From: pstemari@erinet.com (Paul J. Ste. Marie)
Date: Wed, 18 Jan 95 21:16:33 PST
To: joelm@eskimo.com (Joel McNamara)
Subject: Re: TEMPEST
Message-ID: <9501190507.AB17284@eri.erinet.com>
MIME-Version: 1.0
Content-Type: text/plain


At 12:32 PM 1/18/95, Timothy C. May wrote:
> ... And if nothing is seen with our $10K of equipment, what does this
>prove against an attacker who can easily afford to spend 20 or 30
>times that amount to equip a van?
>
>Cypherpunks have been exploiting technology that is comparatively
>_much cheaper_ and which changes the equation.
>
> ... In general, for reasons many of us have written about here before, and in
>particular, because I think spending $10,000 to prove what we already
>know--that RF emissions can be detected and demodulated--is a poor use
>of money. That $10K would go a long way to getting PGP Phone finished. ...

I'm not sure how encryption chages the equation if that van on the street 
can read the data off your screen and/or printer.  Just as cryptanalysis is 
a necessary component of good cryptography, some sort of VanEck analysis 
would seem to be required in order to evaluate the utility of methods to 
block it.

What exactly would one need to do to block Van Eck monitoring?  I've seen 
computer rooms that were completely lined with copper sheathing.  Is it 
really necessary to go to that extent?  Will aluminum foil and power line 
conditioning handle it?  You can't really tell how effective 
counter-measures are unless you have some way to see what reduction in 
emitted signal they provide.

    --Paul J. Ste. Marie
      pstemari@well.sf.ca.us, pstemari@erinet.com