From: dneal@NeoSoft.com (David Neal)
Subject: fax from AT&T on clipper
Organization: NeoSoft Communications Services -- (713) 684-5900
Date: Tue, 18 May 1993 16:40:47 GMT

Last week, someone posted the cpsr server address and I got
the name and number of David Arneke at AT&T from one of the
announcements archived there. Mr. Arneke said he would like
to hear comments on the Clipper chip, and could also forward
them to the "appropriate people" (he works in Secure Communications).
He also faxed me something that I did not see on cpsr, which I
have enclosed below.  Perhaps someone could add it to the cpsr 
server. (cpsr = gopher -p1/cypherpunks gopher.cpsr.org 70 )


David Arneke, AT&T
Media Relations/Marketing Communications
RM C3D18
P.O. Box 20046
Guilford Center, Greensboro, N.C. 27420

(919) 279-7680 (voice)
(919) 279-6841 (fax)
darneke@attmail


                             CLIPPER CHIP TECHNOLOGY

CLIPPER is an NSA developed, hardware oriented, cryptographic
device that implements a symmetric encryption/decryption
algorithm and a law enforcement satisfying key escrow system.
While the key escrow management system design is not completely
designed, the cryptographic algorithm (SKIPJACK) is completely
specified (and classified SECRET).

The crytographic algorithm (called CA in this PAPER) has the
following characteristics:

     1.    Symmetric, 80-bit key encryption/decryption algorithm;
     2.    Similar in function to DES (i.e., basically a 64-bit
           code book transformation that can be used in the same
           four modes of operation as specified for DES in FIPS
           81);
     3.    32 rounds of processing per single encrypt/decrypt
           operation;
     4.    Design started by NSA in 1985; evaluation completed in 
           1990.

The CLIPPER CHIP is just one implementation of the CA. The
CLIPPER CHIP designed for the AT&T commercial secure voice
products has the following characteristics:

     1.    Functions specified by NSA; logic designed by
           MYKOTRONX; chip fabricated by VLSI, INC.: manufactured
           chip programmed (made unique) by MYKOTRONX to security
           equipment manufacturers willing to follow proper 
           security procedures for handling and storage of the
           programmed chip; equipment sold to customers;

     2.    Resistant to reverse engineering against a very
           sophisticated, well funded adversary;

     3.    15-20 MB/S encryption/decryption constant throughout
           once cryptographic synchronization is established with
           distant CLIPPER Chip;

     4.    The chip programming equipment writes (one time) the
           following information into a special memory (called
           VROM or VIA-Link) on the chip:

           a.    (unique) serial number
           b.    (unique) unit key
           c.    family key
           d.    specialized control software

     5.    Upon generation (or entry) of a session key in the
           chip, the chip performs the following actions:

           a.    Encrypts the 80-bit session key under the unit key
                 producing an 80-bit intermediate rsult;

           b.    Concatenates the 80-bit result with the 25-bit
                 serial number and a 23-bit authentication pattern
                 (total of 128 bits);

           c.    Enciphers this 128 bits with family key to produce
                 a 128-bit cipher block chain called the Law
                 Enforcement Field (LEF);

           d.    Transmits the LEF at least once to the intended
                 receiving CLIPPER chip;

           e.    The two communicating CLIPPER chips use this field
                 together with a random IV to establish 
                 Crytographic Synchronization.

     6.    Once synchronized, the CLIPPER chips use the session 
           key to encrypt/decrypt data in both directions;

     7.    The chips can be programmed to not enter secure mode if
           the LEF field has been tampered with (e.g., modified,
           superencrypted, replaced);

     8.    CLIPPER chips will be available from a second source in
           the future;

     9.    CLIPPER chips will be modified and upgraded in the 
           future;

    10.    CLIPPER chips presently cost $16.00 (unprogrammed) and
           $26.00 (programmed).