From: chris.liljenstolpe@SSDS.com (Christopher Liljenstolpe)
Date: Fri, 26 Jul 1996 12:04:50 +0800
To: abostick@netcom.com (Alan Bostick)
Subject: Re: Bare fibers
In-Reply-To: <Pine.BSF.3.91.960723170725.23791A-100000@mcfeely.bsfs.org>
Message-ID: <31f7ee7d.29626488@denver.ssds.com>
MIME-Version: 1.0
Content-Type: text/plain


Greetings,

	There are other ways of detecting the application of the tap,
but at this time, the chance of detecting the existance of the tap is
reallistically pretty slim. 

	If the fiber is enclosed in a pressurised conduit, then a drop
in the conduit pressure indicates that someone MAY be trying to gain
access to the fiber.  While a pressurized glove-box around the conduit
may allow a break in the conduit to be made without detection, varying
the pressure in the conduit makes that a lot more difficult.  It all
depends on what the value is of the data you are trying to
protect/access.

	-=Chris

On Thu, 25 Jul 1996 11:52:12 -0700, the sage abostick@netcom.com (Alan
Bostick) scribed:

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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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