The present invention relates generally to radio communication systems with mobiles. In particular, it relates to a system supporting authenticated direct communication between mobile communication terminals.

PRIOR ART

Mobile telecommunications networks, such as cellular networks defined by the 3GPP consortium, such as networks based on GSM, UMTS, LTE (“Long Term Evolution”), and its evolution LTE-A (“Advanced LTE”), standards, enable high-speed communications between mobile terminals. The architecture of these networks is generally based on a set of base stations, called eNodeBs (from the English “evolved Node B”) in the LTE standard, which are fixed network nodes forming the radio portion of the network, called the eUTRAN in the LTE standard, and which establish wireless communications with mobile terminals, called UEs (from the English “User Equipment”) in the LTE standard, via a specific radio interface, called the Uu interface in the LTE standard.

Authentication of mobile communication terminals in telecommunication networks generally uses secrets shared between an HSS (for “Home Subscriber Server”, in English) server in the core network, and a USIM (for “Universal Subscriber Identity Module”, in English) card, of mobile communication terminals, using the EMM (from the English “EPS Mobility Management”) protocol between an MME (for “Mobility Management Entity”, in English) entity and a mobile communication terminal (UE) via an eNodeB and the LTE-Uu radio interface between said eNodeB and said UE.

Authentication of mobile communication terminals within the network must necessarily go through the core of the network, called the EPC (from the English “Evolved Packet Core”) in the LTE standard. In other words, mobile communication terminals in telecommunication networks cannot authenticate each other directly, but only via the network core.

In some cases, however, it may be desirable to be able to establish a communication link between two authenticated individual pieces of equipment without any communication infrastructure from which such equipment access the telecommunications network.

A typical use case is, for example, that of security forces, especially in the context of external operations, and rescue forces (police, fire brigade, ambulances, etc.) who need to be able to collaborate and communicate with each other following, for example, an interruption of conventional communication services due to a system overload or a natural disaster, such as an earthquake or a tidal wave, with the immediate consequence that the shore-based communication participating in the network core are shut down. There is therefore a need for a solution for setting up a substitution network between the mobile terminals and/or mobile cells, to compensate for the failure of the standard network and/or the equipment of the network core.

In summary, especially, but not only, in the context mentioned above, it may be useful for specific applications to establish communication links between several mobile communication terminals, in order to make the data exchanges between these mobile structures autonomous with respect to the network core. Nevertheless, in this context, there is the issue of the protocol for establishing a direct or indirect link between mobile communication terminals and in particular the level of security associated therewith. Indeed, in general, on conventional NB systems (for example Tetra or P25), there is no authentication or even encryption possible at the level of radio D2D exchange nor integrity management. The only possibility is to secure communications at the level of the application flow, for example by means of group communication keys.

For example, a two-way professional digital mobile radio system has been proposed, comprising a plurality of mobile communication terminals. Such mobile communication terminals can communicate in a direct mode, where each mobile communication terminal exchanges with another terminal without going through a base station, or use the infrastructure of a communication network through a base station. This allows direct communications in situations where the network's radio coverage has been lost. This functionality allows, for example, direct communications in basements or areas with poor radio coverage. Such a digital radio system can carry several types of data communication. Packet-mode data or circuit-switched data communication use channels dedicated to this traffic. The security relating to the traffic of this data is ensured by encrypting said data when it is sent or by end-to-end encryption.

In addition, this communication system generally operates on a band frequency below one Giga Hertz (GHz). Indeed, digital radio systems operate in a frequency spectrum generally between 160 MHz and 400 MHz, in particular as defined in standards EN 300 392-1 and EN 300 392-2. As a result, the data transfer is slow (of the order of 7.2 kbit/s per time-slot), the usable data rate is only 3.5 kbit/s. This rate can be increased moderately by using up to four combined time slots, for example by using mainly four interleaved channels in a 25 Kilo Hertz (KHz) carrier using a time division multiple access “TDMA” (for “time division multiple access” in Anglo-Saxon terminology). Thus, such a digital radio system can only support a much smaller number of mobile communication terminals than a conventional network, such as GSM (for “Global System for mobile” in Anglo-Saxon terminology), UMTS (for “Universal Mobile Telecommunications System” in Anglo-Saxon terminology), LTE (for “Long term Evolution” in Anglo-Saxon terminology) or advanced LTE networks allow in a given geographical area and similar technologies allow in a given sector.

A solution could be based on establishing a link of the direct-mode link type so as to create a link between a mobile communication terminal and one or more other mobile communication terminals. However, this type of link no longer allows the use of the network infrastructure usually used to manage the security aspects according to known techniques of the LTE standards of the 3GPP consortium, for example.

Indeed, when establishing a dUE-dUE connection (in a mode called a “D2D mode”, for “device to device” in Anglo-Saxon terminology, in the present description), the eNodeb and the Uu interface are not used. The framework provided in the LTE standards for security management using the USIM module and the HSS server (shared secret exchange) therefore cannot be used as it stands for authentication, encryption and integrity control.

There is therefore a need for a method or system for managing the authentication of one or more mobile communication terminals for the establishment of direct-mode, secure and high-speed communications, while eliminating the need for the infrastructure of a fixed communication network.

Technical Problem

The invention aims to overcome the disadvantages of the prior art. In particular, the invention aims to provide an alternative for dispensing with the fixed network infrastructure for the management of authentication aspects, in particular the authentication of a mobile communication terminal participating in the establishment of a direct mode link with another mobile communication terminal, while using standardized authentication techniques and making it possible to support the most recent and advanced security techniques.

BRIEF DESCRIPTION OF THE INVENTION

To this end, a first aspect of the invention relates to a communication system comprising a local mobile communication terminal and a remote mobile communication terminal, said remote mobile communication terminal including an electronic safe configured to store at least one security key, said local mobile communication terminal being configured to establish a direct mode link with said remote mobile communication terminal,

said communication system being characterized in that said local mobile communication terminal includes:a subscription database configured to store at least one security key, each of the security keys forming a secret shared between a local mobile communication terminal and one or more remote mobile communication terminals and to generate at least one authentication vector from the at least one security key;a security management entity emulator, configured to emulate an access interface to the subscription database of said local mobile communication terminal and to generate an authentication request from the at least one authentication vector; and,a proxy module configured to relay the authentication request, between the security management entity emulator and the remote mobile communication terminal, said authentication request including a signaling portion of a protocol conforming to the direct mode link, for the authentication of said remote mobile communication terminal to the subscription database of said local mobile communication terminal.

The invention is based in particular on the use of a local subscription database (that is of a local mobile communication terminal), as well as the unique identifier of the remote mobile communication terminal wishing to establish a communication in a direct mode with the local mobile communication terminal, in order to manage the security of each mobile communication terminal and to prevent unauthorized mobile communication terminals from connecting and disrupting or intercepting communications between mobile communication terminals. The present invention allows, in particular, the right of a given mobile communication terminal to connect to a remote mobile communication terminal to be managed. An advantage of the invention, in particular, is that it allows the use of mobile communication terminals using known authentication techniques for the establishment of direct communication. The new transport path implemented by a system according to the invention advantageously allows the use of an identification module such as a USIM module and conventional access protocols to authenticate a remote mobile communication terminal. Thus, the logical protocol used remains as close as possible to existing protocols to ensure ease of use and support as close as possible to standard protocols and their evolution. There is therefore a possible support of the most recent and advanced security techniques.

A further advantage of the fact that authentication aspects are supported by the direct link between mobile communication terminals is that it is possible to use (in addition to unicast) a point-to-multipoint protocol that allows multiple signaling acquisitions to be performed.

Finally, a communication system according to the invention has the advantage of making it possible to dispense with the use of an advanced base station or an MME (from the English “Mobility Management Entity” for mobility management entity) type entity and an HSS (from the English “Home Subscriber Server”) associated with a telecommunication infrastructure. Therefore, the communication system according to the invention advantageously allows a connection to be made between two mobile communication terminals, preferably in a direct mode, based on mutual authentication at the outset, in order to prevent unwanted or unauthorized terminals from connecting.

According to other advantageous features of the system, the latter may optionally include one or more of the following features, alone or in combination:the authentication request comprises random data as well as a signaling portion of a protocol conforming to the direct mode link.The proxy module is further configured to receive an authentication response from the remote mobile communication terminal, said authentication response including a signaling portion of a protocol conforming to the direct mode link and an authentication result.The security management entity emulator is further configured to check the correspondence between the authentication result transmitted by the remote mobile communication terminal and an authentication token generated by the subscription database. This allows the correspondence between the security keys stored on the electronic safe of the remote mobile communication terminal and the subscription database of the local mobile communication terminal, respectively, to be checked indirectly.the local mobile communication terminal and/or the remote mobile communication terminal include an electronic safe adapted to store a unique identifier associated with said local mobile communication terminal and the remote mobile communication terminal, respectively;the proxy module is configured to carry an integrity check message when establishing the communication between the local mobile communication terminal and the remote mobile communication terminal;the local mobile communication terminal is configured to establish a direct mode link with a plurality of remote mobile communication terminals according to a point-to-point or multipoint protocol. Indeed, although the direct mode link is the main subject of the present invention, the link can be other, the purpose being to access a remote ‘authenticator’ terminal;the local mobile communication terminal is configured to allow a plurality of remote mobile communication terminals to authenticate with the local mobile communication terminal having the subscription database and then communicate with each other.the mobile communication terminals are configured so as to be able to use a mobile communication network selected from an LTE, 5G, Wimax, 3G, Wifi or Bluetooth network; These technologies are preferred; Nevertheless, the present invention can be used with any other ‘physical’ technology allowing the implementation of a point-to-point or multipoint protocol and requiring at least one authentication.the security management entity emulator is adapted to support an access interface to the subscription database based on a S6a-like interface of the LTE standards of the 3GPP consortium;the proxy module is adapted to support an access interface to the security management entity emulator based on an EMM protocol of the LTE standards of the 3GPP consortium;the security management entity emulator of a local mobile communication terminal is adapted to allow the remote mobile communication terminal to perform the authentication request without passing through the radio interface of a base station. Thus, the system can operate even in the event of a malfunction of the accessible base stations;the local mobile communication terminal is configured to use a specific radio channel for the authentication of remote mobile communication terminals. The use of a radio channel dedicated to authentication makes it possible not to use the radio resources of remote mobile communication terminals which are already communicating on a radio channel dedicated to communication.

According to another aspect, the invention relates to an authentication method between a local mobile communication terminal and a remote mobile communication terminal of a communication system according to the invention, for the establishment of a direct mode link between said mobile communication terminals, said method including the steps of:transmitting to the local mobile communication terminal an authentication request to the subscription database of said mobile communication terminal from the remote mobile communication terminal;transmitting, via a proxy module of the mobile communication terminal, the received authentication request to the security management entity emulator of said local mobile communication terminal; and,presenting, to the subscription database of the mobile communication terminal, by the security management entity emulator, the authentication request from the remote mobile communication terminal, for the authentication of said mobile communication terminal to the subscription database of the local mobile communication terminal.

The invention relates to a method for authenticating a remote mobile communication terminal to a local mobile communication terminal, said method including:sending an attachment message, by the remote mobile communication terminal, said attachment message preferably including the unique identifier of said remote mobile communication terminal;sending, by the local mobile communication terminal, an authentication request generated from an authentication vector, said authentication vector being generated by a subscription database of said local mobile communication terminal, said authentication request including a signaling portion of a protocol conforming to the direct mode link;sending an authentication response, by the remote mobile communication terminal, said authentication response including a signaling portion of a protocol conforming to the direct mode link for the authentication of said remote mobile communication terminal to the subscription database of said local mobile communication terminal.

In addition, as will be detailed, this method may include authentication, by the mobile communication terminal, of the local mobile communication terminal; thus constituting mutual authentication of the mobile communication terminals.

According to another aspect, the invention relates to a mobile communication terminal comprising:a subscription database configured to store at least one security key, each of the security keys forming a secret shared between a local mobile communication terminal and one or more remote mobile communication terminals and to generate at least one authentication vector from the at least one security key;a security management entity emulator, configured to emulate an access interface to the subscription database of said local mobile communication terminal and to generate an authentication request from the at least one authentication vector; and,a proxy module configured to relay the authentication request, between the security management entity emulator and the remote mobile communication terminal, said authentication request including a signaling portion of a protocol conforming to the direct mode link, for the authentication of said remote mobile communication terminal to the subscription database of said local mobile communication terminal.

