From: Ethan D Schartman <es5c+@andrew.cmu.edu>
Date: Wed, 20 Apr 94 09:52:01 PDT
To: cypherpunks@toad.com
Subject: Re: What the heck is this? Optical noise encryption?
In-Reply-To: <199404200614.CAA17953@eff.org>
Message-ID: <0hhJpdu00awQ43bWUj@andrew.cmu.edu>
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I don't know much about his "optical noise" encryption, but Scientific
American ran an article in the Amatuer Scientist column outlining an
encryption scheme involved much the same ideas.  Their scheme was to
find, and digitize a chaotic source as a carrier signal and then add the
information to the signal. Decryption involved subracting the source
signal from the encoded one.   Information encrypted this way would be
positively unbreakable by anyone without the chaotic source, as the
whole scheme is entirely random. 

The biggest problem is of course, transmitting the source in a secure
manner.  It is not enough to know the configuration of the generator of
the source, unless you also the _exact_ initial conditions (which are,
of course, impossible).

One solution to this problem might be to use a recursive equation to
generate a source from a small (one-hundred+ digit)  seed, and the
number of iterations necessary to reproduce the source.  The nice thing
about this is that the equation could also be customized, something 
like: x= (k)(x^2)+a,  where "a" and "k" are constants that may be
altered, thus providing two methods of encryption. This scheme would
also be a solution to the problem of the source being corrupted during
transmission (which would ruin any attempts to use it).  But the
equation and the seed would still have to be transmitted somehow.
Hmmm.... you could openly send the seed and  the encoded information,
and then call the reciever to tell them to convert a given sentence into
decimal equivalent...etc