[2481] in cryptography@c2.net mail archive
Re: Secure Cell Phones for State
daemon@ATHENA.MIT.EDU (Dave Emery)
Mon Apr 13 12:03:00 1998
Date: Fri, 10 Apr 1998 21:21:06 -0400
From: Dave Emery <die@die.com>
To: John Young <jya@pipeline.com>
Cc: cryptography@c2.net
Reply-To: die@die.com
In-Reply-To: <199804102300.TAA05198@camel7.mindspring.com>; from John Young on Fri, Apr 10, 1998 at 07:00:14PM -0400
On Fri, Apr 10, 1998 at 07:00:14PM -0400, John Young wrote:
>
> Finally, are the TAC-2000 units useful for the Secretary's
> global travels? If so, are they supported by military networks
> overseas? Or do American officials use a different system
> when traveling?
Reading the Motorola specs makes clear that the CipherTAC 2000
module interfaces an analog cellphone (AMPS NAMPS or ETACS) using V.32
modem tones at 4.8 kbs to remote STU IIIs. This would make these phones
useful anywhere analog service was available. Security (and voice
quality) would be the same as STU III, EG end to end Type I with up to
Top Secret possible.
The product sounds like a Newt memorial quick fix...
Most places the Secretary travels actually use GSM phones rather
than the various US digital systems, although many of those places still
have some of the AMPS analog stuff or the European version of it (ETACS)
still operating so the cipherTAC-2000 would probably still work.
I do know that within the US the WHCA people have been using
cellphone STU III links to the President's limos for years (but the
primary secure system called Yankee/Zulu is set up by WHCA at the trip
site and operates on Federal VHF frequencies using military crypto gear
and a direct satellite link back to the White House Secure Switchboard
(Royal Crown) from a satellite terminal located at the USSS/WHCA command
post). How much of the time the WHCA limos use special digital CDPD
links and how much they use plain old AMPS with modem tones I don't
really know.
Both military (UHF fleetsat) and INMARSAT satellites are extensively
used by traveling diplomats to call home, one suspects often in preference
to using local telephone systems. Both of these satellite systems support
secure voice (INMARSAT directly supports use of STU IIIs). The terminals
use portable dish antennas carried in baggage and unfolded and pointed
at the satellite from hotel or conference sites. A hand carried STU III
cellphone would be more conveniant for diplomats than the satcom terminals
and might have significantly lower delay and easier talking as a result.
I think the general intent is to provide cell phones that can
interoperate with STU IIIs as the primary method. Old fashioned analog
cell phones can carry modem tones and be used with variable results
with ordinary STU IIIs (the same problems with modem tones over cell
apply here as they do to other data over analog cell - dropouts, bursts of
errors, renegotiation of connections etc). Digital cell phones cannot
carry high speed modem tones directly and need to be interfaced to
devices at the MTSO that offload the digital data and shovel it down
a regular modem toward the far end. To the extent that such devices
are provided by the network infrastructure a digital cellphone can be
used for secure voice. But see Phil's comment on this.
--
Dave Emery N1PRE, die@die.com DIE Consulting, Weston, Mass.
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2 5D 27 BD B0 24 88 C3 18
