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From: nelson@sgi.com (Nelson Bolyard)
Newsgroups: comp.dcom.telecom
Subject: Re: Secure Phones
Message-ID: <16354@accuvax.nwu.edu>
Date: 24 Jan 91 03:30:34 GMT
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X-Telecom-Digest: Volume 11, Issue 61, Message 3 of 10


In article <16161@accuvax.nwu.edu> CAPEK%YKTVMT.BITNET@cunyvm.cuny.edu 
(Peter G. Capek) writes:

>[...] how is the key management performed?  It can't be that all
>the phones use the same key, as compromising that key would render all
>the phones useless (and perhaps not even be noticed).  
>I don't think it can be that the key is negotiated when the call is
>setup, as that would be subject to eavesdropping (although that could
>be done under a universal key, but that would be subject to compromise
>as above).  

>Does anyone KNOW how this is done?  

Yes, Whitfield Diffie wrote a wonderful paper entitled "The First Ten
Years of Public-Key Cryptography", published in the Proceedings of the
IEEE, Volume 76, Number 5, May 1988, pages 560-577, in which he
answers questions such as yours about the STU-III and the Racal-Milgo
Datacryptor II, in some detail.

Dr.  Diffie, together with Martin E. Hellman, developed and patented
the Diffie-Hellman Public Key distribution system, which was a
forerunner of the public key encryption systems that followed.  Their
algorithm was first published in the IEEE Transactions on Information
Theory, Volume IT-22, Number 6, November 1976, pages 644-654.  The
patent for this algorithm is now held by Public Key Partners, who also
hold the RSA patent, among others.

The Diffie-Hellman algorithm permits two communicants to exchange one
pair of messages, after which both have knowledge of a secret which
may be used for a symmetric key or an initialization vector (e.g. for
DES).  Prior to communicating, both communicants share a common piece
of information, but that is not secret, and may be published.

Your nearby university library should have these issues available in
bound volumes or on microfilm.


Nelson Bolyard      nelson@sgi.COM      {decwrl,sun}!sgi!whizzer!nelson
Disclaimer: Views expressed herein do not represent the views of my employer.