Rolling code security system

• US 20030118187A1
• Filed: 08/14/2002
• Published: 06/26/2003
• Est. Priority Date: 05/17/1995
• Status: Active Grant

• Current Assignee: The Chamberlain Group, Inc. (The Chamberlain Group LLC)
• Original Assignee: The Chamberlain Group, Inc. (The Chamberlain Group LLC)
• Inventors: Fitzgibbon, James J.
• Granted Patent: US 7,492,905 B2
• Time in Patent Office: Days
• US Class Current: 380/270
• CPC Class Codes: G07C 2009/00214 by one push button
• CPC Class Codes: G07C 2009/0023 with encription of the transmittted data signal
• CPC Class Codes: G07C 2009/00238 the transmittted data signal containing a code which is changed
• CPC Class Codes: G07C 2009/00253 dynamically, e.g. variable code - rolling code
• CPC Class Codes: G07C 2009/00555 comprising means to detect or avoid relay attacks
• CPC Class Codes: G07C 2009/00587 by battery
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 2009/00928 for garage doors
• CPC Class Codes: G07C 2209/06 Involving synchronization or resynchronization between transmitter and receiver; reordering of codes
• CPC Class Codes: G07C 2209/08 With time considerations, e.g. temporary activation, valid time window or time limitations
• CPC Class Codes: G07C 9/00182 operated with unidirectional data transmission between data carrier and locks
• CPC Class Codes: G08C 2201/62 Rolling code
• CPC Class Codes: H04L 2209/80 Wireless
• CPC Class Codes: H04L 2209/84 Vehicles
• CPC Class Codes: H04L 9/3226 using a predetermined code, e.g. password, passphrase or PIN network architectures or network communication protocols for supporting authentication of entities using passwords in a packet data network H04L63/083

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. To provide even greater security, the transmitter is limited in the number of times it may perform a resynchronization procedure. 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. In a barrier movement system comprising a receiver for storing an expected code which responds to rolling codes transmitted by a transmitter, the method comprising:

resynchronizing the receiver to the transmitted rolling code when a first predetermined condition exists between a transmitted code and the stored expected code;

establishing a second predetermined condition;

detecting whether the second predetermined condition has been met; and

inhibiting the performance of the resynchronizing step when the second condition has been met.

2. The method of claim 1, wherein the establishing step comprises establishing a maximum number of times a transmitter is permitted to initiate performance of the resynchronizing step.

3. The method of claim 1, wherein the detecting step comprises the steps of:

setting a maximum number of times a transmitter is permitted to initiate performance of its resynchronizing step;

counting each time the transmitter initiates performance of the resynchronization; and

indicating that the second predetermined condition has been met.

4. The method of claim 1, further comprising the step of visually indicating that the second predetermined condition has been met.

5. The method of claim 1, further comprising the step of aurally indicating that the second predetermined condition has been met.

6. The method of claim 1, further comprising the step of permanently preventing the transmitter from further operating the receiver upon the predetermined condition being met.

7. The method of claim 1, further comprising the step of enabling the receiver to disregard codes transmitted from the transmitter for a set duration of time when the predetermined second condition is met.

8. The method of claim 1, wherein the detecting step further comprises the steps of:

storing in a memory a maximum number of times the receiver is allowed to perform the resynchronizing step;

counting the number of times the receiver performs the synchronizing step;

comparing the counted value with the maximum number stored in the memory; and

detecting whether the counter value equals the number stored in memory.

9. The method of claim 1, wherein the transmitter has an identity and comprising:

recording in memory the identity of a transmitter that has initiated performance of the synchronizing step; and

denying performance of the resynchronization step in response to a code transmitted from a transmitter having an identity matching an identity recorded in memory by the recording step.

10. The method of claim 1, wherein the second predetermined condition comprises a predetermined amount of time between successive transmissions from the transmitter and the detecting step detects that the amount of time between successive transmissions from the transmitter is less than the predetermined amount of time.

11. The method of claim 1 comprising:

disallowing the performance of the resynchronizing step.

12. The method of claim, 1 wherein the first predetermined condition represents a number of code transmissions from the transmitter.

13. The method of claim 1, wherein the resynchronizing step comprises issuing a command for barrier movement and updating the value of the expected code stored in the receiver.

14. The method of claim 13, wherein the inhibiting step comprises inhibiting the issuance of a command for barrier movement.

15. The method of claim 14, wherein the inhibiting step comprises inhibiting the updating of the value of the expected code stored in the receiver.

16. The method of claim 1, wherein the first predetermined condition comprises a value representing a number of transmissions by the transmitter;

and

the resynchronizing step comprises;

changing the value representing the number of transmissions to another value.

17. The method of claim 16, wherein the changing step changes the value by a random amount.

18. The method of claim 1 comprising:

measuring the time between successive transmissions from the transmitter.

19. The method of claim 18, wherein the inhibiting step is performed when the measured time is less than a first predetermined time limit.

20. The method of claim 19, wherein the inhibiting step is performed when the measured time is greater than a second predetermined time limit.

21. The method of claim 1 comprising:

establishing a value of rolling code as the second predetermined condition;

detecting whether a received rolling code exceeds the value established as the second predetermined condition; and

inhibiting its performance of the resynchronizing step when the received rolling code exceeds the value established as its second predetermined condition.