EP1152108B1 - Hand-free access system for a motor vehicle - Google Patents

Hand-free access system for a motor vehicle Download PDF

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Publication number
EP1152108B1
EP1152108B1 EP20010401095 EP01401095A EP1152108B1 EP 1152108 B1 EP1152108 B1 EP 1152108B1 EP 20010401095 EP20010401095 EP 20010401095 EP 01401095 A EP01401095 A EP 01401095A EP 1152108 B1 EP1152108 B1 EP 1152108B1
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EP
European Patent Office
Prior art keywords
signal
identification device
piracy
bit
vehicle
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP20010401095
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German (de)
French (fr)
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EP1152108A2 (en
EP1152108A3 (en
Inventor
Guy Lelandais
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Delphi Technologies Inc
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Delphi Technologies Inc
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Publication date
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Publication of EP1152108A2 publication Critical patent/EP1152108A2/en
Publication of EP1152108A3 publication Critical patent/EP1152108A3/en
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Publication of EP1152108B1 publication Critical patent/EP1152108B1/en
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    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00Individual registration on entry or exit
    • G07C9/00174Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C9/00309Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated with bidirectional data transmission between data carrier and locks
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00Individual registration on entry or exit
    • G07C9/00174Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C9/00309Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated with bidirectional data transmission between data carrier and locks
    • G07C2009/00555Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated with bidirectional data transmission between data carrier and locks comprising means to detect or avoid relay attacks
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00Individual registration on entry or exit
    • G07C9/00174Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C2009/00753Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys
    • G07C2009/00769Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys with data transmission performed by wireless means
    • G07C2009/00793Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys with data transmission performed by wireless means by Hertzian waves
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C2209/00Indexing scheme relating to groups G07C9/00 - G07C9/38
    • G07C2209/06Involving synchronization or resynchronization between transmitter and receiver; reordering of codes
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C2209/00Indexing scheme relating to groups G07C9/00 - G07C9/38
    • G07C2209/60Indexing scheme relating to groups G07C9/00174 - G07C9/00944
    • G07C2209/63Comprising locating means for detecting the position of the data carrier, i.e. within the vehicle or within a certain distance from the vehicle

Definitions

  • the present invention relates to an access system said hands free for a motor vehicle, ie a system of wireless communication to enter the vehicle without key.
  • This system can also be applied to hands-free startup of the vehicle, ie when starting without a key.
  • Such a system generally comprises a device identification to be worn by a user and able to establish bidirectional remote and wireless communication with a unit central control unit on the vehicle, to authenticate the user and control means of condemnation / unlocking door locks when the user has been recognized authentic.
  • Initialization of the communication protocol can be activated by operating the outside door handle, for hands-free access, or by pressing a start button, in the hands-free start mode.
  • the system is capable of establishing bidirectional communication when the identification device is located at a distance less than a predetermined distance from the vehicle, usually of the order of a few meters, to avoid, on the one hand, interference with other sources of the environment and, on the other hand, to avoid the system at such a distance that the user is too far from the vehicle to be aware of the operations performed by the said system.
  • Some currently proposed systems use magnetic induction at very short range, both to supply energy and transport information from the central unit of the vehicle to the identification device that is in the field electromagnetic generated by the antennas of the vehicle.
  • a Such a system allows communication only at a very short distance from the vehicle of the order of a few cm.
  • Another common system proposed is to use low-frequency carrier waves, the order of 125 kHz for communication from the vehicle to the identification device, and ultra-high carrier waves frequency, for example of the order of 434 or 868 MHz, for the zone Europe, and 315 or 902 MHz for the USA zone.
  • the identification device must include a battery to power its own electronic circuits. To minimize consumption electric device, it can be provided, for example, that the device identification is dormant for 9 ms and waking for 1 ms, while periods of 10 ms.
  • FIG. 1 of the accompanying drawings there is shown a example of encryption system already known.
  • a vehicle V which comprises in its central unit a memory 1 containing a secret key K and a number generator random 2, the random numbers R generated having, for example, a length of 56 bits.
  • This random number R is sent to the identification device I, as indicated by the arrow 3.
  • this same random number R is mixed with the key secret K according to a complex associative function f, in a mixer 4 which is connected to its input to the memory 1 and to the generator random numbers 2.
  • the mixer 4 delivers, as output, a signal representative of the mixture of the secret key K and the random number R, namely the signal f (R, K).
  • This signal is stored in a memory 5 connected to the output of the mixer 4.
  • This signal is sent to the device identification number I, in the form of a signal of a length example of 28 bits, as indicated by the arrow 6.
  • the signal f (R, K) is mixed again with the secret key K in a mixer 7, which is connected to its input to memories 1 and 5 above.
  • This mixer 7 mixes the two signals according to a function associative complex g.
  • the vehicle V then memorizes in a 8 connected to the output of the mixer 7 the signal representative of the mixture, namely the signal g (R, f, K).
  • the same secret key K is stored in a memory 11 and a mixer 14 having the same associative function f receives as input the secret key provided by the memory 11 of the identification device I and the random number R received by the identification device from the vehicle.
  • the identification device I stores the output signal of the mixer 14 in a memory 15 and compares this signal in a comparator 16 with the signal received according to arrow 6 from vehicle V. If the two signals are not identical, subject to the time of hardware and signal delay in the authorized transmission, the identification device interrupts the communication as being unauthorized. On the other hand, if both signals match, the signal is mixed in a mixer 17 with the secret key provided by the device memory 11 identification I, according to the same associative function g mentioned above.
  • the output signal of the mixer 17 is stored in a memory 18 of the identification device to be then sent to the vehicle following the arrow 9 in the form of a signal having a length per example of 20 bits.
  • the signal received by arrow 9 is compared with the signal received from the memory 8 of the vehicle in a comparator 10. If both signals match, subject to delays due to hardware response time and signal transmission in the authorized zone, the rest of the communication is authorized and the unit central office of the vehicle may, if necessary, order the condemnation or unlocking of locks vehicle.
  • another encryption protocol can be used to secure the transmission of data.
  • This signal 21 sent by the vehicle is received by a coil 22 of the relay housing 20, which is connected to a receiver 23 at 125 kHz.
  • This receiver 23 is connected to a transmitter at broadband at high frequency, of the order of several MHz.
  • the transmitter 24 transmits via its antenna 25, as represented by the arrow 26, to a second relay housing 30, which is worn by another hacker who closely follows the user U.
  • the exchange of information between the two relay housings 20 and 30 being performed at very high frequency, it It is possible to perform this communication over a long distance.
  • the second relay housing 30 includes an antenna 31 to receive the signal 26 emitted by the relay housing 20.
  • the antenna 31 is connected to a broadband receiver at the same frequency as the transmitter 24 of the first relay box 20.
  • the signal thus received is retransmitted at low frequency at 125 kHz by a transmitter 33 which is connected to a coil transmission 34 to send a signal 35 to the device identification I which complies with the signal 21 emitted by the vehicle.
  • the signal 35 being the repetition of the authentic signal of the vehicle, the identification device I will recognize it and emit in turn its response signal 36, said response signal 36 being sent high frequency and received by an antenna 37 of the second relay housing 30, by example at 434 MHz.
  • the antenna 37 is connected to a receiver 38, which will convert the 434 MHz signal into a signal at a different frequency, for example at 315 MHz.
  • the signal is then emitted by a transmitter at broadband 39 via an antenna 40 to the first relay housing 20, this difference of frequency being necessary so that the different signals do not interfere with each other.
  • the frequency of signal 41 sent back by the second relay housing 30 is different both the frequency of the signal 26 and the signal 36.
  • This signal 41 is taken by an antenna 27 of the first relay housing 20, said antenna 27 being connected to a broadband receiver 28 of the same frequency as the transmitter 39.
  • the receiver 28 is connected to a transmitter 29 which transforms the 315 MHz signal into a 434 MHz signal that is sent via the antenna 42 of the first relay housing 20 to the vehicle V, as represented by the zig-zag arrow 43.
  • the total communication can be in the order of 20 to 40 ms, and the duration total operation of the system to trigger the unlocking or condemning electric locks can be of the order of 100 ms.
  • a solution could be to measure the propagation time of UHF radio waves, comparing this measured time with a time predetermined amount corresponding to a communication in a zone limited allowed around the vehicle.
  • a fast communication rate for example of the order of 20 to 40 Mb / s.
  • a bandwidth With such a rate of communication, It is necessary to operate at very high frequency, for example at 2.4 GHz. But to measure very short times, it is necessary to have a bandwidth very important, which comes up against the applicable regulations that severely restrict bandwidth allowed to avoid saturation of the environment by electromagnetic.
  • EP-A-0 992 408 discloses a system according to preamble of claim 1.
  • the object of the invention is to eliminate the aforementioned drawbacks and to propose a system of access said hands-free for motor vehicle, to detect hacking of the system, in particular by intermediates relay boxes, taking into account the time of signal propagation between the vehicle and the identification device.
  • the invention relates to an access system said hands free for motor vehicle, according to claim 1.
  • said predetermined threshold value is given by a window of time that corresponds to the total duration theoretical transmission of the anti-piracy bitstream, when the identification device is at a distance less than or equal to the predetermined limit distance.
  • This window of time is a constant precise generated for example by a quartz controlled oscillator associated with a counter under control of the microcontroller which indicates the number of periods to count.
  • the central control unit is suitable to determine said hacking attempt when the total number of bits the anti-piracy train was not issued or received by the Central Unit of command in said window.
  • the central unit may comprise in memory a double-entry correspondence table, namely the number of transmitted bits and the corresponding actual transmission duration, for output the actual distance between the identification device and the central unit, the data of said table being previously acquired by experimentation and which can be periodically updated, when the user wearing the identification device is sitting on the driver's seat of the vehicle, the distance from the identification device to the central unit of the vehicle then being substantially constant.
  • a double-entry correspondence table namely the number of transmitted bits and the corresponding actual transmission duration
  • the count of the number of bits sent is stopped when the central unit detects the reception of the last bit of the train anti-piracy.
  • the identification device comprises a line to analog delay to re-transmit the signal received from the vehicle to the vehicle with a predetermined delay time.
  • the central control unit has an oscillator generating radio carrier waves frequency, connected to a phase modulator, which is controlled by the anti-piracy bitstream generated by the central unit of the vehicle.
  • the anti-piracy bit stream is generated by the CPU after the transmission of data encrypted authentication to the identification device.
  • the identification device may comprise a phase inverter to selectively invert the phase of the signal representative of the bits anti-piracy received by the identification device from the vehicle, said inverter being controlled, for each bit of anti-piracy, by an encrypted digital authentication response signal identification device, at a slower rate than that of the anti-piracy bitstream.
  • the central unit of the vehicle comprises a phase demodulator to demodulate the signal received by the vehicle from the identification device, a logic gate Exclusive OR whose entries are respectively linked to audit phase demodulator and a digital signal retarder, said self-timer being able to delay a useful bit every bit of the train anti-piracy generated by the central unit, said logic gate being capable of outputting a digital signal representative of the signal encrypted response of the identification device.
  • the signal delivered in output of the aforementioned exclusive OR logic gate is compared by the unit central to an encrypted digital signal of authentication generated by the central unit, in order to authenticate the identification device.
  • the output of said door OR logic is connected to an input of a second gate Exclusive OR logic whose other input receives a digital signal encrypted authentication generated by the central unit, in order to deliver output a signal representative of successive time offsets of each bit of the anti-piracy train, the latter being received at the input of an integrator to sum the related response times at each anti-piracy bit shift slot, the output of said integrator being connected to a comparator to compare said sum response time with a predetermined time-out value, beyond which an attempted hacking is detected.
  • the signal coming from the identification device is received by the Central Unit and transmitted to the input of an envelope detector for detecting the rising edge of said signal, the detection of this rising edge being able to trigger, a part, the incrementation of a unit of the number of bits counter and, on the other hand, the transmission of the next bit in the anti-piracy bit stream, after a predetermined duration which corresponds to a bit time useful possibly increased by extra time to avoid any interference between the transmission and the reception of the signal by the unit Central.
  • the central unit comprises a modulator says all or nothing to switch the CPU in the transmission or reception of signals to or from identification device, said all-or-nothing modulator being controlled by detecting the rising edge of the signal received in from the identification device.
  • the identification device comprises a receiver to receive low-speed wakefulness signals, this receiver comprising successively a static envelope detector low-threshold radio frequency and a low frequency amplifier.
  • the useful bit time can be between 50 and 200 ns.
  • the motor vehicle V comprises in its central unit a micro-controller 50, which is usually in a state of semi-sleep or waiting for an alarm clock.
  • a micro-controller 50 which is usually in a state of semi-sleep or waiting for an alarm clock.
  • an activation signal is sent to the micro-controller 50, as indicated by the arrow 51.
  • the micro-controller sends a general power signal, as represented by the arrow 52, to supply the different components electronic units of the central unit.
  • the microcontroller 50 generates a series of low speed signals sk, for example of the order of 2 to 100 Kb / s on line V5.
  • the data conveyed on line V5 are successively an awakening signal e, a signal representative of a number random R of a length for example of 56 bits, a signal representative of the function f (R, K) with a length of, for example, 28 bits, and a signal representative of service data s, for example from 100 to 5000 bits, for example data on the maintenance, vehicle tuning, etc. (see Figure 5).
  • Line V5 is connected to a transmitter 53 for transmitting via an antenna 54 the signals to the identification device I as represented by the arrow E.
  • the transmitter 53 comprises, as best seen in FIG. oscillator 55 to generate an ultra high carrier wave frequency, said oscillator being powered by line 52.
  • the oscillator 55 is connected to a phase modulator 56, which is in turn connected to a all-or-nothing modulator 57, the latter having an input connected to the line V5 and its output connected to the antenna 54 above.
  • the phase modulator is inactive.
  • the all-or-nothing modulator 57 is intended alternatively allow the transmission of a signal and the reception of a signal by the unit center of the vehicle, as explained later.
  • the amplitude of the transmitted signal is of the order of 2 V effective.
  • the emitted signal E is received by an antenna 100 of the device with an attenuation of the order of -40 dBm, which represents an attenuation coefficient of 100 times, ie the signal received by the identification device has an amplitude of the order of 20 mV.
  • the antenna 100 is connected to a radio frequency filter 101 (only shown in Figure 4) to eliminate the parasitic frequencies.
  • the output of the filter 101 is connected to a branch, on the one hand, to a low rate receiver and low consumption 102 and, on the other hand, to a delay line 103. Low-speed sk signals are not transmitted by the delay line 103, but essentially pass through the receiver 102. As best seen in FIG.
  • the receiver 102 comprises successively a radio frequency envelope detector 104 for reconstruct the low-speed signals on line I5, which correspond to those of line V5.
  • the detector output envelope 104 is connected to a low frequency amplifier 105, which the output is connected in parallel, on the one hand, to a sequence decoder 106 and on the other hand to a microcontroller 107 of the device identification I via a line 108.
  • the decoder 106 is powered by permanence by the battery of the identification device.
  • waking data are decoded by the decoder 106, in order to send a wakefulness command at the microcontroller 107, at the output of the decoder 106.
  • micro-controller 107 then wakes up all the other components electronic identification device. So the data following, namely the signals R, f and s, are transmitted directly to the micro-controller 107 via the parallel line 108.
  • the microcontroller 50 of vehicle V After transmission of the service data, the microcontroller 50 of vehicle V generates bits of anti-piracy h at slow rate sk of the microprocessor, said anti-piracy bits being received by a buffer with random binary sequence generator 58, for outputting the anti-piracy bits at a high rate fk, on a line V7.
  • the output of the buffer 58 is connected to a branching, on the one hand, with the phase modulator 56 for phase modulating the carrier wave generated by the oscillator 55, and on the other hand, with a digital timer of a useful bit time 59, whose function will be explained later. Every bit of anti-piracy is transmitted in the form of a radio frequency signal via the antenna 54 in direction of the identification device I.
  • the overall transmission frame V2 signals by the antenna 54 is illustrated in Figures 5 and 7.
  • the beginning is shown the interrogation frame of the anti-piracy bits h on the line V2.
  • each bit of anti-piracy is carried by a very high frequency oscillating wave having a bit time Tb for example between 50 and 200 ns.
  • the show anti-piracy bits h1, h2 ... hn is allowed by the modulator while or nothing 57, depending on a control signal V1 that is emitted by a time base management unit 60 of the vehicle V, which unit 60 is able to deliver the low clock rate signals sk, average cadence mk and high rate fk.
  • unit 60 is connected to the microcontroller 50, as indicated by the double arrow 61. The generation of the V1 signal will be explained later.
  • the identification device I receives via its antenna 100 on the line I1 (see FIG. 6) a signal corresponding to the anti-piracy bit h1 emitted by the vehicle V, with a delay time ⁇ which corresponds to the signal propagation time between the vehicle and the device Identification.
  • the signal then passes through the analog delay line 103, which may for example be constituted by a copper winding, which makes it possible to reduce the energy consumption by the device identification because this delay line does not need to be powered in energy.
  • FIG. 8 shows the signal I2v which corresponds to to the virtual signal at the output of the analog delay line 103, it is say to the envelope of said analog signal, said signal being delayed of a predetermined duration Dl.
  • the output of the delay line 103 is connected to the input of a phase inverter 109 to reverse the phase of the analog signal transmitted by the delay line 103, according to a encrypted authentication control signal g, whose frame is represented on line I6.
  • a encrypted authentication control signal g whose frame is represented on line I6.
  • the bit rate of the signal g is at medium rate mk, weaker than the high rate fk anti-piracy bits h.
  • the microcontroller 107 of the device of identification transmits at low speed sk the signal g to a memory buffer 110 which outputs the signal g at the average rate mk to the phase inverter 109.
  • the phase inverter 109 outputs an analog signal, whose virtual signal is represented in I7v which represents the envelope said signal.
  • the output of the phase inverter 109 is connected to a amplifier 111 having a gain of + 20 dB to emit the signal with an amplitude of the order of 200 mV.
  • This amplified signal is represented on the line I4 and corresponds to the transmission bit h1 with the delay ⁇ due to the propagation of the signal and to the analog delay Dl due to the delay line 103.
  • This signal 14 is reemitted by an antenna 112 to the vehicle V, as represented by the arrow RE.
  • this first bit of anti-piracy will trigger the generation of the encrypted signal authentication device g by the identification device in order to control the phase inverter 109.
  • the output of the amplifier 111 is also connected to a trigger line 113 which has in series a diode 114 and a trigger 115 for activate a basic time management unit 116 which delivers low rate clock signals sk and medium rate mk, said unit 116 being connected to the microcontroller 107, as indicated by the double arrow 117.
  • the duration of transmission of the signals is of the order of 3 ns per meter of distance between the vehicle and the identification device I.
  • the propagation time ⁇ would be the order of 30 ns.
  • the response time of the electronic circuits which could be of the order of a few ns or tens of ns, according to the bandwidth allocated to the carrier.
  • the signal reissued RE by the identification device is received by a receiver 62 via an antenna 63, with attenuation of the order of - 40 dBm, which represents an attenuation coefficient of 100 times, that is, the signal received by the vehicle has an amplitude of the order of 2 mV.
  • the receiver 62 has a radio frequency filter 64 connected to the antenna 63, whose output signal is represented by line V3, this signal being delivered to the input of a logarithmic amplifier 65 which has a gain of 80 dB, which makes it possible to reach a multiplication coefficient up to 10,000 times, and in particular to output this amplifier 65 a signal of the order of 2V effective.
  • the amplifier 65 is connected at the output to a junction between, on the one hand, a amplitude demodulator 66, which makes it possible to detect the envelope of the received signal, and on the other hand, a phase demodulator 67.
  • envelope detector 66 outputs a digital signal represented on line V4, said signal being delivered at the input of the unit of time base management 60 above.
  • the time base management unit 60 Upon receipt of the anti-piracy bit received in return, the time base management unit 60 triggers the emission of the anti-piracy bit following h2 with an offset corresponding to the useful bit time Tb + ⁇ , ⁇ corresponding to a weak delay in order to avoid any overlap between transmission and the reception of the signals by the vehicle.
  • the reception of the bit anti-piracy back by the vehicle triggers the clock stroke following at the rate fk as well as the tilting of the modulator all or nothing 57, via line V1.
  • the small delay ⁇ is close to 0 s.
  • Each new clock tick at the rate fk triggered by the receiving the previous anti-piracy bit causes the incrementation of a unit in a counter 68, which counter 68 counts the number of bits received as a function of time.
  • the receiving a bit triggers the emission of a next anti-piracy bit
  • the unit 60 sends a signal Fr to stop counting of anti-piracy bits and to cause the counter 68 to send a representative signal the number of bits counted at the microcontroller 50, as indicated by the arrow 69.
  • micro-controller 50 can calculate the actual distance between the vehicle V and the identification device I, according to a table of previously memorized correspondence. If this distance exceeds authorized distance, the call is interrupted as the result of a hacking attempt or simply as being communication at too great distance from the vehicle.
  • This counter thus makes it possible to detect piracy using relay boxes between the vehicle and the identification device.
  • an attacker could try to trap this system by anticipating on the signal to be transmitted by the identification device.
  • the pirate detects with a relay box the emission by the vehicle of a bit of anti-piracy, it can cause the emission anticipation of a signal-heel, in the preamble to the reissue of the signal delayed by the delay line of the identification device.
  • this signal-heel would have a duration that would correspond to the signal propagation time over the extra distance between the identification device and the vehicle, in relation to the distance maximum allowed.
  • the envelope detector 66 of the vehicle V detect, in the first place, the reception of this signal-heel, causing in turn the anticipated emission of the second bit of anti-piracy.
  • the system according to the invention also makes it possible, thanks counter 68, to determine whether the total number of anti-piracy bits has have been received during a maximum reception window Fm, shown in Figure 5.
  • the timing diagrams of Figures 5 to 9 correspond to a non-pirated transmission of the signal.
  • the real end Fr of the reception of the anti-piracy bitstream is, in these figures, well located in the maximum reception window Fm, as represented in FIG. 5.
  • n the duration of 2d propagation which is a direct function of the distance between the device identification and the vehicle. So, if it is difficult to detect with electronic circuits at low cost durations of the order of a few tens of ns, it is much easier to detect durations of the order of n x a few tens of ns, ie durations of the order of ms. However, if the hacker anticipates on the retransmission of the signal by the identification device, the variable 2n ⁇ will remain within the acceptable limit and so the system will not be able to detect piracy.
  • the phase demodulator 67 delivers a signal representative of the goh function on line V9 which is connected to an entrance of a door logical OR exclusive 70.
  • This logic gate 70 receives on its other input a signal V8 representative of the function h, delivered at the output of digital retarder 59.
  • the logic gate 70 could be replaced by another type of mixer, as shown in FIG. signal V8 corresponds to the signal V7 with a delay corresponding to Dl offset of the analog timer 103 of the identification device I.
  • the logic gate 70 outputs a signal V10, which is representative of the offset between the signals V8 and V9, ie a signal representative of the encrypted authentication signal g transmitted by the identification device I, with a small offset corresponding to the signal propagation time which is equal to 2 ⁇ , as visible on the figure 8.
  • the output of logic gate 70 is connected to a branch between, on the one hand, a low-pass filter 71 at the average rate mk which is the cadence corresponding to the signal g and, on the other hand, another Exclusive OR logic gate 73.
  • the low-pass filter 71 is connected to a buffer 72, which transforms said signal from the rate mk to the cadence sk before sending it to the micro-controller 50 that will compare the signal g received from the authentication device with the signal g generated at the level of the vehicle, for the purpose of communication, which corresponds to the last step 10 illustrated in the diagram of Figure 1.
  • the microcontroller 50 delivers the signal g specific to the vehicle to a buffer 74 at the rate sk, so that it returns to the rate mk at the other input of the aforementioned logic gate 73.
  • the logic gate 73 mixes the signals V10 and V11 in order to output only the offsets due the propagation time of the signal between the vehicle V and the device I, as shown on line V12.
  • the exit of the logic gate 73 is connected to the input of an integrator 75, which will to output a signal V13 which will climb up stairs according to of time, for each slot C representative of the time of signal propagation.
  • Line V13 is connected to the entrance of a unit 76 receiving on another input a threshold limit value 77 which corresponds to a maximum acceptable total propagation delay n ⁇ 2 ⁇ ⁇ T max, with ⁇ corresponding to the propagation time on a allowed distance.
  • a threshold limit value 77 which corresponds to a maximum acceptable total propagation delay n ⁇ 2 ⁇ ⁇ T max, with ⁇ corresponding to the propagation time on a allowed distance.
  • the integrator 75 can detect an attempted hacking, even in case the hacker adds an anticipation stub to the signal reissued by the identification device. Indeed, if this signal-heel can trap the counter 68, however the logic gate 73 will interpret this signal-heel as a wrong signal at least with a chance on two, and therefore will output a slot equivalent to this signal-heel, which slot will be added by the integrator 75 of the same only for delay due to propagation delay.
  • microcontroller 50 can deliver different signals of output to the other components of the vehicle by the track 80 shown on Figures 3 and 4.
  • the intermediate clock rate mk is between 20 and 60 times less than the rate fk.
  • the antennas 54 and 63 of the V vehicle by a single antenna 82 shown in broken lines in FIG. 4, which antenna 82 would be connected to a diplexer 81 shown in broken lines in FIG. 4, in order to switch between the reception mode and the transmission mode as appropriate.
  • a diplexer 81 shown in broken lines in FIG. 4
  • the diplexers 81 and 120 could thus communicate with each other, as indicated by the double arrow T.
  • the central unit is connected to at least two, for example three, transmit / receive antennas such as the single antenna 82, arranged in several points of the vehicle V. Distance measurements are then performed sequentially between the identification device I and each of the transmitting / receiving antennas of the vehicle V. These measurements of distance are achieved via the propagation time ⁇ anti-piracy bits using the correspondence table above. In this variant, it is possible to locate precisely, for example a few centimeters or tens of centimeters, the position of the identification device I by a calculation of triangulation carried out by the central unit.
  • This variant can obviously also be carried out with transmitting and receiving antennas separated.
  • the delay line 103 of the device identification I allows to postpone the retransmission of each anti-piracy bit compared to receiving it in order to use the same frequency radio for the transmission of corresponding signals in the direction from the vehicle V to the identification device I (arrow E or T) and in the direction from the identification device I to the vehicle V (arrow RE or T).
  • the vehicle V receives from the device identification a signal hos where s represents service data which modulate the signal h by phase inversion, like this was the case for the signal g whose length is less than that of signal h.
  • the sequence of anti-piracy bits h being a binary sequence random or pseudo-random, it entails a spread of the spectrum of radiofrequency signals used to transmit the vehicle to the identification device and vice versa. This spread spectrum is all the more important as the modulation rate fk used for transmit the sequence of anti-piracy bits h is high.
  • Such Spread spectrum is known to be advantageous from the point of view of robustness of signal against interference and echoes multiple, which facilitates multiple transmissions of the signal, example the round trip signal between the vehicle and the device Identification.
  • the demodulation of the encrypted signal of authentication g at the level of the central unit of the vehicle is made all the more difficult as the spectrum of the signal RE is spread out.
  • the arrangement of the delay line 103 to re-transmit the bits anti-hacking successive h delayed a useful bit time as a high rate modulation fk of the encrypted authentication signal g, itself being transmitted at the average rate mk, ensures the corresponding demodulation key, that is, the same random sequence of anti-piracy bits h, is always available at level of the central control unit when receiving the signal RE, which makes it possible to demodulate the received signal RE regardless of the degree of spread of the spectrum of this signal.
  • the robustness of the access system with respect to echoes multiples is ensured by the fact that the identification device I always responds to the first received signal, which can only be the signal transmitted directly.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
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  • Selective Calling Equipment (AREA)
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Description

La présente invention concerne un système d'accès dit mains libres pour véhicule automobile, c'est à dire un système de communication non filaire permettant d'entrer dans le véhicule sans clé. Ce système peut également s'appliquer au démarrage mains libres du véhicule, c'est à dire au démarrage sans clé.The present invention relates to an access system said hands free for a motor vehicle, ie a system of wireless communication to enter the vehicle without key. This system can also be applied to hands-free startup of the vehicle, ie when starting without a key.

Un tel système comporte généralement un dispositif d'identification destiné à être porté par un utilisateur et apte à établir une communication bidirectionnelle à distance et sans fil avec une unité centrale de commande embarquée sur le véhicule, pour authentifier l'utilisateur et commander des moyens de condamnation/décondamnation des serrures des ouvrants lorsque l'utilisateur a été reconnu authentique. L'initialisation du protocole de communication peut être activée en actionnant la poignée extérieure de porte, pour l'accès mains libres, ou en appuyant sur un bouton de démarrage, dans le mode démarrage mains libres. Le système est apte à établir ladite communication bidirectionnelle lorsque le dispositif d'identification est situé à une distance inférieure à une distance limite prédéterminée du véhicule, généralement de l'ordre de quelques mètres, pour éviter, d'une part, les interférences avec d'autres sources de signaux de l'environnement, et, d'autre part, pour éviter le fonctionnement du système à une distance telle que l'utilisateur est trop éloigné du véhicule pour être conscient des opérations effectuées par ledit système.Such a system generally comprises a device identification to be worn by a user and able to establish bidirectional remote and wireless communication with a unit central control unit on the vehicle, to authenticate the user and control means of condemnation / unlocking door locks when the user has been recognized authentic. Initialization of the communication protocol can be activated by operating the outside door handle, for hands-free access, or by pressing a start button, in the hands-free start mode. The system is capable of establishing bidirectional communication when the identification device is located at a distance less than a predetermined distance from the vehicle, usually of the order of a few meters, to avoid, on the one hand, interference with other sources of the environment and, on the other hand, to avoid the system at such a distance that the user is too far from the vehicle to be aware of the operations performed by the said system.

Certains systèmes actuellement proposés utilisent des systèmes à induction magnétique à très courte portée, pour à la fois alimenter en énergie et transporter les informations depuis l'unité centrale du véhicule vers le dispositif d'identification qui se trouve dans le champ électromagnétique engendré par les antennes du véhicule. Toutefois, un tel système ne permet une communication qu'à très courte distance du véhicule de l'ordre de quelques cm. Un autre système couramment proposé consiste à utiliser des ondes porteuses à basse fréquence, de l'ordre de 125 kHz pour la communication depuis le véhicule vers le dispositif d'identification, et des ondes porteuses à ultra haute fréquence, par exemple de l'ordre de 434 ou 868 MHz, pour la zone Europe, et de 315 ou 902 MHz pour la zone USA. Toutefois, dans ce cas, le dispositif d'identification doit comporter une pile pour alimenter ses circuits électroniques propres. Pour minimiser la consommation électrique, on peut prévoir, à titre d'exemple, que le dispositif d'identification soit en sommeil pendant 9 ms et en éveil 1 ms, pendant des périodes de 10 ms.Some currently proposed systems use magnetic induction at very short range, both to supply energy and transport information from the central unit of the vehicle to the identification device that is in the field electromagnetic generated by the antennas of the vehicle. However, a Such a system allows communication only at a very short distance from the vehicle of the order of a few cm. Another common system proposed is to use low-frequency carrier waves, the order of 125 kHz for communication from the vehicle to the identification device, and ultra-high carrier waves frequency, for example of the order of 434 or 868 MHz, for the zone Europe, and 315 or 902 MHz for the USA zone. However, in this In this case, the identification device must include a battery to power its own electronic circuits. To minimize consumption electric device, it can be provided, for example, that the device identification is dormant for 9 ms and waking for 1 ms, while periods of 10 ms.

Bien entendu, la communication bidirectionnelle entre le véhicule et le dispositif d'identification est cryptée, afin d'éviter tout fonctionnement intempestif du système et pour le sécuriser vis à vis des malfaiteurs. Sur la figure 1 des dessins annexés, on a représenté un exemple de système d'encryptage déjà connu. Sur cette figure 1, on a représenté un véhicule V qui comporte dans son unité centrale une mémoire 1 contenant une clé secrète K et un générateur de nombres aléatoires 2, les nombres aléatoires R engendrés ayant, par exemple, une longueur de 56 bits. Ce nombre aléatoire R est émis vers le dispositif d'identification I, comme indiqué par la flèche 3. Simultanément, ce même nombre aléatoire R est mélangé avec la clé secrète K suivant une fonction associative complexe f, dans un mélangeur 4 qui est relié à son entrée à la mémoire 1 et au générateur de nombres aléatoires 2. Le mélangeur 4 délivre, en sortie, un signal représentatif du mélange de la clé secrète K et du nombre aléatoire R, à savoir le signal f(R, K). Ce signal est mémorisé dans une mémoire 5 reliée à la sortie du mélangeur 4. Ce signal est envoyé au dispositif d'identification I, sous la forme d'un signal d'une longueur par exemple de 28 bits, comme indiqué par la flèche 6. Dans le véhicule V, le signal f(R, K) est mélangé à nouveau à la clé secrète K dans un mélangeur 7, qui est relié à son entrée aux mémoires 1 et 5 précitées. Ce mélangeur 7 mélange les deux signaux suivant une fonction associative complexe g. Le véhicule V mémorise alors dans une mémoire 8 reliée à la sortie du mélangeur 7 le signal représentatif du mélange, à savoir le signal g(R, f, K).Of course, two-way communication between the vehicle and the identification device is encrypted, in order to avoid any inadvertent operation of the system and to secure it against malefactors. In Figure 1 of the accompanying drawings, there is shown a example of encryption system already known. In this figure 1, we have represented a vehicle V which comprises in its central unit a memory 1 containing a secret key K and a number generator random 2, the random numbers R generated having, for example, a length of 56 bits. This random number R is sent to the identification device I, as indicated by the arrow 3. Simultaneously, this same random number R is mixed with the key secret K according to a complex associative function f, in a mixer 4 which is connected to its input to the memory 1 and to the generator random numbers 2. The mixer 4 delivers, as output, a signal representative of the mixture of the secret key K and the random number R, namely the signal f (R, K). This signal is stored in a memory 5 connected to the output of the mixer 4. This signal is sent to the device identification number I, in the form of a signal of a length example of 28 bits, as indicated by the arrow 6. In the vehicle V, the signal f (R, K) is mixed again with the secret key K in a mixer 7, which is connected to its input to memories 1 and 5 above. This mixer 7 mixes the two signals according to a function associative complex g. The vehicle V then memorizes in a 8 connected to the output of the mixer 7 the signal representative of the mixture, namely the signal g (R, f, K).

Du côté du dispositif d'identification, la même clé secrète K est mémorisée dans une mémoire 11 et un mélangeur 14 ayant la même fonction associative f reçoit en entrée la clé secrète fournie par la mémoire 11 du dispositif d'identification I et le nombre aléatoire R reçu par le dispositif d'identification en provenance du véhicule. Le dispositif d'identification I mémorise le signal en sortie du mélangeur 14 dans une mémoire 15 et compare ce signal dans un comparateur 16 avec le signal reçu suivant la flèche 6 en provenance du véhicule V. Si les deux signaux ne sont pas identiques, sous réserve du temps de retard propre au matériel et à la transmission du signal dans la zone de transmission autorisée, le dispositif d'identification interrompt la communication comme étant non-autorisée. En revanche, si les deux signaux correspondent, le signal est mélangé dans un mélangeur 17 avec la clé secrète fournie par la mémoire 11 du dispositif d'identification I, suivant la même fonction associative g précitée. Le signal de sortie du mélangeur 17 est mémorisé dans une mémoire 18 du dispositif d'identification pour être ensuite envoyé vers le véhicule suivant la flèche 9 sous la forme d'un signal ayant une longueur par exemple de 20 bits. Enfin, le signal reçu par la flèche 9 est comparé avec le signal reçu de la mémoire 8 du véhicule dans un comparateur 10. Si ces deux signaux correspondent, sous réserve des retards dus au temps de réponse du matériel et de la transmission du signal dans la zone autorisée, le reste de la communication est autorisé et l'unité centrale du véhicule pourra, le cas échéant, commander la condamnation ou la décondamnation des serrures des ouvrants du véhicule. Bien entendu, un autre protocole de cryptage pourra être utilisé pour sécuriser la transmission des données.On the identification device side, the same secret key K is stored in a memory 11 and a mixer 14 having the same associative function f receives as input the secret key provided by the memory 11 of the identification device I and the random number R received by the identification device from the vehicle. The identification device I stores the output signal of the mixer 14 in a memory 15 and compares this signal in a comparator 16 with the signal received according to arrow 6 from vehicle V. If the two signals are not identical, subject to the time of hardware and signal delay in the authorized transmission, the identification device interrupts the communication as being unauthorized. On the other hand, if both signals match, the signal is mixed in a mixer 17 with the secret key provided by the device memory 11 identification I, according to the same associative function g mentioned above. The output signal of the mixer 17 is stored in a memory 18 of the identification device to be then sent to the vehicle following the arrow 9 in the form of a signal having a length per example of 20 bits. Finally, the signal received by arrow 9 is compared with the signal received from the memory 8 of the vehicle in a comparator 10. If both signals match, subject to delays due to hardware response time and signal transmission in the authorized zone, the rest of the communication is authorized and the unit central office of the vehicle may, if necessary, order the condemnation or unlocking of locks vehicle. Of course, another encryption protocol can be used to secure the transmission of data.

Toutefois, malgré ce protocole de cryptage, il existe une façon de pirater le système, sans connaítre ni la clé secrète, ni les différentes fonctions associatives du protocole d'encryptage. Ce procédé de piratage est représenté sur la figure 2. Selon ce procédé, on suppose que l'utilisateur U qui porte le dispositif d'identification I est situé à une distance du véhicule V supérieure à la distance autorisée de communication, par exemple de 10 à 100 m de distance du véhicule. Dans ce cas, un pirate équipé d'un premier boítier relais 20 peut s'approcher du véhicule V à une distance suffisante pour communiquer avec celui-ci, par exemple à une distance de l'ordre de 1 à 5 m. Ce pirate actionne le début de la communication, par exemple en tirant sur la poignée extérieure de portière. Ceci déclenche l'émission des signaux basse fréquence par le véhicule vers le boítier relais 20, comme indiqué par la flèche en zig-zag 21. Ce signal 21 envoyé par le véhicule est reçu par une bobine 22 du boítier relais 20, qui est reliée à un récepteur 23 à 125 kHz. Ce récepteur 23 est relié à un émetteur à large bande à haute fréquence, de l'ordre de plusieurs MHz. L'émetteur 24 émet via son antenne 25, comme représenté par la flèche 26, vers un deuxième boítier relais 30, qui est porté par un autre pirate qui suit de près l'utilisateur U. L'échange d'informations entre les deux boítiers relais 20 et 30 s'effectuant à très haute fréquence, il est possible d'effectuer cette communication à grande distance. Le deuxième boítier relais 30 comporte une antenne 31 pour recevoir le signal 26 émis par le boítier relais 20. L'antenne 31 est reliée à un récepteur large bande à la même fréquence que l'émetteur 24 du premier boítier relais 20. Le signal ainsi reçu est retransmis à basse fréquence à 125 kHz par un émetteur 33 qui est relié à une bobine d'émission 34 afin d'envoyer un signal 35 vers le dispositif d'identification I qui soit conforme au signal 21 émis par le véhicule. Le signal 35 étant la répétition du signal authentique du véhicule, le dispositif d'identification I va le reconnaítre et émettre à son tour son signal de réponse 36, ledit signal de réponse 36 étant envoyé à haute fréquence et reçu par une antenne 37 du deuxième boítier relais 30, par exemple à 434 MHz. L'antenne 37 est reliée à un récepteur 38, qui va convertir le signal à 434 MHz en un signal à une fréquence différente, par exemple à 315 MHz. Le signal est alors émis par un émetteur à large bande 39 via une antenne 40 vers le premier boítier relais 20, cette différence de fréquence étant nécessaire pour que les différents signaux n'interfèrent pas entre eux. Bien entendu, la fréquence du signal 41 émis en retour par le deuxième boítier relais 30 est différente à la fois de la fréquence du signal 26 et du signal 36. Ce signal 41 est capté par une antenne 27 du premier boítier relais 20, ladite antenne 27 étant reliée à un récepteur large bande 28 de la même fréquence que l'émetteur 39. Le récepteur 28 est relié à un émetteur 29 qui transforme le signal à 315 MHz en un signal à 434 MHz qui est envoyé via l'antenne 42 du premier boítier relais 20 vers le véhicule V, comme représenté par la flèche en zig-zag 43.However, despite this encryption protocol, there is a way to hack the system, without knowing either the secret key or the different associative functions of the encryption protocol. This method of Piracy is shown in Figure 2. According to this method, it is assumed that the user U who carries the identification device I is located at a distance of the vehicle V greater than the authorized distance of communication, for example from 10 to 100 m distance from the vehicle. In this case, a pirate equipped with a first relay box 20 can approach vehicle V at a sufficient distance to communicate with it, for example at a distance of the order of 1 to 5 m. This hacker activates the beginning of the communication, for example by the outside door handle. This triggers the emission of low frequency signals from the vehicle to the relay housing 20, as indicated by the arrow in zig-zag 21. This signal 21 sent by the vehicle is received by a coil 22 of the relay housing 20, which is connected to a receiver 23 at 125 kHz. This receiver 23 is connected to a transmitter at broadband at high frequency, of the order of several MHz. The transmitter 24 transmits via its antenna 25, as represented by the arrow 26, to a second relay housing 30, which is worn by another hacker who closely follows the user U. The exchange of information between the two relay housings 20 and 30 being performed at very high frequency, it It is possible to perform this communication over a long distance. The second relay housing 30 includes an antenna 31 to receive the signal 26 emitted by the relay housing 20. The antenna 31 is connected to a broadband receiver at the same frequency as the transmitter 24 of the first relay box 20. The signal thus received is retransmitted at low frequency at 125 kHz by a transmitter 33 which is connected to a coil transmission 34 to send a signal 35 to the device identification I which complies with the signal 21 emitted by the vehicle. The signal 35 being the repetition of the authentic signal of the vehicle, the identification device I will recognize it and emit in turn its response signal 36, said response signal 36 being sent high frequency and received by an antenna 37 of the second relay housing 30, by example at 434 MHz. The antenna 37 is connected to a receiver 38, which will convert the 434 MHz signal into a signal at a different frequency, for example at 315 MHz. The signal is then emitted by a transmitter at broadband 39 via an antenna 40 to the first relay housing 20, this difference of frequency being necessary so that the different signals do not interfere with each other. Of course, the frequency of signal 41 sent back by the second relay housing 30 is different both the frequency of the signal 26 and the signal 36. This signal 41 is taken by an antenna 27 of the first relay housing 20, said antenna 27 being connected to a broadband receiver 28 of the same frequency as the transmitter 39. The receiver 28 is connected to a transmitter 29 which transforms the 315 MHz signal into a 434 MHz signal that is sent via the antenna 42 of the first relay housing 20 to the vehicle V, as represented by the zig-zag arrow 43.

Il suffit que les pirates utilisent des boítiers relais ayant des liaisons à large bande, par exemple supérieure à 50 MHz, ce qui est possible car les systèmes pirates n'ont pas à respecter les réglementations ; le temps de transit supplémentaire dû à la distance peut être alors de l'ordre de quelques nanosecondes, ce qui est négligeable en comparaison avec les constantes de temps nécessaires pour la transmission normale autorisée. A titre d'exemple, la communication totale peut être de l'ordre de 20 à 40 ms, et la durée totale du fonctionnement du système pour déclencher la décondamnation ou la condamnation des serrures électriques peut être de l'ordre de 100 ms.It is sufficient for hackers to use relay boxes with broadband links, for example greater than 50 MHz, which is possible because pirated systems do not have to respect the regulations; additional transit time due to distance can then be of the order of a few nanoseconds, which is negligible in comparison with the necessary time constants for normal authorized transmission. For example, the total communication can be in the order of 20 to 40 ms, and the duration total operation of the system to trigger the unlocking or condemning electric locks can be of the order of 100 ms.

Pour détecter un tel piratage et interrompre la communication, une solution pourrait consister à mesurer le temps de propagation des ondes radio UHF, en comparant ce temps mesuré avec un temps prédéterminé correspondant à une communication dans une zone limitée autorisée autour du véhicule. Toutefois, pour détecter le temps de retard dû à la distance, par rapport à un temps de communication global, il est nécessaire de disposer de large bande passante, ce qui correspond à une cadence de communication rapide, par exemple de l'ordre de 20 à 40 Mb/s. Avec une telle cadence de communication, il est nécessaire d'opérer à très haute fréquence, par exemple à 2,4 GHz. Mais pour mesurer des temps très courts, il est nécessaire d'avoir une bande passante très importante, ce qui vient se heurter aux réglementations applicables qui limitent fortement les bandes passantes autorisées, pour éviter une saturation de l'environnement par des ondes électromagnétiques.To detect such hacking and interrupt the communication, a solution could be to measure the propagation time of UHF radio waves, comparing this measured time with a time predetermined amount corresponding to a communication in a zone limited allowed around the vehicle. However, to detect the time delay due to distance, compared to a communication time overall, it is necessary to have a high bandwidth, which corresponds to a fast communication rate, for example of the order of 20 to 40 Mb / s. With such a rate of communication, It is necessary to operate at very high frequency, for example at 2.4 GHz. But to measure very short times, it is necessary to have a bandwidth very important, which comes up against the applicable regulations that severely restrict bandwidth allowed to avoid saturation of the environment by electromagnetic.

Le document EP-A-0 992 408 décrit un système conforme au préambule de la revendication 1.EP-A-0 992 408 discloses a system according to preamble of claim 1.

L'invention a pour but d'éliminer les inconvénients précités et de proposer un système d'accès dit mains libres pour véhicule automobile, permettant de détecter un piratage du système, notamment par l'intermédiaire de boítiers relais, en prenant compte du temps de propagation du signal entre le véhicule et le dispositif d'identification.The object of the invention is to eliminate the aforementioned drawbacks and to propose a system of access said hands-free for motor vehicle, to detect hacking of the system, in particular by intermediates relay boxes, taking into account the time of signal propagation between the vehicle and the identification device.

A cet effet, l'invention a pour objet un système d'accès dit mains libres pour véhicule automobile, conforme à la revendication 1. For this purpose, the invention relates to an access system said hands free for motor vehicle, according to claim 1.

On entend par "temps d'émission utile" le temps d'émission de l'information binaire dudit bit par rapport au temps total de la cellule à laquelle est associé ledit bit qui comprend généralement ledit temps utile et un temps de silence pour permettre la réception du signal réémis par le dispositif d'identification pendant ledit temps de silence."Transmission time" useful "the transmission time of the bit information of said bit relative to the total time of the cell with which is associated said bit which comprises generally said useful time and a time of silence to allow the receiving the signal re-transmitted by the identification device during said silence time.

Avantageusement, ladite valeur de seuil prédéterminée est donnée par une fenêtre de temps qui correspond à la durée totale théorique d'émission du train de bits d'anti-piratage, lorsque le dispositif d'identification est à une distance inférieure ou égale à la distance limite prédéterminée. Cette fenêtre de temps est une constante précise engendrée par exemple par un oscillateur piloté par quartz associé à un compteur sous contrôle du micro-contrôleur qui indique le nombre de périodes à compter. L'unité centrale de commande est apte à déterminer ladite tentative de piratage lorsque le nombre total de bits du train d'anti-piratage n'a pas été émis ou reçu par l'unité centrale de commande dans ladite fenêtre.Advantageously, said predetermined threshold value is given by a window of time that corresponds to the total duration theoretical transmission of the anti-piracy bitstream, when the identification device is at a distance less than or equal to the predetermined limit distance. This window of time is a constant precise generated for example by a quartz controlled oscillator associated with a counter under control of the microcontroller which indicates the number of periods to count. The central control unit is suitable to determine said hacking attempt when the total number of bits the anti-piracy train was not issued or received by the Central Unit of command in said window.

Selon une autre caractéristique, l'unité centrale peut comporter en mémoire une table de correspondance à double entrée, à savoir le nombre de bits émis et la durée d'émission réelle correspondante, pour donner en sortie la distance réelle entre le dispositif d'identification et l'unité centrale, les données de ladite table étant préalablement acquises par expérimentation et pouvant être périodiquement réactualisées, lorsque l'utilisateur portant le dispositif d'identification est assis sur le siège conducteur du véhicule, la distance du dispositif d'identification à l'unité centrale du véhicule étant alors sensiblement constante.According to another characteristic, the central unit may comprise in memory a double-entry correspondence table, namely the number of transmitted bits and the corresponding actual transmission duration, for output the actual distance between the identification device and the central unit, the data of said table being previously acquired by experimentation and which can be periodically updated, when the user wearing the identification device is sitting on the driver's seat of the vehicle, the distance from the identification device to the central unit of the vehicle then being substantially constant.

A titre d'exemple, le comptage du nombre de bits émis est arrêté lorsque l'unité centrale détecte la réception du dernier bit du train d'anti-piratage.For example, the count of the number of bits sent is stopped when the central unit detects the reception of the last bit of the train anti-piracy.

De préférence, le dispositif d'identification comporte une ligne à retard analogique pour réémettre le signal reçu du véhicule vers le véhicule avec un temps de retard prédéterminé.Preferably, the identification device comprises a line to analog delay to re-transmit the signal received from the vehicle to the vehicle with a predetermined delay time.

Selon une autre caractéristique, l'unité centrale de commande comporte un oscillateur générateur d'ondes porteuses en radio fréquence, relié à un modulateur de phase, qui est commandé par le train de bits d'anti-piratage engendré par l'unité centrale du véhicule.According to another characteristic, the central control unit has an oscillator generating radio carrier waves frequency, connected to a phase modulator, which is controlled by the anti-piracy bitstream generated by the central unit of the vehicle.

Selon une caractéristique de l'invention, le train de bits d'anti-piratage est engendré par l'unité centrale après l'émission des données d'authentification cryptées vers le dispositif d'identification. Dans ce cas, le dispositif d'identification peut comporter un inverseur de phase pour inverser sélectivement la phase du signal représentatif des bits d'anti-piratage reçu par le dispositif d'identification en provenance du véhicule, ledit inverseur étant commandé, pour chaque bit d'anti-piratage, par un signal numérique d'authentification crypté de réponse du dispositif d'identification, à une cadence plus lente que celle du train de bits d'anti-piratage.According to one characteristic of the invention, the anti-piracy bit stream is generated by the CPU after the transmission of data encrypted authentication to the identification device. In this In this case, the identification device may comprise a phase inverter to selectively invert the phase of the signal representative of the bits anti-piracy received by the identification device from the vehicle, said inverter being controlled, for each bit of anti-piracy, by an encrypted digital authentication response signal identification device, at a slower rate than that of the anti-piracy bitstream.

On peut prévoir alors que l'unité centrale du véhicule comporté un démodulateur de phase pour démoduler le signal reçu par le véhicule en provenance du dispositif d'identification, une porte logique OU exclusif dont les entrées sont reliées respectivement audit démodulateur de phase et à un retardateur de signal numérique, ledit retardateur étant apte à retarder d'un temps bit utile chaque bit du train d'anti-piratage engendré par l'unité centrale, ladite porte logique étant apte à délivrer en sortie un signal numérique représentatif du signal crypté de réponse du dispositif d'identification. One can then foresee that the central unit of the vehicle comprises a phase demodulator to demodulate the signal received by the vehicle from the identification device, a logic gate Exclusive OR whose entries are respectively linked to audit phase demodulator and a digital signal retarder, said self-timer being able to delay a useful bit every bit of the train anti-piracy generated by the central unit, said logic gate being capable of outputting a digital signal representative of the signal encrypted response of the identification device.

Dans une première forme de réalisation, le signal délivré en sortie de la porte logique OU exclusif précitée est comparé par l'unité centrale à un signal numérique crypté d'authentification engendré par l'unité centrale, afin d'authentifier le dispositif d'identification.In a first embodiment, the signal delivered in output of the aforementioned exclusive OR logic gate is compared by the unit central to an encrypted digital signal of authentication generated by the central unit, in order to authenticate the identification device.

Dans une autre forme de réalisation, la sortie de ladite porte logique OU exclusif est reliée à une entrée d'une deuxième porte logique OU exclusif dont l'autre entrée reçoit un signal numérique crypté d'authentification engendré par l'unité centrale, afin de délivrer en sortie un signal représentatif des décalages temporels successifs de chaque bit du train d'anti-piratage, ce dernier signal étant reçu à l'entrée d'un intégrateur pour faire la somme des temps de réponse liés à chaque créneau de décalage de bit d'anti-piratage, la sortie dudit intégrateur étant reliée à un comparateur pour comparer ladite somme de temps de réponse avec une valeur de durée limite prédéterminée, au-delà de laquelle est détectée une tentative de piratage.In another embodiment, the output of said door OR logic is connected to an input of a second gate Exclusive OR logic whose other input receives a digital signal encrypted authentication generated by the central unit, in order to deliver output a signal representative of successive time offsets of each bit of the anti-piracy train, the latter being received at the input of an integrator to sum the related response times at each anti-piracy bit shift slot, the output of said integrator being connected to a comparator to compare said sum response time with a predetermined time-out value, beyond which an attempted hacking is detected.

Avantageusement, on peut prévoir que le signal en provenance du dispositif d'identification est reçu par l'unité centrale et transmis à l'entrée d'un détecteur d'enveloppe pour détecter le front montant dudit signal, la détection de ce front montant étant apte à déclencher, d'une part, l'incrémentation d'une unité du compteur de nombre de bits et, d'autre part, l'émission du bit suivant dans le train de bits d'anti-piratage, après une durée prédéterminée qui correspond à un temps bit utile éventuellement augmenté d'un temps supplémentaire pour éviter toute interférence entre l'émission et la réception du signal par l'unité centrale.Advantageously, it can be expected that the signal coming from the identification device is received by the Central Unit and transmitted to the input of an envelope detector for detecting the rising edge of said signal, the detection of this rising edge being able to trigger, a part, the incrementation of a unit of the number of bits counter and, on the other hand, the transmission of the next bit in the anti-piracy bit stream, after a predetermined duration which corresponds to a bit time useful possibly increased by extra time to avoid any interference between the transmission and the reception of the signal by the unit Central.

Dans ce cas, on peut prévoir que l'unité centrale comporte un modulateur dit tout ou rien pour faire basculer l'unité centrale dans le mode émission ou réception des signaux vers ou en provenance du dispositif d'identification, ledit modulateur tout ou rien étant commandé par la détection du front montant du signal reçu en provenance du dispositif d'identification.In this case, it can be provided that the central unit comprises a modulator says all or nothing to switch the CPU in the transmission or reception of signals to or from identification device, said all-or-nothing modulator being controlled by detecting the rising edge of the signal received in from the identification device.

Avantageusement, le dispositif d'identification comporte un récepteur pour recevoir des signaux d'éveil à faible cadence, ce récepteur comprenant successivement un détecteur d'enveloppe statique radio-fréquence à faible seuil et un amplificateur basse fréquence. Advantageously, the identification device comprises a receiver to receive low-speed wakefulness signals, this receiver comprising successively a static envelope detector low-threshold radio frequency and a low frequency amplifier.

A titre d'exemple, le temps bit utile peut être compris entre 50 et 200 ns.By way of example, the useful bit time can be between 50 and 200 ns.

L'invention sera mieux comprise, et d'autres buts, détails, caractéristiques et avantages de celle-ci apparaítront plus clairement au cours de la description explicative détaillée qui va suivre d'un mode de réalisation particulier de l'invention, donné uniquement à titre illustratif et non limitatif, en référence au dessin schématique annexé, dans lequel :

  • la figure 1 est un schéma synoptique fonctionnel représentant le protocole d'encryptage pour sécuriser la transmission bidirectionnelle de données entre un véhicule et un dispositif d'identification ;
  • la figure 2 est un schéma synoptique fonctionnel illustrant un moyen de piratage du système d'encryptage par l'intermédiaire de deux boítiers relais ;
  • la figure 3 est un schéma synoptique fonctionnel simplifié d'un système d'accès mains libres conforme à l'invention ;
  • la figure 4 est un schéma synoptique fonctionnel plus détaillé correspondant au schéma de la figure 3 ;
  • la figure 5 représente plusieurs chronogrammes illustrant les trames complètes d'interrogation émises par le véhicule et reçues en réponse par le véhicule ;
  • la figure 6 est une vue partielle et agrandie d'une portion des chronogrammes de la figure 5, indiquée par la flèche VI, correspondant au début de la séquence d'anti-piratage ;
  • la figure 7 reprend les deux premiers chronogrammes de la figure 5;
  • la figure 8 est une vue partielle et agrandie d'une portion des chronogrammes de la figure 7, indiquée par la flèche VIII, au cours de la séquence d'anti-piratage ; et
  • la figure 9 est une vue partielle et agrandie d'une portion des chronogrammes de la figure 5, indiquée par la flèche IX, et correspondant à la fin de la procédure d'anti-piratage.
The invention will be better understood, and other objects, details, features and advantages thereof will appear more clearly in the following detailed explanatory description of a particular embodiment of the invention, given only to illustrative and nonlimiting, with reference to the appended schematic drawing, in which:
  • FIG. 1 is a functional block diagram illustrating the encryption protocol for securing the bidirectional transmission of data between a vehicle and an identification device;
  • FIG. 2 is a functional block diagram illustrating a means of piracy of the encryption system by means of two relay boxes;
  • Figure 3 is a simplified block diagram of a hands-free access system according to the invention;
  • FIG. 4 is a more detailed functional block diagram corresponding to the diagram of FIG. 3;
  • FIG. 5 represents several timing diagrams illustrating the complete interrogation frames transmitted by the vehicle and received in response by the vehicle;
  • Figure 6 is a partial and enlarged view of a portion of the timing diagrams of Figure 5, indicated by the arrow VI, corresponding to the beginning of the anti-piracy sequence;
  • Figure 7 shows the first two chronograms of Figure 5;
  • Fig. 8 is a partial and enlarged view of a portion of the timing diagrams of Fig. 7, indicated by arrow VIII, during the anti-piracy sequence; and
  • Figure 9 is a partial and enlarged view of a portion of the timing diagrams of Figure 5, indicated by the arrow IX, and corresponding to the end of the anti-piracy procedure.

On va maintenant se référer aux figures 3 et 4, qui représentent le système d'accès mains libres selon l'invention respectivement sous forme simplifiée et plus détaillée. We will now refer to Figures 3 and 4, which represent the hands-free access system according to the invention respectively under Simplified form and more detailed.

Le véhicule automobile V comporte dans son unité centrale un micro-contrôleur 50, qui est généralement dans un état de semi-sommeil ou d'attente d'un réveil. Lorsque l'utilisateur actionne la poignée extérieure de porte, un signal d'activation est envoyé au micro-contrôleur 50, comme indiqué par la flèche 51. En réponse, le micro-contrôleur envoie un signal d'alimentation général, comme représenté par la flèche 52, pour alimenter les différents composants électroniques de l'unité centrale. Puis, le micro-contrôleur 50 engendre une série de signaux à faible cadence sk, par exemple de l'ordre de 2 à 100 Kb/s sur la ligne V5. Les données véhiculées sur la ligne V5 sont successivement un signal d'éveil e, un signal représentatif d'un nombre aléatoire R d'une longueur par exemple de 56 bits, un signal représentatif de la fonction f (R,K) d'une longueur par exemple de 28 bits, et d'un signal représentatif de données de service s, par exemple d'une longueur de 100 à 5 000 bits, par exemple des données sur la maintenance, le réglage du véhicule, etc (voir figure 5). La ligne V5 est reliée à un émetteur 53 pour émettre via une antenne 54 les signaux vers le dispositif d'identification I comme représenté par la flèche E. L'émetteur 53 comporte, comme mieux visible sur la figure 4, un oscillateur 55 pour engendrer une onde porteuse à ultra haute fréquence, ledit oscillateur étant alimenté par la ligne 52. L'oscillateur 55 est relié à un modulateur de phase 56, qui est à son tour relié à un modulateur tout ou rien 57, ce dernier ayant une entrée reliée à la ligne V5 et sa sortie reliée à l'antenne 54 précitée. Lors de l'émission des données à faible cadence sk sur la ligne V5, le modulateur de phase est inactif. Le modulateur tout ou rien 57 est destiné à alternativement permettre l'émission d'un signal et la réception d'un signal par l'unité centrale du véhicule, comme expliqué plus loin. A titre d'exemple, l'amplitude du signal émis est de l'ordre de 2 V efficace.The motor vehicle V comprises in its central unit a micro-controller 50, which is usually in a state of semi-sleep or waiting for an alarm clock. When the user operates the outside door handle, an activation signal is sent to the micro-controller 50, as indicated by the arrow 51. In response, the micro-controller sends a general power signal, as represented by the arrow 52, to supply the different components electronic units of the central unit. Then, the microcontroller 50 generates a series of low speed signals sk, for example of the order of 2 to 100 Kb / s on line V5. The data conveyed on line V5 are successively an awakening signal e, a signal representative of a number random R of a length for example of 56 bits, a signal representative of the function f (R, K) with a length of, for example, 28 bits, and a signal representative of service data s, for example from 100 to 5000 bits, for example data on the maintenance, vehicle tuning, etc. (see Figure 5). Line V5 is connected to a transmitter 53 for transmitting via an antenna 54 the signals to the identification device I as represented by the arrow E. The transmitter 53 comprises, as best seen in FIG. oscillator 55 to generate an ultra high carrier wave frequency, said oscillator being powered by line 52. The oscillator 55 is connected to a phase modulator 56, which is in turn connected to a all-or-nothing modulator 57, the latter having an input connected to the line V5 and its output connected to the antenna 54 above. When issuing low-rate data sk on line V5, the phase modulator is inactive. The all-or-nothing modulator 57 is intended alternatively allow the transmission of a signal and the reception of a signal by the unit center of the vehicle, as explained later. For exemple, the amplitude of the transmitted signal is of the order of 2 V effective.

Le signal émis E est reçu par une antenne 100 du dispositif d'identification I avec une atténuation de l'ordre de -40 dBm, ce qui représente un coefficient d'atténuation de 100 fois, c'est à dire que le signal reçu par le dispositif d'identification présente une amplitude de l'ordre de 20 mV. L'antenne 100 est reliée à un filtre radio-fréquence 101 (uniquement représenté sur la figure 4) pour éliminer les fréquences parasites. La sortie du filtre 101 est reliée à un embranchement, d'une part, vers un récepteur à faible cadence et à faible consommation 102 et, d'autre, part à une ligne à retard analogique 103. Les signaux à faible cadence sk ne sont pas transmis par la ligne à retard 103, mais passent essentiellement via le récepteur 102. Comme mieux visible sur la figure 4, le récepteur 102 comprend successivement un détecteur d'enveloppe radio-fréquence 104 pour reconstituer les signaux à faible cadence sur la ligne I5, qui correspondent à ceux de la ligne V5. La sortie du détecteur d'enveloppe 104 est reliée à un amplificateur basse fréquence 105, dont la sortie est reliée en parallèle, d'une part, à un décodeur de séquence d'éveil 106 et, d'autre part, à un micro-contrôleur 107 du dispositif d'identification I via une ligne 108. Au démarrage de la communication avec le véhicule, seul le décodeur 106 est alimenté en permanence par la pile du dispositif d'identification. Autrement dit, les données d'éveil e sont décodées par le décodeur 106, afin d'envoyer un ordre d'éveil au micro-contrôleur 107, à la sortie du décodeur 106. Le micro-contrôleur 107 éveille alors tous les autres composants électroniques du dispositif d'identification. Ainsi, les données suivantes, à savoir les signaux R, f et s, sont transmis directement au micro-contrôleur 107 via la ligne en parallèle 108.The emitted signal E is received by an antenna 100 of the device with an attenuation of the order of -40 dBm, which represents an attenuation coefficient of 100 times, ie the signal received by the identification device has an amplitude of the order of 20 mV. The antenna 100 is connected to a radio frequency filter 101 (only shown in Figure 4) to eliminate the parasitic frequencies. The output of the filter 101 is connected to a branch, on the one hand, to a low rate receiver and low consumption 102 and, on the other hand, to a delay line 103. Low-speed sk signals are not transmitted by the delay line 103, but essentially pass through the receiver 102. As best seen in FIG. 4, the receiver 102 comprises successively a radio frequency envelope detector 104 for reconstruct the low-speed signals on line I5, which correspond to those of line V5. The detector output envelope 104 is connected to a low frequency amplifier 105, which the output is connected in parallel, on the one hand, to a sequence decoder 106 and on the other hand to a microcontroller 107 of the device identification I via a line 108. At the start of the communication with the vehicle, only the decoder 106 is powered by permanence by the battery of the identification device. In other words, waking data are decoded by the decoder 106, in order to send a wakefulness command at the microcontroller 107, at the output of the decoder 106. micro-controller 107 then wakes up all the other components electronic identification device. So the data following, namely the signals R, f and s, are transmitted directly to the micro-controller 107 via the parallel line 108.

Après émission des données de service s, le micro-contrôleur 50 du véhicule V engendre des bits d'anti-piratage h à la cadence lente sk du micro-processeur, lesdits bits d'anti-piratage étant reçus par une mémoire tampon à générateur de séquences binaires aléatoires 58, pour délivrer en sortie les bits d'anti-piratage à haute cadence fk, sur une ligne V7. La sortie de la mémoire tampon 58 est reliée à un embranchement, d'une part, avec le modulateur de phase 56 pour moduler en phase l'onde porteuse engendrée par l'oscillateur 55, et d'autre part, avec un retardateur numérique d'un temps bit utile 59, dont la fonction sera expliquée plus loin. Chaque bit d'anti-piratage est transmis sous la forme d'un signal radio-fréquence via l'antenne 54 en direction du dispositif d'identification I. La trame globale d'émission V2 des signaux par l'antenne 54 est illustrée sur les figures 5 et 7. En se référant plus particulièrement à la figure 6, on a représenté le début de la trame d'interrogation des bits d'anti-piratage h sur la ligne V2. Sur la ligne V2 de la figure 6, on constate que chaque bit d'anti-piratage est porté par une onde oscillante à très haute fréquence ayant un temps bit Tb compris par exemple entre 50 et 200 ns. L'émission des bits d'anti-piratage h1, h2...hn est autorisée par le modulateur tout ou rien 57, en fonction d'un signal de commande V1 qui est émis par une unité de gestion de base de temps 60 du véhicule V, laquelle unité 60 est apte à délivrer les signaux d'horloge à faible cadence sk, à moyenne cadence mk et à haute cadence fk. Bien entendu, l'unité 60 est reliée au micro-contrôleur 50, comme indiqué par la double flèche 61. La génération du signal V1 sera expliquée plus loin.After transmission of the service data, the microcontroller 50 of vehicle V generates bits of anti-piracy h at slow rate sk of the microprocessor, said anti-piracy bits being received by a buffer with random binary sequence generator 58, for outputting the anti-piracy bits at a high rate fk, on a line V7. The output of the buffer 58 is connected to a branching, on the one hand, with the phase modulator 56 for phase modulating the carrier wave generated by the oscillator 55, and on the other hand, with a digital timer of a useful bit time 59, whose function will be explained later. Every bit of anti-piracy is transmitted in the form of a radio frequency signal via the antenna 54 in direction of the identification device I. The overall transmission frame V2 signals by the antenna 54 is illustrated in Figures 5 and 7. In Referring more particularly to Figure 6, the beginning is shown the interrogation frame of the anti-piracy bits h on the line V2. On line V2 of FIG. 6, it can be seen that each bit of anti-piracy is carried by a very high frequency oscillating wave having a bit time Tb for example between 50 and 200 ns. The show anti-piracy bits h1, h2 ... hn is allowed by the modulator while or nothing 57, depending on a control signal V1 that is emitted by a time base management unit 60 of the vehicle V, which unit 60 is able to deliver the low clock rate signals sk, average cadence mk and high rate fk. Of course, unit 60 is connected to the microcontroller 50, as indicated by the double arrow 61. The generation of the V1 signal will be explained later.

Le dispositif d'identification I reçoit via son antenne 100 sur la ligne I1 (voir figure 6) un signal qui correspond au bit d'anti-piratage h1 émis par le véhicule V, avec un temps retard δ qui correspond au temps de propagation du signal entre le véhicule et le dispositif d'identification. Le signal passe alors par la ligne à retard analogique 103, qui peut par exemple être constituée par un bobinage en cuivre, ce qui permet de réduire la consommation d'énergie par le dispositif d'identification, car cette ligne à retard n'a pas besoin d'être alimentée en énergie. On a représenté sur la figure 8 le signal I2v qui correspond au signal virtuel en sortie de la ligne à retard analogique 103, c'est à dire à l'enveloppe dudit signal analogique, ledit signal étant retardé d'une durée prédéterminée Dℓ. La sortie de la ligne à retard 103 est reliée à l'entrée d'un inverseur de phase 109 pour inverser la phase du signal analogique transmis par la ligne à retard 103, en fonction d'un signal de commande crypté d'authentification g, dont la trame est représentée sur la ligne I6. Comme visible sur la ligne I6 représentée sur la figure 8, la cadence des bits du signal g est à moyenne cadence mk, plus faible que la haute cadence fk des bits d'anti-piratage h. A cet effet, on prévoit que le micro-contrôleur 107 du dispositif d'identification transmet à faible cadence sk le signal g à une mémoire tampon 110 qui délivre en sortie le signal g à la cadence moyenne mk vers l'inverseur de phase 109.The identification device I receives via its antenna 100 on the line I1 (see FIG. 6) a signal corresponding to the anti-piracy bit h1 emitted by the vehicle V, with a delay time δ which corresponds to the signal propagation time between the vehicle and the device Identification. The signal then passes through the analog delay line 103, which may for example be constituted by a copper winding, which makes it possible to reduce the energy consumption by the device identification because this delay line does not need to be powered in energy. FIG. 8 shows the signal I2v which corresponds to to the virtual signal at the output of the analog delay line 103, it is say to the envelope of said analog signal, said signal being delayed of a predetermined duration Dℓ. The output of the delay line 103 is connected to the input of a phase inverter 109 to reverse the phase of the analog signal transmitted by the delay line 103, according to a encrypted authentication control signal g, whose frame is represented on line I6. As visible on line I6 shown in FIG. 8, the bit rate of the signal g is at medium rate mk, weaker than the high rate fk anti-piracy bits h. In this Indeed, it is expected that the microcontroller 107 of the device of identification transmits at low speed sk the signal g to a memory buffer 110 which outputs the signal g at the average rate mk to the phase inverter 109.

L'inverseur de phase 109 délivre en sortie un signal analogique, dont le signal virtuel est représenté en I7v qui représente l'enveloppe dudit signal. La sortie de l'inverseur de phase 109 est reliée à un amplificateur 111 ayant un gain de + 20 dB pour émettre le signal avec une amplitude de l'ordre de 200 mV. Ce signal amplifié est représenté sur la ligne I4 et correspond au bit d'émission h1 avec le retard δ dû à la propagation du signal et au retard analogique Dℓ dû à la ligne à retard 103. Ce signal 14 est réémis par une antenne 112 vers le véhicule V, comme représenté par la flèche RE. Lors de la réception du premier bit d'anti-piratage h1 par le dispositif d'identification, ce premier bit d'anti-piratage va déclencher la génération du signal crypté d'authentification g par le dispositif d'identification en vue de commander l'inverseur de phase 109. A cet effet, la sortie de l'amplificateur 111 est reliée également à une ligne de déclenchement 113 qui comporte en série une diode 114 et un déclencheur 115 pour activer une unité de gestion de temps de base 116 qui délivre des signaux d'horloge à faible cadence sk et à moyenne cadence mk, ladite unité 116 étant reliée au micro-contrôleur 107, comme indiqué par la double flèche 117.The phase inverter 109 outputs an analog signal, whose virtual signal is represented in I7v which represents the envelope said signal. The output of the phase inverter 109 is connected to a amplifier 111 having a gain of + 20 dB to emit the signal with an amplitude of the order of 200 mV. This amplified signal is represented on the line I4 and corresponds to the transmission bit h1 with the delay δ due to the propagation of the signal and to the analog delay Dℓ due to the delay line 103. This signal 14 is reemitted by an antenna 112 to the vehicle V, as represented by the arrow RE. When receiving of the first anti-piracy bit h1 by the identification device, this first bit of anti-piracy will trigger the generation of the encrypted signal authentication device g by the identification device in order to control the phase inverter 109. For this purpose, the output of the amplifier 111 is also connected to a trigger line 113 which has in series a diode 114 and a trigger 115 for activate a basic time management unit 116 which delivers low rate clock signals sk and medium rate mk, said unit 116 being connected to the microcontroller 107, as indicated by the double arrow 117.

En partant de l'hypothèse que les signaux électromagnétiques transmis se propagent à la vitesse de la lumière, à savoir 3.108 m/s, on peut considérer que la durée de transmission des signaux est de l'ordre de 3 ns par mètre de distance entre le véhicule et le dispositif d'identification I. Autrement dit, pour un trajet aller-retour entre le véhicule V et le dispositif d'identification I, espacé d'une distance d'environ 5 mètres, la durée de propagation δ serait de l'ordre de 30 ns. A cette durée de propagation δ, on pourrait ajouter le temps de réponse des circuits électroniques, qui pourrait être de l'ordre de quelques ns ou dizaines de ns, selon la bande passante attribuée à la porteuse.Assuming that the transmitted electromagnetic signals propagate at the speed of light, ie 3.10 8 m / s, we can consider that the duration of transmission of the signals is of the order of 3 ns per meter of distance between the vehicle and the identification device I. In other words, for a round trip between the vehicle V and the identification device I, spaced a distance of about 5 meters, the propagation time δ would be the order of 30 ns. At this propagation time δ, one could add the response time of the electronic circuits, which could be of the order of a few ns or tens of ns, according to the bandwidth allocated to the carrier.

Le signal réémis RE par le dispositif d'identification est reçu par un récepteur 62 via une antenne 63, avec une atténuation de l'ordre de - 40 dBm, ce qui représente un coefficient d'atténuation de 100 fois, c'est à dire que le signal reçu par le véhicule présente une amplitude de l'ordre de 2 mV. Comme mieux représenté sur la figure 4, le récepteur 62 comporte un filtre radio-fréquence 64 relié à l'antenne 63, dont le signal de sortie est représenté par la ligne V3, ce signal étant délivré à l'entrée d'un amplificateur logarithmique 65 qui présente un gain de 80 dB, ce qui permet d'atteindre un coefficient de multiplication allant jusqu'à 10 000 fois, et notamment de délivrer en sortie dudit amplificateur 65 un signal de l'ordre de 2V efficace. L'amplificateur 65 est relié en sortie à un embranchement entre, d'une part, un démodulateur d'amplitude 66, qui permet de détecter l'enveloppe du signal reçu, et, d'autre part, un démodulateur de phase 67. Le détecteur d'enveloppe 66 délivre en sortie un signal numérique représenté sur la ligne V4, ledit signal étant délivré à l'entrée de l'unité de gestion de base de temps 60 précitée. A la réception du bit d'anti-piratage reçu en retour, l'unité de gestion de base de temps 60 déclenche l'émission du bit d'anti-piratage suivant h2 avec un décalage correspondant au temps bit utile Tb + ε , ε correspondant à un faible retard de sécurité afin d'éviter tout chevauchement entre l'émission et la réception des signaux par le véhicule. Ainsi, la réception du bit d'anti-piratage en retour par le véhicule déclenche le coup d'horloge suivant à la cadence fk ainsi que le basculement du modulateur tout ou rien 57, via la ligne V1. Bien entendu, on pourrait également prévoir que le petit retard ε soit proche de 0 s.The signal reissued RE by the identification device is received by a receiver 62 via an antenna 63, with attenuation of the order of - 40 dBm, which represents an attenuation coefficient of 100 times, that is, the signal received by the vehicle has an amplitude of the order of 2 mV. As best shown in FIG. 4, the receiver 62 has a radio frequency filter 64 connected to the antenna 63, whose output signal is represented by line V3, this signal being delivered to the input of a logarithmic amplifier 65 which has a gain of 80 dB, which makes it possible to reach a multiplication coefficient up to 10,000 times, and in particular to output this amplifier 65 a signal of the order of 2V effective. The amplifier 65 is connected at the output to a junction between, on the one hand, a amplitude demodulator 66, which makes it possible to detect the envelope of the received signal, and on the other hand, a phase demodulator 67. envelope detector 66 outputs a digital signal represented on line V4, said signal being delivered at the input of the unit of time base management 60 above. Upon receipt of the anti-piracy bit received in return, the time base management unit 60 triggers the emission of the anti-piracy bit following h2 with an offset corresponding to the useful bit time Tb + ε, ε corresponding to a weak delay in order to avoid any overlap between transmission and the reception of the signals by the vehicle. Thus, the reception of the bit anti-piracy back by the vehicle triggers the clock stroke following at the rate fk as well as the tilting of the modulator all or nothing 57, via line V1. Of course, we could also foresee that the small delay ε is close to 0 s.

Chaque nouveau coup d'horloge à la cadence fk déclenché par la réception du bit d'anti-piratage précédent, provoque l'incrémentation d'une unité dans un compteur 68, lequel compteur 68 compte le nombre de bits reçus en fonction du temps. Toutefois, comme la réception d'un bit déclenche l'émission d'un bit d'anti-piratage suivant, on peut aussi bien compter directement le nombre de bits d'anti-piratage émis en fonction du temps. Lorsque la fin réelle du train de bits d'anti-piratage est détectée par l'unité centrale du véhicule, l'unité 60 envoie un signal Fr pour arrêter le comptage des bits d'anti-piratage et pour provoquer l'envoi par le compteur 68 d'un signal représentatif du nombre de bits comptés au micro-contrôleur 50, comme indiqué par la flèche 69. Si la fin réelle Fr est comprise dans la fenêtre de réception maximale Fm, comme indiqué à la figure 5, cela signifie que la transmission n'a pas été piratée. En fonction du nombre de bits, le micro-contrôleur 50 peut calculer la distance réelle entre le véhicule V et le dispositif d'identification I, en fonction d'une table de correspondance préalablement mémorisée. Si cette distance dépasse la distance autorisée, la communication est interrompue comme étant le résultat d'une tentative de piratage ou tout simplement comme étant une communication à trop grande distance du véhicule. Each new clock tick at the rate fk triggered by the receiving the previous anti-piracy bit, causes the incrementation of a unit in a counter 68, which counter 68 counts the number of bits received as a function of time. However, as the receiving a bit triggers the emission of a next anti-piracy bit, we can also count directly the number of anti-piracy bits issued as a function of time. When the actual end of the train bits of anti-piracy is detected by the vehicle's central unit, the unit 60 sends a signal Fr to stop counting of anti-piracy bits and to cause the counter 68 to send a representative signal the number of bits counted at the microcontroller 50, as indicated by the arrow 69. If the actual end Fr is included in the window of maximum reception Fm, as shown in Figure 5, this means that the transmission was not hacked. Depending on the number of bits, micro-controller 50 can calculate the actual distance between the vehicle V and the identification device I, according to a table of previously memorized correspondence. If this distance exceeds authorized distance, the call is interrupted as the result of a hacking attempt or simply as being communication at too great distance from the vehicle.

Ce compteur permet ainsi de détecter un piratage utilisant des boítiers-relais entre le véhicule et le dispositif d'identification. Toutefois, un pirate pourrait essayer de piéger ce système en anticipant sur le signal devant être émis par le dispositif d'identification. A titre d'exemple, dès que le pirate détecte avec un boítier-relais l'émission par le véhicule d'un bit d'anti-piratage, il peut provoquer l'émission anticipée d'un signal-talon, en préambule à la réémission du signal retardé par la ligne à retard du dispositif d'identification. Avantageusement, ce signal-talon aurait une durée qui correspondrait à la durée de propagation du signal sur la distance supplémentaire entre le dispositif d'identification et le véhicule, par rapport à la distance maximale autorisée. Ainsi, le détecteur d'enveloppe 66 du véhicule V détecterait, en premier lieu, la réception de ce signal-talon, provoquant à son tour l'émission anticipée du second bit d'anti-piratage.This counter thus makes it possible to detect piracy using relay boxes between the vehicle and the identification device. However, an attacker could try to trap this system by anticipating on the signal to be transmitted by the identification device. As for example, as soon as the pirate detects with a relay box the emission by the vehicle of a bit of anti-piracy, it can cause the emission anticipation of a signal-heel, in the preamble to the reissue of the signal delayed by the delay line of the identification device. Advantageously, this signal-heel would have a duration that would correspond to the signal propagation time over the extra distance between the identification device and the vehicle, in relation to the distance maximum allowed. Thus, the envelope detector 66 of the vehicle V detect, in the first place, the reception of this signal-heel, causing in turn the anticipated emission of the second bit of anti-piracy.

Le système selon l'invention permet également, grâce au compteur 68, de déterminer si le nombre total de bits d'anti-piratage a bien été reçu pendant une fenêtre de réception maximale Fm, représentée sur la figure 5. Les chronogrammes des figures 5 à 9 correspondent à une transmission non piratée du signal. La fin réelle Fr de la réception du train de bits d'anti-piratage est, sur ces figures, bien située dans la fenêtre maximale de réception Fm, comme représenté sur la figure 5. La durée totale Tt de réception des bits d'anti-piratage est calculée selon la formule suivante : Tt = n(Dℓ + Tb + ε + 2 δ). Ainsi, on constate qu'avec un train de n bits d'anti-piratage, on multiplie par la variable n la durée de propagation 2δ qui est fonction directe de la distance entre le dispositif d'identification et le véhicule. Ainsi, s'il est difficile de détecter avec des circuits électroniques à faible coût des durées de l'ordre de quelques dizaines de ns, il est beaucoup plus facile de détecter des durées de l'ordre de n x quelques dizaines de ns, c'est à dire des durées de l'ordre de la ms. Toutefois, si le pirate anticipe sur la réémission du signal par le dispositif d'identification, la variable 2n δ restera dans la limite acceptable et ainsi le système ne pourra pas détecter le piratage. The system according to the invention also makes it possible, thanks counter 68, to determine whether the total number of anti-piracy bits has have been received during a maximum reception window Fm, shown in Figure 5. The timing diagrams of Figures 5 to 9 correspond to a non-pirated transmission of the signal. The real end Fr of the reception of the anti-piracy bitstream is, in these figures, well located in the maximum reception window Fm, as represented in FIG. 5. The total duration Tt of reception of the bits anti-piracy is calculated according to the following formula: Tt = n (Dℓ + Tb + ε + 2δ). Thus, we see that with a train of n bits of anti-piracy, we multiply by the variable n the duration of 2d propagation which is a direct function of the distance between the device identification and the vehicle. So, if it is difficult to detect with electronic circuits at low cost durations of the order of a few tens of ns, it is much easier to detect durations of the order of n x a few tens of ns, ie durations of the order of ms. However, if the hacker anticipates on the retransmission of the signal by the identification device, the variable 2n δ will remain within the acceptable limit and so the system will not be able to detect piracy.

A cet effet, on peut prévoir, en alternative ou en supplément, une autre façon de calculer le temps de retard dû à la propagation du signal.For this purpose, it is possible to provide, alternatively or in addition, another way of calculating the delay time due to the propagation of the signal.

Le démodulateur de phase 67 délivre un signal représentatif de la fonction goh sur la ligne V9 qui est reliée à une entrée d'une porte logique OU exclusif 70. Cette porte logique 70 reçoit sur son autre entrée un signal V8 représentatif de la fonction h, délivré en sortie du retardateur numérique 59. La porte logique 70 pourrait être remplacée par un autre type de mélangeur, comme représenté sur la figure 3. Le signal V8 correspond au signal V7 avec un retard correspondant au décalage Dℓ du retardateur analogique 103 du dispositif d'identification I. La porte logique 70 délivre en sortie un signal V10, qui est représentatif du décalage entre les signaux V8 et V9, c'est à dire un signal représentatif du signal encrypté d'authentification g émis par le dispositif d'identification I, avec un petit décalage correspondant au temps de propagation du signal qui est égal à 2 δ, comme visible sur la figure 8.The phase demodulator 67 delivers a signal representative of the goh function on line V9 which is connected to an entrance of a door logical OR exclusive 70. This logic gate 70 receives on its other input a signal V8 representative of the function h, delivered at the output of digital retarder 59. The logic gate 70 could be replaced by another type of mixer, as shown in FIG. signal V8 corresponds to the signal V7 with a delay corresponding to Dℓ offset of the analog timer 103 of the identification device I. The logic gate 70 outputs a signal V10, which is representative of the offset between the signals V8 and V9, ie a signal representative of the encrypted authentication signal g transmitted by the identification device I, with a small offset corresponding to the signal propagation time which is equal to 2 δ, as visible on the figure 8.

La sortie de la porte logique 70 est reliée à un embranchement entre, d'une part, un filtre passe-bas 71 à la cadence moyenne mk qui est la cadence correspondant au signal g et, d'autre part, une autre porte logique OU exclusif 73. Le filtre passe-bas 71 est relié à une mémoire tampon 72, qui transforme ledit signal de la cadence mk à la cadence sk avant de l'envoyer au micro-contrôleur 50 qui va comparer le signal g reçu en provenance du dispositif d'authentification avec le signal g engendré au niveau du véhicule, en vue de l'authentification de la communication, ce qui correspond à la dernière étape 10 illustrée sur le schéma de la figure 1.The output of logic gate 70 is connected to a branch between, on the one hand, a low-pass filter 71 at the average rate mk which is the cadence corresponding to the signal g and, on the other hand, another Exclusive OR logic gate 73. The low-pass filter 71 is connected to a buffer 72, which transforms said signal from the rate mk to the cadence sk before sending it to the micro-controller 50 that will compare the signal g received from the authentication device with the signal g generated at the level of the vehicle, for the purpose of communication, which corresponds to the last step 10 illustrated in the diagram of Figure 1.

Le micro-contrôleur 50 délivre le signal g propre au véhicule à une mémoire tampon 74 à la cadence sk, afin qu'il la renvoie à la cadence mk à l'autre entrée de la porte logique 73 précitée. On a représenté sur la ligne V11 le signal g qui correspond exactement au signal g engendré par le dispositif d'identification et émis sur la ligne I6, comme représenté sur la figure 8. La porte logique 73 mélange les signaux V10 et V11 afin de ne délivrer en sortie que les décalages dus au temps de propagation du signal entre le véhicule V et le dispositif d'identification I, comme représenté sur la ligne V12. La sortie de la porte logique 73 est reliée à l'entrée d'un intégrateur 75, qui va délivrer en sortie un signal V13 qui va monter par escalier en fonction du temps, pour chaque créneau C représentatif du temps de propagation du signal. La ligne V13 est reliée à l'entrée d'une unité 76 recevant sur une autre entrée une valeur limite de seuil 77 qui correspond à un temps de propagation total maximal acceptable n x 2δ ≤ T max, avec δ correspondant au temps de propagation sur une distance autorisée. Selon que l'amplitude du signal de sortie sur la ligne V13 est supérieure ou non à cette valeur limite 77, un signal de tentative de piratage sera envoyé ou non via la ligne 78 au micro-contrôleur 50.The microcontroller 50 delivers the signal g specific to the vehicle to a buffer 74 at the rate sk, so that it returns to the rate mk at the other input of the aforementioned logic gate 73. We have represented on line V11 the signal g which corresponds exactly to the signal g generated by the identification device and transmitted on the line I6, as shown in FIG. 8. The logic gate 73 mixes the signals V10 and V11 in order to output only the offsets due the propagation time of the signal between the vehicle V and the device I, as shown on line V12. The exit of the logic gate 73 is connected to the input of an integrator 75, which will to output a signal V13 which will climb up stairs according to of time, for each slot C representative of the time of signal propagation. Line V13 is connected to the entrance of a unit 76 receiving on another input a threshold limit value 77 which corresponds to a maximum acceptable total propagation delay n × 2δ ≤ T max, with δ corresponding to the propagation time on a allowed distance. Depending on whether the amplitude of the output signal on the line V13 is greater than or not this limit value 77, a signal of hacking attempt will be sent or not via line 78 to the micro-controller 50.

L'intégrateur 75 permet de détecter une tentative de piratage, même dans le cas où le pirate ajoute un talon d'anticipation au signal réémis par le dispositif d'identification. En effet, si ce signal-talon peut piéger le compteur 68, en revanche la porte logique 73 interprétera ce signal-talon comme un signal erroné au moins avec une chance sur deux, et donc délivrera en sortie un créneau équivalent à ce signal-talon, lequel créneau sera additionné par l'intégrateur 75 de la même façon que pour les retards dus au temps de propagation.The integrator 75 can detect an attempted hacking, even in case the hacker adds an anticipation stub to the signal reissued by the identification device. Indeed, if this signal-heel can trap the counter 68, however the logic gate 73 will interpret this signal-heel as a wrong signal at least with a chance on two, and therefore will output a slot equivalent to this signal-heel, which slot will be added by the integrator 75 of the same only for delay due to propagation delay.

Enfin, le micro-contrôleur 50 peut délivrer différents signaux de sortie aux autres composants du véhicule par la voie 80 représentée sur les figures 3 et 4.Finally, the microcontroller 50 can deliver different signals of output to the other components of the vehicle by the track 80 shown on Figures 3 and 4.

A titre d'exemple, la cadence d'horloge intermédiaire mk est entre 20 et 60 fois inférieure à la cadence fk.For example, the intermediate clock rate mk is between 20 and 60 times less than the rate fk.

En variante, on pourrait remplacer les antennes 54 et 63 du véhicule V par une antenne unique 82 représentée en traits interrompus sur la figure 4, laquelle antenne 82 serait reliée à un diplexeur 81 représenté en traits interrompus sur la figure 4, afin de commuter entre le mode de réception et le mode d'émission selon le cas. De manière analogue, on pourrait remplacer les antennes 100 et 112 du dispositif d'identification par une antenne unique 121 reliée à un diplexeur 120, représentés en traits interrompus sur la figure 4. Les diplexeurs 81 et 120 pourraient ainsi communiquer entre eux, comme indiqué par la double flèche T.Alternatively, the antennas 54 and 63 of the V vehicle by a single antenna 82 shown in broken lines in FIG. 4, which antenna 82 would be connected to a diplexer 81 shown in broken lines in FIG. 4, in order to switch between the reception mode and the transmission mode as appropriate. So analogous, one could replace the antennas 100 and 112 of the device identification by a single antenna 121 connected to a diplexer 120, represented in broken lines in Figure 4. The diplexers 81 and 120 could thus communicate with each other, as indicated by the double arrow T.

Dans une variante du mode de réalisation représenté à la fig ure 4, l'unité centrale est reliée à au moins deux, par exemple trois, antennes d'émission/réception telles que l'antenne unique 82, disposées en plusieurs points du véhicule V. Des mesures de distance sont alors réalisées séquentiellement entre le dispositif d'identification I et chacune des antennes d'émission/réception du véhicule V. Ces mesures de distance sont réalisées par l'intermédiaire de la durée de propagation δ des bits anti-piratage à l'aide de la table de correspondance susmentionnée. Dans cette variante, il est possible de localiser précisément, par exemple à quelques centimètres ou dizaines de centimètres près, la position du dispositif d'identification I par un calcul de triangulation effectué par l'unité centrale. Ceci permet en outre de prendre en compte la position du dispositif d'identification I par rapport au véhicule V, par exemple, de quelle portière il se trouve le plus proche, lors des prises de décision réalisées dans l'unité centrale pour commander la condamnation ou la décondamnation des serrures des ouvrants du véhicule. Cette variante peut évidemment aussi être réalisée avec des antennes d'émission et de réception séparées.In a variant of the embodiment shown in fig ure 4, the central unit is connected to at least two, for example three, transmit / receive antennas such as the single antenna 82, arranged in several points of the vehicle V. Distance measurements are then performed sequentially between the identification device I and each of the transmitting / receiving antennas of the vehicle V. These measurements of distance are achieved via the propagation time δ anti-piracy bits using the correspondence table above. In this variant, it is possible to locate precisely, for example a few centimeters or tens of centimeters, the position of the identification device I by a calculation of triangulation carried out by the central unit. This allows in addition to taking into account the position of the identification device I relative to the vehicle V, for example, which door it is the closest when making decisions in the unit central to order the conviction or the decon- locks of the opening of the vehicle. This variant can obviously also be carried out with transmitting and receiving antennas separated.

Dans tous les cas, la ligne à retard 103 du dispositif d'identification I permet de différer la réémission de chaque bit anti-piratage par rapport à sa réception afin d'utiliser une même fréquence radio pour la transmission des signaux correspondants dans le sens depuis le véhicule V vers le dispositif d'identification I (flèche E ou T) et dans le sens depuis le dispositif d'identification I vers le véhicule V (flèche RE ou T).In all cases, the delay line 103 of the device identification I allows to postpone the retransmission of each anti-piracy bit compared to receiving it in order to use the same frequency radio for the transmission of corresponding signals in the direction from the vehicle V to the identification device I (arrow E or T) and in the direction from the identification device I to the vehicle V (arrow RE or T).

Comme visible sur la figure 5, sur la ligne V3, après la réception du signal hog, le véhicule V reçoit en provenance du dispositif d'identification un signal hos où s représente des données de service qui viennent moduler le signal h par inversion de phase, comme cela était le cas pour le signal g dont la longueur est inférieure à celle du signal h.As shown in Figure 5, on line V3, after the reception of the hog signal, the vehicle V receives from the device identification a signal hos where s represents service data which modulate the signal h by phase inversion, like this was the case for the signal g whose length is less than that of signal h.

La séquence des bits anti-piratage h étant une séquence binaire aléatoire ou pseudo-aléatoire, elle entraíne un étalement du spectre des signaux radiofréquences utilisés pour la transmettre du véhicule vers le dispositif d'identification et inversement. Cet étalement de spectre est d'autant plus important que la cadence de modulation fk utilisée pour transmettre la séquence des bits anti-piratage h est élevée. Un tel étalement de spectre est connu pour être avantageux du point de vue de la robustesse du signal vis à vis des interférences et des échos multiples, ce qui facilite les transmissions multiples du signal, par exemple l'aller-retour du signal entre le véhicule et le dispositif d'identification. En revanche, la démodulation du signal crypté d'authentification g au niveau de l'unité centrale du véhicule est rendue d'autant plus difficile que le spectre du signal RE est étalé.The sequence of anti-piracy bits h being a binary sequence random or pseudo-random, it entails a spread of the spectrum of radiofrequency signals used to transmit the vehicle to the identification device and vice versa. This spread spectrum is all the more important as the modulation rate fk used for transmit the sequence of anti-piracy bits h is high. Such Spread spectrum is known to be advantageous from the point of view of robustness of signal against interference and echoes multiple, which facilitates multiple transmissions of the signal, example the round trip signal between the vehicle and the device Identification. On the other hand, the demodulation of the encrypted signal of authentication g at the level of the central unit of the vehicle is made all the more difficult as the spectrum of the signal RE is spread out.

L'agencement de la ligne à retard 103 pour réémettre les bits anti-piratage h successifs retardés d'un temps bit utile en tant que modulation à cadence élevée fk du signal crypté d'authentification g, lui-même étant transmis à la cadence moyenne mk, permet d'assurer que la clé de démodulation correspondante, c'est-à-dire la même séquence aléatoire des bits anti-piratage h, est toujours disponible au niveau de l'unité centrale de commande lors de la réception du signal RE, ce qui permet de réaliser la démodulation du signal RE reçu indépendamment du degré d'étalement du spectre de ce signal.The arrangement of the delay line 103 to re-transmit the bits anti-hacking successive h delayed a useful bit time as a high rate modulation fk of the encrypted authentication signal g, itself being transmitted at the average rate mk, ensures the corresponding demodulation key, that is, the same random sequence of anti-piracy bits h, is always available at level of the central control unit when receiving the signal RE, which makes it possible to demodulate the received signal RE regardless of the degree of spread of the spectrum of this signal.

En outre, la robustesse du système d'accès vis à vis des échos multiples, par exemple dans le cas où le signal E émis par l'unité centrale est reçu par le dispositif d'identification I sous la forme d'un signal transmis directement et d'un écho ayant subi une réflexion sur un obstacle, est assurée par le fait que le dispositif d'identification I réagit toujours au premier signal reçu, qui ne peut être que le signal transmis directement.In addition, the robustness of the access system with respect to echoes multiples, for example in the case where the signal E emitted by the unit central station is received by the identification device I in the form of a signal transmitted directly and an echo that has been reflected on an obstacle, is ensured by the fact that the identification device I always responds to the first received signal, which can only be the signal transmitted directly.

Bien que l'invention ait été décrite en liaison avec un exemple particulier de réalisation, il est bien évident qu'elle n'y est nullement limitée et qu'elle comprend tous les équivalents techniques des moyens décrits ainsi que leurs combinaisons si celles-ci entrent dans le cadre de l'invention telle que définie par les revendications.Although the invention has been described in connection with an example particular realization, it is obvious that it is not at all limited and that it includes all the technical equivalents of the means described and their combinations if these fall within the scope of the invention as defined by the claims.

Claims (12)

  1. Hands-free access system for motor vehicle (V), comprising an onboard central control unit on the vehicle and an identification device (I) designed to be carried by a user (U) and for setting up a remote and wireless bidirectional communication with said central unit, to authenticate the user and to control the door lock disabling/enabling means when the user has been authenticated, said system being designed to set up said bidirectional communication when the identification device is located at a distance less than a predetermined limit distance from the vehicle, the central unit being designed to send encrypted authentication data (R, f) to the identification device (I), said identification device being designed to generate an encrypted digital authentication response signal (g), characterized by the fact that said central unit is designed to generate, in the communication after the transmission of said encrypted authentication data (R, f), an anti-piracy bit stream (h), each bit of said stream being sent to the identification device (I) in the form of a radiofrequency signal representative of said bit, the identification device (I) including a phase inverter (109) for selectively inverting the phase of the signal representative of the anti-piracy bits received by the identification device from the vehicle (V), said inverter being controlled, for each anti-piracy bit, by said encrypted digital authentication response signal (g) from the identification device, at a rate slower (mk) than that (fk) of the anti-piracy bit stream, such that when the identification device receives said signal representative of an anti-piracy bit, the latter is retransmitted by the identification device with a delay time (Dl) greater than or equal to the useful transmission time (Tb) of the bit in a form modulated by said encrypted digital authentication response signal (g), and that the reception by the central control unit of said retransmitted signal triggers the transmission by the central unit of the signal representative of the next bit in said stream, the number of bits of said stream sent or received being counted by a counter (68) of the central unit, such that the latter compares said number and the actual time (Tt) corresponding to the transmission or reception of said number of bits, in order to determine, beyond a predetermined threshold value, a piracy attempt provoking the termination of said communication.
  2. System according to Claim 1, characterized by the fact that said predetermined threshold value is given by a time window (Fm) which corresponds to the total theoretical transmission time of the anti-piracy bit stream, when the identification device (I) is at a distance less than or equal to the predetermined limiting distance, and the central control unit is designed to determine said piracy attempt when the total number of bits of the anti-piracy bit stream has not been sent or received by the central control unit within said window.
  3. System according to Claim 1 or 2, characterized by the fact that the central unit includes in memory a double-input mapping table, giving the number of bits sent and the corresponding actual transmission time, to provide at the output the actual distance between the identification device and the central unit, the data of said table being acquired previously by experimentation and able to be re-updated at periodic intervals.
  4. System according to one of Claims 1 to 3, characterized by the fact that the counting of the number of bits sent is stopped when the central unit detects the receipt of the last bit (hn) of the anti-piracy stream.
  5. System according to one of Claims 1 to 4, characterized by the fact that the identification device (I) includes an analogue delay line (103) for retransmitting the signal received from the vehicle (V) to the vehicle with a predetermined delay time (Dl).
  6. System according to one of Claims 1 to 5, characterized by the fact that the central control unit includes an oscillator (55) generating radiofrequency carrier waves, linked to a phase modulator (56), which is controlled by the anti-piracy bit stream (h) generated by the central unit of the vehicle (V).
  7. System according to one of Claims 1 to 6, characterized by the fact that the central unit of the vehicle (V) includes a phase demodulator (67) for demodulating the signal received by the vehicle from the identification device (I), an exclusive OR logic gate (70), the inputs of which are respectively linked to said phase demodulator and to a digital signal delay unit (59), said delay unit being designed to delay by one useful bit time (Tb) each bit of the anti-piracy stream (h) generated by the central unit, said logic gate being designed to output a digital signal (V10) representative of the encrypted response signal from the identification device.
  8. System according to Claim 7, characterized by the fact that the signal (V10) output by the abovementioned exclusive OR logic gate (70) is compared by the central unit to an encrypted digital authentication signal (g) generated by the central unit, in order to authenticate the identification device (I).
  9. System according to Claim 7 or 8, characterized by the fact that the output of said exclusive OR logic gate (70) is linked to an input of a second exclusive OR logic gate (73), the other input of which receives an encrypted digital authentication signal (g) generated by the central unit, in order to output a signal (V12) representative of the successive time offsets of each bit of the anti-piracy stream, the latter signal being received at the input of an integrator (75) to obtain the sum of the response times associated with each anti-piracy bit offset pulse (C), the output of said integrator being linked to a comparator (76) to compare said sum of response times with a predetermined limit time value (77), beyond which a piracy attempt is detected.
  10. System according to one of Claims 1 to 9, characterized by the fact that the signal from the identification device (I) is received by the central unit and transmitted to the input of an envelope detector (66) to detect the rising edge of said signal, the detection of this rising edge being designed to trigger, on the one hand, the incrementing by one unit of the number-of-bits counter (68) and, on the other hand, the transmission of the next bit in the anti-piracy bit stream, after a predetermined time which corresponds to a useful bit time, possibly increased by an additional time (ε) to avoid any interference between the transmission and the reception of the signal by the central unit.
  11. System according to Claim 10, characterized by the fact that the central unit includes an on-off modulator (57) to switch the central unit to the mode for transmitting or receiving signals to or from the identification device (I), said on-off modulator being controlled by the detection of the rising edge of the signal received from the identification device.
  12. System according to one of Claims 1 to 11, characterized by the fact that the identification device includes a receiver (102) for receiving low rate (sk) alert signals (e), this receiver including in succession a low-threshold, static radiofrequency envelope detector (104) and a low-frequency amplifier (105).
EP20010401095 2000-05-03 2001-04-27 Hand-free access system for a motor vehicle Expired - Lifetime EP1152108B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0005626A FR2808549B1 (en) 2000-05-03 2000-05-03 HANDS-FREE ACCESS SYSTEM FOR MOTOR VEHICLE
FR0005626 2000-05-03

Publications (3)

Publication Number Publication Date
EP1152108A2 EP1152108A2 (en) 2001-11-07
EP1152108A3 EP1152108A3 (en) 2001-12-05
EP1152108B1 true EP1152108B1 (en) 2005-10-05

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP20010401095 Expired - Lifetime EP1152108B1 (en) 2000-05-03 2001-04-27 Hand-free access system for a motor vehicle

Country Status (3)

Country Link
EP (1) EP1152108B1 (en)
DE (1) DE60113762T2 (en)
FR (1) FR2808549B1 (en)

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DE10247719A1 (en) * 2002-10-12 2004-04-22 Conti Temic Microelectronic Gmbh Determining distance between two transmitter-receiver stations, used for vehicle keyless entry, involves weighted summation of count sums allocated to each message corresponding to sum/mean of counter value determined during reception
US20090206989A1 (en) 2004-09-30 2009-08-20 Nxp B.V. Electronic communication system, in particular access control system for p(assive)k(eyless)e(ntry), as well as method for detecting a relay attack thereon
AT516569A1 (en) * 2014-11-20 2016-06-15 Evva Sicherheitstechnologie Method and device for access control
EP3306576B1 (en) 2016-10-05 2023-03-15 The Swatch Group Research and Development Ltd Method and system for secure access to a determined space by means of a portable object
EP4004879A1 (en) * 2019-07-30 2022-06-01 ams Sensors Singapore Pte. Ltd. Authenticating proximity via time-of-flight

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Also Published As

Publication number Publication date
DE60113762D1 (en) 2006-02-16
FR2808549B1 (en) 2003-06-13
FR2808549A1 (en) 2001-11-09
EP1152108A2 (en) 2001-11-07
EP1152108A3 (en) 2001-12-05
DE60113762T2 (en) 2006-07-13

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