From: tcmay@got.net (Timothy C. May)
Date: Wed, 24 Jul 1996 14:38:45 +0800
To: cypherpunks@toad.com
Subject: Re: Bare fibers
Message-ID: <ae1ac24201021004c36e@[205.199.118.202]>
MIME-Version: 1.0
Content-Type: text/plain


At 6:56 PM 7/23/96, Bill Frantz wrote:
>At 12:30 AM 7/23/96 -0500, Douglas R. Floyd wrote:

>>Not really sure how.  I have had heard of ways to tap a fibre optic link
>>noninvasively, but its not related to Van Eck or anything like that.
>
>You could break the fiber and add a repeater (if you know enough about the
>light protocol).  Plastic fiber can be cut with a pocket knife, glass
>requires a machine which will make a square cut and polish the end.  Those
>machines are not yet cheap.

Fibers can be tapped noninvasively, and without cutting them, by placing
detectors in direct proximity to the fiber. That is, touching the glass or
plastic.

For fibers relying on total internal reflection at the fiber boundary, the
waves actually partly exist beyond the boundary (with an imaginary
component). Another fiber or a detector placed near this boundary can make
this imaginary component become "real," and hence detect the wave. This is
"tunneling," of course.

(A simple demonstration is done with a glass prism reflector, a reflector
relying on total internal reflection. If a symmetrical prism is placed up
against the first prism, the "total reflector" ceases to be.)

--Tim May

Boycott "Big Brother Inside" software!
We got computers, we're tapping phone lines, we know that that ain't allowed.
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Timothy C. May              | Crypto Anarchy: encryption, digital money,
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