From: abostick@netcom.com (Alan Bostick)
Date: Fri, 26 Jul 1996 07:02:12 +0800
To: cypherpunks@toad.com
Subject: Re: Bare fibers
In-Reply-To: <Pine.BSF.3.91.960723170725.23791A-100000@mcfeely.bsfs.org>
Message-ID: <cJ89x8m9LseL085yn@netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


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In article <Pine.BSF.3.91.960723170725.23791A-100000@mcfeely.bsfs.org>,
Rabid Wombat <wombat@mcfeely.bsfs.org> wrote:

> ob crypto/privacy: Anybody have a good idea for detecting a tap on 
> exterior fiber? I'd expect an attacker to have to interupt connectivity, 
> terminate both ends of a break, and insert an active device. Thoughts?

As has been mentioned earlier, all an attacker has to do is encourage
some of the light to exit the fiber, by bending it, contacting it with
a detector, etc.

If the detector is sensitive enough, the loss induced by this is minimal.

This sort of tapping is exactly the sort of thing quantum cryptography
is supposed to prevent, or at least identify.  Nothing short of quantum
methods is going to spot the tap, unless you happen to come across the 
tap by inspecting the entire length of the fiber.

- -- 
Alan Bostick               | [Spielberg's] latest is TWISTER, a film that
mailto:abostick@netcom.com | gives whole new meaning to the phrase "giant
news:alt.grelb             | sucking sound."  -- Patrick Taggart
http://www.alumni.caltech.edu/~abostick

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