From: jim bell <jimbell@pacifier.com>
Date: Sun, 12 May 1996 17:23:01 +0800
To: cypherpunks@toad.com
Subject: Re: Again: [hrdware] anti-Tempest video settings
Message-ID: <199605120337.UAA32475@pacifier.com>
MIME-Version: 1.0
Content-Type: text/plain


At 08:02 PM 5/11/96 +0000, Jean-Francois Avon wrote:

>Or, to the contrary, is it reasonable to assume that modern Tempest 
equipment can
>work around theses impediments almost all of the time, therefore 
>making any attempts at this futile?

It's probably worth investigating. Chances are good that as long as the 
total beam current remains as constant as possible, the signal will be much 
harder to interpret.  One way to investigate this comparatively easily is to 
measure the total power consumption of a monitor when the screen is filled 
with different colors at different saturations, etc.  Supply the AC to the 
monitor through a 1-ohm resistor, measure the AC voltage across the resistor 
to 1 mv accuracy or better, and you have a pretty good way to distinguish 
different beam currents.

 I'm waiting for cheap flat-panel displays for desktop computers to arrive, 
because they will probably be almost impossible to detect usably by Tempest 
systems.


Jim Bell
jimbell@pacifier.com