Abstract:
In order to allow a display of the latest transactions, a smart card  100   c  for secure transactions comprises at least one secure chip  101   c , for example of the EMV type, with at least one communication interface to communicate with a card reader in order to carry out a transaction, an electronic display  103 , an independent battery  104 , a card reader circuit  150   c  connected to a communication interface of the secure chip in order to access the information contained in the secure chip to be able to display it on the display.

Description:
BACKGROUND OF THE INVENTION 
     Bank cards have electronic chips for transaction security. The EMV standard was created by Europay, MasterCard and Visa, the initials of which relate to the definition of an interoperability and security standard between smart bank cards. For a card to have EMV certification, it must have a chip, which is itself certified and has a contact type interface according to the standard ISO 7816 and/or a contactless interface according to the standard ISO 14443. To limit the risks of hacking, EMV chips do not have any other communication interface. 
     Besides, the making of smart cards with a screen and one or more pushbuttons to communicate with the cardholder is also known. These cards are not currently widespread and are used for generating single-use passwords for computer transactions. Such cards generally have a chip with a contact or contactless smart card communication interface and a communication port designed for communication with other integrated circuits such as for example an I2C communication interface or General Purpose Input/Output (GPIO) ports. It is thus possible for a smart card microcontroller to communicate with a display controller that controls a liquid crystal display or a so-called “electronic ink” display. 
     One idea would be to make a bank card with a screen to display the latest transactions completed. That raises a problem if the smart card is to be made according to the EMV standard. These chips do not have an additional input/output port for such an application, and for security reasons, the addition of other input/output ports is not preferable. 
     As a result, it is not possible to steer the display from an EMV chip. A solution is thus required to be able to display the latest transactions completed on a smart card. 
     SUMMARY 
     The invention is a solution to the problem posed. To allow the display of the latest transactions, a second microcontroller is added to the smart card in order to provide a card reader function to read the data relating to the latest transactions completed from the EMV chip. 
     More particularly, the invention is a smart card for secure transactions comprising at least one secure chip with a communication interface in order to communicate with a card reader in order to carry out a transaction. That card further comprises an electronic display, an independent battery and a card reader circuit connected to the communication interface of the secure chip in order to be able to access the information contained in the secure chip so as to be able to display it on the display. 
     Preferentially, the reader circuit only accesses public information of the secure chip. Public information includes the amounts of the transactions completed. 
     Further, the card may comprise an actuator to allow a holder of the said card to trigger reading and display the information read. That actuator may be a motion sensor. 
     In one alternative, the card may comprise a usage sensor to inhibit or allow the working of the reader circuit. The usage sensor may be a light sensor. 
     According to different embodiments, the communication interface may be a contact type interface in which the reader circuit is connected in parallel to the contacts of the card through controlled switches and/or the communication interface may be a contactless interface with a first antenna formed of turns inside the card and in which the reader circuit has a second antenna formed of turns inside the card, the first and the second antenna sharing a common electromagnetic flux. If the card has a contactless interface, the communication interface can disable the working of the card reader circuit if an external field is detected. If the secure chip has two communication interfaces, then at least one communication interface is connected to the reader circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and other particularities and benefits will become clear in the description below, which refers to the attached drawings, among which  FIGS. 1 to 3  represent three embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a functional chart of a first embodiment of the invention. In this embodiment, the bank card  100  is a contact type smart card comprising a secure chip  101  with a communication interface in accordance with the standard ISO 7816 connected to a connector  102  comprising contact pads that are also defined by the standard 7816. The secure chip  101  is for example a chip that meets the EMV standard and comprises restricted-access data and other so-called public data. The restricted-access data require the use of a password or encrypted messages whereas public data may be accessed for reading and/or writing by any reader that complies with the standard ISO 7816. 
     During a payment that uses the secure chip  101 , the bank card  100  is inserted in a secure reader which verifies a PIN number entered by the holder of the card to verify that the card holder is the right one, followed by the exchange of secure information via encrypted messages between the card, the reader and possibly a remote server to verify if the card debit is or is not authorised. When the transaction is completed, the information is updated in the card and the reader to indicate the amount of the transaction completed and possibly the balance remaining in the card. The completed transaction amounts that are stored in the card have no legal value and do not contain confidential information, and are thus generally saved in a non-secure memory zone, which is thus accessible by any type of reader that complies with the standard ISO 7816. 
     In order to display the latest transactions completed, the bank card  100  has an electronic display  103 , a battery  104  and a card reader circuit  150 . The card reader circuit  150  may be made of a single integrated circuit or possibly several circuits. In terms of manufacturing, the reader circuit  150  may be laminated on a substrate in the card body using a known method with contact with the rear side of the contact pads of the connector  102  according to a known technique. 
     The electronic display  103  may be of the liquid crystal type or the electronic-ink type using micro-balls. What matters is that the electronic display  103  must be sufficiently fine to be integrated into a smart card and must also have low power requirements. The battery  104  is an ultra-flat battery that can be integrated into a smart card. Depending on the required life of the card and the consumption of the reader circuit  150  and the electronic display  103 , a rechargeable or non-rechargeable battery may be chosen. 
     The card reader circuit  150  comprises a microcontroller  151  constituting the intelligence of the device and comprising the programs required for the working of the whole, a steering circuit  152  to control the electronic display  103 , a communication interface  153  in accordance with the standard ISO 7816 but on the reader side, a switching circuit  154  placed between the interface  153  and the secure chip, a power supply regulator  155  and a pushbutton  156 . 
     The microcontroller  151  is the main control component of the card reader circuit. The steering circuit  152  is used for transforming a number to write supplied by the microcontroller  151  into electronic signals to control the electronic display  103 . The power supply regulator  155  is used for transforming the voltage supplied by the battery into power voltage for the 20 display electronic  103 , the reader circuit  150  and also the secure chip when the reader circuit reads the card. The power supply regulator  155  may also act as a battery charger if the battery  104  is of the rechargeable type. The battery is recharged when the card is connected to an external reader during a transaction. In that case, the regulator must not be connected directly to the 25 power supply contact pads without going through the switch circuit  154 . 
     The pushbutton  156  is an actuator accessible by the card holder to trigger the working of the card reader. Typically, following an action on the pushbutton  156 , the microcontroller  151  acts on the switching circuit  154  to connect the secure chip to the interface  153  and the power supply regulator  155 , so that the battery  104  powers the secure chip  101 . The microcontroller  151  will then control the interface  153  to initiate communication with the secure chip  101  and read the amount of the last transaction completed. Once the data are read, the microcontroller  153  sends a control sequence to the steering circuit  152  to display the amount on the electronic display  103 . 
     Pressing the pushbutton  156  once again can lead to the readout and display of the previous transaction. Keeping the button pressed down can stop the reading of transactions and switch to standby mode, where the power supply of the secure chip  101 , the display  103 , the interface  153  and the steering circuit is switched off and where only the microcontroller  151  is powered for the part allowing the device to wake up when the pushbutton is pressed once again. If the pushbutton  156  is not pressed for a predefined long time, such as for example 1 to 2 minutes, that puts the system into standby. 
     As an alternative, it is also possible that the first action on the pushbutton  156  triggers a series of readings of all the transactions accessible in the secure chip  101 . The microcontroller  151  then stores the transaction information locally. When the pushbutton  156  is pressed once again, the microcontroller  151  merely displays the previous transactions that have already been read. 
       FIG. 2  is a functional chart of a second embodiment of the invention. In order to simplify the description, the components that are shared between the first and second embodiments have the same references and will not be described further. Also, the equivalent components will have a reference that also refers to the first embodiment by adding a ‘b’. 
     In this second embodiment, the bank card  100   b  is a contactless type smart card comprising a secure chip  101   b  with a communication interface in accordance with the standard ISO 14443 connected to an antenna  105  made up of turns placed inside the card body. The secure chip  101   b  is for example a chip that meets the EMV standard and comprises restricted-access data and other so-called public data. The restricted-access data require the use of passwords or encrypted messages whereas public data may be accessed for reading and/or writing by any reader that complies with the standard ISO 14443. 
     During a payment that uses the secure chip  101   b , the bank card  100   b  is placed before the antenna of a secure reader and secure information is exchanged via encrypted messages between the card, the reader and possibly a remote server to verify if the card debit is or is not authorised. When the transaction is completed, the information is updated in the card and the reader to indicate the amount of the transaction completed and possibly the balance remaining in the card. The completed transaction amounts that are stored in the card have no legal value and do not contain confidential information, and are thus generally saved in a non-secure memory zone, which is thus accessible by any type of reader that complies with the standard ISO 14443. 
     In order to display the latest transactions completed, the bank card  100   b  has an electronic display  103 , a battery  104  and a card reader circuit  150   b . The card reader circuit  150   b  differs from the first embodiment in that it uses a communication interface  157  that complies with the standard ISO 14443, connected to an antenna  158 . The antenna  158  is an antenna made up of several turns and is also placed inside the card body. The antennas  105  and  158  are made so as to share common electromagnetic flux in order to allow the secure chip  101   b  to be powered by antenna coupling and communication between the secure chip  101   b  and the interface  157 . These two antennas are further configured to not disturb each other when they share the electromagnetic flux of a reader located outside the card. 
     The interface  157  also makes it possible to recover energy from an external reader in order to make it possible to recharge the battery  104  by means of a power supply regulator  104 . Further, the interface  157  makes it possible to detect an external field created by another reader and can inhibit the working of the card reader circuit  150   b  in case of detection, in order to avoid disturbing a transaction. 
       FIG. 3  represents a functional diagram of a third embodiment of the invention, which further incorporates improvements that can also be used in combination with one of the embodiments described above. In order to simplify the description, the components that are shared between the second and third embodiments have the same references and will not be described further. Also, the equivalent components will have a reference that also refers to the other embodiments by adding a ‘c’. 
     In this third embodiment, the bank card  100   c  is a hybrid smart card comprising a secure chip  101   c  with a communication interface in accordance with the standard ISO 7816 connected to a connector  102  comprising contact pads that are also defined by the standard ISO 7816 and also a communication interface in accordance with the standard ISO 14443 connected to an antenna  105  made up of turns placed inside the card body. The secure chip  101   c  is for example a chip that meets the EMV standard and comprises restricted-access data and other so-called public data. The restricted-access data require the use of a password or encrypted messages whereas public data may be accessed for reading and/or writing by any reader that complies with the standard ISO 7816 or the standard ISO 14443. 
     In order to display the latest transactions completed, the bank card  100   c  has an electronic display  103 , a battery  104  and a card reader circuit  150   c . The card reader circuit  150   c  differs from the two previous embodiments in that it uses both a communication interface  153  that complies with the standard ISO 7816 and a switching circuit  154  placed between the interface  153  and the secure chip and a communication interface  157  that complies with the standard ISO 14443 and is connected to an antenna  158 . In practice, only one interface  153  or  157  is sufficient if the secure chip  101   c  has registers accessible regardless of the type of communication interface used. 
     Among the other changes, the pushbutton  156  is replaced by an accelerometer  170  in order to avoid problems relating to wear and tear and loose contacts associated with pushbuttons, which are particularly sensitive on smart cards. Thus, the reader can be powered up in a movement for card reading, and movement signatures can be used to differentiate whether a particular type of transaction is to be viewed. 
     Also, the use of a pushbutton or even an accelerometer can start up the reader circuit when the card is already in a reader. Such double access can lead to problems. In order to remedy possible problems, a light sensor  180  is used and coupled with the microcontroller  151  to not power the secure chip  101   c  by the battery  104  and block all card communication if the sensor does not sense sufficient light. That further prevents discharging the battery by unintentional activation in a pocket subject to pressure.