FR2774120A1 - Remote security lock for vehicles - Google Patents

Abstract

The vehicle key (30) contains a remote control module comprising a code transmitter (31) and a key identification circuit (32) sharing a common memory. The code (Ci) is pseudo-randomly based a key code and the number of times the key has been operated. In the vehicle there is a code detector (10) which tracks the remote code and can operate the door locks. This detector connects through a data bus (B) to a key authentication circuit (20). When remote unlock is activated by a key user to unlock the vehicle, a security code is transmitted by the key. If the detector recognises the code then the doors are unlocked and vehicle functionality is enabled. If the code is not recognised, for instance when the evolving codes in the vehicle and the key become out of synchronization, then the doors have to be manually unlocked and vehicle starting remains disabled. Under these circumstances, when the key is placed in the ignition switch the vehicle key authentication system communicates bi-directionally with the key identity circuit by magnetic induction coupling. If the key is identified as valid, the code detect system resynchronises itself to the latest code received from the key, and vehicle functionality is enabled.

Description

Locking system for motor vehicles with evolving code and identification
The present invention relates to a system for locking the doors of a motor vehicle comprising a remote control with an evolving code, and more particularly to such a system making it possible to initialize and / or resynchronize this code in a reliable manner and economic.

 For obvious security reasons, current motor vehicles use door lock / unlock devices employing progressive code systems. A remote control transmitter, located in the key, sends a different coded message to each device linked to the vehicle. The remote control receiver, included in the locking control device linked to the vehicle, receives this coded message, compares it with an expected code and unlocks the doors if the two messages are identical. For such a system to work, it is necessary that the transmitter and the receiver start from identical code values and evolve synchronously over time.

The prior art is known, for example from the patent
US 4,825,210, such a remote control locking system using an evolving code. In this document, the initialization of the remote control transmitter and receiver to common values is carried out by means of a wired link carried out in the factory of the automobile manufacturer. Such a link requires connectors, both on the receiver and on the key, and its implementation is costly.

In addition, another problem encountered in these systems is the desynchronization between the sequence of codes transmitted by the transmitter and the sequence of codes expected by the receiver. The document cited above proposes, to resolve this problem, to compare the code received with a first list of codes known as the capture sequence, and if the code received belongs to this list, to immediately unlock the doors.

If the code received does not belong to this first list, it is compared to an extended list called synchronization sequence, and we await the reception of a second code, immediately following in the sequence to confirm the authorization of unlock, and resynchronize the receiver to the transmitter sequence.

However, such a system, if it is satisfactory when the desynchronization comes from repeated presses on the remote control key outside the vehicle reception field, has a certain drawback when the desynchronization comes from a change of battery of the remote control. Indeed, in this latter case, the sequence of codes transmitted can start from a random point in the sequence of possible codes and have no code common with the synchronization sequence, unless this latter covers all the possible codes , which is costly in terms of memory and computation time, or even impossible with codes comprising several billion possible combinations.

 The object of the present invention is therefore to propose a system which allows reliable and economical initialization and resynchronization between transmitter and receiver.

 To do this, advantage is taken of the coexistence in the key of the aforementioned remote control transmitter and an identification responder, also called a transponder, used for example by a vehicle immobilization device, as described in GB patents 2,051,442 or US 4,738,334.

 These objects of the invention are achieved, as well as others which will appear in the remainder of this description, by means of a locking system for a motor vehicle, comprising a device for locking / unlocking the doors of the adapted vehicle. to receive a door locking / unlocking code and to command unlocking if the code received corresponds to an expected code, said code being of the evolving type composed from a first basic keyword and a second pseudo keyword random, an identification device and at least one key comprising on the one hand a remote control transmitter adapted to transmit to the device for controlling the doors of the vehicle, by a first channel, a code for locking / unlocking the doors, on the other hand an identification responder adapted to transmit, by a second channel, an identification code of the key in response to a request from the dis positive identification.

 According to the invention, during an initialization or resynchronization of the system, at least one of the keywords of the door locking / unlocking code is exchanged between the control device and the key via the identification responder and the identification device using the second transmission channel.

 According to an important characteristic of the present invention, the key further comprises storage means common to the remote control transmitter and to the identification responder.

 According to a first aspect of the invention, during an initialization of the system, the first basic keyword is transmitted by the key to the control device, that is to say that the first basic keyword is deduced from the identification code of the key, either that it is predefined in storage means specific to the identification responder and transmitted only during the first transmission. According to a variant making use of the storage means common to the remote control transmitter and to the identification responder, the first basic keyword can be predefined in these and transmitted only during the first transmission.

 Advantageously, the second communication channel can be bidirectional, and during an initialization of the system, the first basic keyword is transmitted by the control device to the key, and stored by the identification responder in the storage means. common.

 According to a second aspect of the invention, during a resynchronization of the system, the second keyword is transmitted by the key to the control device via the identification responder and the identification device, after positive identification of the key by this first. As before, when the second communication channel is bidirectional, the second keyword is transmitted to the key by the control device via the identification device and the identification responder, after positive identification of the key. by this last one.

According to an advantageous characteristic, the second keyword is reset to a random value.

Other characteristics and advantages of the system according to the invention will appear on reading the description which follows and on examining the appended drawings in which:
- Figure I shows the locking system in a configuration
making use of the first channel of transmission,
- Figure 2 shows the locking system in a configuration
making use of the second transmission channel, and
- Figure 3 shows a diagram of the key comprising means of
memorization common to the remote control transmitter and the answering machine
identification.

 Referring to Figure 1 in which there is shown a vehicle 1 equipped with a door locking / unlocking control device 10 conventionally comprising a remote control receiver, a decoder adapted to comoar a received code with an expected code and means for controlling motors or actuators operating the vehicle door locks. These means, well known in the prior art, will not be detailed further and are not shown explicitly in the drawing. The vehicle 1 is also equipped with an identification device 20, possibly forming part of a vehicle immobilization device. The control device 10 and the identification device 20 are interconnected by a communication bus B. FIG. 1 also shows a key 30, equipped on the one hand with a remote control transmitter 31, and d 'other hand of an identification responder 32. In this configuration of the locking system, the key 30 is located outside the vehicle 1, at a certain distance from it, a few tens of meters for example. To unlock the doors of the vehicle, the driver presses a switch 33 (FIG. 3), which induces the remote control transmitter 31 to send an unlocking code Ci to the locking control device 10. This transmission takes place according to a first RF communication channel, by means of electromagnetic waves in radio frequencies, or even by emission of infrared radiation. Due to the necessary scope and the low directivity of this communication channel, it is possible that the transmission is spied on in order to appropriate the transmitted code for malicious purposes. To make these hacking attempts unsuccessful, the code Ci issued is of the evolving type, that is to say that successive codes are different from each other. This code is conventionally produced by combining, by an algorithm f, a first basic keyword Cb with a second pseudo-random keyword Ni. This second keyword is generally developed from the number of presses on the switch 33 from an initialization step in which the control device 10 and the remote control transmitter 31 have been programmed with the same basic keyword. Cb and an identical value No for the second keyword. This value is then regularly incremented, on the one hand each time the switch 33 is pressed for the key, and on the other hand, each time a code Ci is received for the control device 10. When the control device 10 receives an unlocking code Ci, it compares it with an expected code, developed by the same algorithm f, from the basic keyword Cb and the current image N'i of the second keyword it holds. If the code received corresponds to the expected code, the vehicle doors are unlocked.

 As we saw previously, the RF communication channel is not very secure, and requires the use of an evolving code which imposes an initialization of the basic keyword Cb and a possible resynchronization of the second pseudo-random keyword Ni when the values stored in the locking device and the key differ.

 Referring now to Figure 2, where there is shown a second configuration of the locking system in which use is made of a second communication channel which is advantageously taken advantage of to solve the initialization and resynchronization problems . In this configuration, the key 30 is located inside the vehicle, and preferably inserted in the contact barrel of the vehicle. In this position, the identification device 20 and the identification responder 32 of the key 30 are spatially very close, of the order of a few centimeters. In a manner known per se, the identification device 20 and the identification responder 32 exchange an identification code Xp by means of a communication channel BM with very short range, for example by magnetic coupling. Due to the very short range of the BM communication channel, it is unlikely to be spied on and therefore constitutes a very safe communication channel. It can then be used to transmit between the key and the vehicle confidential information such as the basic keyword Cb and / or the second keyword Ni.

This transmission takes place from the key 30 to the identification device 20, which, suitably programmed, transmits this information to the control device 10 via the communication bus B.

 We take advantage of this possibility in several cases. For example, during the initialization of the locking system in the manufacturer's factory, it is possible to save on the wired link usually used to program the control device 10 with the basic keyword Cb. As an example of such an initialization process, it suffices to insert the key 30 into the contact barrel. On power-up, the control device 10, then blank, sends a request to the attention of the identification device 20, also blank. The latter then activates the second communication channel BM and obtains from the identification responder 32 of the key an identification code Xp which it stores. The identification device 20 is therefore initialized.

Several solutions are possible for the basic keyword Cb.

 According to a first variant, during the production of the key, a basic keyword Cb has been programmed in the remote control transmitter 31 deducing from the identification code Xp by a particular transformation. in this case, the identification device 20 applies the same transformation to the stored code Xp and transmits this transformed code as a basic keyword Cb to the control device 10 which stores it in memory. The locking system initialization process is then completed for this key and can be repeated for as many keys as it is intended to supply with the new vehicle.

 According to a second variant, a copy of the basic keyword Cb can be saved during the production of the key, in addition to the code Xp, in the memory of the identification responder 32, if the size allows it. In this case, after transmission and storage of the code Xp, the identification device 20 keeps the communication channel BM open until reception of the basic keyword Cb which it then transmits to the control device 10. Advantageously, it will be possible to provide in the programming of the key that this transmission can only take place once to avoid that a malicious person temporarily entering the possession of the key cannot subsequently obtain this basic keyword Cb.

 It will be noted that in the two variants exposed above, the remote control transmitter 31 and the identification responder 32 are independent of each other, the link between the two being limited to suitable programming carried out by the manufacturer. of the key. We will now describe in relation to FIG. 3, a key 30 comprising optional means allowing other possibilities. This figure shows a key 30, equipped on the one hand with a remote control transmitter 31, controlled by a switch 33 and powered by a battery 34, and on the other hand with an identification responder 32. The key 30 further comprises storage means 35 common to the remote control transmitter 31 and to the identification responder 32. These storage means 35 may consist of a RAM memory saved by the battery 34 and / or a electrically erasable permanent memory (EEPROM), and can be read and written by the remote control transmitter 31 and the identification responder 32.

 In the case where the key 30 is thus equipped with common storage means 35, a third variant consists in recording in these means the basic keyword Cb which will thus be jointly used by the identification responder 32 during initialization as seen in the second variant, and by the remote control transmitter in normal operation.

 Advantage can be taken advantage of these common storage means when the second communication channel BM is bidirectional. Indeed, it is then possible for the control device 10 to transmit to the identification device 20 a request to write the basic keyword Cb in the storage means 35 via the identification responder 32. In this case, we can use a completely blank system, including the key, and the basic keyword Cb can be imposed by the manufacturer by connecting to bus B or can be defined randomly and arbitrarily by the system autonomously.

 A locking system has thus been described which allows economical initialization, by making use of a second short-range communication channel instead of a wired connection between vehicle and key. In addition, this system has a security advantage over a system that would use the first RF communication channel to replace the wired link during initialization. Indeed, on a production line, the vehicles are close to each other, and the use of the first RF communication channel could cause disturbances from one vehicle to another given its range.

 In addition, the advantages of such a locking system are not limited to the vehicle initialization phase alone, but also provide increased security during resynchronization phases between the control device 10 and the remote control transmitter 31 Indeed, as we saw in the preamble, repeated presses on the switch 33 out of range of the vehicle, or a change of the battery 34 can cause a break in the continuity of the sequence of the second keyword Ni between the remote control transmitter 31 and the control device 10, resulting in the non-recognition of the code Ci and therefore the non-operation of the locking or unlocking of the doors remotely. In this case, the driver only has to open a door by means of the mechanical lock and insert the key into the contact barrel of the vehicle. This action then triggers a key identification process by means of the identification device 20, which sends an identification request via the second communication channel, for example a magnetic coupling loop, request to which the answering machine identification 32 placed in the key responds by modulating the magnetic field emitted according to the identification code Xp. This identification code is compared to the reference code programmed in the identification device 20, to authenticate the key and for example authorize the engine to start in the event of a match. At the same time, the control device 10, having detected a loss of synchronization, for example by receiving an incorrect Ci code followed within a predetermined period by manual opening of the door, transmits to the identification device 20 a request to transmit the second keyword Ni. The identification device, after positive identification of the key, keeps the second communication channel open or reactivates it according to a predetermined process, which induces the identification responder 32 to extract from storage means 35 the current value of the second word key Ni and to transmit it by the second communication channel. The second keyword is then redirected to the control device 10 by the identification device 20 by means of the bus B, for updating. Consequently, the control device 10 is resynchronized with the remote control transmitter 31, and the next transmission of a code Ci by the first communication channel can be carried out successfully.

 Of course, for the sake of simplification, the second keyword Ni could be systematically transmitted after each positive identification of the key.

 When the transmission can be carried out bidirectionally by the second communication channel, it is conceivable to program the control device 10 so that it transmits to the remote control transmitter 31, via the identification device 20 , the second communication channel and the identification responder 32, a new value of the second keyword Ni, either systematically, or following a loss of synchronization, after positive identification of the key.

 Whether the transmission of the second keyword Ni takes place from the remote control transmitter 31 to the control device 10 or vice versa, the value of this second keyword can be chosen randomly. Therefore, in the event of systematic transmission, the code Ci then becomes purely random, thus reinforcing the security of the system.

Claims (10)

 a request from the identification device, characterized in that during an initialization or resynchronization of the system, at least one of the key words (Cb, Ni) of the door locking / unlocking code is exchanged between the control device and the key via the identification responder and the identification device using the second transmission channel.  a second channel (BM), an identification code (Xp) of the key in response to  c on the other hand an identification responder (32) adapted to transmit, by  (RF), a code (Ci) for locking / unlocking the doors,  vehicle door control device, via a first track  r firstly a remote control transmitter (31) adapted to transmit to the  CLAIMS 1. Locking system for a motor vehicle, comprising a) a control device (10) for locking / unlocking the doors of the vehicle adapted to receive a code (Ci) for locking / unlocking the doors and for controlling unlocking if the code received corresponds to an expected code, said code being of the evolving type composed from a first basic keyword (Cb) and a second pseudo-random keyword (Ni) b) an identification device (20), and c) at least one key (30) comprising 2. Locking system according to claim 1, characterized in that the key further comprises storage means (35) common to the remote control transmitter and the identification responder. 3. Locking system according to claim 1, characterized in that during initialization of the system, the first basic key word (Cb) is transmitted by the key (30) to the control device (10). 4. Locking system according to claim 3, characterized in that the first basic key word (Cb) is deduced from the identification code (Xp) of the key. 5. Locking system according to claim 3, characterized in that the first basic keyword (Cb) is predefined in storage means specific to the identification responder (32) and transmitted only during the first transmission. 6. Locking system according to claims 2 and 3, taken in combination, characterized in that the first basic keyword (Cb) is predefined in the common storage means (35) and transmitted only during the first transmission. 7. Locking system according to claim 2, characterized in that the second communication channel (BM) is bidirectional, and in that during an initialization of the system, the first basic keyword (Cb) is transmitted by the control device (10) to the key (30), and stored by the identification responder in the common storage means (35). 8. Locking system according to any one of the preceding claims, characterized in that during a resynchronization of the system, the second key word (Ni) is transmitted by the key to the control device via the answering machine. identification and the identification device, after positive identification of the key by the latter. 9. Locking system according to any one of claims 2 to 6, characterized in that during a resynchronization of the system, the second key word (Ni) is transmitted to the key by the control device via the identification device and the identification responder, after positive identification of the key by the latter. 10. Locking system according to claim 8 or 9, characterized in that the second key word (Ni) is reset to a random value.