EP1093101A1 - Method for automatic synchronization of a remote control key and an associated calculator - Google Patents

Abstract

Procedure consists of: (a) transmission by computer of message having desynchronizing , challenge code and associated response code (60); (b) receipt and analysis (70) by key of message, then emission of second message with its response to the challenge code (75); (c) receipt (80) by the computer of the message and code verification, if verified re-synchronize with the key using the challenge code as new base code (100) for opening the vehicle. Method of automatic synchronization between a vehicles remote locking key and a computer placed onboard the vehicle which exchanges controls between it and the key using a code which permits locking and unlocking of the vehicles doors. The method has the following stages: (a) transmission of a locking/unlocking code for opening the vehicles doors (20); (b) receipt by the onboard computer of the transmitted code and analysis of the code (30); (c) detection of de-synchronization between an expected code by the computer and the code transmitted by the key (40).

Description

The present invention relates to a synchronization method automatic between a remote control key and an associated computer. More in particular, it is a remote control for locking / unlocking opening of a vehicle.

Such remote controls are widely used these days. They allow, for example, to open or close the doors of a vehicle. To do this, and in order to avoid any unauthorized fraud or opening, the codes issued, between the key and the computer controlling the lock / unlock doors, no longer use fixed codes but so-called revolving codes.

Indeed, if the code emitted by the key is always the same, as it was case before, it was enough for a malicious person to copy this code to then have easy access to the vehicle. To overcome these frauds, the codes issued between the key and the computer are so-called revolving codes. Such codes are calculated on each transmission from an algorithm known by the key and by the calculator according to the previous code and an increment. Such codes turns give good results, since the code sent by a key to a given vehicle is never the same. Thus, it is no longer enough to copy a code issued to gain access to the vehicle.

However, this type of code has a major drawback, namely a risk of desynchronization between the key and the computer. Indeed, each of these devices (key and calculator) calculates a code according to the same algorithm, but this completely independently. So if for some reason the last code sent by the key and the last code received by the computer are not the same, it is no longer possible to remotely control the computer from the key. This happens especially when you press the key, voluntarily or not, while it is out of range of the computer. There is desynchronization. The slight desynchronizations (i.e. if the key is one step ahead fifty codes on the computer) are already resolved and this will not be detailed here. On the other hand, important desynchronizations (the computer and the key no longer find common elements in their code list) remain a important problem.

In the event that such significant desynchronization is detected, it it is possible to resynchronize the key and the computer by procedures manual. However, these require the active participation of the driver and sometimes take considerable time.

The object of the present invention is to establish a method of resynchronization between a key and a computer automatically, from the as transparently and quickly as possible for the user.

• l'émission par la clef d'un code de condamnation / décondamnation des ouvrants du véhicule,
• la réception par le calculateur du code émis et l'analyse de ce code,
• la détection d'une désynchronisation entre un code attendu par le calculateur et le code émis par la clef,

le dit procédé étant caractérisé en ce qu'il consiste en outre en :

• l'émission par le calculateur d'un premier message comportant un code de désynchronisation, un code dit de défi et son code de réponse associé, tel que déterminé par le calculateur selon un algorithme propre au dit calculateur et connu de la clef,
• la réception par la clef du premier message et son analyse de manière à informer la clef de la désynchronisation et à valider le code réponse envoyé par le calculateur, la clef émet alors un second message comportant sa propre réponse à ce même code défi, cette réponse étant déterminée à partir d'un algorithme propre à la clef et connu du calculateur, la clef mémorise le code défi envoyé par le calculateur en tant que code de base, et
• la réception par le calculateur du second message et son analyse, pour vérifier que le code réponse envoyé est bien celui de la clef affectée au véhicule et dans ce cas le calculateur se resynchronise avec la clef en utilisant le code défi comme nouveau code de base pour la télécommande des ouvrants du véhicule.

To this end, the present invention relates to an automatic synchronization method between a remote control key and a computer placed in a motor vehicle assigned to this key, the exchange of commands between the key and the computer being carried out using a rolling code and allowing at least the locking / unlocking of the opening of the vehicle, the said process consisting of:

• the issuance by the key of a locking / unlocking code for the opening parts of the vehicle,
• the reception by the computer of the code transmitted and the analysis of this code,
• the detection of a desynchronization between a code expected by the computer and the code sent by the key,

said process being characterized in that it also consists of:

• the sending by the computer of a first message comprising a desynchronization code, a so-called challenge code and its associated response code, as determined by the computer according to an algorithm specific to said computer and known to the key,
• the reception by the key of the first message and its analysis so as to inform the key of the desynchronization and to validate the response code sent by the computer, the key then emits a second message comprising its own response to this same challenge code, this response being determined from an algorithm specific to the key and known to the computer, the key stores the challenge code sent by the computer as a basic code, and
• reception by the computer of the second message and its analysis, to verify that the response code sent is that of the key assigned to the vehicle and in this case the computer resynchronizes with the key using the challenge code as the new base code for the remote control of the vehicle's windows.

Synchronization therefore requires only normal support by the driver on the key, the first and second messages being generated automatically and quickly leading to resynchronization. The driver may very well not not realize that the key has been resynchronized, because the transmission of the set of messages is very fast.

Preferably, the messages are transmitted by radio frequency which limits the completion of the resynchronization procedure to a few meters around the vehicle (about 4 to 5 m). This limits the possibility of copying or to analyze the messages exchanged, because it would be necessary that the person wrong be placed next to the vehicle.

As a variant, communication in the vehicle / key direction is performed using a low frequency (LF) of the order of 125 KHz per example. This results in a reduced range for the corresponding signal (of the order 1 m). This further limits the possibility of hacking between the vehicle and the key.

In addition, even if a malicious person was near the vehicle, as the challenge code sent is random and the response codes associates are consequently also, it is impossible to perform a dummy resynchronization to try to reuse the same codes. This would not work.

Indeed, two successive resynchronizations carried out between the same key and the same computer do not cause the exchange of the same codes and furthermore do not subsequently give access to the same code lists.

• la figure 1, est une vue schématique représentant une clef et un véhicule automobile associé, et
• La figure 2 est un diagramme présentant, de manière schématique, les différentes étapes du procédé selon l'invention.

Other objects, characteristics and advantages of the present invention will emerge from the description which follows, by way of nonlimiting example, and with reference to the appended drawings in which:

• FIG. 1 is a schematic view showing a key and an associated motor vehicle, and
• Figure 2 is a diagram showing, schematically, the different steps of the method according to the invention.

According to Figures 1 and 2, the resynchronization method according to the present invention is carried out between a key 10 and a motor vehicle 11 to which it is affected.

This key 10 is provided with an electronic computer 12 comprising radiofrequency signal transmission and reception units, as well as means of creating such signals. These means are well known in them and do not are not detailed here. In particular, the key 10 has means of memorization M1 of an algorithm specific to the vehicle and the means of M2 memorization of an algorithm specific to the key. The electronic computer 12 is adapted to manage all of these means.

Correspondingly and also known per se, the vehicle automobile 11 is provided with a computer 13 managing means M1 of memorizations of the vehicle's own algorithm and M2 means of memorizations of the algorithm specific to the key. This computer 13 is suitable for order at least the condemnation / unlocking of the opening of the vehicle 11. The computer 13 exchanges radio frequency signals with the electronic computer 12 placed in the key 10.

As a variant, this computer 13 exchanges low frequency signals (LF) with the key.

As shown in FIG. 2, when the key 10 and the computer 13 of the vehicle are synchronized, the sending of a condemnation C or unlocking command D ( step 20 ) by the key is received ( step 30 ) by the computer 13 of the vehicle. This computer 13 controls the condemnation C or unlocking D ( step 50 ) of the opening elements, after checking ( step 40 ) that the code sent by the key is indeed in its list of available codes (this list is continuously updated in a known manner in itself).

To make it easier to read Figure 2, the operations performed by the key are presented in a hatched frame, while the operations carried out by the computer 13 are presented in a simple frame.

When in step 40 , the computer 13 detects a significant desynchronization, the method according to the present invention ( steps 60 to 100 ) is implemented.

It is recalled that a significant desynchronization corresponds to the fact that the code issued by the key is not found by the computer 13 in the list of 50 or 100 codes available according to the last code listed by the computer.

• un code logique indiquant qu'une désynchronisation a été détectée,
• un code défi, et
• un code réponse associé à ce code de défi.

In this case, the code sent by the key does not correspond to one of the codes expected by the computer 13. The computer 13 then sends a first message ( step 60 ) to the key. This first message includes:

• a logic code indicating that a desynchronization has been detected,
• a challenge code, and
• a response code associated with this challenge code.

The challenge code is a random number generated by the computer 13. The code response associated with this challenge code is the code obtained by the calculator when it applies the M1 algorithm to the random number (challenge code). This M1 algorithm is an algorithm specific to the computer and is known from the key.

• sa propre réponse à ce code défi.

When the key 10 receives ( step 70 ) this first message. First, it notes that a desynchronization has been detected, then it verifies (in a validation step of the first message received) that the response code sent by the calculator is indeed identical to the one it finds itself by applying the M1 algorithm. When this is the case, it sends a second message comprising:

• his own response to this challenge code.

The response of key 10 to the challenge code sent by the computer is obtained by applying the M2 algorithm specific to the random number key (challenge code). This algorithm M2 is also known to the computer 13.

In addition, the key 10 stores the challenge code and considers it as its new basic code for the remote control. It thus updates its basic code ( step 75 ).

The computer 13 receives this second message (step 80) and checks that it is correct. To this end, it checks that it finds the same response code by applying the M2 algorithm. If this is the case, the computer 13 updates its base code ( step 100 ) by taking the challenge code as the new base code. The condemnation or unlocking requested by the key is then authorized ( step 50 ).

It follows that the key and the computer 13 are again synchronized. The new basic code for the remote control being the challenge code sent by the calculator.

If the response code sent by the key is not correct, the resynchronization process stops ( step 90 ).

Note that this resynchronization procedure is substantially transparent (not detectable) for the user. The time taken to exchange first and second messages are insignificant and do not extend significant the classic conviction / unlocking procedure. Only the range of the remote control is reduced for the duration of the resynchronization.

It will also be noted that since the exchange of signals between the key and calculator are carried out by radio or low frequency messages frequency, this automatic resynchronization procedure cannot be carried out only within a limited perimeter around the vehicle (a few meters).

As a variant, it is possible to use as new basic code, not not the challenge code but the response code (which is a function of the challenge code). However, the scope of the key being important, the use of this response code facilitates spying on transmissions between the key and the computer. For some applications, this may not be a disadvantage.

Of course the present invention is not limited to the mode of implementation work described and encompasses any variant within the reach of ordinary skill in the art. So the new conviction / unlock code (also known as the base code) could not be the challenge code sent by the key but a function of this code challenge.

Claims (6)

Method of automatic synchronization between a remote control key (10) and a computer (13) placed in a motor vehicle assigned to this key, the exchange of commands between the key and the computer being carried out using a rolling code and allowing at least the locking / unlocking of the openings of the vehicle, the said process consisting of: the transmission by the key of a locking / unlocking code for the opening parts of the vehicle (step 20), the reception by the computer of the code transmitted and the analysis of this code (step 30), the detection of a desynchronization between a code expected by the computer and the code sent by the key (step 40), said process being characterized in that it also consists of: the sending by the computer (13) of a first message comprising a desynchronization code, a so-called challenge code and its associated response code as determined by the computer according to an algorithm (M1) specific to said computer and known from the key (step 60), reception (step 70) by the key of the first message and its analysis so as to inform the key of the desynchronization and to validate the response code sent by the computer, the key then sends a second message comprising its own response to this same code challenge, this response being determined from an algorithm (M2) specific to the key and known to the computer, the key stores the challenge code sent by the computer as a basic code (step 75), and reception (step 80) by the computer of the second message and its analysis, to verify that the response code sent is that of the key assigned to the vehicle and in this case the computer resynchronizes with the key using the challenge code as new basic code (step 100) for the remote control of the vehicle's windows. Method according to claim 1, characterized in that the challenge code emitted by the computer is a random code. Method according to claim 1 or 2, characterized in that the exchange of control between the key and the calculator is carried out using signals radio frequency. Method according to claim 3, characterized in that the synchronization of the vehicle key and computer is carried out in a radius of around 4 m around the vehicle. Method according to claim 1 or 2, characterized in that the exchange for controlling the computer (13) to the key (10) is produced using a signal low frequency (LF). Method according to any one of the preceding claims, characterized in that the new basic code is a function of the challenge code.

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