Wipe function?

Thomas Sjögren thomas@northernsecurity.net
Thu Aug 28 12:06:02 2003

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On Wed, Aug 27, 2003 at 10:08:39PM -0700, Joseph Bruni wrote:
> Obviously, the better way would be to pull out a number of bytes from=20
> /dev/random to seed your PRNG and then use the output from that to wipe=
> the file in question.

Actually, the "cat /dev/urandom > file" in my initial post was just an
example how to minimize the impact a filesystem could have on the wiping
process. Maybe not a good example, but still just an example.

If you read the Gutmann paper [1] you'll se that only eight random
characters are needed, not a constant stream om random characters, the
rest (pass number 5 to 31) has fixed characters.=20

> I noticed that /dev/random is also writable -- allowing one to add=20
> additional entropy to the pool. That's kinda cool. I could probably hit=
> infinite improbability by writing my checking account balance into=20
> /dev/random!! With my luck my computer would turn into a bowl of=20
> petunias saying, "Not again!"

Check out http://www.fourmilab.ch/hotbits/generate.html, generate a
binary file, write it to /dev/random. Now you got fresh radiactive
decay present in your computer.=20

[1] http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

=3D=3D thomas@northernsecurity.net | thomas@se.linux.org
=3D=3D Encrypted e-mails preferred | GPG KeyID: 114AA85C

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