thoughts on one time pads

Trei, Peter ptrei at
Sat Jan 28 12:14:11 EST 2006

You missed the old standby - the microwave oven.

The disk remains physically intact (at least after the
5 seconds or so I've tried), but a great deal of pretty
arcing occurs in the conductive data layer. Where the
arcs travel, the data layer is vapourized. 

The end result is an otherwise intact disk in which the
data layer is broken up into small intact islands 
surrounded by clear channels. It might be interesting
to try a longer burn, in which case you might also
want to put a glass of water in with the disk(s) to
preserve the microwave's electronics.

This is probably less effective than the other methods
you've described, but its very fast and leaves no noxious
residues. It also uses a very commonly available tool.

Peter Trei

-----Original Message-----
From: owner-cryptography at
[mailto:owner-cryptography at] On Behalf Of Peter Gutmann
Sent: Saturday, January 28, 2006 2:25 AM
To: cryptography at; jthorn at
Subject: Re: thoughts on one time pads

Jonathan Thornburg <jthorn at> writes:

>Melting the CD should work... but in practice that takes a specialized
>(I seriously doubt my home oven gets hot enough), and is likely to 
>produce toxic fumes, and leave behind a sticky mess (stuck to the 
>surface of the specialized oven).

For no adequately explored reason I've tried various ways of physically
destroying CDs:

- Hammer on hard surface: Leaves lots of little fragments, generally
still stuck
  together by the protective coating.

- Roasting over an open fire: Produces a Salvador Dali effect until they
  fire, then huge amounts of toxic smoke ("fulfilling our carbon tax
  was one comment) and equally toxic-looking residue.

- Propane torch: Melts them without producing combustion products.

- Skilsaw: Melts them together at the cutting point, rest undamaged.

- Axe: Like skilsaw but without the melting effect.

- Using the propane torch and hammer to try and drop-forge a crude
  density CD: Messy.


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