WO2020089565A1

WO2020089565A1 - System for improved monitoring of connected sensors

Info

Publication number: WO2020089565A1
Application number: PCT/FR2019/052584
Authority: WO
Inventors: Francis CHATAIN
Original assignee: Airbus Defence And Space Sas
Priority date: 2018-10-30
Filing date: 2019-10-30
Publication date: 2020-05-07

Abstract

The invention relates to a monitoring system comprising terminals and a gateway in communication with an external network, the gateway comprising at least one radio frequency receiver for connecting to the terminals, a computer and a memory. According to the invention, each terminal comprises at least one power supply, a sensor module connected to a management module, management module identifiers being associated with at least one decryption parameter in a table stored in the gateway, the sensor module comprising at least one sensor and a memory storing information relating to at least one communication protocol, the management module comprising at least one computer, a memory storing at least its identifier and storing data representative of the measurements taken, an encryption module, a radio frequency transmitter and an interface module, the interface module controlling the exchanges with the sensor module according to the information read in the memory of said module, the encryption module encrypting measurement data of said sensor and service and/or control data comprising at least one data item representative of the sensor module, the management module sending at least the encrypted data and the non-encrypted identifier of the management module to the gateway via the radio frequency transmitter module, the gateway comprising a decryption module performing decryption according to the decryption parameter associated in the table with the identifier received from the management module.

Description

IMPROVED MONITORING SYSTEM FOR CONNECTED SENSORS

FIELD OF THE INVENTION

The present invention relates to the field of connected objects in a context of industrial use also called MOT (Industrial Internet of Things). Industry 4.0 is indeed marked by ultra-connectivity allowing advanced supervisory functions.

STATE OF THE ART

Vulnerability to cyber attacks is a major concern that must be addressed by system architects. We know wired private networks not connected to the Internet for which the physical protection of their site of establishment offers a good security. Opening up to the Internet can however prove to be a major competitive advantage that cannot be ignored. In addition, wired connections entail a particularly high installation cost.

Communication systems using radio waves, such as WiFi, allow easy monitoring of sensors connected to home networks secured by symmetric encryption key. A camera can thus be installed and configured to communicate with a remote security center, via the Internet. However, we understand that this type of installation is difficult to transpose, or even incompatible with the world of industry due to installation or maintenance constraints arising from the much larger number of sensors to be monitored.

There is thus a need for simplification in the supervision of connected objects, while retaining increased security so as to allow a massive secure and agile deployment of connected objects.

PRESENTATION OF THE INVENTION

The object of the invention is to at least partially remedy the drawbacks of the prior art by proposing a supervision system comprising a plurality of terminals and a gateway in communication link with an external network, the gateway comprising at least one receiver module radio frequency of connection with the plurality of terminals, a computer and a memory, characterized in that each terminal comprises at least one electrical supply, a sensor module connected via a connector to a management module, a plurality of identifiers of management modules each being associated with at least one parameter of decryption in a table stored in the gateway, the sensor module, comprising at least one sensor and at least one memory storing information relating to at least one communication protocol and the useful pins of the connector, the management module, comprising at least one computer, a memory memorizing at least its identifier and also storing data representative of the measurements carried out, an encryption module, a radiofrequency transmitter module and an interface module, the interface module controlling the exchanges with the sensor module in function information, read in memory of the sensor module, relating to said communication protocol and to the useful pins, the encryption module carrying out the encryption of the data representative of the measurements carried out by said sensor and of service and / or control data comprising at least one data representative of the sensor module, the management module performing the env at the gateway, via the radiofrequency transmitter module, at least the encrypted data and the unencrypted identifier of the management module, the gateway comprising a decryption module performing a decryption as a function of said associated decryption parameter, in the table, with the identifier received from the management module.

According to a characteristic of the invention, the gateway comprises a radiofrequency transmitter module for connection with the plurality of terminals, each terminal comprising a radiofrequency receiver module, the encrypted data transmitted by each terminal comprising a control code, the gateway comprising a module sending a response message,

and in that each response message, following the reception of data coming from the management module, comprises at least the control code retransmitted to this management module as acknowledgment of receipt.

According to another characteristic of the invention, each management module comprises an acknowledgment of receipt verification module triggering a standby of the transmitter and receiver modules in the event of confirmation of reception or triggering in the event of reception failure, at beyond a determined time delay, a retransmission of the same message, the transmission power being increased.

According to another characteristic of the invention, the number of retransmissions and successive increases in transmission power are limited, the management module triggering the sending of an alert message after a determined number of failed transmissions. re-broadcasts. According to another characteristic of the invention, the response message comprises a command to configure said terminal or an actuator command.

According to another characteristic of the invention, the gateway performs an authentication of the management module by a success during the decryption of the message received.

According to another characteristic of the invention, the interface module comprises a connection detection module and initialization of the interface module triggering a reading in memory of configuration data of the sensor module comprising at least the information relating to said protocol. and useful pins.

According to another characteristic of the invention, the configuration data also includes data representative of the type of said sensor, of the format of the measured data as well as of an associated channel in the event of a plurality of sensors.

According to another characteristic of the invention, the connection detection and initialization module also triggers the sending of an encrypted frame, to the gateway, representative of the configuration of the sensor module comprising the configuration data.

According to another characteristic of the invention, the gateway is in encrypted communication link with a dedicated server of the external network comprising at least one dedicated application for the exploitation of measurement data, the management module carrying out an encryption of the control data. decipherable by the gateway and by the dedicated application and an encryption of the measurement data decipherable only by the dedicated application.

According to another characteristic of the invention, the dedicated application comprises a module for sending encrypted commands to the management modules, each command being decipherable only by each management module to which this command is addressed.

According to another characteristic of the invention, the gateway comprises a module for cutting off the supply of its communication link with the dedicated server and for re-energizing in the event of a request by one of the management modules. Advantageously, the supervision system according to the invention is highly versatile and allows rapid and secure deployment. Indeed, this system can be fully managed by a client, by locating the terminals and the gateway on its premises.

Advantageously still, the structure of the terminals allows a supervision presenting an increased agility. One or more new sensors can easily replace a previous sensor for upgrading or maintenance purposes. The secure placement of additional connected objects is also facilitated.

Advantageously, for maintenance operations or predictive or preventive maintenance of supervision systems in companies, the invention will bring gains in particular in:

- increased operational efficiency of equipment,

- lower operating costs for equipment,

- the increased quality of manufacturing or in general of the production of products in the company,

- energy savings of resources or equipment.

Another advantage is the simple, fast and secure recovery of surveillance data.

An advantage is also great agility for the deployment of supervision solutions that can meet various technical constraints. The same supervision system will thus be able to respond simultaneously to several use cases such as the energy supervision of a building, the supervision of a production line and the support of logistics tools.

Advantageously, a protocol breaking mechanism integrated into the gateway allows increased resistance to attacks.

An advantage is also that the structure relying on an independent radio frequency micro-network allows energy saving while reinforcing security by limited radiation.

DESCRIPTION OF THE FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which should be read with reference to the appended drawings in which: FIG. 1 schematically represents an example of a supervision system according to the invention,

FIG. 2 schematically represents a more detailed example of a terminal.

FIG. 3 schematically represents a more detailed example of a gateway.

FIGS. 4a to 4c schematically represent three types of configuration of a supervision system according to the invention,

FIG. 5 schematically represents a method of transmitting data generated by a sensor within a supervision system,

FIGS. 6a and 6b show an example of the structure respectively of a message sent by a terminal and of a message sent in response by a gateway,

- Figure 7 shows schematically a protocol for creating encryption keys used for transmissions within the supervision system.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

The supervision system 1 as shown in FIG. 1 allows for example the recovery of data representative of measurements made by sensors within an installation. Advantageously, the supervision system 1 according to the invention does not include a core network, also designated by server network, as in a conventional IoT architecture. Thus, according to the present invention, all the components can easily be installed in the premises of the organization which wishes to access and exploit the data generated by its sensors. Components installed on the organization's premises may include terminals and gateway (s). The components installed in the organization's premises can also include the application server, for example integrated into the gateway. The customers are generally distant for operational needs, but one could also consider one or more customers using the dedicated application, located on the premises of the organization.

The supervision system 1 comprises a plurality of terminals 10 and one or more gateways 20 in communication link with an external network 32 such as for example the Internet, WiFi or wired intranet networks or mobile telephone networks. The data generated by the terminals is automatically and securely centralized by the dedicated application via the gateway (s). The gateways 20 collect the data and retransmit it to the application in the server 30. The dedicated application allows, for example, the clients 40 to carry out remote operation and supervision.

The terminal is divided into three functional blocks including a power supply

13, a management module 12 and a sensor module 11. The sensor module 11 may include one or more types of sensors and advantageously is interchangeable. As explained below, an automatic initialization of the management module 12 is provided as a function of the connected sensor module.

Likewise, as explained below, an automatic connection is provided between a plurality of sensors and a gateway. For example, a gateway is preconfigured to automatically connect to a determined number of management modules referenced in memory. It is thus easy to install new supervisory sensors or simply replace a management module or a sensor module during maintenance operations, while ensuring data security and checking the authenticity of the terminals.

Among the possible applications for connected objects, there are many in the field of industry, where the use of connected objects in a supervision system according to the invention gives hope for substantial savings in costs and efficiency. , For example:

Equipment monitoring, and implementation of predictive or preventive maintenance,

Resource and infrastructure consumption management, Efficiency of logistics processes,

The supervision system advantageously presents a hardware architecture and a software organization which meets the security requirements while keeping a great ease of deployment. The hardware components are extremely modular, making it very easy to adapt to needs as different as they are varied with common technical bricks. In addition, the structure of the supervision system is advantageously based on pairing procedures, advanced hardware management and advanced and secure configurations.

Referring to Figure 2, each terminal 10 includes at least one power supply 13, for example a battery or a rechargeable battery. The power supply may also include a transformer connected to the electrical network. The power supply 13 can be housed in the management module or in a separate module adapted to be removably mounted on the management module 12.

Each terminal 10 also includes a sensor module 11 and a management module 12 connected to each other via a two-part connector 14a and 14b. The connector is for example formed by GPIO ports (for the acronym General Purpose Input / Output) carried by the sensor module 1 1 and the management module 12. The connector can support, for example, an I2C bus, a bus SPI, a UART bus such as RS232 or RS485 or digital or analog input or output lines.

The sensor module 1 1 is for example a module that can be removably assembled to the management module 12. The sensor module 1 1 then comprises a housing in which components of the sensor module are arranged, this housing being shaped to be able to be mounted from removably to a housing of the management module in which the components of the management module are arranged. The connection between the sensor module 11 and the management module 12 can be made by a removable mechanical connection, for example with snap-fastening.

The sensor module 1 1 comprises at least one sensor 1 10, and may comprise several sensors 1 10a and 1 10b. The sensors can be of a wide variety of types, for example:

- environmental monitoring sensors, suitable for reading at least quantities such as temperature, pressure, humidity, brightness, air quality,

- sensors for monitoring consumption of electricity, water, gas,

- sensors for monitoring an electrical installation by measuring current or voltage,

- mechanical magnitude sensors by measuring vibrations, accelerations, shock, movement detection, deformation measurement, door opening, etc.

- position sensors.

The sensor module 1 1 also includes a memory 1 1 1 storing information 1 1 1 a relating to at least one communication protocol and the useful connector pins ensuring the connection between the sensor module and the management module.

In particular, the memory 1 1 1 stores information 1 1 1 a relating to the number of sensors 1 10 present in the sensor module and information specific to each sensor, referenced 1 10, 1 10a or 1 10b, contained in the sensor module 1 1. This last information can include, for each sensor:

- the type of sensor,

- an identifier of the sensor,

- a communication protocol with the sensor, identifying for example the type or format of the data generated by the sensor (for example whole number, floating point, character string ...), the mode of access to the data or the frequency of data access,

- a mode of operation of the sensor such as a trigger following a monitoring threshold crossed, a variation deviation detected or a change in value detected.

Each sensor module 1 1 of a terminal may further comprise one or more actuators and may also include a computer 1 12. This computer 1 12 may for example be configured to control the actuator (s) of the terminal. The computer can for example be in the form of a processor, a microprocessor or a microcontroller.

The sensor module 1 1 may comprise functional modules for collecting data 13 and transferring data 1 14 to the management module, these modules 1 13 and 1 14 can be in the form of programs or subroutines recorded in memory 1 1 1.

The management module 1 2 can also provide direct accesses to the memory of the sensor module 1 1.

The management module 12 comprises at least one computer 121, such as for example a microcontroller, a microprocessor or a microcomputer and a memory 122. The memory 122 stores in particular the identifier ID1 of the management module.

The memory can also store data 127 representative of the measurements made by the sensor or sensors of the sensor module 11. For example, this data 127 can be supplied by the sensor or sensors and temporarily stored by the memory 122 while awaiting their sending to the gateway 20. The management module 12 can include an interface module 129 with the sensor module 11, carrying out the control of the exchanges with the sensor module, and in particular piloting the recovery of the data generated by the sensors, as a function of the information 1 1 1 read in memory 1 1 of the sensor module, relating to the communication protocol and the useful pins of the connector. Thus, this interface module 129 can access the memory of the sensor module for reading, to deduce the recovery methods therefrom, then recover data representative of the measurements carried out by the sensor or sensors.

We can also consider information 1 1 1 a in the form of a determined code representative of the configuration of the sensor 1 1, in order to save bandwidth during the retransmission of this information 1 1 1 a to the server.

The interface module 129 can also comprise a connection detection and initialization module 126. This detection and initialization module 126 in particular triggers a reading, in the memory of the sensor module, of the data 1 1 1 a of configuration of the sensor module, comprising at least the information relating to the communication protocol and to the useful pins of the connector. The configuration data 1 1 1 a may also include data representative of the type of sensor, of the format of the measured data or of a channel associated with each sensor, in the event of a plurality of sensors in the sensor module.

This initialization with reception of the configuration data can be implemented when the terminal is powered up. This allows in particular, in the case where the terminal comprises a removable and interchangeable sensor module, that the sensor module 11 carries all the information necessary for the recovery and processing of the data generated by its sensors, all this information being recovered by the management module 12 for example during a first connection. This advantageously makes it possible to use a wide variety of different sensors with immediate deployment.

The management module 12 also includes an encryption module 123 for example of data representative of the measurements generated by the sensors of the sensor module and of service and / or control data. Service and / or control data include in particular at least one data representative of the sensor module. The representative data of the sensor module includes for example the configuration data 1 1 1 a.

The management module can also include a decryption module 152 in particular for the decryption of a received command.

The encryption module 123 can for example be implemented by the computer 121 and / or by a secure cryptographic component. The secure cryptographic component stores, for example, encryption / decryption keys. The secure cryptographic component can also perform derivative operations of a key selected as a function of a counter internal to the cryptographic component, the derived key then being used as session key.

The encryption performed by the management module is symmetric encryption by one or more session keys for each message. The session key (s) can be changed regularly or even with each new message. The session key (s) are advantageously specific to each management module. The session keys used by each management module are obtained in particular by using data specific to the management module such as the identifier ID1 of the management module. The identifier ID1 of the management module is also transmitted in clear in the message, the gateway being able to find this identifier in memory. The management module 12 can for example comprise a transfer module 128 for the implementation of the sending of data to the gateway, via the transmitter module. Each message includes for example an unencrypted header, encrypted generated data, encrypted service information and / or encrypted control information. The generated data, the service information and the control information are preferably encrypted independently of each other.

The encryption module 123 also generates one or more session keys for each new message by using a memorized counter of the number of messages sent, the gateway being moreover able to increment a counter in memory associated with the identifier of the terminal. , with each message received.

Symmetric key encryption / decryption uses, for example, AES 128 CCM ^* encryption or AES256 encryption. he

The key generation subroutine can for example be in the form of a secret derivation protocol such as NIST-800-108-KDF, X9.63- KDF, NIST-800-56-KDF- A / B, NIST-800-56-KDF-C or HKDF.

The generation subroutine can for example derive a key as a function of one or more parameters such as a message counter, an identifier, a hazard or a counter stored in a security component.

K ’= F (K, Cmpt)

The derivative key K ’by the derivation function F is for example obtained from the key K and the counter Cmpt. Several parameters can also be aggregated or combined to form one of the variables of function F.

The management module 12 also includes a radio frequency transmitter module 124. The management module 12 can also include a radio frequency receiver module 125. These two modules can be formed by the same radiofrequency transmitter / receiver module.

The radiofrequency emissions between the terminals and the gateway or gateways are for example carried out in the ISM (industrial, scientific and medical) bands. These frequency bands can be used in particular in a reduced space for industrial applications.

The functional modules of the management module 12 may consist of software or hardware components, or a combination of programs or subroutines implemented one or more hardware components. For example, it can be software bricks stored in a memory and executed by the computer 121. As a variant, these functional modules can be implemented by respective computers.

As shown in FIG. 3, the gateway 20 comprises at least one radio frequency receiver module 21 for linking with the plurality of terminals 10, a computer 23, and a memory 24. The gateway 20 can also include a microcomputer comprising the computer and the memory .

The gateway 20 may also include at least one radiofrequency transmitter module 22 for connection with the plurality of terminals, each terminal then also comprising a radiofrequency receiver module 125. A control code is for example added to each message sent by each terminal, this code control being decrypted before being returned, by a module 51 for sending response messages, to the terminal concerned. Each management module includes an acknowledgment of receipt module 151. This module remains awaiting an acknowledgment of receipt for a determined time delay and can then carry out one or more new sendings of the previously sent message. The power is for example increased with each new sending of the same message.

The acknowledgment of receipt module 151 receiving the acknowledgment of receipt can also read a configuration data contained in the response message, such as for example an increase or a decrease in the transmission power. The transmission power can advantageously be adjusted to the minimum necessary.

The acknowledgment of receipt module 151, in the absence of an acknowledgment, can also send an alert message, for example on a generic frequency and according to a generic communication protocol compatible with any gateway. This is for example a broadcast type broadcast. The alert message aims in particular to signify the absence of connection of the management module with a gateway.

The gateway can also include several radio frequency transmitter / receiver. The terminals can for example communicate with the gateway each via two channels, one of which is used for reception and the other for transmission.

The memory 24 of the gateway stores in a table T a plurality of terminal identifiers corresponding for example to the identifiers of their management module, with which the gateway is paired. In this table T, each terminal identifier is associated with at least one parameter for decrypting a message sent by the terminal.

The encryption and decryption methods using symmetric keys will be described in more detail below.

The memory 24 can also include a decryption module 25. This decryption module 25 comprises for example a secure cryptographic component, in which are stored decryption keys. The decryption module also stores the decryption programs. In particular, the decryption module is configured to decrypt at least part of the encrypted data received from a terminal. The gateway can also include an encryption module, in particular when the application server is included in the gateway in an “edge computing” type configuration.

Thus, the gateway attempts to decrypt a message whose symmetric key is not stored by the gateway but generated by the latter as a function of the identifier of the management module. The parameter associated with the identifier ID1 of the terminal in the table T is also variable over time and corresponds, for example, to the number of messages received from this terminal. Thus, a success in deciphering the message coming from the management module corresponds to an authentication of this management module.

The gateway 20 is also in communication link with the external network 32 such as for example the Internet, an intranet network or a mobile telephone network, via a dedicated interface. In this regard, it can include a protocol break module 26 to isolate and protect the data exchanged. The protocol break module 26 notably includes an optical interface in connection on both sides with two pieces of equipment supplied by separate power sources. In addition, the communication protocol is also modified on either side of the protocol break module by passing, for example, from a serial protocol to an Ethernet protocol. For the management of communication with the external network, the protocol breaking module uses for example a microcontroller which can be switched off in the event of the absence of data to be transmitted, thus limiting the cyber attack surface of the gateway. Power to the microcontroller is cut off. The microcontroller is then turned on again for a new transmission on the external network.

The gateway 20 also includes a module 28 for sending responses to the terminals following the reception of a message from a terminal.

With reference to FIGS. 4a to 4c, the supervision system further comprises a server 30 comprising a dedicated application for the exploitation of the supervision data, that is to say allowing the exploitation and the visualization of the supervision data in liaison with client entities 40.

In a case shown schematically in FIG. 4a, this server 30 is integrated into the gateway 20. Clients 40 (client applications hosted for example on PC, tablet, smartphone) can access this server 30 via the external network such as an intranet 32a. The application may also include a module for sending encrypted commands to management modules 12. Each command can, for example, only be deciphered by each management module 12 to which this command is addressed.

In another case shown diagrammatically in FIG. 4b, the server 30 hosting the application is distant from the gateway 20 and connected to the latter via an intranet link. Clients 40 can access this application server 30 via the external network such as an intranet network 32a. The gateway can also include a module 27 for placing its communication link with the dedicated server 30 on standby, and for waking up in the event of solicitation by one of the terminal management modules. The link between the gateway 20 and the application server 30 is for example encrypted so as to perform an over-encryption. The HTTPS protocol is for example implemented between the application server 30 and the gateway 20. The application can moreover comprise a module 251 for sending encrypted commands to the management modules 12. Each command is, for example, only decipherable by each management module 12 to which this command is addressed.

In another case shown diagrammatically in FIG. 4c, the server 30 is distant from the gateway 20 and connected to the latter via the external network such as the Internet or WiFi. Clients 40 can for example access this server 30 via the external Internet network 32b. The gateway 20 can also include a module 27 for placing its communication link with the dedicated server on standby, and for waking up in the event of solicitation by one of the terminal management modules. The application can also comprise a module 251 for sending encrypted commands to the management modules 12. Each command can for example be deciphered only by each management module 12 to which this command is addressed.

The link between the gateway 20 and the application server 30 is for example encrypted so as to perform an over-encryption. The HTTPS protocol is for example implemented between the application server 30 and the gateway 20. The sending of data to the application comprises for example:

- energizing the electronics at the gateway outlet,

- sending a Server Application certificate and a request

establishing a secure HTTPS connection - sending messages with over encryption of the TLS layer (Transport layer Secure) including supervision data.

Referring to Figure 7, we will describe examples of symmetric encryption keys used for encryption and decryption of messages exchanged within the supervision system.

The set of keys used within the supervision system is for example derived from a unique Kapp key which belongs for example to the organization in which the supervision system is installed.

From at least this unique Kapp key and an identifier of the gateway, a master key of the gateway KCGTW is derived, which is stored in the gateway as for example in a secure component of the gateway. From this master key of the gateway KCGTW is derived, for each terminal, and thanks to at least one identifier of the terminal, a service master key, KCT, which is specific to each terminal.

A secure component is for example of the Java Card type.

The service master key KCT is derived to generate first local keys KCTERM #, also specific to each terminal, and which are stored in their respective terminal. These first local KCTERM # keys are for example stored, in the form of a list, in the secure component of the terminal. The KCT service master key is preferably not stored in the terminal.

The first local keys KCTERM # are for example derived from at least the master key specific to the KCT terminal and from a rank number in the list of first keys. The rank number is for example an integer ranging from 1 to 6. The rank number can also be in the form of an integer ranging from 7 to 12.

The session key KSC # is determined from the list of first local keys KCTERM # according to a local counter. This can for example be a selection of the key located in the row corresponding to the message counter sent. The rank of the selected key corresponds for example to the counter modulo the number of first keys.

It can also be, for example, a selection of the key found at the rank calculated according to a message counter sent where each first key is used successively a determined number of times before moving to the next rank or returning to the initial rank. . It is also possible, following the selection of the key as a function of the message counter sent, to perform a derivation operation as a function of the selected key and of an internal counter in a secure cryptographic component, this component also memorizing the list of first keys and performing the bypass operation.

A KDT application master key, specific to each terminal, is also derived from the unique Kapp key from an identifier of the server dedicated to the application 30, the identifier of the gateway and the identifier of the terminal.

This application master key KDT is used to derive second local keys KDTERM #, and third local keys KATERM # which are stored from the factory in each terminal, for example in a secure cryptographic component of each terminal, in the form of respective lists.

The second local keys KDTERM # and the third local keys KATERM # are for example derived from at least the master application key KDT and rank numbers of the keys in their respective list.

A counter is likewise used to make at least one selection from the list of second or third keys.

The KSD # or KSA # session keys can be obtained by selecting from their respective list.

KSD # or KSA # session keys can also be obtained by making a selection from their respective list and then a derivation operation based on the counter or an internal counter in a security component. The internal counter is for example updated as a function of the counter external to the security component.

The server can only hold the unique Kapp key without storing the KDT data master key, which improves security.

Each terminal includes, for example, all of the first local keys KCTERM #, second local keys KDTERM # as well as counters of messages received and of messages sent by the terminal.

The terminal can also include all of the third local keys and a counter for the number of orders received, according to which a decryption key is determined.

In the case of determining the session key by derivation of a local key, for encryption or decryption, the local key list can be stored in the secure cryptographic component which also performs the derivation operation.

The gateway also stores a table comprising each terminal identifier with which it is paired associated with at least one counter specific to each terminal. This counter can be used to record the number of messages received by the gateway from the corresponding terminal. This table can be stored in a secure component of the gateway. The gateway can also store, for each terminal, an additional counter for the number of uses of each local key by the terminal.

The server 30 dedicated to the application comprises a computer and a memory, in which the identifiers of the gateway 20 and of the terminals 10 are stored, as well as the unique key Kapp.

The server 30 also stores a table comprising each terminal identifier associated with at least one counter specific to each terminal. This counter can be used to record the number of messages received by the application server from the corresponding terminal. This table can be stored in a secure component of the server. The server can also store, for each terminal, an additional counter for the number of uses of each local key by the terminal. The application server can also store a counter of encrypted commands sent to each terminal in the table. The counter for the number of commands sent can be associated with a second counter for the number of successive uses of the encryption key used.

The memorization of the unique Kapp key as well as the derivation operations for obtaining the application master key KDT, the second local keys KDTERM # and the third local keys KATERM # can also be carried out by a highly secure component for example HSM (High Secure Module) type. This highly secure component can be implemented in a second server in communication link with the application server. The application server for example transmits its identifier as well as the gateway and terminal identifiers to the highly secure component which transmits, in return, to the application server, the second local keys KDTERM # and the third local keys KATERM #. With reference to FIGS. 5, 6a and 6b, we will now describe a data transmission method implemented by a supervision system according to the invention.

This method may include a preliminary step 90, carried out when a terminal is powered up, for recovering configuration data from the sensor module by the detection and initialization module.

This step is for example followed by the sending 91 of an encrypted frame, to the server, via the gateway, representative of the configuration of the sensor module. The frame transmitted 91 to the gateway is retransmitted 92 to the application. This frame can in particular include a list of sensors, the corresponding channel numbers, or the types of sensors, this to allow the application to subsequently identify the data of the sensors in the frames subsequently sent by the management module, function for example of their size and position. For the encryption of this frame, one uses for example one of the symmetric encryption keys stored by the terminal or a key derived from one of these keys, the selection and derivation being for example carried out as a function of the message counter transmitted by the terminal.

The method then comprises a step 100 of recovering data representative of the measurements carried out by the sensor or sensors, using the interface module 129, then the encryption 110, by means of the encryption module on the one hand of the recovered data and d on the other hand, service and / or control data comprising at least one data representative of the sensor module. The service and / or control data can also include terminal configuration information. Advantageously, this service and / or control data can include an ACK control code then used as acknowledgment of receipt. The ACK control code differs for example for each message and is for example generated using a random and a variable corresponding for example to an internal clock.

Advantageously, the symmetric encryption key used for the encryption of the service and / or control data may be different from the key used for the encryption of the data representative of the measurements carried out by the sensors. These two session keys come, for example, from two separate lists KCTERM # and KDTERM #. For the service and / or control data, the encryption key used is a session key KSC # determined from one of the first local keys KCTERM # and from the message sending counter of the terminal.

Advantageously, the first local keys can be used successively a predetermined number of times before using the next key in the list. The selection of the first local key used for the KSC # session key is carried out by means of a variable determined as a function of a counter stored in the terminal.

For example, the value of the terminal's message sending counter makes it possible, by knowing the maximum number of successive uses of a first local key, to determine the rank in the list of the first local key to use. The session key can result from this selection or be generated by an additional operation, such as for example a derivation operation using a secure cryptographic component.

For the data representative of the measurements carried out by the sensors, the encryption key used is a session key KSD # determined from one of the second local keys KDTERM # and from the message sending counter of the terminal.

The second local keys KDTERM # can also be used a predetermined number of times, and the selection of the second local key used to determine the session key KSD # is carried out on the basis of a variable determined according to a counter of the terminal. .

For example, the value of the counter for the number of messages sent by the terminal makes it possible, by knowing the maximum number of successive uses of the same second local key, to determine the rank in the list of the second local key used. The session key can result from this selection or be generated by an additional operation, such as for example a derivation operation using a secure cryptographic component.

The management module 12 then sends 200, to the gateway 20, via the radiofrequency transmitter module, of a message M comprising encrypted data and the unencrypted identifier, in plain text, of the terminal.

In an exemplary embodiment shown diagrammatically in FIG. 6a, the message M sent comprises: - a clear block Bl comprising at least the identifier of the terminal and, where appropriate, an identifier of the gateway, an identifier of the type of network (for example point to point or star) as well as a mode of use of the network to a dedicated gateway or on a generic frequency),

a service / configuration data block BS, encrypted with a KSC # session key determined from first local KCTERM # keys, and

- a block BD of supervision data generated by sensors, encrypted with a session key KSD # determined from second local keys KDTERM #.

The counter of sent messages stored by the terminal is incremented

210 after the sending step. A timer is also started to monitor the receipt of an acknowledgment message from the gateway.

The method can then comprise a step 300 of reception, by the gateway, of the message transmitted by the terminal.

The method then comprises a following step of generation 310 of the session key having enabled the encryption of the service data and / or of control of the message. The gateway here allows the decryption of the service or control part of the message, the whole message being decrypted subsequently by the application.

The gateway thus implements a search, in the stored table, of the identifier of the terminal which was contained in clear in the message, in order to recover in particular the stored value of the message sending counter associated with the identifier of the terminal, in this table.

The KCT service master key, specific to the terminal, is generated by the gateway by deriving the KCGTW master key memorized by the gateway with at least the terminal identifier as a derivation parameter.

The gateway is then capable of finding at least one of the first local KCTERM # keys obtained by deriving the service master key KCT and a parameter calculated as a function of the message counter. The rank is for example calculated according to the number of messages and according to the number of successive uses of each of the first KCTERM # keys.

The determination of the session key KSC # can correspond to the first rank key corresponding to the number of messages received or an additional operation can be carried out on this first key, such as for example a new operation to derive this first key and a parameter such as a counter for successive uses of the same key.

Once the session key has been obtained, the gateway increments the counter for received messages associated with the terminal identifier, in the stored table, during a step 320.

The method then comprises the decryption 330 of the control and / or service data contained in the message and encrypted with the session key.

If 340 decryption fails, the message is not processed. The steps 310 and 320 of generating the KSC # session key and incrementing the counter are then repeated by the gateway, to make at least one further attempt to decrypt the message with an incremented value of the counter. This allows, in the event that a previous message sent by the terminal was not received by the gateway, that the gateway increments its counter so that it catches up with the value of the terminal counter. The gateway repeats for example these steps of decryption attempt a determined maximum number of times, for example 3 times.

If the decryption of the message is successful, the gateway will on the one hand have access to control or service data and in addition the gateway will have verified the identity of the terminal by decrypting the coding specific to this terminal.

Terminal authentication can also be carried out via a MIC (Message Interchange Control) code.

Following the decryption, the gateway implements two actions. A first action 350 is to send, to the terminal, a response message M ′ comprising an acknowledgment of receipt ACK formed for example by the control code contained in the block of control / service data BS.

The response message can also include a command for parameterizing the terminal, such as for example a command for adjusting the lowering or increasing of the transmission power level of the terminal, or a command for an actuator of the terminal, or any other command to be executed by the terminal. The commands are preferably encrypted by the application, in the case of a response provided by the application, via the gateway.

The response message M 'can be at least partly encrypted. For example, with reference to FIG. 6b, it may include a clear block BG comprising the identifier of the terminal and / or that of the gateway, as well as the acknowledgment of receipt, and an encrypted block BC comprising, where appropriate, a command to be executed by the terminal. As will be seen in more detail below, the commands preferably come from the application server 30 and the encryption is carried out by the application.

Each terminal management module can include an acknowledgment module, suitable for triggering a standby of the terminal sender and receiver modules in the event of good reception of the acknowledgment. This acknowledgment module can also increment a response or command counter received by the terminal.

On the other hand, in the event of reception failure, the management module 12 retransmits the same message during a new step 200, by increasing the transmission power, and without incrementing its counter of sent messages.

Following a re-transmission of the message, if the terminal then receives an acknowledgment signal from the gateway, the management module 12 stores for example the transmission power level allowing good reception by the gateway.

On the other hand, if still no acknowledgment message arrives, the terminal repeats the step of re-transmission of the message by increasing the power, a determined number of times, for example three times. After the determined number of failures, the terminal generates an alert message during a step 220. The alert message can be a message on a frequency called factory, that is to say a frequency common to all supervision systems and in particular all gateways, the message being sent at full power.

A second action performed by the gateway 20 once the module has been authenticated is to transfer 400 the message received from the terminal 10, that is to say with a block BS of encrypted control / service data, and a block of data BD of the sensors also encrypted, to the server 30 dedicated to the application. The identifier of the clear gateway is aggregated at the header of the retransmitted message.

In the case where the server 30 dedicated to the application is integrated into the gateway 20, it is the gateway which performs the following steps described below.

In the case where the server 30 dedicated to the application is a remote server, the connection between the gateway and the application server is advantageously a secure connection, so as to provide an over-encryption of the transmitted messages. The server 30 dedicated to the application, storing the unique key KAPP, is able to decrypt on the one hand the control / service data block BS and on the other hand the data block BD, by successive derivations from this KAPP key.

For the block BS, the server 30 derives, from the unique key KAPP and the terminal identifier contained in clear in the message, the master key of the gateway KCGTW, then derives successively from this key the master key of service KCT, a first local key KCTERM # and determines a session key KSC # using a memorized counter of received messages associated with each terminal identifier. In this regard, the server can also include the counter or counters making it possible to determine the rank of first local key making it possible to determine the key KSC #.

The server 30 can also decrypt the data block BD by determining the session key KSD # used by the terminal for the encryption of the block BD, as follows:

- derivation of the unique Kapp key from the identifiers of the gateway, the terminal and the application server,

- derivation of the KDT application master key from the terminal identifier and the gateway contained in clear in the identification block Bl of the message,

- then determination of the second local keys KDTERM # by derivation of the key KAT and of a variable determined according to a counter memorized by the server,

- then determination of the KSD # session key from the second local keys and the message counter received by the server.

For the determination of the second local key, the rank of the second key is determined from the value of the counter of messages received by the server. A second counter specific to each second local key KDTERM #, memorized by the server, can also be used. The rank is for example taken into account. After the selection of the local key, a new derivation can be made taking, for example, an internal counter as a parameter.

The encryption mode used allows for example that the control / service block can be decrypted by the gateway and by the server dedicated to the application, while the data block generated by the sensors is only decipherable by the server dedicated to the application. On receipt of a message transmitted by the gateway, the server dedicated to the application therefore derives the encryption keys from the message and decrypts the message during a step 410.

This server 40 can then process the data, allow their remote downloading and their viewing on client applications, etc., during a step 420.

The application server 40 can also include a module for sending encrypted commands to the terminal management modules, for example to send configuration or control commands, or for example commands for actuators of the terminals, to the terminals during 'a step 430.

In this case, the command is advantageously encrypted by the application so that it can only be deciphered by the terminal management module to which this command is addressed.

In this regard, the encryption key used is advantageously a KSA # session key determined from a third local KATERM # key as a function of a command counter sent by the server to each terminal. The third local KATERM # keys are themselves derived by the server from the KDT application master key and from a rank determined according to a counter of the server. For example, the rank of the third local KATERM # key to be used can be determined from the value of the command counter sent by the server.

The encrypted command sent by the application server is for example sent to the gateway, which stores it and adds it to a next acknowledgment message M ’sent to the terminal. The order can also be transmitted directly to the terminal by the gateway. The gateway is not able to decrypt the encrypted command here.

On the other hand, the terminal, which has the third local keys KATERM # and a counter of received commands, can determine the session key KSA # making it possible to decrypt the command block.

The communication protocol used by the supervision system, and the structure of the encryption keys used makes it possible to secure the data from end to end, that is to say from their acquisition by the sensors to their reception by the server. application. Thus, according to one embodiment, a secure method of transmitting data between a plurality of terminals and a gateway is provided, characterized in that it comprises for each terminal:

a step of determining a session key, by the terminal, as a function of at least one counter stored in the terminal, by at least one selection, as a function of said counter, in a stored list of local keys, these local keys originating from at least one operation of deriving a master key specific to the terminal and from a variable determined as a function of said counter,

-a symmetric encryption step using the session key of at least part of the data generated by the terminal,

-a step of incrementing said counter memorized by the terminal

-a step of sending at least one message comprising at least the encrypted data concatenated with an unencrypted identifier of the terminal,

a step of reception of said message by the gateway,

a step for generating the session key, by the gateway, comprising:

- a search in a stored table of the terminal identifier, this identifier being associated with at least one counter

a generation of the session key by at least one derivation of a master key stored by the gateway and of the terminal identifier to obtain the master key specific to the terminal, then by at least one derivation of the master key specific to the terminal and a variable determined as a function of said counter memorized by the gateway to obtain the session key,

- an increment of said counter associated with the terminal identifier - a decryption step and in the event of decryption failure, a jump to the step of generating the session key.

According to a particular feature of this process, the counter memorized by the terminal corresponds to the number of messages sent, each local key being used a determined number of times before using the next local key in the list.

According to another particular feature of this method, said variable determined as a function of said counter is calculated as a function of at least the rank of the local key in the list.

According to another particularity of this method, in the event of successful decryption, the gateway transmits to the terminal a response message comprising an acknowledgment of receipt, the terminal in the event of non-receipt of the acknowledgment reception, sending again the same encrypted message, its message counter not being incremented and the transmission power being increased.

According to another particular feature of this method, following a re-transmission of its encrypted message, the terminal stores the transmission power level in the event of reception confirmed by the gateway by an acknowledgment of receipt and in the event of reception failure by the gateway, the terminal sends the encrypted message again, its message counter not being incremented and the transmission power being increased, the number of retransmissions and successive increases in the transmission power being limited, a message alert being generated by the terminal after a determined number of retransmission failures.

According to another particular feature of this method, the response message comprises a configuration of said terminal.

According to another particular feature of this method, the response message including the acknowledgment of receipt further comprises an instruction to lower or increase the level of transmission power.

According to another particular feature of this method, the gateway is in communication link with an application for exploiting the data generated by the terminals, each terminal performing at least two ciphers with at least two separate session keys using at least two local key lists, part of the message from each terminal being decrypted by the gateway and another part being decrypted only by the application using an additional session key, each message received by the application comprising the identifier of the terminal and a gateway identifier from which the two session keys are generated, decryption by the additional session key being carried out by at least:

- a step of generating the additional session key comprising:

- a search in a stored table of the identifier of the terminal concatenated with the identifier of the gateway, this identifier being associated with at least one counter

a generation of the additional session key by at least one derivation of a stored master key and of the identifier of the terminal concatenated with the identifier of the gateway, in order to obtain an additional master key specific to the terminal, then by at least a derivation of this master key additional specific to the terminal and a variable determined as a function of said memorized counter to obtain the additional session key,

- an incrementation of said counter associated with the identifier of the terminal concatenated with the identifier of the gateway,

-a decryption step using the additional session key and in the event of decryption failure, a jump to the generation step of the additional session key.

According to another particular feature of this method, a command message is sent to the terminal by the application, via the gateway, this command message being encrypted or respectively decrypted by a command key originating from at least one selection from a list in function of a counter for the number of commands stored in association with the terminal identifier and respectively by the terminal.

According to another particular feature of this method, said counter of commands sent and respectively received is incremented with each command sent by the application and respectively received by the terminal.

According to another particular feature of this process, the command aims to modify the behavior of the terminal.

Claims

1. Supervision system comprising a plurality of terminals (10a, 10b, 10c) and a gateway (20) in communication link with an external network (32), the gateway (20) comprising at least one radio frequency receiver module

(21) for connection with the plurality of terminals, a computer (23) and a memory (24), characterized in that

each terminal (10) comprises at least one power supply (13), a sensor module (1 1) connected via a connector (14a, 14b) to a management module (12),

a plurality of identifiers of management modules each being associated with at least one decryption parameter in a table (T) stored in the gateway (20),

the sensor module (1 1), comprising at least one sensor (1 1 0) and at least one memory (1 1 1) storing information (1 1 1 a) relating to at least one communication protocol and the useful pins of the connector,

the management module (12), comprising at least one computer (121), a memory (122) memorizing at least its identifier (ID1) and also storing data representative of the measurements carried out (127), an encryption module (123 ), a radiofrequency transmitter module (124) and an interface module (129),

the interface module (129) controlling the exchanges with the sensor module (1 1) as a function of the information (1 1 a), read in memory of the sensor module, relating to said communication protocol and to the useful pins,

the encryption module (123) carrying out the encryption of the data representative of the measurements carried out by said sensor and of service and / or control data comprising at least one data representative of the sensor module,

the management module (1 2) sending, to the gateway (20), via the radiofrequency transmitter module (12), at least the encrypted data and the unencrypted identifier of the management module ( 12),

the gateway (20) comprising a decryption module (25) performing a decryption as a function of said associated decryption parameter, in the table (T), with the identifier (ID1) received from the management module (1 1).

2. Supervision system according to claim 1, characterized in that the gateway comprises a radiofrequency transmitter module (22) for connection with the plurality of terminals, each terminal comprising a radiofrequency receiver module (125), the encrypted data transmitted by each terminal comprising a control code, the gateway comprising a module (51) for sending a response message (M '),

and in that each response message (M ’), following the reception of data coming from the management module (1), comprises at least the control code retransmitted to this management module as acknowledgment of receipt.

3. Supervision system according to claim 2, characterized in that each management module (12) comprises a module (151) for acknowledgment of receipt triggering a standby of the transmitter (124) and receiver (125) modules in the event of confirmation of reception or triggering in the event of reception failure, beyond a determined time delay, a retransmission of the same message (M), the transmission power being increased.

4. Supervision system according to claim 3, characterized in that the number of retransmissions and successive increases in transmission power are limited, the management module (1 1) triggering the sending of a message alert after a set number of reissue failures.

5. Supervision system according to one of claims 2 to 4, characterized in that the response message (M ’) comprises a command to configure said terminal or an actuator command.

6. Supervision system according to one of the preceding claims, characterized in that the gateway (20) authenticates the management module (1 1) by a success during the decryption of the message (M) received.

7. Supervision system according to one of the preceding claims, characterized in that the interface module (129) comprises a connection detection module (126) and initialization of the interface module triggering a reading in memory ( 1 1 1) of configuration data (1 1 1 a) of the sensor module (1 1) comprising at least the information relating to said communication protocol and to the useful pins.

8. Supervision system according to the preceding claim, characterized in that the configuration data (1 1 1 a) also include data representative of the type of said sensor (1 10, 1 10a, 1 10b), of the format of the measured data as well as of an associated channel in the event of a plurality of sensors.

9. Supervision system according to claim 7 or 8, characterized in that the connection detection and initialization module (126) also triggers a sending (91) of an encrypted frame, to the gateway (20), representative of the configuration of the sensor module (1 1) comprising the configuration data (1 1 1 a).

10. Supervision system according to one of the preceding claims, characterized in that the gateway (20) is in encrypted communication link with a server (30) dedicated to the external network comprising at least one dedicated application for data exploitation measurement, the management module (12) performing an encryption of the decryptable control data by the gateway and by the dedicated application and an encryption of the decipherable measurement data only by the dedicated application.

1 1. Supervision system according to claim 10, characterized in that the dedicated application comprises a module (251) for sending encrypted commands to the management modules (12), each command being decipherable only by each management module ( 12) to whom this command is addressed.

12. Supervision system according to claim 10 or 1 1, characterized in that the gateway (20) comprises a module (27) cutting power to its communication link with the server (30) dedicated and power up in the event of solicitation by one of the management modules (12).