[19831] in cryptography@c2.net mail archive
Re: CD shredders, was Re: thoughts on one time pads
daemon@ATHENA.MIT.EDU (Jack Lloyd)
Thu Feb 2 10:19:22 2006
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Wed, 1 Feb 2006 13:16:27 -0500
From: Jack Lloyd <lloyd@randombit.net>
To: cryptography@metzdowd.com
Mail-Followup-To: cryptography@metzdowd.com
In-Reply-To: <d4f1333a0602010350k15f01a0cg1d4fafbf05ebe6f4@mail.gmail.com>
On Wed, Feb 01, 2006 at 05:50:24AM -0600, Travis H. wrote:
> On 1/28/06, dan@geer.org <dan@geer.org> wrote:
> > In our office, we have a shredder that happily
> > takes CDs and is designed to do so. It is noisy
> > and cost >$500.
>=20
> Here's one for $40, although it doesn't appear to "shred" them so much
> as make them pitted:
>=20
> http://www.thinkgeek.com/gadgets/security/6d7f/
If you packaged up your OTP material into blocks using an all-or-nothing
transform you could probably be certain that this would suffice, as long as=
the
blocks you used were large enough that it was at least statistically probab=
le
that 'enough' bits of each block were destroyed or made unreadable. I belie=
ve
specifically you'd want to make sure that 2^n is an infeasible amount of wo=
rk,
where n is the minimum number of bits that will be lost from any block by t=
he
destruction process. This seems to generalize nicely, for example if an ent=
ire
CDs worth of material was processed as a single block under an all-or-nothi=
ng
transform, just snapping the disk in half might suffice to prevent any
(computationally feasible) data recovery [though it would be quite annoying=
in
practice, since you'd have to process the entire disk to read even a single=
bit
=66rom it]
-Jack
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