From: bruce@omega.co.nz
Date: Thu, 14 Mar 1996 14:16:18 -0500
To: cypherpunks@toad.com
Subject: CD-reading for random keys
In-Reply-To: <4i5gtu$99i@news2.realtime.net>
Message-ID: <4i91h4$lp5@nero.omega.co.nz>
MIME-Version: 1.0
Content-Type: text/plain


>Doe anyone know where sample code exists to enable one to read the digital
>stream from an audio CD?  If so, I'd appreciate some pointers to it via
>email.  It seems to me like an Audio Cd would make the perfect one-time

cdgrab (registered) will let you read "frames" (1/75sec of audio) directly into
a wav file. From there it's easy.. But:

>crypto system.  You merely start reading at a specific spot, tossing away
>bytes using a reproducable random number generator, then permuting
>those to form a XOR one time key of any length you want.

The "entropy" or randomness of audio data is LOW. That's why audio compresses
so well. However, the idea of keeping a one-time key on CD-ROM is good. I would
suggest recording thermal noise (Eg the hiss from an untuned FM radio), perhaps
XORing with a pseudo-random sequence to remove residual bias. Record 600M of
this onto a pair of writable CDs, and have your friend come and collect one of
them personally. Then you can send up to 600M of totally secure data before you
dispose of the disks (Microwave oven is fun :) and write a new pair.

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