Abstract:
A telecommunication device including a battery capable of providing a first power supply voltage to circuits of the device, among which at least one security module; a near-field communication module capable of providing a second power supply voltage to the security module; and a circuit for activating the provision of the second power supply voltage, including a switch controllable at least by one element accessible from outside of the device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage patent application based on International patent application number PCT/EP2011/064643, filed on Aug. 25, 2011, which application claims the priority benefit of French patent application number 10/56913, filed on Aug. 31, 2010, which applications are hereby incorporated by reference to the maximum extent allowable by law which is hereby incorporated by reference to the maximum extent allowable by law. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure generally relates to mobile telecommunication devices equipped with a near field communication circuit (NFC). 
     2. Discussion of the Related Art 
     Cell phones are more and more often equipped with a near field communication interface, which enables combining electromagnetic transponder functions with mobile telephony functions. In particular, this adds contactless card type electromagnetic transponder emulation functions to the mobile telecommunication device, of personal digital assistant, cell phone, smartphone, or other type. This enriches the features of the mobile device, which can then be used, for example, as an electronic purse, as a debit or credit system, as an access validation device, as a transport ticket, etc. 
     To emulate the operation of a contactless chip card, the mobile telecommunication device is equipped with a contactless front-end integrated circuit (CLF), also called an NFC router. This router is equipped with a radio frequency transceiver front head associated with a low-range antenna to communicate like an electromagnetic transponder. The router uses the capacities of the mobile device processor(s) for data processing and storage operations. For access control, electronic purse, payment, and other applications, a secure element enabling to authenticate the user is used. This secure element is either integrated to the mobile telecommunication device (dedicated integrated circuit, circuit welded to the printed circuit board) or contained in a microcircuit supported by a subscriber identification module (SIM), or any other removable card, for example in the standard format of a memory card. 
     A specificity of such a mobile telecommunication device is that it is capable of operating in NFC when it is off or, more generally, when its circuits are not powered by the battery or another power supply element of the mobile device. 
     In this case, the NFC router draws the power necessary to its operation, like an electromagnetic transponder, from the field radiated by a nearby terminal. It then provides the power supply necessary to the security module circuits to validate near-field transactions. 
     When the device is powered by its battery and its internal circuits are operating, different security mechanisms may be implemented, for example, to avoid a hacking of the SIM card. However, when the device is only powered via the NFC router, such mechanisms may be difficult to implement. This is a weakness of such a mobile telecommunication device. 
     SUMMARY 
     It would be advantageous to overcome all or part of the disadvantages of mobile telecommunication devices associated with a near-field transmission module. 
     It would be advantageous to improve the security against a hacking attempt when the device is only powered by its near-field transmission module. 
     It would be advantageous to provide a solution compatible with usual subscriber identification modules. 
     An embodiment provides a telecommunication device comprising: 
     a battery capable of providing a first power supply voltage to circuits of the device, among which at least one security module; 
     a near-field communication module capable of providing a second power supply voltage to the security module; and 
     a circuit for activating the provision of the second power supply voltage, comprising a switch controllable at least by one element accessible from the outside of the device. 
     According to an embodiment, said switch is a mechanical switch. 
     According to an embodiment, said switch is an electronic switch controlled by at least one signal having its state conditioned at least by that of said control element. 
     According to an embodiment, the electronic switch can be actuated both when the device is powered by the first voltage and when it is powered by the second voltage. 
     According to an embodiment, said switch is capable of short-circuiting two conductors for providing said second power supply voltage. 
     According to an embodiment, said switch is on in the idle state. 
     According to an embodiment, said switch is in series with a current-to-voltage conversion element, a signal indicative of the state of the switch being sampled from the junction point of these components towards the near-field communication module. 
     Another embodiment provides a method for controlling a near-field communication module, wherein a response to a request originating from a terminal having the device in its field is only authorized if the switch is off. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features, and advantages of the embodiments will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings. 
         FIG. 1  very schematically shows a mobile telecommunication device of the type to which the embodiments apply as an example and its surrounding system; 
         FIG. 2  is a block diagram illustrating the power supply of the circuits internal to the telecommunication device; 
         FIG. 3  very schematically shows an embodiment of a circuit for securing a security module; 
         FIG. 4  very schematically shows an embodiment of a mobile telecommunication device equipped with the circuit of  FIG. 3 ; 
         FIG. 5  is a block diagram of a variation of the circuit of  FIG. 3 ; and 
         FIG. 6  schematically illustrates an example of exchanges between a reader, a router, and a security module. 
     
    
    
     DETAILED DESCRIPTION 
     The same elements have been designated with the same reference numerals in the different drawings. For clarity, only those elements and steps which are useful to the understanding of the embodiments have been shown and will be described. In particular, the coding and communication protocols, be it for near-field transmissions or for telecommunications in GSM mode, have not been detailed, the described embodiments being compatible with usual protocols. Further, the circuits forming the mobile communication device have not been detailed either, the described embodiments being here again compatible with usual devices. 
     The embodiments will be described in relation with a cell phone. They however more generally apply to any telecommunication device adapted to a mobile network (for example, Wifi, Bluetooth, WiMax, etc.) and associated with a contactless near-field transmission module. 
       FIG. 1  very schematically shows a mobile telecommunication device  1  (for example, a cell phone). 
     Device  1  comprises a central processing unit  12  (CPU/TH) formed of at least one microprocessor forming the device core. This microprocessor is presently called a terminal host. For the telecommunication operation over a network (GSM,  3 G, UMTS, etc.), this microprocessor uses identification and authentication data provided by a subscriber identification module  14  (SIM), forming a security module of the device. Microprocessor  12  is capable of using one or several internal memories (not shown) of the telephone. The different elements of interface with the user (keyboard, display, speaker, etc.) have not been shown. 
     The mobile devices to which the described embodiments apply combine the telecommunication function with that of a near-field contactless transmission system. To achieve this, device  1  comprises a circuit  18  (CLF) forming a near-field communication module, like an electromagnetic transponder. Module  18  is associated with an antenna  182  distinct from an antenna  20  intended for the mobile telephony network. The near-field communication module will be called an “NFC router” since it generally integrates all the functions useful to the emulation of a contactless card within a same circuit, but the described embodiments apply to any NFC-type module. 
     The different elements of device  1  communicate according to various protocols. For example, circuits  12  and  18  communicate over a link  1218  of I2C, SPI, or other type, and SIM card  14  communicates with microprocessor  12  over a link  1214  according to ISO standard 7816-3. Router  18  communicates with the SIM card, for example, over a single-wire bus  1418  (SWP—Single Wire Protocol). Other versions of protocols and links are, of course, possible. 
     As illustrated in  FIG. 1 , device  1  is capable of communicating over a telecommunication network (for example, GSM) symbolized by a relay antenna  3 , for example, with another mobile device  1 ′. In near field, the CLF router is capable of communicating with a reader  5  (READER), for example, an NFC terminal or any other contactless communication terminal. 
       FIG. 2  is a block diagram illustrating the power supply of the different circuits of mobile device  1 . 
     The device generally comprises a battery  16  or a power supply capable of providing (generally via a voltage regulator, not shown) a voltage VCC to the different electronic circuits and in particular to NFC router  18 , to SIM card  14  (or other security module), to central processing unit  12 , as well as to the other circuits (not shown) of the device (keyboard, display, etc.). A switch  162  is functionally interposed between battery  16  and a power supply rail  164  providing voltage VCC. Switch  162 , generally electronic, is controlled under the action of a mechanical switch accessible by the user from outside of device  1 . 
     When the mobile device is off (switch  162  open) or when it is in a so-called low-power operating mode (for example, at standby), NFC router  18  remains capable of extracting a power supply voltage from a magnetic field (RF FIELD) radiated by a near-field communication reader (not shown in  FIG. 2 ). Router  18  comprises power regulation means (symbolized by a block  182 —REG). Regulator  182  provides a power supply voltage NFC VCC to the different circuits of router  18  as well as, over a link  1814 , to SIM card  14 . This enables the router to access the security module to obtain authentication or identification elements enabling to validate a transaction with the reader, even when the other device circuits are not powered. 
       FIG. 3  schematically shows an embodiment of a circuit  6  for securing the SIM card when the telecommunication device operates in NFC mode. Circuit  6  is a circuit for activating the SIM card power supply. 
     According to this embodiment, link  1814  between router  18  and security module(s)  14  is connected to ground  166  by a switch  62 . The function of this switch is to pull link  1814  to ground as long as a transaction is not authorized. 
     Preferably, and as illustrated in  FIG. 3 , a resistor  64  is interposed between switch  62  and link  1814 . Resistor  64  forms a current-to-voltage converter and the junction point of the resistor and of switch  62  is connected, by a link  66 , to a gate of router  18 . The signal present over link  66  indicates, by its state, the state of switch  62 , and thus the authorization or not of a near-field operation. Router  18  can use this information to enable/disable some of its internal functions. For example, the router is only authorized to respond to a request from the reader when this signal is active. 
     In the idle state, switch  62  is on. This means that, by default, the security module is not powered by router  18 , even if the latter generates a voltage NFC VCC. 
       FIG. 4  schematically shows a device  1  equipped with the system of  FIG. 3 . 
     According to this embodiment, switch  62  is mechanical and can be actuated by a push-button  68  accessible from outside of the device. Accordingly, a near-field transaction is only authorized when the user presses push-button  68 . 
       FIG. 5  shows another embodiment according to which switch  62  is an electronic switch. Circuit  6  receives a signal  682  transmitting the state of push-button  68  and a control signal CT that comes from another external authorization element when the device is powered by its battery. This embodiment enables to take advantage of the protection function (near-field transaction authorization) in all device power supply modes. For example, signal CT is controlled, when the device is active (powered by the battery), by an action of the user on a key of the keyboard or on an area of a touch screen. 
       FIG. 6  schematically illustrates an example of exchanges between reader  5 , router  18 , and the SIM card. 
     When the device enters field RF FIELD of the reader and it is not powered by its battery, the router detects the presence of the magnetic field (IN RF FIELD). It then transmits a control signal (EVT_FIELD_ON) to card  14  to indicate this event. The reader periodically sends requests to the possible routers in its field. When the router receives a request, if the state of signal  66  indicates an authorization (OK), the router responds (ATQ) to the reader. Otherwise, the router remains mute (MUTE) as long as such an authorization has not been received. Then, an anti-collision procedure is implemented between the reader and the router. Then, the router activates the SIM card with a control signal EVT_CARD_ACTIVATED. The card and the reader then communicate (EVT_SEND_DATA) via the router. 
     In its simplified embodiment (with no link  66 ), the implementation is particularly simple. It is sufficient to add to the device a switch short-circuiting by default power supply voltage NFC VCC (connecting link  1814  to ground) and to provide an actuator  68  accessible from outside of the mobile device. 
     It should be noted that the described embodiments require no modification of the SIM card. 
     Various embodiments have been described, various alterations and modifications will occur to those skilled in the art. For example, switch  62  may be interposed on link  1814  and is then off in the idle state. However, the embodiment illustrated by  FIG. 3  eases the extraction of a state signal towards the NFC router. 
     Such alterations, modifications, and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention is limited only as defined in the following claims and the equivalents thereto.