Rolling code security system

• US 6,154,544 A
• Filed: 06/11/1997
• Issued: 11/28/2000
• Est. Priority Date: 05/17/1995
• Status: Expired due to Term

• Current Assignee: The Chamberlain Group, Inc. (The Chamberlain Group LLC)
• Original Assignee: The Chamberlain Group, Inc. (The Chamberlain Group LLC)
• Inventors: Fitzgibbon, James J., Farris, Bradford L.
• Primary Examiner(s): Laufer, Pinchus M.
• Assistant Examiner(s): SONG, HOSUK
• Application Number:
  US08/873,149
• Time in Patent Office: 1,266 Days
• Field of Search: 380/23, 380/28, 380/48, 380/49, 380/25, 380/259, 380/260, 380/261, 380/262, 380/44, 340/825.72, 340/825.25, 340/825.31, 340/825.69, 341/176
• US Class Current: 380/262
• CPC Class Codes: G07C 2009/00214 by one push button
• CPC Class Codes: G07C 2009/00253 dynamically, e.g. variable code - rolling code
• CPC Class Codes: G07C 9/00182 operated with unidirectional data transmission between data carrier and locks
• CPC Class Codes: H04L 2209/80 Wireless
• CPC Class Codes: H04L 2209/84 Vehicles
• CPC Class Codes: H04L 9/32 including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials
• CPC Class Codes: H04W 12/02 Protecting privacy or anonymity, e.g. protecting personally identifiable information [PII]
• CPC Class Codes: H04W 12/033 of the user plane, e.g. user's traffic
• CPC Class Codes: H04W 12/80 Arrangements enabling lawful interception [LI]
• CPC Class Codes: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

A rolling code transmitter is useful in a security system for providing secure encrypted RF transmission comprising an interleaved trinary bit fixed code and rolling code. A receiver demodulates the encrypted RF transmission and recovers the fixed code and rolling code. Upon comparison of the fixed and rolling codes with stored codes and determining that the signal has emanated from an authorized transmitter, a signal is generated to actuate an electric motor to open or close a movable barrier.

Claims

1. A transmitter for sending an encrypted signal to control an actuator, comprising:

oscillator for generating a radio frequency oscillatory signal;

apparatus for enabling the sending of an encrypted signal;

binary code generator responsive to the enabling apparatus for generating a variable binary code, said variable code being different for each enabling by the enabling device;

trinary code generator for generating a three-valued or trinary code responsive to the variable binary code; and

transmitting apparatus for modulating the radio frequency oscillatory signal with the trinary code to produce a modulated trinary coded variable radio frequency signal for operation or control of a secure actuator.

2. A transmitter for sending an encrypted signal to control an actuator according to claim 1, further comprising apparatus for receiving said variable binary signal and producing a mirrored binary signal, said mirrored binary signal being supplied to said trinary code generator for generating the trinary signal from the variable binary signal.

3. A transmitter for sending an encrypted signal to control an actuator according to claim 1, comprising apparatus for producing a fixed code signal and for combining said fixed code signal with a rolling code signal.

4. A transmitter for sending an encrypted signal to control an actuator according to claim 3, comprising apparatus for interleaving trinary bits derived from said fixed code signal with trinary bits derived from said rolling code signal to produce a trinary interleaved fixed and rolling code signal.

5. A transmitter for sending an encrypted signal to control an actuator according to claim 1, comprising incrementing apparatus for altering said variable code by adding a fixed value with each enabling apparatus actuation.

6. A transmitter for sending an encrypted signal to control an actuator according to claim 5, wherein said means for incrementing said variable code increments said variable code by a prime number value.

7. A transmitter for sending an encrypted signal to control an actuator according to claim 1, wherein said binary code generator for generating a variable binary code includes a non-volatile memory for storing a variable binary code.

8. A transmitter for sending an encrypted signal to control an actuator according to claim 1, wherein said binary code generator for generating said variable code includes storage means holding a previous cycle variable code signal from which the variable code is generated.

9. A remote security system for communicating an encrypted signal to a control actuator, comprising:

binary code generator for generating a sequence of variable binary codes according to a predetermined algorithm, successive codes in the sequence being different from preceding codes in the sequence;

trinary code generator for converting said generated variable binary code to a trinary code;

a transmitter for modulating a transmitted radio frequency signal with said trinary code;

a radio-frequency receiver for demodulating said transmitted modulated radio frequency signal and providing a received trinary code;

trinary code convertor for converting said received trinary code to a received binary code;

a controller responsive to a positive comparison of said received binary code and a reference variable binary code; and

update apparatus responsive to said positive comparison for updating said reference variable binary code according to said received binary code.

10. A remote security system according to claim 9, wherein said update apparatus updates said reference variable binary code by performing said predetermined algorithm on said reference variable binary code.

11. A remote security system according to claim 9, wherein said positive comparison results if said received binary code and said reference variable binary code lie within a predetermined numerical limit of one another.

12. A remote security system according to claim 11, wherein said positive comparison results if the numerical difference of said received binary code minus said reference variable binary code is a positive number less than said predetermined limit.

13. A remote security system according to claim 12, wherein said predetermined limit is about 1000.

14. A remote security system according to claim 12, wherein said positive comparison results if at least two said received binary codes transmitted in succession, each of which is numerically different from said reference variable binary code by a number outside the range of said predetermined limit, represent successive results of said predetermined algorithm.

15. A remote security system according to claim 14, wherein said positive comparison results if said successively transmitted codes which represent successive results of said preselected algorithm, each yield a difference when subtracted from said reference variable binary code outside the range of zero to a second predetermined limit.

16. A remote security system according to claim 15, wherein said second predetermined limit is about 300.

17. A remote security system according to claim 11, wherein the variable binary code is a rolling code and the system further comprises a binary code combiner for combining a binary fixed code with said binary rolling code and providing the combination to said trinary code generator.

18. A remote security system according to claim 17, further comprising apparatus for interleaving trinary bits derived from said binary fixed code with trinary bits derived from said binary rolling code to provide an interleaved trinary fixed-and-rolling code to said transmitter.

19. A remote security system according to claim 18, further comprising apparatus for receiving said output of said radio-frequency receiver and separating said interleaved fixed-and-rolling code and providing to said trinary code convertor a received trinary fixed code and a received trinary rolling code.

20. A remote security system according to claim 19, wherein said trinary code convertor provides a received binary fixed code in response to said received trinary fixed code and a received binary rolling code in response to said received trinary rolling code, and further comprising addressing apparatus for using said received binary fixed code to address said reference variable binary code in a memory.

21. A remote security system according to claim 20, further comprising means for mirroring said binary rolling code and providing it to said trinary code generator.

22. A remote security system according to claim 21, further comprising apparatus for mirroring said received binary rolling code and providing it to said controller and to said update apparatus.

23. A remote security system according to claim 22, wherein said predetermined algorithm generates a variable binary code by adding a numeric constant to it.

24. A remote security system according to claim 23, wherein said predetermined algorithm generates a variable binary code by adding the value 3 to it.

25. A remote security system according to claim 15, further comprising second update apparatus for updating said reference variable binary code according to one of the set of said successively transmitted received binary codes.