ronys wrote:
Hi Shachar,
'urban legend' may be a bit strong. The reference I had in mind was
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html
<http://www.cs.auckland.ac.nz/%7Epgut001/pubs/secure_del.html>
which is a bit dated (circa 1996, plus a couple of undated epilogues),
but still an interesting read.
Of course, if you're going to keep sensitive data on magentic media,
it's *much* easier to use an encrypted partition (e.g., dm-crypt
http://www.saout.de/misc/dm-crypt/ or TrueCrypt
http://www.truecrypt.org/) and securely destroy the keys.
Rony
Thanks. That seems like an excellent resource (with reasoning, unlike
what I'm used to :-).
I haven't delved into it, yet, but its description of how the drive
actually writes data to the disk differs dramatically from what I
remember described the last time I saw a description of the recovery
process (it claims the 1 and 0 are merely encoded as magnetic polarity,
while I remember them being modulated on a sine wave). Which it actually
is, I'm not sure, but the reasoning your article states for using random
data (create as low a frequency as possible given the disk's RLE) is
negated if the data is actually modulated.
Unfortunately, I have lost track of my previous source, but pending
further analysis, I'm willing to retract my definitive claim that
needing to use random data is an urban myth.
Shachar
--
Shachar Shemesh
Lingnu Open Source Consulting Ltd.
http://www.lingnu.com
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