NSA tapping undersea fibers?

Peter Fairbrother peter.fairbrother at ntlworld.com
Tue Jun 5 06:56:53 EDT 2001

Transoceanic cables vary from about 15 to 23 mm diameter. Until recently
they had 4 pairs of fibres maximum.

The SL21 from Tycom is a typical modern transoceanic cable. It has a
diameter of 21 mm, weighs about 1.25 kg/m, working load 17,500 lb. It has 8
fibre pairs in a steel-wire and copper tube construction, in a polyethylene
sheath. The copper tube is the current carrier as well as hydrostatic

Max depth in seawater is about 7 km, beyond which it breaks under it's own
weight. At a typical 4 km depth it is almost vertical when it is laid or
lifted. It cannot be lifted uncut from this depth.


The Jimmy Carter has an "ocean interface" suitable for a large cable reel,
and it can covertly lay cable for backhaul. Cable laid from a submarine can
be thinner and cheaper than cable laid from the surface, especially if the
depth is not too great.

Cables up to 4,500 km can be repeaterless, also greatly reducing the cable
size and cost as no conductor is required, and with higher capacity, as the
number of fibres is not limited by power requirements (to run repeaters).
Cables up to about 800km long, at depths around 400m, can be very cheap
(comparatively). A cable like this would easily fit into the Jimmy Carter.

The Jimmy Carter could also act as an undetectable support ship for a deep
submersible, which could tap cables at oceanic depths.


Re: tapping US cables: Canadian, French, Belgian, German and Bermudan
companies, I stopped looking, install and run cables that make landfall in
the US. Tapping on land could not go unnoticed by these companies. Legal
threats to imprison their employees would not work, as they are not US
citizens. Threats against their licences to operate should be reported to
their Boards, under due diligence laws.

Wholesale consensual tapping of these cables by the NSA could not reasonably
be expected to be kept secret from eg European Parliamentary Investigators,
at least to the extent of a quiet word in someone's ear, if senior staff in
these companies were aware of it. I have a hard time believing it could be
kept secret from US "cyberwarriors" and freedom of speech / privacy
campaigners, USC 18;798 or no. I have an even harder time believing the NSA
might think it could be kept secret, it's just not in their nature to trust
anyone outside the Agency.

Botton line? If the NSA used wholesale tapping on land, we would probably
have evidence of it.

Would they want to tap these cables? To quote Perry Metzger, "The US is not
a terminus for all the world's communications, although it is involved in a
surprising fraction of international calls..." It's like robbing banks, you
go where the money is. A recent UK-France traceroute I did went through the
US twice. Twice was slightly unusual, but once isn't.

I could not find "the law that allows the NSA to tap cables wholesale",
though I looked at several.  Can anyone help? If they tap offshore does the
take becomes "Foreign Intelligence"?

-- Peter

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