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From: roeber@cithe1.cithep.caltech.edu (Frederick Roeber)
Newsgroups: comp.dcom.telecom
Subject: Dr. Stoll's Secure Phone Calls
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Date: 12 Jan 91 14:31:42 GMT
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I believe the confusion over the "secure phone" mentioned in the book,
The Cuckoo's Egg, arises from Dr. Stoll describing a few phone calls
he received: One day, he answered his phone only to hear a recording
"This is not a secure phone..."  The person on the other end hung up
and tried again, with the same result.  After a couple tries, he
finally got through, and was able to start questioning Dr. Stoll.  Dr.
Stoll replied, "This is not a secure phone..."

A friend of mine, who does military security work, said this is the
result of calling a non-secure phone from the government's secure
phone system and trying to initiate a secure call.  When making a
secure call on this system, one first makes an ordinary phone call --
over any network, FTS, AT&T, or whoever.  When the other end has been
reached, one presses the `secure' button.  This makes each end call
the main computer that controls the secure phone system.  Through an
encrypted conversation, the main computer sends each phone two
numbers: a key with which they can communicate with each other (for
that conversation only), and a key to be used for the next call to the
main computer.  Then the main computer drops out, and the phones can
send encrypted traffic to each other.  Of course, if you hit `secure'
when other end is a regular phone, the main computer realizes it can't
set up an encrypted link, and plays the warning message.  It also logs
the attempt.

So Dr. Stoll need not have been anywhere near a secure phone to get
such a call.


Frederick G.M. Roeber | e-mail: roeber@caltech.edu or roeber@vxcern.cern.ch
r-mail: CERN/PPE, 1211 Geneva 23, Switzerland | telephone: +41 22 767 31 80