EP1665195A1

EP1665195A1 - Inter-object communication method

Info

Publication number: EP1665195A1
Application number: EP04744332A
Authority: EP
Inventors: Claude Desbiolles
Original assignee: Somfy SA
Current assignee: Somfy SA
Priority date: 2003-09-16
Filing date: 2004-08-31
Publication date: 2006-06-07
Also published as: FR2859854A1; FR2859854B1; WO2005027074A1

Abstract

A communication method for controlling electrical building comfort and/or security equipment. The method is based on a protocol in which the communication signals have a common frame format containing an instruction and a frame integrity check code computed for every transmitted signal. Said method is characterised in that a signal frame integrity check code computation algorithm is assigned to each transmitter type, and in that, for each transmission between an instruction transmitter and an instruction receiver, the receiver probabilistically identifies the transmitter type by comparing a first integrity check code transmitted with the signal frame with a second integrity check code computed by the receiver from the received signal.

Description

Communication method between objects

The invention relates to a communication method according to the preamble of claim 1. It also relates to an installation for the implementation of such a method.

The protocols used in current home automation networks have drawbacks.

On the one hand, when defining a protocol for a home automation network, it is very difficult to determine the lifetime of a protocol and the number of elements that will use it. Indeed, the need existing during the design of the network can evolve. It can in particular increase and the number of available addresses, an address which is desired to be unique for each element using the protocol, may then be lacking. The designed protocol can no longer meet the need. However, it is important to ensure the sustainability or compatibility of home automation networks over time.

On the other hand, during the lifetime of the protocol, it can be interesting to personalize the relationships between the different elements using the same communication protocol. One can in particular create relations between the elements of the network so that certain elements communicate only with others (partitioning) or create relations between the elements so that a maximum of elements communicate with each other (interoperability).

Document DE 197 54377 discloses an installation providing elements of solutions to these drawbacks. This document describes a receiver containing two decoding algorithms in memory to allow the reception of information from different transmitters. It is thus possible to receive information from two different types of transmitter (a manufacturer transmitter, a universal transmitter, whose coding algorithm is to be recorded in the receiver). These coding and decoding algorithms are of the rolling code type. A such an installation could be applied to a home automation application but it would however have some drawbacks. Indeed, the receiver must at each transmission of a signal by a command transmitter decode the signal and read the corresponding message before determining if it is authorized to receive information from this transmitter. These operations, in particular the decoding operation, use significant computation resources of the receiver. It is therefore easy to understand that if such an installation is used for a home automation application, the computing resources of the various receivers of the network would frequently be used to decode orders that are not intended for them. This is particularly problematic in the case of standalone applications.

Also known from US Patent 5,917,840, a factory production control installation. In a first embodiment, this installation makes it possible to secure a message without transmitting the identifier of the receiver: a control value is generated by calculation from the identifier of the expected receiver and of the message. On receipt of the message, a new control value is calculated by the receiver from the message and its identifier. If the control values are equal, the message is accepted. It is therefore a means of identifying a receiver via the control value without sending the identifier of the receiver in the message. In a second embodiment, the frames of the messages sent by the sensors are composed in several different ways depending on the degree of criticality of the information they contain. Each message thus created includes the generation of a control value from the code associated with the information if the latter is non-critical and from the identifier of the receiver and from the code associated with the information if the latter is critical, with or without transmission of the receiver identifier. The communication method described uses a calculation algorithm, for example of the CRC (Cyclic Redundancy Check) type, to generate the different control values, these then being each the result of a function of different variables. The purpose of this embodiment is to eliminate any possible interference in the context of a complex monitoring system employing a large number of controllers and actuators. It does not provide a solution in terms of interoperability or compartmentalization of certain transmitters.

There is known from US Pat. No. 6,026,165 a protocol making it possible to distinguish two types of received frames (encrypted or unencrypted) by reiterating the calculation of a cyclic redundancy code (CRC) by the same given function, on a portion of a message then on the full message. The first CRC calculation result is compared to a code transmitted in the portion of the message. If the two values differ, the frame received is considered either invalid or encrypted. If the result of the second calculation gives a result equivalent to a code transmitted in the complete message, the frame is then considered to be encrypted and valid. A second calculation is then performed on the complete message. This protocol does not make it possible to create relationships between elements of the network so that certain elements communicate only with certain others (partitioning) or to create relationships between elements so that a maximum of elements communicate with each other (interoperability) .

Document EP 0 805 575 discloses a method for securing communications between a command transmitter and a command receiver. In this document, the verification method by calculating a cyclic redundancy code is used simultaneously to generate a digital signature. In a first step (learn mode), a certain amount of information is shared between the sender and the receiver (identifiers, addresses, cyclic redundancy code calculation algorithm, encryption keys). In a second step (encryption mode), this sharing of information is verified from a random number, without the encryption keys being transmitted again (generation and calculation of a cyclic redundancy code initialized by the keys encryption). This information is then locked. In normal mode, the system works as in encryption mode, i.e. say by authorizing a reading of the message received by a cyclic redundancy code calculation algorithm initialized by the shared encryption keys. Each cyclic redundancy code calculation function therefore corresponds to a cyclic redundancy code calculation algorithm whose parameters are the encryption keys exchanged. A cyclic redundancy code calculation function is assigned to one or more transmitters and / or receivers which share the same encryption keys. The cyclic redundancy code calculation functions are determined during pairing between the receiver and the transmitter. This document clearly responds to a concern for improving security during the transmission of information. In no case does this document describe the creation of relationships between elements of the network so that certain elements communicate only with certain others (partitioning) or the creation of relationships between elements so that a maximum of elements communicate with each other. (interoperability).

The object of the invention is to provide a method which overcomes the aforementioned drawbacks and which presents an improvement over the known methods of the prior art. In particular, the method according to the invention allows partitioning or interoperability of the various elements making up the network. It also makes it possible to minimize the demand on the means of calculation of the receivers when an order received by the receiver is not intended for it.

The remote communication method according to the invention is characterized by the characterizing part of claim 1.

Different modes of carrying out the method according to the invention are defined by dependent claims 2 to 10.

The installation according to the invention is defined by independent claim 11. The accompanying drawing shows, by way of example, methods of carrying out the method according to the invention and an installation for its implementation.

Figure 1 is a diagram of an installation according to the invention.

Figure 2 is a diagram of a communication signal frame between the different elements of the installation.

FIGS. 3 and 4 are flowcharts illustrating certain steps of the method according to the invention.

FIG. 5 is a flowchart illustrating certain steps in configuring the method according to the invention.

The installation 1 shown in FIG. 1 comprises two command transmitters 3a of a first type, a command transmitter 3b of a second type and two command receivers 2. The command transmitters 3a, 3b and the order receivers 2 are designed to communicate with each other according to the same protocol. The order receivers are intended to receive orders from the order issuers and to control electrical equipment as a function thereof providing comfort functions in a building.

The transmitters of orders and the receivers of orders can also communicate with each other in a bidirectional manner.

The command transmitters 3a, 3b each comprise a logic processing unit 8 connected, on the one hand, to a memory 9 and, on the other hand, to means 7 for transmitting radioelectric signals.

The command receivers 2 each comprise a logic processing unit 5 connected, on the one hand, to a memory 6 and, on the other hand, to means for receiving radioelectric signals.

The communication signals between the transmitters and the receivers could also be electrical signals transmitted on a wired bus link or infrared signals or of any other nature. The memories 6 of the command receivers and the memories 9 of the command transmitters are intended to store, among other functions, algorithms for calculating frame integrity control codes.

These calculation algorithms make it possible to define the different types to which the order issuers belong. In the example described the two transmitters of orders 3a are of the same type because they each contain in memory the same algorithm for calculating control codes fa, and the transmitter of orders 3b is of another type because that it contains in memory another algorithm for calculating control codes fb different from the algorithm fa.

The order receivers themselves also contain algorithms for calculating control codes and, as will be seen below, these different algorithms make it possible to determine whether the order receivers must accept or not a signal emitted by a radio transmitter. 'orders.

Thus, the interoperability between the different elements (transmitters and receivers) of the installation is obtained by putting in memory at the level of each order receiver, all of the algorithms for calculating control codes used by the different transmitters of 'installation orders.

The partitioning is obtained by recording in each order receiver the only control code calculation algorithms used by the order issuers from which it is supposed to receive orders.

The transmitters of orders 3a are for example capable of producing a signal comprising a control code calculated by the function fa, the transmitter 3b is capable of producing a signal comprising a control code calculated by the function fb. One of the receivers 2 comprising, for example in memory, the algorithm fa is capable of causing the electrical equipment which it controls to execute orders sent by the transmitters 3a. The other receiver 2 comprising for example in memory the algorithms fa and fb is capable of causing the electrical equipment which it controls to execute orders emitted by the transmitters 3a and by the transmitter 3b.

The method of communication between a transmitter of orders and a receiver of orders comprises various stages.

First of all, the order transmitter generates a control frame for an action of an item of equipment as a function of an action exerted on it by a user. This frame includes a command code associated with the action that the user wants the equipment to perform. The frame may further include, as shown in Figure 2, an address, a rolling code and an encryption key. This frame includes for example 8 bits of encryption key, 24 address bits (16 million possible addresses), 16 bits of rolling code, 4 command bits (coding the command orders) and 4 bits of control code (2 ⁴ possible results) by which the integrity of the transmitted frame is verified.

Of course, the operation of this method is all the more certain the greater the number of bits allocated to the control in a frame.

In a frame construction step, the transmitter optionally encrypts the content of the frame, without acting on the control code bits.

In a second step, the command transmitter calculates a control code from the calculation algorithm it contains in memory and all or part of the frame.

In a third step, the order transmitter concatenates the frame and the control code. In a fourth step, it transmits the frame obtained in the form of radio waves.

In a fifth step referenced 100 in FIG. 3, all the command receivers of the installation being within range of the command transmitter receive the frame.

In a sixth step referenced 101, each of the command receivers calculates control codes from the algorithms which they contain in memory and from the frame received and successively compares these with the control code transmitted by the transmitter of orders. The comparison is carried out by means of comparison 11 included in the logical processing units 5 of the receivers.

In the case where the code calculated by the transmitter is not equal to any of the codes calculated by the receiver, no action is performed by the equipment controlled by the receiver. Indeed, the frame received is then considered to be non-integral or coming from an emitter of an unidentified type.

Otherwise, the action associated with the control code contained in the frame is executed by the electrical equipment optionally ordered after the frame has been decrypted and the identity of the transmitter has been verified.

The order of calculations and comparisons can be changed. Preferably, the calculation algorithms are applied in an alternating order, on a frame received several times.

The order can also be random.

It is also possible, during step 101, to test the different algorithms before going to step 102, so as to detect situations where multiple algorithms check the integrity check code.

This process makes it possible to increase the number of elements of a network capable of communicating with one another. Indeed, several order issuers can have the same identifier, but a different control code calculation algorithm. Thus, even in the extremely unlikely case, in which two transmitters from the same network or from two neighboring networks have the same identifier, the control code calculation algorithm can make it possible to distinguish them.

The assignment to a command transmitter or to a command receiver of a given control code calculation algorithm can be made at the factory or at the time of installation, for example. It can be irreversible or reversible. The solution is available for several customers using the same protocol.

It is optionally possible, as described above, to use, in this communication method using control code calculation algorithms, steps for verifying the identification of a command transmitter.

In fact, if the number of control code bits is too limited, the use of two different control code algorithms may possibly result in the calculation of the same result. Thus, a message could be accepted by an order receiver while the order transmitter is not configured to send orders to it.

In order to make the identification of the elements of the network more secure, several solutions are possible: - each transmitter of orders, a particular key can be assigned on the encryption function for example, this key being defined by the manufacturer and known in advance to order senders and order receivers, - if the concept of pairing is sufficient, an address or an identifier of the transmitter not known to the receiver constitutes a means of selection and verification of the origin of the message.

This last solution is the most flexible and the least expensive to implement.

Thus, as shown in FIG. 4, a frame transmitted by a command transmitter in the form of a signal (step 200) can firstly be verified by the calculation of a control code (step 201) then by the verification of the address of the order transmitter (step 202). If the address of the transmitter is known to the receiver, the latter executes the transmitted order (step 203). Otherwise, the program performs a new test with another control code calculation algorithm (step 204). Again, if the test result is positive, the receiver executes the command (step 203) only if the address of the transmitter, contained in the frame is known to the receiver (step 205).

Other verification means, as indicated above, can be implemented, such as different encryption keys for example, independently or in combination with the pairing verification.

If interoperability is desired, the receivers contain in memory all the algorithms for calculating order transmitters capable of controlling them (including those sold by different customers of the same manufacturer). The control code of a received signal is then successively compared to the different control codes calculated by the different algorithms in memory of the receiver from the received signal.

In the case where partitioning solutions are preferred, for example to distinguish different transmitters marketed by several customers of the same manufacturer, one of the algorithms will be selected to be used in the communication process. This operation can be performed by a selection between different algorithms stored in memory of the receiver. This selection can be made at the factory or during installation, more precisely, during pairing between a command transmitter and a command receiver.

During a first pairing, in a programming mode, a command transmitter transmits to a command receiver a message containing a control code calculated with an algorithm. The receiver checks, using each algorithm stored in the command receiver, the integrity of the frame.

The algorithm by which the integrity of the frame is recognized is then selected. This selection is made for example by storing this algorithm in a particular memory area. Thus, each time the signal receiver receives the signal, the integrity of the frame of this signal will be checked using this algorithm only.

Means of informing the user or the installer can be provided when, during successive tests, different algorithms make it possible to successfully verify the integrity of a frame, so that it can, for example , repeat the first pairing with a different transmitter or by sending a different signal from the same transmitter.

Another solution would be, as shown in Figure 5, to perform a multiple pairing operation between one or more transmitters of the same type and a receiver. The algorithm would then be selected only when the same control code calculation algorithm had made it possible to verify the integrity of a frame at least twice. Such a procedure considerably decreases the probability of coincidence between the results of control code calculations carried out with different algorithms.

In a procedure for double pairing of an order transmitter and of an order receiver shown in FIG. 5, during a first step 300a, the order receiver receives a signal from the order transmitter . The command receiver then calculates control codes from the different algorithms f1, f2, ... which it contains in memory and compares these control codes to the control code calculated by the command transmitter from l 'algorithm fe in a step 301a. During a step 302a, the algorithm which has successfully verified the integrity of the frame is put in memory. All of these steps are then repeated a second time, with the same transmitter and for a different signal or with another transmitter of the same type. These repeated steps are referenced with an index b. Thus, two algorithms could be put in memory. During a test step 303, the equality of the algorithms is tested. If these algorithms are the same then the algorithm stored is validated in step 304, that is to say that it is subsequently used by the receiver to calculate the frame integrity control codes. received.

For each comparison step, if none of the algorithms of the receiver makes it possible to verify successfully the integrity of a frame or if several algorithms of the receiver makes it possible to verify the integrity of the frame, it is either terminated procedure and the records are deleted, or the procedure is resumed at the start of step 300a or 300b.

Another procedure would be to test the second signal received first with the first algorithm stored in memory. A new verification of the control code could then validate the selection of the algorithm.

Personalization could also be done by an action performed on the power supply, so as to avoid conflicts between several algorithms: different power cut sequences could then be used to select an algorithm from those stored in the receiver d 'orders.

The algorithms can be used to calculate the image of all or part of the frame (address, rolling code, encryption key, command). They may consist of simple arithmetic functions or more complex functions such as those of the CRC (Cyclic Redundancy Check) type. It can also be the same multi-variable algorithm, one of the variables of which is constituted by a value defining each algorithm.

Claims

Claims:

1. A method of remote communication by signals between one or more command transmitters each belonging to a type of command transmitter and a command receiver intended to control electrical equipment for comfort and / or security in a building, based on a protocol in which the communication signals have the same frame format containing at least one order and a frame integrity control code calculated for each signal transmitted during a communication, characterized in that • each type of transmitter is assigned an algorithm for calculating the integrity code of the signal frame, • and that, for each communication between a transmitter of orders and the receiver of orders, receiver probably identifies the type of transmitter by comparison between a first integrity control code, transmitted by this command transmitter with the signal frame, and at least a second control code integrity role calculated by the receiver from the received signal and an algorithm that it contains in memory.

2. Communication method according to claim 1, characterized in that the receiver includes in memory several algorithms, stored in the receiver during manufacture or installation and in that, for each communication, the first control code d integrity is compared to the different integrity control codes calculated from the different algorithms stored in memory in the receiver.

3. Communication method according to claim 1, characterized in that the receiver comprises in memory several algorithms, stored in the receiver during manufacture or installation and in that one of these algorithms, corresponding to a type of transmitter, was selected, during a prior installation step, to perform the calculation integrity control codes.

4. Communication method according to claim 3, characterized in that the prior installation step is recognition of a type of command transmitter, by comparison, in a programming mode, between a first control code of integrity, transmitted by a transmitter of orders with the frame of the signal, and the various codes of control of integrity calculated by the receiver from the received signal and the various algorithms which it contains in memory.

5. Communication method according to claim 3, characterized in that the prior installation step is a sequence of cutting the supply of the command receiver.

6. Communication method according to one of claims 3 to 5, characterized in that the selection of an algorithm is only active after at least one step of confirming the choice of this algorithm.

7. Communication method according to one of the preceding claims, characterized in that each type of transmitter is also assigned an encryption algorithm and in that it comprises, during a communication, a step of decrypting the frame by at least one decryption algorithm corresponding to the level of the command receiver, conditioned by the probable identification of the type of the command transmitter which sent the signal.

8. Communication method according to the preceding claim, characterized in that it comprises a step of verifying the identification of the type of the order transmitter, comprising a consistency test of the decrypted signal.

9. Communication method according to one of the preceding claims, characterized in that it comprises, during a communication, a step of testing the identifier of the transmitter of orders contained in the frame of the signal.

10. Communication method according to one of the preceding claims, characterized in that it further comprises a step of execution of the order contained in the signal, conditioned by the probable identification of the type of the transmitter of orders having sent the signal and / or by the result of the verification step and / or the result of the identifier test step.

11. Installation for the implementation of the method according to one of the preceding claims, comprising at least one command transmitter having a memory and a logic processing unit for the calculation of codes for checking the integrity of the frames to be transmitted and a command receiver having a memory and a logic processing unit for the calculation of codes for checking the integrity of the received frames and a means for comparing the control codes.