Rolling code security system

• US 7,492,905 B2
• Filed: 08/14/2002
• Issued: 02/17/2009
• Est. Priority Date: 05/17/1995
• Status: Expired due to Fees

• Current Assignee: The Chamberlain Group, Inc. (The Chamberlain Group LLC)
• Original Assignee: The Chamberlain Group, Inc. (The Chamberlain Group LLC)
• Inventors: Fitzgibbon, James J.
• Primary Examiner(s): Parthasarathy; Pramila
• Application Number:
  US10/219,829
• Publication Number:
  US 20030118187A1
• Time in Patent Office: 2,379 Days
• Field of Search: 380/270
• US Class Current: 380/283
• 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 storing an expected code which responds to rolling codes transmitted by a transmitter, a method comprising:

a) receiving a transmitted first rolling code;

b) operating the barrier movement system and updating the expected code when the received rolling code is within a predetermined range of the received rolling code;

c) not operating the barrier movement system when the expected rolling code is not within the predetermined range of the received rolling code and not updating the expected code;

d) receiving a subsequent rolling code after the performance of the not operating step and resynchronizing the receiver when the subsequent rolling code was transmitted by the same transmitter as the first rolling code;

e) counting the number of times that step d) is performed and storing value representing the count;

f) inhibiting the further performance of the resynchronizing of step d) when the stored number of performances of step d) exceeds a predetermined value.

2. The method of claim 1, further comprising the step of visually indicating that the performance of step d) is being inhibited.

3. The method of claim 1, further comprising the step of aurally indicating that the performance of step d) is being inhibited.

4. The method of claim 1, further comprising the step of permanently preventing the transmitter from further operating the receiver after the inhibition step is performed.

5. 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 after the step f is performed.

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

storing a maximum number of times the receiver is allowed to perform the step d;

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

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

7. The method of claim 1, wherein the transmitter has an identity and the inhibiting step comprises:

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

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

8. The method of claim 1 wherein the step d comprises inhibiting the issuance of a command for barrier movement.

9. The method of claim 1 wherein the step d comprises inhibiting the updating of the value of the expected code stored in the receiver.

10. The method of claim 1 comprising:

measuring the time between successive transmissions from the transmitter.

11. The method of claim 10, wherein the inhibiting step is performed when the measured time is less than a first predetermined time limit.

12. In a barrier movement system comprising a receiver storing an expected code which responds to rolling codes transmitted by a transmitter, a method comprising:

a) receiving a transmitted first rolling code;

b) operating the barrier movement system and updating the expected code when the received rolling code is within a predetermined range of the received rolling code;

c) not operating the barrier movement system when the expected rolling code is not within the predetermined range of the received rolling code and not updating the expected code;

d) receiving a subsequent rolling code after the performance of the not operating step and resynchronizing the receiver when the subsequent rolling code was transmitted by the same transmitter as the first rolling code;

e) counting the number of times that step d) is performed and storing value representing the count;

f) measuring the time between the performance of step c and receiving a subsequent rolling code; and

g) inhibiting the performance of the resynchronizing of step d) when the measured time is less than a predetermined value.

13. The method of claim 12, further comprising the step of visually indicating that the performance of step d is being inhibited.

14. The method of claim 12, further comprising the step of aurally indicating that the performance of step d is being inhibited.

15. The method of claim 12, further comprising the step of permanently preventing the transmitter from further operating the receiver after the inhibiting step is performed.

16. The method of claim 12, further comprising the step of enabling the receiver to disregard codes transmitted from the transmitter for a set duration of time after the step f is performed.

17. The method of claim 12, wherein the inhibiting step further comprises the steps of:

storing a time value;

comparing the measured time with the stored time value; and

determining whether the measured time exceeds the stored time value.

18. The method of claim 12, wherein the transmitter has an identity and the inhibiting step comprises:

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

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

19. The method of claim 12 wherein the step d comprises inhibiting the updating of the value of its expected code stored in the receiver.