building a true RNG (was: Quantum Computing ...)

[Arnold G. Reinhold]

At 3:39 PM -0700 7/22/02, David Honig wrote:
>At 04:24 PM 7/22/02 -0400, John S. Denker wrote:
>>
>
>...
>>A detuned FM card is a bad idea, because it is just
>>begging the opponent to sit next door with an FM
>>transmitter.
>
>So work in a Faraday cage...
>
At 8:21 PM -0400 7/22/02, John S. Denker replied:
>
>Tee, hee.  Have you ever worked in a Faraday cage?
>Very expensive.  Very inconvenient.
>
>

You don't have to put yourself inside the cage, just the FM radio. 
several layers of aluminum foil should work. The radio can run on 
batteries. Getting the audio out without allowing FM signal in is a 
bit tricky. The bast answer is to use fiber optics to carry the 
audio, but a good low-pass filter should work. Instead of detuning 
the receiver, tune it to the strongest station in your area. You'll 
know the shielding is effective when the signal is no longer 
detectable.  Of course if an attacker gets a high power transmitter 
close to you, all bets are off, but simply listening to another 
receiver nearby tuned to the same station would make such an attack 
obvious.

The same technique with a portable TV set and a video digitizer 
should be a good source of high bandwidth noise. In both cases you 
are just using the receivers as high gain amplifiers of the thermal 
noise at the antenna terminals.

Arnold Reinhold

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