From: tcmay@got.net (Timothy C. May)
Date: Wed, 21 Feb 1996 13:39:48 +0800
To: cypherpunks@toad.com
Subject: Re: Chaotic physical systems as random number sources
Message-ID: <ad4f7bb904021004607c@[205.199.118.202]>
MIME-Version: 1.0
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At 6:46 PM 2/20/96, E. ALLEN SMITH wrote:
>        I'm curious if anyone knows of any attempts to use a chaotic physical
>system (such as the famous double pendulum) as a source of random numbers. I
>did an Alta Vista check on the problem, and all I turned up was a paper (in
>postscript, so I couldn't read it) on all mathematical pseudorandom number
>generators being logical chaotic systems. (It's at
>http://csl.ncsa.uiuc.edu/~herring/publications/rand.ps).
>        One problem that I can see is that of strange attractors. While the
>path through each time would be different, they're still _close_ to each other,
>and a practical mechanical system might not be sensitive enough to pick up the
>differences.

This has come up several times. As I recall, some guys at a Navy research
lab (San Diego?) were claiming to have a "chaotic encryption" system.

As to using chaotic systems for PRNGs or RNGs, the "turbulent flow over
disk drive platters causes speed variations" idea, described recently, is
of course an example of nominally using a chaotic/turbulent system to
defeat predictability.

I have at least a couple of paragraphs on chaos and crypto in my Cyphernomicon.

--Tim


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