Issuer of a vehicle identifier and issuer of a vehicle

Abstract

The invention relates to a first transmitter (10) of a vehicle identifier (1) for a vehicle (2), characterized in that said first transmitter (10) is configured to: - generate a first FSK signal (S_Fsk), - apply a Hamming filter (Ham_f) to said first FSK signal (S_Fsk), - transmit said filtered first FSK signal (S_Fsk) to a second receiver (21) of said vehicle (2) for a distance measurement between said identifier (1) and said vehicle (2). Figure for abbreviation: Fig. 1

Description

Title of the invention: Vehicle identifier transmitter and vehicle transmitter

[0001] The present invention relates to a transmitter of an identifier for a vehicle. It also relates to a transmitter of a vehicle. It finds a particular but non-limiting application in motor vehicles.

[0002] In the field of motor vehicles, it is known to use an identifier for remote access, or remote access and starting of a vehicle.

[0003] A so-called man-in-the-middle attack known to those skilled in the art consists of recovering a signal emitted by the vehicle or by the identifier on the transmitter side, modifying it and relaying it to the identifier or vehicle side respectively, so that the identifier appears to be close to the vehicle or in the passenger compartment of the vehicle in order to access it and / or start it fraudulently.

[0004] One of the means used to carry out this man-in-the-middle attack is the use of a method called EDLC, called "Early Detect Last Commit" in English, in which a first attacker close to the vehicle intercepts the signal emitted by the vehicle and sends it to a second attacker close to the identifier by reducing the time of the rising and falling edges. The second attacker relays it thus modified to a receiver of the identifier with a shorter delay compared to the real signal emitted by the vehicle and which must be received by the receiver of the identifier. For this purpose, the first attacker must detect as early as possible the rising and falling edges in the signal emitted by the vehicle.

[0005] The second attacker initially emits a signal emitted with default bits, some of which will therefore be modified in comparison with the signal received from the first attacker. The second attacker returns this signal thus modified to the receiver of the identifier. The return of the signal thus modified is done on the fly, namely as the bits of the signal emitted arrive at the second attacker. It is propagated before the real signal emitted by the vehicle arrives at the receiver of the identifier. The return of the signal thus modified by the second attacker makes it possible to make the receiver of the identifier, which analyzes the signal it receives, believe that the identifier is close enough to the vehicle to give it access by unlocking the doors of the vehicle, or even in the passenger compartment of the vehicle to start it.

[0006] It will be noted that the same attack principle works if the first attacker is close to the identifier and therefore intercepts a signal emitted by the identifier and the second attacker is close to the vehicle and sends a modified signal back to the vehicle.

[0007] In order to counter this attack, a means known to those skilled in the art is to detect the bit changes made by the second attacker and to detect the parasitic peaks called "glitches" in English linked to these bit changes between the bit emitted by default of the signal emitted by default by the second attacker and the bit emitted by the second attacker after receiving the signal emitted by the first attacker. If glitches are detected, the receiver of the vehicle or of the identifier deduces that the signal it received has been corrupted. It does not take this emitted signal into account and access and / or starting of the vehicle is not authorized.

[0008] A disadvantage of this cited prior art is that glitch analysis is complex and requires a lot of computing resources.

[0009] In this context, the present invention aims to propose a first transmitter of a vehicle identifier and a second transmitter of a vehicle which propose to solve the mentioned drawback.

[0010] To this end, the invention proposes a first transmitter of a vehicle identifier, characterized in that said first transmitter is configured to: - generate a first FSK signal, - applying a Hamming filter to said first FSK signal, - transmitting said first filtered FSK signal to a second receiver of said vehicle for a distance measurement between said identifier (1) and said vehicle.

[0011] Thus, as will be seen in detail later, the combination of the FSK signal and filtering by a Hamming filter makes it possible to obtain a useful transmission signal with steep rising and falling edges and to limit the level of secondary harmonics outside the useful channel used for the useful transmission signal. In this way, an attacker cannot detect the start of rising edges or only detects them very late, so that the transmitted signal that he is going to modify will not be able to be transmitted to the receiver of the identifier or the vehicle before the true signal transmitted by the first transmitter or the second transmitter arrives at said receiver. It will be propagated after or at the same time as the true useful transmission signal. The fraudulent transmitted signal cannot therefore replace the true useful transmission signal.In addition, the noise from secondary harmonics is low and therefore does not interfere with the transmission of the useful transmission signal and does not interfere with communications in adjacent channels.

[0012] According to non-limiting embodiments, said first transmitter may further comprise one or more additional characteristics taken alone or in all technically possible combinations, among the following.

[0013] According to a non-limiting embodiment, said distance measurement is based on a time-of-flight measurement of the rising and falling edges of said first FSK signal.

[0014] According to a non-limiting embodiment, said first FSK signal is transmitted according to a BLE communication protocol.

[0015] According to a non-limiting embodiment, said identifier is a hands-free access and / or start identifier.

[0016] There is further provided a vehicle identifier characterized in that said identifier comprises a first transmitter according to any one of the preceding characteristics.

[0017] According to a non-limiting embodiment, said identifier is further configured to comprise a first receiver configured to receive from a second transmitter of said vehicle a second FSK signal filtered by a Hamming filter.

[0018] According to a non-limiting embodiment, said identifier is a hands-free access and / or start identifier.

[0019] There is further provided a second transmitter of a vehicle, characterized in that said second transmitter is configured to: - generate a second FSK signal, - applying a Hamming filter to said second FSK signal, - transmitting said second filtered FSK signal to a first receiver of an identifier for a distance measurement between said identifier and said vehicle.

[0020] According to non-limiting embodiments, said second transmitter may further comprise one or more additional characteristics taken alone or in all technically possible combinations, among the following.

[0021] According to a non-limiting embodiment, said distance measurement is based on a time-of-flight measurement of the rising and falling edges of said second FSK signal.

[0022] According to a non-limiting embodiment, said second FSK signal is transmitted according to a BLE communication protocol.

[0023] According to a non-limiting embodiment, said identifier is a hands-free access and / or start identifier.

[0024] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures:

[0025] [Fig. 1] is a schematic view of a first transmitter of a vehicle identifier configured to generate a first transmission signal and communicate with a second receiver of said vehicle, according to a non-limiting embodiment of the invention,

[0026] [Fig.2] is a schematic view of a second transmitter of a vehicle configured to generate a second transmission signal and communicate with a first receiver of an identifier, according to a non-limiting embodiment of the invention,

[0027] [Fig.3] is a diagram illustrating an FSK signal generated by the first transmitter of [Fig.l] or by the second transmitter of [Fig.2] superimposed on a transmission signal useful GFSK whose bandwidth response time is equal to 0.5, according to a non-limiting exemplary embodiment,

[0028] [Fig.4] is a diagram illustrating an FSK signal generated by the first transmitter of [Fig.l] or by the second transmitter of [Fig.2] superimposed on a useful GFSK transmission signal whose bandwidth response time is equal to 10, according to a non-limiting exemplary embodiment,

[0029] [Fig.5] is a diagram illustrating an FSK signal generated by the first transmitter of [Fig.l] or by the second transmitter of [Fig.2] which has been filtered by a Hamming filter, and superimposed on a useful GFSK transmission signal whose bandwidth response time is equal to 0.5, according to a non-limiting exemplary embodiment,

[0030] [Fig.6] illustrates a response of a Hamming filter which has filtered the generated FSK signal of [Fig.3] or 4, according to a non-limiting exemplary embodiment,

[0031] [Fig.7] illustrates a response of a Gaussian filter that has filtered an FSK signal for obtaining a GSFK transmission signal of [Fig.3], according to a non-limiting exemplary embodiment,

[0032] [Fig.8] illustrates a response of a Gaussian filter that has filtered an FSK signal for obtaining a GSFK transmission signal of [Fig.4], according to a non-limiting exemplary embodiment.

[0033] Identical elements, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

[0034] The first transmitter 10 of an identifier 1 for a vehicle 2 according to the invention is described with reference to FIGS. 1 to 8. The second transmitter 20 of a vehicle 2 according to the invention is described with reference to FIGS. 2 to 8. In a non-limiting embodiment, the vehicle 2 is a motor vehicle. By motor vehicle is meant any type of motorized vehicle. This embodiment is taken as a non-limiting example in the remainder of the description. In the remainder of the description, the vehicle 2 is thus otherwise called motor vehicle 2.

[0035] In a non-limiting embodiment, the identifier 1 is a hands-free access identifier for hands-free access and / or starting of said motor vehicle 2. Thus, the identifier 1 can be used for a PEPS (Passive Entry Passive Start) application which allows a user of the motor vehicle 2 to unlock / lock and start the motor vehicle 2 using this identifier 1 without physically introducing said identifier 1 into a lock of said motor vehicle 2 for unlocking / locking or into a contactor of said motor vehicle 2 for starting. Thus, when it is located near the motor vehicle 2, the openings can be unlocked, and when it is located inside the motor vehicle 2, the engine of the motor vehicle 2 can be started.

[0036] In non-limiting embodiments, said identifier 1 is: - a Smartphone, or - a key with buttons, otherwise called a remote control, or - a starter card in credit card format, subscription card in non-limiting examples, - a connected object such as wireless headphones or a smart watch. The smartphone or connected object is thus used as a key to access and / or start the motor vehicle 2.

[0037] For remote access and / or starting, the identifier 1 or the motor vehicle 2 are configured to perform a distance measurement between them to determine whether the identifier 1 is close enough to the motor vehicle 2 to authorize access or whether it is in the passenger compartment of the motor vehicle 2 to authorize starting. In a non-limiting embodiment, the distance measurement is based on a TOF time of flight measurement. This TOF time of flight measurement being known to those skilled in the art, it is not described here. The distance measurement between the identifier 1 and the motor vehicle 2 can be performed either from a first useful transmission signal emitted from the identifier 1 to the motor vehicle 2, or from a second useful transmission signal emitted from the motor vehicle 2 to the identifier 1.

[0038] As illustrated in [Fig.l], the first transmitter 10 of the identifier 1 is configured to generate a first FSK (for “Frequency Shift Key Coding” in English) which will be transmitted after filtering and used for the distance measurement between the identifier 1 and the motor vehicle 2 (illustrated function fl0(10, S_Fsk)). The first FSK signal is referenced S_Fsk in [Fig.l].

[0039] The first transmitter 10 is further configured to transmit this first FSK signal thus filtered to a receiver 21 of the motor vehicle 2, called first receiver 21 (illustrated function f 12( 10, 21, S_Fsk). This first filtered FSK signal transmitted is thus a useful transmission signal. It is subsequently used to carry out the distance measurement between the identifier 1 and the motor vehicle 2.

[0040] The receiver 21 is therefore configured to receive said first filtered FSK signal as illustrated in [Fig.l] (illustrated function f21(21, 10, S_Fsk)).

[0041] In a non-limiting embodiment, the first FSK signal is transmitted according to a BLE communication protocol. It is recalled that a BLE communication takes place between 30 and 50 meters. Thus, if the identifier 1 is within the BLE range, namely around 30 to 50 meters, of the motor vehicle 2, access can be authorized. It is transmitted towards a receiver 21 of the motor vehicle 2. It is recalled that the BLE frequency is between 2.4GHz and 2.48GHz and the bandwidth of a transmission channel is 2MHz. The useful frequency band of a channel considered is 1MHz, or 500KHz on each side of a channel.

[0042] Drawing (a) of [Fig.3] illustrates a first generated FSK signal and a useful transmission signal GSFK whose bandwidth time BT is 0.5 and this for a fundamental frequency (otherwise called 1st harmonic or central frequency) of 2.44 GHz. The time is represented on the abscissa, and the amplitude of the signal on the ordinate. The first FSK signal is referenced S_Fsk and the useful transmission signal GFSK is referenced S_Gfsk in [Fig.3]. The useful transmission signal GFSK is an FSK signal to which a Gaussian filter has been applied.

[0043] As can be seen in drawing (a), the first FSK signal has rising edges r and falling edges f with a steep slope, while the useful transmission signal GFSK has rising edges r and falling edges f with a gentler slope. Drawing (b) is a zoom on a part of drawing (a). Due to the gentle slope of the useful transmission signal GFSK, it is understood that an EDLC attack is possible. Furthermore, in drawing (b), it can be seen that the generation of the FSK signal has a rapid change (otherwise called transition) referenced T between its continuous part A (which is flat) and the falling edge r'. The same is true for the rising edge r which is not shown. Furthermore, it can be seen that the useful transmission signal GFSK does not have a rapid change (otherwise called transition).

[0044] Drawing (a) of [Fig.4] illustrates a first generated FSK signal and a useful transmission signal GSFK whose bandwidth time BT is 10 and this for a fundamental frequency (otherwise called 1st harmonic or central frequency or channel) of 2.44 GHz. As can be seen, the two FSK and GSFK signals have the same shape, namely rising edges r and falling edges r' with a steep slope. Drawing (b) is a zoom on a part of drawing (a) of [Fig.4]. In drawing (b), it can be seen that the generation of the FSK signal presents a rapid change (otherwise called transition) referenced T between its continuous part A (which is flat) and the falling edge r'. The same is true for the rising edge r which is not shown.The same is true for the useful GFSK transmission signal which has a rapid change (otherwise called transition) referenced T between its continuous part A (which is flat) and the falling edge r. This rapid change indicates that the secondary harmonics have a significant signal level which disturbs the signals in the other adjacent channels when the useful GFSK transmission signal is transmitted.

[0045] The first transmitter 10 of the identifier 1 is further configured to apply a Hamming filter (referenced Ham_f) to the first generated FSK signal (illustrated function fl 1(10, Ham_f(FSK)). The Hamming filter Ham_f makes it possible to slowly vary the transition between the continuous part A of the first FSK signal and the falling edges r' as illustrated in [Fig.5]. The same applies to the rising edges r. Note that the rising edges r and the falling edges r' always have a steep slope. They remain fast.

[0046] Due to the slope which always remains steep of the FSK signal thus filtered, it is understood that an EDLC attack is not possible. Indeed, in this case, the first attacker will not be able to detect the start of a rising edge or will detect it too late so that the propagation of the FSK signal by the first attacker will not be able to take place before that of the true first filtered FSK signal transmitted by the first transmitter 10 to the receiver 21 of the motor vehicle 2. Thus, even if the identifier 1 is outside the BLE range, thanks to the emission of a filtered FSK signal, an EDLC attack will not be possible unlike an emission of a useful GFSK transmission signal.Furthermore, on the FSK signal thus filtered, due to the smooth transition T between its continuous part A (which is flat) and the falling edge r' (or the rising edge r not illustrated here), the fact of transmitting this filtered FSK signal to the receiver 21, the result is that we get rid of the noise generated by the secondary harmonics.

[0047] The diagram in [Fig.6] illustrates the frequency response of the Hamming filter Ham_f applied to the FSK signal. The frequency fq is represented on the abscissa in KHz and the amplitude of the FSK signal in db is represented on the ordinate. As can be seen, on the 1st channel Cl which is the useful transmission channel, for example at the fundamental frequency of 2.44GHz, which is centered on the value 0 on the abscissa, we have a signal level of Odb. For the 2nd channel C2 for example at the frequency of 2.442GHz, whose center is spaced 2MHz from the 1st channel and centered on the value 2000 on the abscissa, which is adjacent to the 1st channel, we have a signal level of -80db which amounts to 10000 times less than the FSK signal on the 1st channel. Remember that 201og(l / 10000) = -80db. Thus, the further away we are from the useful transmission channel, the weaker the signal will be.Thus, thanks to Hamming filtering, we obtain a filtered FSK signal which has rising edges r and falling edges r' with a steep slope, and low secondary harmonics compared to the 1st harmonic which is the fundamental frequency. The filtered FSK signal is thus a fast signal with little noise outside the useful transmission channel. The fact that we reduce the noise avoids disturbing other communications with other electronic devices which take place in a channel different from the frequency band of the FSK signal. For example, listening to a communication by identifier 1 which is a Smartphone is not bothered by parasitic noise.

[0048] Figures 7 and 8 illustrate frequency responses of a Gaussian filter G_f. As will be seen below, the Gaussian filter is not effective in reducing noise from secondary harmonics, nor in increasing the slope of the rising edges r and falling edges r' of a first FSK signal.

[0049] The diagram in [Fig.7] illustrates the frequency response of a Gaussian filter G_f relative to a useful GFSK transmission signal for a bandwidth time BT=0.5. The frequency fq is represented on the abscissa and the signal level in db is represented on the ordinate. As can be seen, on the 1st channel Cl which is the useful transmission channel, for example at the fundamental frequency of 2.44GHz, which is centered on the value 0 on the abscissa, we have a signal level of Odb. For the 2nd channel C2, for example at the frequency of 2.442GHz, whose center is spaced 2MHz from the 1st channel and centered on the value 2000 on the abscissa, which is adjacent to the 1st channel, we have a signal level of -60db which is 1000 times less than the FSK signal on the 1st channel. Thus, the further we are from the useful transmission channel, the weaker the signal will be. We can conclude that the secondary harmonics, especially the 2nd harmonics, are not very important and that consequently the noise is not very present on the two adjacent channels on either side of the 1st channel.However, the useful GFSK transmission signal is slow due to the gentle slope of the rising edges r and the falling edges r' as seen previously.

[0050] The diagram in [Fig.8] illustrates the frequency response of a Gaussian filter G_f relative to a useful GFSK transmission signal for a bandwidth time BT=10. This amounts to having a frequency response of an FSK signal without Hamming filtering Ham_f. Indeed, as illustrated in [Fig.4], the two FSK and GFSK signals have the same shape, namely rising edges r and falling edges r' with a steep slope.

[0051] The frequency fq is represented on the abscissa and the signal level in db is represented on the ordinate. As can be seen, on the 1st channel which is the useful transmission channel, for example at the fundamental frequency of 2.44GHz, which is centered on the value 0 on the abscissa, we have a signal level of Odb. For the 2nd channel, for example at the frequency of 2.442GHz, whose center is spaced 2MHz from the 1st channel and centered on the value 2000 on the abscissa, which is adjacent to the 1st channel, we have a signal level of -6dB which is only half as much as the FSK signal on the 1st channel. The noise emitted in the 2nd channel corresponds to the FSK signal of the 1st channel divided by two. We can conclude that the secondary harmonics, especially the 2nd harmonics, are significant and that the noise is very present on the two adjacent channels on either side of the 1st channel.

[0052] From the diagrams in Figures 7 and 8 which illustrate the frequency response of a Gaussian filter, we can deduce that: - the greater the value of the bandwidth time BT (case BT=10), the less filtering there is, namely the greater the secondary harmonics and consequently the greater the noise, noise which therefore interferes with other communications between the motor vehicle 2 and other electronic devices or between the identifier 1 and other electronic devices, - the smaller the value of the BT bandwidth time (case BT=0.5), the more filtering, namely the lower the secondary harmonics and therefore the lower the noise. However, the slower the useful transmitted signal is since it has a low slope for the rising edges r and the falling edges r' which results in a weakness of the first transmitter 10 with respect to a man-in-the-middle attack.

[0053] As illustrated in [Fig. 2], the second transmitter 20 of the motor vehicle 2 is configured to generate a second FSK signal (for “Frequency Shift Key Coding” in English) which will be transmitted after filtering and used for the distance measurement between the identifier 1 and the motor vehicle 2 (illustrated function f20(20, S'_Fsk)). The second FSK signal is referenced S'_Fsk in [Fig. 2].

[0054] The second transmitter 20 of the motor vehicle 2 is further configured to apply a Hamming filter Ham_f to this second FSK signal (illustrated function f21(20, Ham_f, S'_Fsk)). The same explanations as for the first FSK signal can be used for the second FSK signal. Thus, the diagrams illustrated in Figures 3, 4, 5, and 6 also apply for the second FSK signal, and diagrams 7 and 8 also apply to explain the differences with a useful GFSK transmission signal. Thus, a signal with rising edges r and falling edges r' with a steep slope is obtained by limiting the noise created by the secondary harmonics.

[0055] The second transmitter 20 of the motor vehicle 2 is further configured to transmit this second FSK signal thus filtered to a receiver 11 of the identifier 1, called second receiver 11 (illustrated function f22(20, 11, S'_Fsk). This second transmitted filtered FSK signal is thus a useful transmission signal. It is subsequently used to carry out the distance measurement between the identifier 1 and the motor vehicle 2.

[0056] The receiver 11 is therefore configured to receive said second FSK signal as illustrated in [Fig.2] (illustrated function fl 1(11, 20, S'_Fsk)).

[0057] In a non-limiting embodiment, the second FSK signal is transmitted according to a BLE communication protocol.

[0058] Of course, the description of the invention is not limited to the embodiments described above and to the field described above. Thus, in another non-limiting embodiment, the first FSK signal and the second FSK signal are transmitted according to the UWB communication protocol called in English "Ultra Wide Band". Thus, in a non-limiting embodiment, the first transmitter 10 and the first receiver 11 of the identifier 1 can form a single transmitter / receiver unit. Thus, in a non-limiting embodiment, the second transmitter 20 and the second receiver 21 of the vehicle 2 can form a single transmitter / receiver unit.

[0059] Thus, the invention described presents in particular the following advantages: - it allows transmission to a first receiver 11 of an identifier 1 or to a second receiver 21 of a vehicle 2 a useful transmission signal which, on the one hand, is fast and which, on the other hand, has low secondary harmonics, which has the consequence of obtaining, on the one hand, a first transmitter 10 and a second transmitter 20 robust against man-in-the-middle attacks, and on the other hand, of reducing the parasitic noise around the 1st transmission channel of the useful transmission signal. An unauthorized person cannot therefore fraudulently access the vehicle 2 and the distance measurement between the identifier 1 and the vehicle 2 is reliable, - thus generating an FSK signal and applying a Hamming filter Ham_f to it and then transmitting it to a first receiver 11 with an identifier 1 or to a second receiver 21 is a more efficient solution than generating an FSK signal and applying a Gaussian filter to it to obtain a useful transmission signal GSFK and then transmitting it to a first receiver 11 with an identifier 1 or to a second receiver 21.

Claims

Claims

1. First transmitter (10) of an identifier (1) for a vehicle (2), characterized in that said first transmitter (10) is configured to: - generate a first FSK signal (S_Fsk), - apply a Hamming filter (Ham_f) to said first FSK signal (S_Fsk), - transmit said first filtered FSK signal (S_Fsk) to a second receiver (21) of said vehicle (2) for a distance measurement between said identifier (1) and said vehicle (2).

2. First transmitter (10) according to claim 1, wherein said distance measurement is based on a time-of-flight (TOF) measurement of the rising and falling edges of said first FSK signal (S_Fsk).

3. First transmitter (10) according to any one of the preceding claims, wherein said first FSK signal (S_Fsk) is transmitted according to a BLE communication protocol.

4. First transmitter (10) according to any one of the preceding claims, wherein said identifier (1) is a hands-free access and / or start identifier.

5. Identifier (1) for vehicle (2), characterized in that said identifier (1) comprises a first transmitter (10) according to any one of the preceding claims.

6. Identifier (1) according to claim 5, according to which it is further configured to comprise a first receiver (11) configured to receive from a second transmitter (20) of said vehicle (2) a second FSK signal (S'_Fsk) filtered by a Hamming filter (Ham_f).

7. Identifier (1) according to claim 5 or claim 6, wherein said identifier (1) is a hands-free access and / or start identifier.

8. Second transmitter (20) of a vehicle (2), characterized in that said second transmitter (20) is configured to: - generate a second FSK signal (S'_Fsk), - apply a Hamming filter (Ham_f) to said second FSK signal (S'.Fsk), - transmit said second filtered FSK signal (S'_Fsk) to a first receiver (11) of an identifier (1) for a distance measurement between said identifier (1) and said vehicle (2).

9. A second transmitter (20) according to claim 8, wherein said distance measurement is based on a time-of-flight (TOF) measurement of the rising and falling edges of said second FSK signal (S'_Fsk).

10. Second transmitter (20) according to claim 8 or claim 9, wherein said second FSK signal (S'_Fsk) is transmitted according to a BLE communication protocol.

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