Key code correlation security

• US 6,332,572 B1
• Filed: 05/03/1999
• Issued: 12/25/2001
• Est. Priority Date: 05/06/1998
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Yamamoto, Keiji, Onishi, Noriyasu
• Primary Examiner(s): Frech, Karl D.
• Application Number:
  US09/303,686
• Time in Patent Office: 967 Days
• Field of Search: 235/382, 235/382.5, 235/385, 235/375, 235/383, 235/384, 705/18
• US Class Current: 235/382
• CPC Class Codes: B60R 25/2072 with means for preventing jamming or interference of a remote switch control signal
• CPC Class Codes: G07C 2009/00388 code verification carried out according to the challenge/response method
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 9/00309 operated with bidirectional data transmission between data carrier and locks

Abstract

A transponder type key security system having a plurality of authorized keys efficiently correlates a key code transmitted by a key-based transponder unit with codes stored in an interrogator unit while inhibiting reception interference by multiple signals transmitted by a plurality of key-based transponder units. The interrogator unit transmits a general request for key-based transponder units having pre-stored key codes allocated thereto to respond by giving their respective key codes. A transponder unit, upon receiving the request, transmits its key code to the interrogator unit. The interrogator unit compares a received key code with key codes previously stored to determine if the transponder unit responding is authorized or not. In the event that multiple transponder units respond to the request, the interrogator unit transmits a key-specific request so that only the targeted key-based transponder unit will respond. This prevents multiple transponder requests from interfering with one another. Usually only a single key is present and there is no need to transmit key-specific requests. Thus, the number of key code requests to be transmitted is reduced and a determination of whether a key is authorized or not can be carried out efficiently.

Claims

1. A key code correlation security arrangement, comprising:

a key;

a transponder associated with the key, the transponder having a memory for storing a predetermined key code, and means for transmitting that key code in response to a key code request transmitted thereto; and

an interrogator for transmitting general and specific key code requests to the transponder, the interrogator having a memory for storing one or more predetermined key codes identifying authorized keys, means for receiving a key code from the transponder in response to a key code request, and means for comparing a received key code with the key codes stored in interrogator memory, the interrogator also having a key code request changing means for differentiating key code requests for a plurality of key codes, and interference determination means for determining whether or not answer signals responding to a key code request interfere with one another, and

wherein if the interference determination means has determined that there is interference of two or more key code responses from transponders in response to a general key code request, the interrogator then transmits specific key code requests that are specific to individual keys, and compares responses received with the key codes of such specific key code requests.

2. An arrangement according to claim 1, wherein the transponder comprises a power supply that receives an electromagnetic wave from the interrogator and stores electric power therefrom for operating the transponder.

3. An arrangement according to claim 1, wherein the interrogator has a coil that transmits electromagnetic waves to the transponder and receives a response signal including a key code therefrom.

4. An arrangement according to claim 1, wherein the interference determination means has means for detecting that the transponder is ready to transmit an answer signal in response to a key code request from the interrogator.

5. An arrangement according to claim 4, further comprising means for detecting insertion of the key into a lock cylinder.

6. An arrangement according to claim 4, wherein the interference determination means determines that there is interference, if it has been detected that the key is ready to transmit an answer signal in response to a key code request from the interrogator and if a key code cannot be recognized despite reception of the answer signal responding to the key code request.

7. An arrangement according to claim 1, wherein the interference determination means determines that there is interference if a key code cannot be recognized despite reception of an answer signal responding to a key code request.

8. An arrangement according to claim 1, wherein if there is no interference and a key code has been received, the received key code is compared to a plurality of key codes previously stored in the interrogator memory according to a predetermined sequence.

9. An arrangement according to claim 1, wherein the interrogator transmits a key code request including a cipher signal, and wherein the transponder returns a ciphered key code in response to the ciphering signal.

10. An arrangement according to claim 1, wherein a key code request from the interrogator comprises a password, and wherein the transponder returns a key code if the key has a password identical to the transmitted password.

11. A key code authorization method, comprising the steps of:

storing a plurality of correlation key codes in an interrogator;

transmitting by the interrogator a key code request;

receiving by a transponder associated with a key the key code request transmitted by the interrogator;

transmitting by the transponder a key code allocated to its associated key; and

receiving by the interrogator the key code transmitted by the transponder;

if it has been determined by the interrogator that there are two or more answer signals responding to the key code request that interfere with one another, transmitting by the interrogator key code requests for specific keys, and comparing received key codes with key codes previously stored in the interrogator.

12. A method according to claim 11, wherein if it has been determined by the interrogator that answer signals responding to a key code request do not interfere with one another, a received key code is compared with key codes stored in the interrogator according to a predetermined sequence.

13. A method according to claim 11, further comprising the step of determining that there is interference if a key code received by the interrogator cannot be recognized despite reception of an answer signal responding to a key code request.

14. A method according to claim 11, further comprising the step of determining that there is interference, if it has been detected that the transponder is ready to transmit an answer signal in response to a key code request from the interrogator and if a key code cannot be recognized despite reception of the answer signal responding to the key code request.