From: Joel McNamara <joelm@eskimo.com>
Date: Thu, 5 Dec 1996 14:19:50 -0800 (PST)
To: stewarts@ix.netcom.com
Subject: Re: Laptops and TEMPEST
Message-ID: <3.0.32.19961205141815.007404a8@mail.eskimo.com>
MIME-Version: 1.0
Content-Type: text/plain


Thinking that LCD screens reduce the risks of emanation monitoring is a
dangerous misconception (at least under a high threat model).  LCDs'
current requirements are pretty small, and they only emanate a low magentic
and electrical field.  However, the gotcha with current laptops is their
backlighting.  Electric and magnetic fields are considerably higher
compared with a low-res/contrast device.

There are documents that circulate within certain security circles that
list just how noisy (and therefore easy to monitor) various off-the-shelf
machines are.  It would be an interesting project for some ham radio type
Cypherpunks to measure their machines, and publish the results.  Or, for
some well connected person just to scan and anonymously post such a
document to the list.  Of course, I'd never encourage anyone to do
something illegal.

Joel