From: "Peter Trei" <trei@process.com>
Date: Thu, 13 Mar 1997 06:18:12 -0800 (PST)
To: Dale Thorn <cynthb@sonetis.com
Subject: Re: TEMPEST protection
Message-ID: <199703131418.GAA03648@toad.com>
MIME-Version: 1.0
Content-Type: text/plain


> Date:          Wed, 12 Mar 1997 21:16:48 -0800
> From:          Dale Thorn <dthorn@gte.net>
> To:            "Cynthia H. Brown" <cynthb@sonetis.com>
> Cc:            cypherpunks@toad.com, cypherpunks@algebra.com
> Subject:       Re: TEMPEST protection
> Reply-to:      Dale Thorn <dthorn@gte.net>

> Cynthia H. Brown wrote:
> > On Tue, 11 Mar 1997, Dale Thorn wrote:
> > > Actually, the computer you type on will be very easy to pick out
> > > of the noise field with modest spy equipment sitting down the street.
> 
> > Other places to look for emissions: the power supply, and the connection
> > points for peripherals.  Make sure you leave adequate ventilation, though
> > (another tricky part).
> 
> Funny thing was, first time I used PGP I was typing in a passphrase
> and apparently PGP was doing something to the keyboard processor
> on my laptop, because all of a sudden I thought I'd gotten bat's
> ears - I could hear interesting new noises every time I pressed a
> key, which I hadn't heard before (at least at an audible volume).
> 
> It occurred to me that typing in a PGP passphrase would be a
> particularly bad time to increase the emissions....

One thing I've heard about laptops - nearly all of them have a video
connector to allow use of a standard CRT monitor. This connector, and
the chips driving it, are always active, and usually unshielded. Thus,
many laptops are spewing video signals out the back.

If you're paranoid (and handy with hardware), I suppose you could 
disconnect the video chip, or at least place an appropriate terminator 
in the video connection socket.

Peter Trei
trei@process.com