From: trimm@netcom.com (Trimm Industries)
Date: Wed, 19 May 93 16:59:15 PDT
To: cypherpunks@toad.com
Subject: tempest
Message-ID: <9305192359.AA16487@netcom4.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



Reply to TO1SITTLER re: tempest

TEMPEST is NACSIM 5100A (there are some new numbers which I
can't remember), a NSA specification for the emission of 
compromising EMI from computers and other digital data processing
equipment.  It is a Faraday cage, except that they divide 
the system into "black" noise circuits and "red" noise
circuits.  An example of black emissions would be the constant
50 KHz signal emitted by a switcher power supply, that contains
no useful information.  You can emit as much black as you want.
You cannot emit ANY red information, that is, CRT guns, data
busses, data transmission lines, etc.  Red information can be
reconstructed easily bu passive interception.

Your PC, for example, has a monitor that emits enough information
to allow unintended interception up to a mile away.

If you need more details, write back.

Gary trimm@netcom.com

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