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United States Patent m
Koopman, Jr. et al.
 PSEUDORANDOM NUMBER GENERATION AND CRYPTOGRAPHIC AUTHENTICATION
 Inventors: Philip J. Koopman, Jr., Hebron; Alan M. Finn, Amston, both of Conn.
 Assignee: United Technologies Automotive, Inc., Dearborn, Mich.
 Appl. No.: 86,080
 Filed: Jun. 30,1993
 IntCI.5 H04L9/32
 U.S. CI 380/23; 380/21;
380/25; 380/43; 380/49; 340/825.31;
 Field of Search 380/4, 9, 23, 24, 25,
380/46, 49, 50, 21, 43; 331/78; 364/717;
 References Cited
U.S. PATENT DOCUMENTS
4,424,414 1/1984 Hellman et al 380/30
4,667,301 5/1987 Chiu et al 364/717
4,691,291 9/1987 Wolfram 364/717
4,876,718 10/1989 Citta et al 380/42
5,001,754 3/1991 Deffeyes 380/46
5,007,016 4/1991 Le Mehaute et al 380/46 X
5,048,086 9/1991 Bianco et al 380/46 X
5,109,152 4/1992 Takagi et al 380/23 X
5,144,667 9/1992 Pogue, Jr. et al 380/25 X
5,146,215 9/1992 Drori 340/825.32
Primary Examiner—Bernarr E. Gregory Attorney, Agent, or Firm—M. P. Williams
[ii] Patent Number: 5,363,448  Date of Patent: Nov. 8,1994
An automobile door lock receiver module (30) and a plurality of keychain fob transmitter units (16) contain identification numbers, secret initial values, and secret feedback masks so as to authenticate encrypted messages from any of the assigned fobs, indicative of commands registered by closing switches on the fob. Each fob is synchronized with the receiving module by means of a truly random number concatenated with a secret initial value and encrypted, through a linear feedback shift register or other operations. A second secret initial value is encrypted and command bits are exclusive ORed into the low order bit positions; the two encrypted numbers are concatenated and encrypted to form a key word which is transmitted with the fob ID. Synchronization includes decrypting to recover the truly random number and the secret initial value concatenated therewith; the truly random number is compared with previously received random numbers in order to avoid copying of recently transmitted synchronization commands. Successive lock-related commands utilize the number encrypted from the truly random number and the second secret initial value as starting values, employing a pseudorandom number of encryption iterations. A half-second delay between responses mitigates gaining access through numerical trials. An authenticated panic alarm command operates the headlights and horn of the vehicle but does not alter the synchronization.
46 Claims, 9 Drawing Sheets