On Aug 20, 2008, at 3:04 AM, Vlad SATtva Miller wrote:
Robert J. Hansen (20.08.2008 09:12):
Bhushan Jain wrote:
I wanted to know how could the file be deleted securely using PGP?
Assuming you meant GnuPG, the answer is 'no'.
Assuming you meant PGP, the answer is 'maybe'. PGP provides a secure
deletion tool, but as far as I know there has never been any serious
independent study of its effectiveness.
It employs Gutmann's methodology on secure file erasure, so there
*is* a
study of its effectiveness.
Note, though, the postscript that Gutmann added on to his paper in
later years:
In the time since this paper was published, some people have treated
the 35-pass overwrite technique described in it more as a kind of
voodoo incantation to banish evil spirits than the result of a
technical analysis of drive encoding techniques. As a result, they
advocate applying the voodoo to PRML and EPRML drives even though it
will have no more effect than a simple scrubbing with random data.
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. As
the paper says, "A good scrubbing with random data will do about as
well as can be expected". This was true in 1996, and is still true
now.
The operative phrase here is "A good scrubbing with random data will
do about as well as can be expected". The world of hard drives has
evolved since 1996, and unless you're pulling your hard drives from
10-15 year old machines, the only relevant parts of the 35-pass
Gutmann methodology are going to be the random ones.
David
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