From: tcmay@netcom.com (Timothy C. May)
Date: Sat, 2 Jul 94 09:47:23 PDT
To: bmorris@netcom.com (Bob MorrisG)
Subject: Re: IS IT POSSIBLE?
In-Reply-To: <199407021616.JAA09281@netcom12.netcom.com>
Message-ID: <199407021647.JAA27109@netcom8.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


> 
> To: cypherpunks@toad.com
> 
> I've heard rumors through the years that CIA/NSA/whoever can aim a
> parabolic antenna at your window, read the electronic pulses surrounding
> your computer, and thusly determine what you are typing.  Is there any
> truth to this?

Yes. PCs, and especially the _monitors_ of PCs, put out a lot of RF.
(Most of you will have seen that turning on your PC or Mac near a
television with an antenna input--as opposed to cable input--will
cause various kinds of "hash" on the t.v.)

It's been possible for many years to build a box which can "tune in"
to the RF and actually see a direct replica of what's on the CRT. This
from some distance. A paper on this was done a while back, from which
the name "van Eck" or "Van Eck" comes. 

How far away, and whether a van parked a block away can do it, is
unknown to me. There are people on this list who have done
this...perhaps they can comment anonymously.

Note that the TEMPEST spec for shielding equipment is directly related
to this.

Is this a concern for ordinary Cypherpunks? Well, I don't worry about
it. I'm presently fairly upfront about my views, and use encryption
very rarely, ironic as that may seem.

What can be done?

* Laptops put out much less RF (try the television test). The LCD
doesn't have the deflector coils of a CRT to radiate in synch with the
screen action, so the problem of snooper is much harder.

(My Powerbook 170 still puts "wavy lines" on an antenna-input t.v., so
_something_ is being emitted....whethe it is _readable_ is another
matter. But then, the NSA has a lot more expertise than most of us
have, so....)

--Tim May


-- 
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Timothy C. May         | Crypto Anarchy: encryption, digital money,  
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