METHOD FOR PREVENTING RELAY-ATTACK ON SMART KEY SYSTEM

• US 20150074805A1
• Filed: 10/25/2012
• Published: 03/12/2015
• Est. Priority Date: 04/17/2012
• Status: Active Grant

• Current Assignee: Seoyon Electrics Co., Ltd.
• Original Assignee: Dae Dong Co., Ltd.
• Inventors: Choi, Sang Kyu, Kim, Shim Soo, Kim, Gyu Ho
• Granted Patent: US 9,210,188 B2
• Time in Patent Office: Days
• US Class Current: 726/22
• CPC Class Codes: B60R 25/24 using electronic identifiers containing a code not memorised by the user
• CPC Class Codes: G07C 2009/00388 code verification carried out according to the challenge/response method
• CPC Class Codes: G07C 2009/00769 with data transmission performed by wireless means
• CPC Class Codes: G07C 9/00309 operated with bidirectional data transmission between data carrier and locks
• CPC Class Codes: G07C 9/20 involving the use of a pass
• CPC Class Codes: H04L 63/0853 using an additional device, e.g. smartcard, SIM or a different communication terminal cryptographic mechanisms or cryptographic arrangements for entity authentication involving additional secure or trusted devices H04L9/3234
• CPC Class Codes: H04L 63/1466 Active attacks involving interception, injection, modification, spoofing of data unit addresses, e.g. hijacking, packet injection or TCP sequence number attacks
• CPC Class Codes: H04W 12/08 Access security
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

The present invention relates to a method for preventing a relay-attack on a smart key system, and in particular, provides an advantage of preventing a vehicle and equipment stored inside the vehicle from being stolen by using predetermined information transmitted and received when the SMK UNIT of the vehicle and a FOB Key wirelessly communicate with each other and enabling a holder of the FOB Key to make the relay-attack once the holder secures visibility from the vehicle.

Claims

1. A method for preventing relay-attack on a smart key system, the method comprising:

a challenge signal receiving step of transmitting a challenge signal including received signal strength information (hereinafter, “

RSSI”

) information of two levels from a smart key unit (hereinafter, “

SMK unit”

) installed in a vehicle to a FOB key carried by a user and receiving the challenge signal by the FOB key;

a first decoding step of decoding at least one information item of information items included in the challenge signal after receiving the challenge signal;

a response signal transmitting step of transmitting a response signal from the FOB key to the SMK unit after the first decoding step;

a second decoding step of decoding at least any one information item included in the response signal received by the SMK unit after the response signal transmitting step; and

a normal user determining step of calculating a current distance between the vehicle and the FOB key using a result interpreted in the second decoding step and determining whether a passive operation signal applied from a door of the vehicle other than the FOB key is normal.

2. The method of claim 1, wherein the response signal transmitting step is a step of the FOB key transmitting transmitting the response signal to the SMK unit in response to the challenge signal only when an RSSI level difference interpreted in the first decoding step is consistent with a set value.

3. The method of claim 1, wherein the vehicle includes a first adjusting unit adjusting a gain of a power amplifier so that the RSSI has two levels.

4. The method of claim 3, wherein the first adjusting unit randomly generates the RSSI level difference.

5. The method of claim 1, wherein the FOB key includes an LFIC identifying the RSSI level difference.

6. The method of claim 1, wherein the challenge signal received by the FOB key in the challenge signal receiving step further includes an encryption code request signal that allows the FOB key to transmit the response signal including an encryption code for normal user authentication.

7. A method for preventing relay-attack on a smart key system, the method comprising:

a challenge signal receiving step of transmitting a modulated/demodulated challenge signal by an SMK unit in a vehicle when a predetermined electrical signal is input to the SMK unit and then receiving the challenge signal by a FOB key; and

a response signal receiving step of the FOB key transmitting to the SMK unit a response signal including predetermined information at a predetermined output strength in response to the challenge signal of the SMK unit after the challenge signal receiving step and the SMK unit receiving the response signal, wherein the response signal transmitting step includes a signal determining process determining whether the challenge signal is an LF signal input to the SMK unit by door handle triggering or an RF signal input to the SMK unit by manipulating a plurality of switches provided on the FOB key, the response signal transmitting step being a step of performing control so that an output strength of the response signal varies depending on the input signal.

8. The method of claim 7, wherein in the response signal receiving step, the output strength of the response signal is controlled by a first adjusting unit adjusting a gain of a power amplifier provided in the FOB key.

9. The method of claim 8, wherein the first adjusting unit adjusts the gain of the power amplifier so that the response signal is output with a set output (hereinafter, “

first output value”

) when the input signal is the RF signal generated by the switch manipulation, and the first adjusting unit adjusts the gain of the power amplifier so that the response signal is output with a second output value smaller than the first output value when the input signal is the LF signal generated by the door handle triggering.

10. The method of claim 9, wherein the response signal receiving step further includes a voltage strength monitoring process of monitoring a current voltage level (hereinafter, “

VL”

) of the FOB key, wherein the set output is set to be in inverse proportion with the VL obtained during the voltage level monitoring process.

11. The method of claim 10, wherein the adjusting unit adjusts the gain of the power amplifier so that the response signal is output with a value larger than the first output value when the VL is less than a set VL and the input signal is the RF signal generated by the switch manipulation.

12. The method of claim 10, wherein the adjusting unit adjusts the gain of the power amplifier so that the response signal is output with a value larger than the second output value when the VL is less than a set VL and the input signal is the LF signal generated by the door handle triggering.

13. The method of claim 12, wherein the value larger than the second output value is smaller than the first output value.

14. The method of claim 12, wherein the value larger than the second output value is a middle value between the first output value and the second output value.

15. A method for preventing relay-attack on a smart key system, the method comprising:

a response signal transmitting step of a FOB key carried by a user receiving a signal applied from an SMK unit installed in a vehicle and then transmitting a response signal including at least two types of information to the SMK unit;

a second decoding step of the SMK unit decoding the received response signal after the response signal transmitting step; and

a normal user determining step of calculating a current distance between the vehicle and the FOB key using a result interpreted in the second decoding step and determining whether a passive operation signal applied from a door of the vehicle other than the FOB key is normal, wherein the response signal includes information on a received signal strength indication (hereinafter, “

RSSI”

) and a current voltage level (hereinafter, “

VL”

) of the FOB key.

16. The method of claim 15, wherein the response signal further includes an encryption code transmitted from the FOB key for normal user authentication in the normal user determining step.

17. The method of claim 15, wherein in the normal user determining step, the VL includes information corresponding to when the VL is not less than a set voltage and information corresponding to when the VL is less than the set voltage, and the RSSI includes information corresponding to when the RSSI is not less than a set strength and information corresponding to when the RSSI is less than the set strength.

18. The method of claim 17, wherein in the normal user determining step, the set strength of the RSSI when the VL is not less than the set voltage (hereinafter, “

first set strength”

) is higher than the set strength of the RSSI when the VL is less than the set voltage (hereinafter, “

second set strength”

).

19. The method of claim 18, wherein the current distance is calculated to be short when the RSSI is not less than the first set strength or the second set strength and to be long when the RSSI is less than the first set strength or the second set strength, and wherein in the normal user determining step, only when calculated to be short, the passive operation signal is determined to be normal, and when calculated to be long, the passive operation signal is determined to be abnormal.

20. The method of claim 19, wherein the set voltage is linearly varied, and wherein the first set strength and the second set strength are variables varying proportionately with the set voltage and are stored in the SMK unit as map data.