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From: minow@decvax.UUCP (Martin Minow)
Newsgroups: sci.crypt
Subject: Cheap more-or-less one-time-pads
Message-ID: <57@decvax.UUCP>
Date: Thu, 7-May-87 19:57:14 EDT
Article-I.D.: decvax.57
Posted: Thu May  7 19:57:14 1987
Date-Received: Sat, 9-May-87 10:05:38 EDT
Reply-To: minow@decvax.UUCP (Martin Minow)
Distribution: world
Organization: Digital Eq. Corp. - Merrimack NH.
Lines: 26
Keywords: DES

I just bought a very nice 20 Mbyte one-time pad for my [imaginary]
encryption device.  I was suprised to discover that it had another
function.  When placed in a CD player, it creates about an hour of
very nice music.

Since these disks are distributed world-wide, (and the bits are
easy to pull off the disks), it seems that two people could set
up a reasonably secure communications path by having a common
disk library and a (secretly transmitted) algorithm for selecting
the disk/track/index for a new message.  This could be as simple
as multiplying the date by the phase of the moon and dividing the
result by the Dow Jones average.  Without knowledge of the disk
library and selection algorithm, an intruder would have a tough
time reading the traffic.

(By the way, the raw cd bits have high redundancy.  There are ways
to turn this into suitably random data.  Even if you tossed all
but the low-order bit of each sample, you still get 1.2 Mbytes
of pretty random data.)

Have I forgotten something?

Martin Minow
decvax!minow

The above does not represent the position of Digital Equipment Corporation