|>
|> Shail Bains wrote:
|> >
|> > Dunno of an equivalent for WipeDisk, though...
|>
|> dd if=/dev/zero of=/dev/hdX : >
|>
|> To be really sure I think that should be followed by /dev/urandom
|> then zero again.

Why urandom ? The safest way to destroy all information on disk should
be to reverse _all_ magnetic particles (flip and flip back)
|>
|> AFAIK DoD military grade wiping is zero->random->zero->random->zero.

A better scheme would be 10101010 - 01010101 - 11111111 - 00000000

BUT:

if I write a bit pattern to the disk - how is it stored ?
Remember, CD data are re-encoded to avoid long 1 or 0 patterns.
I'd guess, with fuzzy bit stuffing nowadays harddisk use similar
techniques... so perhaps a "all ones / all zeroes" pattern is
re-encoded to something that is near ...01010101010...

-- 
Steffen Grunewald = steffen(at)gfz-potsdam.de = fax +49-331-288-1266
My opinions are mine. You can rent them. Just ask me for prices  :-)
"Art is a lie which makes us realize the truth"   -    Pablo Picasso


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