EP1093101B1 - Method for automatic synchronization of a remote control key and an associated calculator - Google Patents

Description

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

Such remotes are widely used nowadays. They allow, for example, to open or close the doors of a vehicle remotely. To do this, and to avoid any fraud or unauthorized opening, the codes issued between the key and the computer controlling the locking / unlocking of the doors, no longer use fixed codes but so-called rotating codes.

Indeed, if the code issued by the key is always the same, as was the case before, it was enough for a malicious person to copy this code to then have access to the vehicle without difficulty. To overcome these frauds, the codes issued between the key and the computer are so-called rotating codes. Such codes are calculated at each transmission from an algorithm known by the key and by the computer according to the preceding code and an increment. Such rotating codes give good results, since the code issued by a key to a given vehicle is never the same. Thus, it is no longer enough to copy a code issued to access the vehicle.

However, this type of code has a major disadvantage, namely a risk of desynchronization between the key and the computer. Indeed, each of these devices (key and calculator) calculates according to the same algorithm a code, but this way quite independently. Thus, if for some reason the last code issued 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 calculator. There is desynchronization. The slight desynchronizations (that is to say if the key is in advance of about fifty codes on the calculator) are already resolved and this will not be detailed here. On the other hand, important desynchronizations (the calculator and the key no longer find common elements in their code list) remain an important problem.

In the event that such significant desynchronization is detected, it is possible to resynchronize the key and the computer by manual procedures. These, however, require the active participation of the driver and sometimes take a significant time. Such a procedure is described in the document US 5,369,706 .

The object of the present invention is to establish a method of resynchronization between a key and a computer automatically, in the most transparent manner and as fast 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.

For this purpose, the present invention relates to a method of automatic synchronization 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 performed using a rotating code and allowing at least the locking / unlocking of the opening of the vehicle, said method consisting of:

• the emission by the key of a code of condemnation / unlocking of the opening of the vehicle,
• the receipt by the computer of the transmitted code and the analysis of this code,
• detecting a desynchronization between a code expected by the computer and the code transmitted by the key,

said process being characterized in that it further comprises:

• the transmission by the computer of a first message comprising a desynchronization code, a challenge code and its associated response code, as determined by the computer according to an algorithm specific to said calculator and known to the key,
• the receipt 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 with its own response to the 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 base code, and
• the receipt 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 a new base code for the remote control of the opening of the vehicle.

Thus, the synchronization requires only a normal support by the driver on the key, the first and second messages being generated automatically and quickly terminating the resynchronization. The driver may not be aware that the key has been resynchronized because the transmission of all messages is very fast.

Preferably, the messages are transmitted radiofrequency which limits the realization 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 ill-intentioned person is placed next to the vehicle.

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

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

Indeed, two successive resynchronizations made between the same key and the same computer do not cause the exchange of the same codes and furthermore do not give access thereafter 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, features and advantages of the present invention will become apparent from the description which follows, by way of nonlimiting example, and with reference to the appended drawings in which:

• the figure 1 , is a schematic view showing a key and an associated motor vehicle, and
• The 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 performed between a key 10 and a motor vehicle 11 to which it is assigned.

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

Correspondingly and also known per se, the motor vehicle 11 is provided with a computer 13 managing means M1 for memorizing the algorithm specific to the vehicle and M2 memory means of the algorithm specific to the key. This computer 13 is adapted to control at least the locking / unlocking of the opening of the vehicle 11. The computer 13 exchanges radiofrequency signals with the electronic computer 12 disposed in the key 10.

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

As shown in figure 2 when the key 10 and the computer 13 of the vehicle are synchronized, the sending of a locking command C or unlocking D ( step 20 ) by the key is received ( step 30 ) by the computer 13 of the vehicle. This computer 13 controls the conviction C or unlocking D ( step 50 ) of the opening, after verification ( step 40 ) that the code sent by the key is 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 performed 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 available codes 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 response code associated with this challenge code is the code obtained by the computer when it applies the algorithm M1 to the random number (challenge code). This algorithm M1 is an algorithm specific to the calculator and is known to the key.

• sa propre réponse à ce code défi.

When the key 10 receives ( step 70 ) this first message. It first 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 computer is identical to the one it finds itself by applying the algorithm M1. When this is the case, it issues a second message including:

• his own answer to this challenge code.

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

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

The computer 13 receives this second message (step 80) and verifies that it is correct. For this purpose, it verifies that it finds the same response code by applying the algorithm M2. 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 conviction or unlocking requested by the key is then allowed ( step 50 ).

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

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

It should be noted that this resynchronization procedure is substantially transparent (not detectable) for the user. The time taken to exchange the first and second messages is insignificant and does not significantly prolong the conventional conviction / unlocking procedure. Only the range of the remote control is reduced for the duration of the resynchronization.

It should also be noted that since the signal exchanges between the key and the computer are carried out by radio frequency or low frequency messages, this automatic resynchronization procedure can only be performed in a restricted area around the vehicle (a few meters).

Alternatively, it is possible to use as the new base code, 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 the spying of the transmissions between the key and the computer. For some applications, this may very well not be a disadvantage.

Of course, the present invention is not limited to the embodiment described and encompasses any variant within the reach of those skilled in the art. Thus, the new code of condemnation / unlocking (still called basic code) could be not the challenge code sent by the key but a function of this code challenge.

Claims (6)

1. Method for automatic synchronisation between a remote control key (10) and a computer (13) onboard an automotive vehicle assigned to this key, the exchange of commands between the key and the computer being carried out using a revolving code and allowing at least the locking/unlocking of the doors and other openings of the vehicle, said method comprising:

   - the emission by the key of a code for locking/unlocking the doors and other openings of the vehicle (step 20)

   - the receipt by the computer of the code emitted and the analysis of this code (step 30)

   - the detection of desynchronisation between a code expected by the computer and the code emitted by the key (step 40),

   said method being characterised in that it also consists in:

   - the emission by the computer (13) of a first message having a desynchronisation code, a so-called challenge code and its associated response code as determined by the computer according to an algorithm (M1) unique to said computer and known to the key (step 60),

   - the receipt (step 70) by the key of the first message and its analysis so as to inform the key of the desynchronisation and validate the response code sent by the computer, the key then emits a second message having its unique response to said challenge code, this response being determined from an algorithm (M2) unique to the key and known to the computer, the key stores the challenge code sent by the computer as a base code (step 75) and

   - the receipt (step 80) by the computer of the second message and its analysis, to check that the response code sent is indeed that of the key assigned to the vehicle and in this case the computer is resynchronised with the key using the challenge code as the new base code (step 100) for remote control of the vehicle doors and other openings.
2. Method according to claim 1, characterised in that the challenge code emitted by the computer is a random code.
3. Method according to claim 1 or 2, characterised in that the exchange of commands between the key and the computer is carried out by means of radio frequency signals.
4. Method according to claim 3, characterised in that the synchronisation of the key and vehicle computer is carried out within a radius of approximately 4 m around the vehicle.
5. Method according to claim 1 or 2, characterised in that the exchange of commands from the computer (13) to the key (10) is carried out by means of a low frequency LF signal.
6. Method according to one of the preceding claims, characterised in that the new base code is a function of the challenge code.

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