From: Adam Back <aba@dcs.ex.ac.uk>
Date: Tue, 20 Aug 1996 09:15:05 +0800
To: eb@comsec.com
Subject: Re: CS8191 data sheet and ordering info...
In-Reply-To: <199608171837.LAA20948@comsec.com>
Message-ID: <199608190407.FAA00152@server.test.net>
MIME-Version: 1.0
Content-Type: text/plain



Eric Blossom <eb@comsec.com> (CSC) writes:
> 
>                 Communication Security Corporation
>             CS8191 Triple-DES Telephone Privacy Device
> [...]
> Specifications:
> 
>  Modem
> 
>  * ITU V.32bis (14,400 bits/sec)
> 
>  * International standard GSM 06.10 full rate speech transcoding 
>    (13,000 bits/sec)
> 
> 
> Cryptographic Details:
> 
> * Unique session key generated for each conversation using Diffie-Hellman
>   exponential key exchange (2048 bit modulus) (U.S. Patent No. 4,200,770
>   licensed by Cylink Corporation)
> 
> * Defense against "man in the middle" active attack using interleave
>   protocol combined with voice verification of six digit key name derived
>   from the public exponentials
>
> * Hardware Random number generator based on Johnson noise
> 
> * Three Key Triple-DES (168 bit key), operating in modified counter mode.

To anyone who's read the PGPfone docs, this sounds very similar,
PGPfone uses 3DES (as one option: also CAST, Blowfish), but it's a 2
key 3DES rather than 3 key (I think).  PGPfone works with
9600/14400/28800 modems, uses Diffie Hellman key exchange, uses a
commitment to exchanges by passing the hashes of the exchanges prior
to traditional dh key-exchange (we'll see if this compares to what is
described here as an `interleave protocol').  PGPfone offers several
GSM codecs.

Do you see any barrier to PGPfone being able to interoperate with your
product once your specs are published?  (Aside from a fast PC/MAC to
keep up -- 3DES is the most computationaly expensive encryption
algorithm used by PGPfone).

Also I believe I read somewhere in your announce that upgrades are
possible -- can these happen in software only?  Flash BIOS upgrade?
If it is software upgradable are you releasing the programming specs
also?

A very nice product, sure beats the hell out of clipper based phones,
and the various snake oil offerings,

Adam
--
#!/bin/perl -sp0777i<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<j]dsj
$/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1
lK[d2%Sa2/d0$^Ixp"|dc`;s/\W//g;$_=pack('H*',/((..)*)$/)