System for enhancing the security of a bi-directional data transmission system controlling access to an enclosed space, notably a vehicle

• US 6,483,425 B1
• Filed: 11/12/1999
• Issued: 11/19/2002
• Est. Priority Date: 11/13/1998
• Status: Expired due to Fees

• Current Assignee: Valeo Securite Habitacle (Valeo SE)
• Original Assignee: Valeo Securite Habitacle (Valeo SE)
• Inventors: Avenel, Jean-Jacques
• Primary Examiner(s): Lieu, Julie
• Application Number:
  US09/439,538
• Time in Patent Office: 1,103 Days
• Field of Search: 340/5.61, 340/5.62, 340/5.1, 340/5.2, 340/5.8, 340/426, 340/5.7, 340/5.71, 340/5.72, 340/5.73, 340/10.2, 455/41
• US Class Current: 340/5.61
• CPC Class Codes: B60R 25/00 Fittings or systems for preventing or indicating unauthorised use or theft of vehicles locks for vehicles E05B77/00-E05B85/00
• CPC Class Codes: G07C 2009/00555 comprising means to detect or avoid relay attacks
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 2209/63 Comprising locating means for detecting the position of the data carrier, i.e. within the vehicle or within a certain distance from the vehicle
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

The disclosure relates to a system providing enhanced security of a bi-directional data transmission controlling access to an enclosed space, including an identification device with a transmitting circuit and a receiving circuit installed in said enclosed space, and an identifier carried by a user wishing to gain access, a data interchange between said identification device and said identifier normally being established when the distance between them is less than a predetermined limit, the access being granted only when said identification device has authenticated said identifier, wherein, to prevent an interchange of identification data at a distance greater than said predetermined limit, notably by interposing an unauthorized repeater, the system includes means of switching that establish a momentary loopback of said transmitting circuit of said identification device, via a return circuit of said identifier , and said identification device includes means of measuring the resonance frequency of the oscillation generated by such a loopback, and means of control able to measure the difference between said resonance frequency and a reference frequency, so as to maintain access interdiction when this difference exceeds a predetermined value. The invention is notably applicable to secure control of access to a vehicle.

Claims

1. A system providing for enhanced security of a bi-directional data transmission controlling access to an enclosed space, including an identification device with a transmitting circuit and a receiving circuit installed in said enclosed space, and an identifier carried by a user wishing to gain access, a data interchange between said identification device and said identifier normally being established when the distance between them is less than a predetermined limit, the access being granted only when said identification device has authenticated said identifier,

wherein, to prevent an interchange of identification data at a distance greater than said predetermined limit, the system includes means of switching that establish a momentary loopback of said transmitting circuit of said identification device, via a return circuit of said identifier, said loopback generating an oscillation having a resonance frequency and said identification device includes means of measuring the resonance frequency of the oscillation generated by such a loopback, and means of control able to measure the difference between said resonance frequency and a reference frequency, so as to maintain access interdiction when this difference exceeds a predetermined value.

2. A system according to claim 1, wherein said means of switching establish said monetary loopback of said transmitting circuit of said identification device during a request for identification, via said return circuit of said identifier, after an identification request has been authenticated by said identifier.

3. A system according to claim 1, wherein said identification device includes a receiving circuit with a radio frequency receiver and an identification management unit with a frequency counter, and a transmitting circuit with a low frequency generator, an amplifier, and a switch able to connect the output of the radio frequency receiver directly to the input of the amplifier, in order to establish said loopback, whereas in normal operation the input of said amplifier is connected to the output of said low frequency generator.

4. A system according to claim 3, wherein said identifier includes a low frequency receiver, a data decoding circuit, an identifier management unit, a radio frequency transmitter, and a switch able to connect the output of said low frequency receiver directly to the input of said radio frequency transmitter, in order to establish said loopback, whereas in normal operation the input of said radio frequency transmitter is connected to said identifier management unit.

5. A system according to claim 4, wherein said monetary loopback is triggered by the emission of an initialization signal by said radio frequency transmitter of said identifier, the initialization signal initializing said frequency counter of said identification management unit of said identification device.

6. A system according to claim 1, wherein said reference frequency with which said measured resonance frequency is compared comprises a value initially memorized, which is learned by the system.

7. A system according to claim 1, wherein the return signal is frequency modulated.

8. A system according to claim 1, wherein the operation makes use of transmitted and received signals of logical “

all or nothing”

type, and of “

on/off”

amplitude modulation.

9. A system according to claim 8, wherein said identification device includes an oscillator having an output that is connected to a transmitting circuit and having an input that is connected to a switch able to connect the output of a radio frequency receiver directly to the input of said oscillator, in order to establish the loopback, whereas in normal operation the input of said oscillator is connected to an output of an operational amplifier having a non-inverter input that is connected to ground via a resistor and having an inverter input that is connected to ground via a capacitor, each of said two inputs being connected via a resistor to the output of said radio frequency receiver.

10. A system according to claim 9, wherein said identifier includes an envelope detector circuit having an input that is connected to a low frequency receiving circuit and having an output that is connected to a data decoding circuit and an identifier management unit and also to a switch able to connect an output of said envelope detector circuit directly to an input of a radio frequency transmitter, in order to establish the loopback, whereas in normal operation the input of the radio frequency transmitter is connected to said identifier management unit.

11. A system according to claim 10, wherein of said transmission-reception loop has a transit time, associated with the time constant RC, where R and C are the respective values of said resistor and said capacitor both connected to the inverter input of said operational amplifier, that results in an oscillation at a specific frequency.