[Nottingham] Re: Secure deletion of files

[Jon Masters]

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James Gibbon wrote:

| I used to work for a firm which did military contract work. Our security
| manager once told me that drives which had to be replaced were subjected
| to an acid bath, followed by a furnace!  I doubt whether quite such
| stringent measures are required for David though, or else he wouldn't have
| that information at home in the first place.

Reading the above, then choosing to interpret it somewhat...

I'm not entirely convinced that David would appreciate being dunked in
an acid bath and then thrown into a furnace.

Seriously though. All the main points have gotten made on this thread -
disks never seek the same two times in a row, data magnetisation is such
that it's possible to recover old data from zones on the disk, and doing
any kind of delete on modern filesystems doesn't guarantee you much.

For the ultimate in tinfoil hat paranoia, I would recommend using a USB
key with a password protected 256+ bit cryptoapi password (assuming you
can't memorise that key - but that would be better in some respects)
used to secure a loopback mounted file of contiguous encrypted data on
your local disk. To remove, run wipe on the file and burn the USB key.

I have not played with the newer ATA commands for secure wipe, but
hdparm tells me that many modern disks I've seen have various security
options one could use - I wouldn't use them if I had data to protect to
that level because I wouldn't trust the implementation to be secure.

Jon.
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