Method for reading a service card

p0001The present invention relates to a method for reading service information in a video-communication provided with receiving means for receiving and deciphering encrypted signals transmitted to the receiver by a television transmitter, said means particularly comprising a microprocessor associated in a random access memory and a read only memory containing instructions, and a deciphering module for deciphering said encrypted signals, which method is introduced into the receiver in a service mode, encrypted information.

p0002It also relates to a video-communication receiver comprising means for receiving and decrypting encrypted signals transmitted to the receiver by a television transmitter, said means particularly comprising a microprocessor associated with a random access memory and a read only memory containing instructions and a decryption module for decrypting said encrypted signals.

p0003It finally relates to a smart card intended for a receiver of the invention.

p0004A television system with image descrambling is known from patent application WO 93/07715 (Thomson). According to this, a specific smart card is used by an installer to perform automatically, in a receiver, updating the allocation of television channels in the reception site.

p0005Such updating a receiver may affect the receiving frequencies but also authentication data subscription of the user. Therefore, it is useful that the service information, or at least some of them, are encrypted to be safe from malicious attacks. It is therefore necessary, in principle, to use a decryption module that delivers data in clear, from encrypted service information on the basis of a secret code and / or decryption instructions to him provided. decryption instructions may also be her own encrypted.

p0006An object of the invention is to simplify the construction of a system capable of receiving and decrypting such information service.

p0007To this end, to decrypt said information, using the deciphering module of the receiver itself, that is to say, a receiver is provided with means for deciphering the service information by its own deciphering module.

p0008Thus a specific decryption module becomes unnecessary.

p0009In a particular embodiment, the encrypted service information is loaded into a random access memory of the receiver and processed by the microprocessor before being treated by the deciphering module of the receiver, that is to say that a receiver is provided with means for loading service information encrypted in the RAM, and to put them in a form which simulates signals transmitted to the receiver by a transmitter before treating them by means of a decryption module.

p0010In another embodiment, the encrypted information is carried by a data stream which simulates signals transmitted to the receiver by a television transmitter, that is to say that this stream is organized into packets of the same size as that of such signals.

p0011Thus information can be transmitted directly to the deciphering module of the receiver.

p0012Alternatively, is used as support for the information introduced into the receiver, a microprocessor service card placed in a card reader of the receiver, that is to say, a receiver equipped with a drive smart card, is provided with means for reading a service card placed in said reader.

p0013According to another variant, is used for entering information into the receiver, a connector for connection with the exterior, carried by the receiver, that is to say that it is provided with means for receiving service information encrypted via this connector.

p0014A service card advantageously produces an encrypted data stream which simulates signals transmitted to the receiver by a transmitter, that is to say that it is organized in packets of the same format as that of such signals.

p0015These aspects of the invention and other more detailed aspects will become clearer from the following embodiment of a description constituting a non-limiting example.

p0016The single figure schematically represents a video-communication receiver, equipped with a microprocessor card reader.

p0017The video-communication receiver shown in Figure comprises a unit for receiving satellite 1-6 and a set of cable reception 7-11.

p0018The satellite receiving system consists of a parabolic antenna 1 and a receiver 2, followed by an intermediate frequency amplifier 3. At this point the signal is modulated by a known method, said QPSK. The intermediate frequency signal is converted into digital values ​​in an analog-digital converter 4 and is then demodulated by the demodulator 5 of QPSK. Finally, some errors in the signal are corrected by error corrector 6 ( "Forward Error Correction"), based on the fact that the signal includes redundancy bits according to a known coding scheme.

p0019The entire cable reception consists, starting from an input signal by a tuner 7 followed by a transposer 8. At this point the signal is modulated by a known method, said 64 QAM. The intermediate frequency signal is converted into digital values ​​in an analog-digital converter 9, and is then demodulated by the demodulator 10 type 64 QAM. Finally, some errors in the signal are corrected by error corrector 11, of the same type as the corrector 6.

p0020At this level, the demodulated signal is called MPEG-2 TS (for "MPEG-2 Transport Stream"): this is a signal of a capacity of about 36 megabits, with up to twenty programs with data and sound, if any, are confused.

p0021A set of satellite reception and cable reception assembly are present together here, although they are made, often in two separate devices. A switch 12 permits here to select the satellite signal or the cable. The signal is then descrambled in a descrambling module 13 connected via a bus 27, a card reader 23 to the microprocessor 17, said smart card, and to a microprocessor 15.

p0022The microprocessor 15 includes a ROM in which are written the basic instructions. It is associated with a random access memory 22 for snapshot data, to a so-called "flash" memory 30 for storing program elements that may be updated, and the card reader 23, a keypad and / or a remote control receiver, a display screen data 25, and optionally to a modem 24.

p0023The descrambled signal is then subjected to the action of a demultiplexer 16, connected to the microprocessor 15, demultiplexer which separates from each other the various programs of MPEG-2 TS signal, one of them being selected by means of a switch 26. the signal from this demultiplexer is still in digital form and requires to be converted into an analog signal for displaying an image on a screen and applying the sound at a loudspeaker. This final transformation is performed on the one hand in a video decoder 19 that delivers a known type of signal, for example says 4-2-2, referred to as YUV, and secondly in a sound decoder 18. These decoders followed by processing circuits ( "post-processing") of the sound 20 and video 21, connected by a connection 28 to the standard circuits of the video and the receiver, if it is a TV, or an external TV, in the case where the receiver described herein is a set top box adapted to be connected to a signal input of a conventional TV type PAL, SECAM or NTSC.

p0024The reader 23 of smart card 17 is, of course, to read the map information necessary for descrambling of television images in a known way. It is used also for introducing into the receiver of the service information, including software. For this, the card of the user, containing personal information such as a distribution key, the characteristics of the subscription to a pay service, etc., is replaced in the same drive, a card Service containing updated information, such as software components, in encrypted form. Clearly, alternatively, this information could also be introduced into the receiver via a connector 32, for example the standard type as IEEE 1284 for the introduction of information, this connector can be connected to a microcomputer of the kind known as "PC", or a device designed for adjustment of the receivers, or a bond, for example of the RS232, to a data-loading station.

p0025To decrypt the service information, using the descrambling module 13 of the receiver itself. Various means can be employed for this purpose:<ul><li>the outgoing information from the card can be fed directly to the descrambling module 13 via a connection 29 provided for this purpose between the card reader 23 and the switch 12 which selects the connection 29 for connecting to the module 13. The card microprocessor then produces a data stream which simulates signals transmitted to the receiver by a transmitter, that is to say that it is organized in packets of the same format as the MPEG-2 TS signal. Suitable software, as the skilled person can write on demand, is of course loaded into a microprocessor memory for the information from the module 13 are recognized as intended to update the software, and are operated as appropriate .</li><li>the information can also be transferred in encrypted form, directly into the memory 22 from the drive 23 or connector 32, and then be made by the microprocessor 15 itself, in the form of the same size packets that the MPEG-2 TS signal, and then applied to the module 13. in this case, it is unnecessary for the smart card produces a data stream that simulates signals transmitted to the receiver by a transmitter.</li></ul>

p0026The information in the card may have a layered organization: a first layer contains the control word necessary for decryption; this control word may be itself in encrypted form. A key, provided by the installer, used to decrypt the control word, which will be decrypted with the other information, forming a second layer. The first layer may also contain various other information about the content of the second layer, and how to decipher it. It is always possible to achieve in some instances the decryption of service information using decryption instructions are directly provided with the information of the first layer, that is to say that do not use the receiver decryption module so it is also indicated in the first layer. This may depend, for example, a choice made by the broadcaster of television programming that is involved in the provision of service information.

p0027Thus, the mode of operation of the assembly is as follows (it is assumed that the transfer is made by means of a microprocessor card): the installer places the card in the receiver, the receiver recognizes a service card ( known way), and then reads the first packet in the map, then dialogue with the installer in order to get from him the key to decipher this first packet; there may be also a signature in the card that can recognize that the key provided by the installer is valid without knowing in advance; different encryption methods like this are known per se. In the case where the invention is implemented, the data thus obtained are transmitted to the module 13, enabling it to decode the rest of the packets contained in encrypted form in the card 17 (second layer). Alternatively, a stand-alone microcontroller 31 may further be loaded read operations and interpretation of information from the first layer. If the information of the first layer indicates that information of the second layer are in a form which is intended to be processed by the descrambling module of the receiver, independent microcontroller 31 then passes control to the main microprocessor 15, which will decrypt the rest of the information, that is to say the second layer.