Pre-payment television system using a memory card associated with a decoder.

D'ENREGI5TREURS NAGRA, SWITZERLAND, INDUSTRIAL AND COMMERCIAL, established in Route de Genève 22, CH-1O33 CHESEAUX S / LAUSANNE, SWITZERLAND, for:

PAYMENT TELEVISION SYSTEM USING A

MEMORY CARD ASSOCIATED WITH A DEDEDIFIER

The present invention relates to a pay-TV system or device using a memory card associated with a decoder.

In pay-TV systems or devices, the video and audio signal intended for broadcasting is firstly interfered with by any process, then merged by radio, satellite or cable and finally received and released. interference at the level of each customer with the aid of a specific device usually called a decoder.

[! On pay television systems perfect! As known today, the decoder essentially comprises an electronic device for the elimination of intercomputing. video image reference. This decoder is associated with j | a memory card intended primarily for controlling the same issues and managing the credit required to purchase such issues

In such pay-TV systems, an arbitrary word for the initialization of a pseudo-random generator that determines a code table is edited at the broadcast level. · This code table is used for video signal interference, then this initialization word is encrypted using a predetermined encryption key, then this encrypted initialization word is broadcast with the video signal · On reception at the client decoder level, the initialization word is deciphered using the same predetermined code key, so as to give back in clear language the said word for use as the initialization word of a pseudo-random generator identical to the one used for issuing and generating, therefore an identical code table · This code table is then used to eliminate interference from the video signal that can then be sent to the TV.

Following this text, it is called provider! of service¹»Every person or company that has the right to broadcast interfering broadcasts (also called coded) and which makes available to its customers a special decoder or special card that will fit a decoder that can also serve as a decoder emissions from other service providers. Following this text, a motherboard is a card or device for

I encrypt the startup word using a specific key from a service provider and is called a customer card ί; the corresponding card or device made available to customers.

• I |! The memory card has numerous advantages ie, among others, that it allows simultaneous scanning by¹

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various service providers, but may also present certain drawbacks linked to the risks of piracy, which will now be exposed. In the case of a memory card intended for use by several service providers, one service provider A may enter his keys and rights on each card and another service provider B may write to his or her own cards or other cards. keys and their rights independently. In this case, it is conceivable for a knowledgeable person to look for a customer card and use it to decrypt the startup word, sent encrypted with the service provider A video signal, then use a motherboard to encrypt this startup word according to the different key used by another service provider, for example service provider B, and thus send to persons who may be complicit the emissions from service provider A, transposed into the service provider's card network B.

The present invention aims to remedy the aforementioned drawback.

The present invention therefore relates to a sisH ** _M pay television theme using a memory card associated with a decoder.

According to a feature of the present invention, on the emission side a number generator provides a random code. which is sent to the input of a motherboard that encrypts &lt;this code using a predetermined key, the encrypted code being then broadcast with the video signal and receiving a

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first device in your entries on the one hand the code i¹ and, on the other hand, the code encrypted by the motherboard and making a determined digital combination of these two codes, this combination being the initialization word of

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a pseudo-random generator for providing a code table for interference with the video signal and, on the receiving side, the decoder receiving the encrypted code, which is deciphered by a customer card, receiving a second device on its enters, on the one hand, the encrypted code and, on the other hand, the code deciphered by the customer's card and making a digital combination of these two codes identical to that of the first device, the result of this ** · combinação * combination is the start word of another pseudorandom generator that provides a code table identical to that of the broadcast and designed to remove interference from the video signal ·

According to one embodiment of the present invention, the first and second devices perform the same digital combination whose function is such that the proca function cannot be determined except by means of a reciprocal test.

According to the invention, the first same digital combination is an OR EXCLUSIVD.

with another embodiment of the presence second devices perform one of binary numbers and whose function is

Other features and advantages of this

A. The invention will be apparent from the description of an example of the following embodiment, illustrated in the accompanying drawings, which figures represent:

Fig. 1, the basic principle of a pay television system.

Fig. 2, the principle of operation of a pay-TV system using a

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memory, now known, also illustrating a possible mode of piracy; and

Fig. 3, the principle of operation of a pay television system according to the present invention, also illustrating the impossibility of piracy.

In fig. 1 distinguishes a device (1), for example a microcomputer, whereby the service provider for predicted and useful emissions data for customers. This data is associated in (2) with the video signal provided by a magnetoscope (3) or any other system. Return lines from the vertical scan of the video signal are generally used to transmit this data.

I

The video signal and associated data are then subjected to interference via an interference source (4) which renders the image unusable by a non-customer. This interfered signal is transmitted by a satellite or cable link to the receiver (9) of each subscriber, allowing a signal neutralizer. interference or decoder (6) a broadcast refund on a television of normal quality (7).

In fig. 2, we distinguish a system for introducing interference (8) into the emission and a system for neutralizing interference, also called a decoder, (9),

Ϊ¹ r at the home reception of the subscriber of this pay-TV system.

j In the interference neutralization system j

(8), distinguish among other things a random number generator (ID) which provides an initialization word (XINI) which is sent to the input of a motherboard (11). This one

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The motherboard encrypts the initialization word (XINI) according to a predetermined key (100), the word thus obtained being associated with the video signal. At the same time, the initialization word (XINI) serves to initialize a pseudo-random generator (12), which thus provides a certain code table at the output which serves to give some interference to the video and sound image. At reception 9 is a client card 13 for decrypting the encrypted initialization word as it is received and decrypting from the same key 100 in order to rediscover the initialization word (XINI) in clear language. This word (XINI) is then sent to initialize a pseudo-random generator (14) of the same design as the pseudo-random generator (12) of the emission. 0 The generator 14 thus produces a code table identical to the one generated in the emission and thus allowing the neutralization of the interference of the video image output. It can at any time, for example every 1 second or every 10 seconds, change the initialization word (XINI) without disturbing an authorized reception at the customer's home.

This system works very well, but it may allow certain hacking by insiders, as will now be explained. It should first be noted that several service providers may use the same network of memory card decoders together and even use the same memory cards. A service provider A may enter his key (100) and his rights and a service provider B may enter his key (200) and his rights independently and in the same network of card decoders, A knowledgeable person, for example a person working at the service provider, can easily decipher or decode the initialization word (XINI) with a client card (13) and extract it in clear language, look for a programmed motherboard (15)

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To encrypt the initialization word according to the key (200) of another service provider, then send in association with the video signal from the service provider A broadcast to a network, for example of cables, to which they are connected. persons with key customer cards (16) (200), who can then see the issuance of service provider A, transposed into service provider system B *

In Fig. 3, a pay-TV and memory card television system of the present invention has been shown, whereby it will be found that the piracy mode described above is impossible. 3, certain elements identical to those of the prior art as shown in FIG. 2 are distinguished and assigned the same reference numerals. The random number generator 10 provides a number which will be referred to in the following by code. random XA · 0 motherboard (ll) cipher, agree with key (100) this XA code and client cards (13) decrypt according to key (10.0) to retrieve the same XAL code ·

A first device (17) receives at its inputs, on the one hand, the random code XA and, on the other hand, the code XB encrypted by the motherboard (11) and makes a determined digital combination of these two codes, this combination being XINI initialization word of the pseudorandom generator (12) to provide a code table for interference with the video signal. Likewise, a second device (18) receives at its entrances, on the one hand, the encrypted code XB and, on the other hand, the code deciphered by the client card (13), which code is identical to XA, and performs a digital combination of these two codes, this combination being identical to that of the first device (17) such that the pseudorandom generator (14) receives the same initialization word XINI as the generator (12) and provides an identical code table to perform accordingly. the neutralization of video signal interference. The digital combination of devices (17) and (IS) may consist simply of an OR EXCLUSIVE circuit or may use any function known per se whose reciprocal function can only be obtained by an exhaustive test. It is clear that whatever combination function is used identically in both devices 17 and 18, the two pseudo-random generators 12 and 14 will be initialized identically and will be obtained. and always correct the interference neutralization, even if the XA code has been changed. On the contrary, if the piracy process described above is applied here from a classical system, we will notice that it does not work. Indeed, the initiated person will be able to rediscover the XA code from a client card (13), but then the person will encrypt the XA code with his key (200) and thus broadcast an XC encrypted code. , other than Xfl. In the decoder, the code XA will indeed be found thanks to the digital decryption of the device (19) which, although identical to the devices (17) and (18), will give a YINI initialization word of the peeudo random generator (20). different from the XINI initialization words of generators (12) or (14) and not the XB and XA codes.

The present invention is not limited to the embodiment just described, but rather encompasses all variants or adaptations that can be imagined by one skilled in the art.