SK16492000A3 - Mechanism for matching a receiver with a security module - Google Patents

Abstract

The invention concerns a system for controlling data transmission between a receiver and a security module, in particular for a pay television system, wherein the transmitted data are encrypted and decrypted by means of an encryption key, stored in the receiver and in the security module.

Description

Technical field

The invention relates to a system for controlling the transmission of information between a receiver and a security module, in particular for a pay-TV system, and to a method of transmitting scrambled information. '

BACKGROUND OF THE INVENTION

The pay-TV descrambling system consists of a receiver and a security module. This module can be removable or fixed. The purpose of the receiver is to descramble the received signals. The main purpose of the security module is to manage this activity by verifying the descrambling authorization and providing, as appropriate, the information necessary to operate the descrambling module, for example by providing descrambling vectors, also called control words (CWs).

Existing systems use receivers that ask about their security modules, and they respond to them by providing the information necessary for descrambling. At the same time, for the same transmitted broadcast, all security modules correspond to the same information. As this information flows between the security module and the receiver at a low rate (around 20 to 30 bytes / s), pirates can use this information to publicly disseminate it, for example, over the Internet.

Such a system is described in the document "DVD Conditional Access" published by David Cutts in the "Electronics & Communicarion Engineering Journal" in February 1997. It describes a standardized system for unscrewing audio and video streams coming from different service providers Security module , called CA (Conditional Access), is responsible for sending control words to CW. In addition, this module can use a smart card (SM) for the des2 crimping function. Once the information in the CA module is decoded, the control words CW are returned to the decoder to obtain the uncoded information.

A previously published article "Conditional Access Broadcasting: Datacare 2, an Over-Air Enabled System for General Purpose Data Channels," published August 1, 1988, from BBC Research and Development Report No 10, describes an independent module (Conditional Access Module). designed to receive and decrypt information necessary for desambling. This module takes care of the key intended for the system and recommends the control words necessary to decipher the video broadcast. In a module of this type, the control words, as soon as they are decrypted, are transmitted unencoded to the descriptor unit.

Then, however, the problem arises of making the receiver and the security module dependent on each other such that:

the security module may only be used in the receiver for which the security module has been designated and the information flow between the receiver and the security module is unique. This uniqueness prevents the public spread of this flow, which would otherwise be possible due to the operation of other receivers without a security module designed for them.

SUMMARY OF THE INVENTION

The proposed solution to the above problem uses at least one receiver-specific encryption key. This (or these) key (s) is called the match key (s). At least one of these keys is different for each receiver. This (or these) key (s) is stored in the permanent memory of the receiver, either during manufacture of said receiver or as follows. The receiver does not allow any way of accessing this key (s) outside.

One possible way to program this key into a security module is to use a central information system that manages a group of receivers and which may include in the transmission of video information data to program this key into the nonvolatile memory of the security modules. The formatting of this transmission is, of course, kept secret.

When transferring secret information and / or information necessary for the operation of the system from the security module to the receiver (usually control words, but other data may also be transmitted), the security module encrypts this information using one or more unambiguous keys of chance common to each pair of security module - receiver. Any encoding method may be used provided that the security module knows it and the receiver knows the corresponding decrypting method. As soon as the receiver acquires this information, the information is decrypted by said receiver using that decrypting method and the match key is then stored in non-volatile memory. Said information is then decoded and can be used by said receiver.

Thus, the present invention provides a system for controlling the transmission of information between a receiver and a security module, in particular for a pay television system, in which the transmitted information is encrypted and decrypted by means of at least one encryption key stored on one side in the receiver and on the other in the security module.

The present invention also relates to systems for descrambling scrambled information and a pay-TV system comprising a transmission control system.

In addition, the invention relates to a method for controlling the transmission of information between a receiver and a security module, in particular for a pay-TV system, characterized in that at least one unique key is stored on one side in the receiver and on the other in the security module and and the security module is encrypted and decrypted using at least one of said unique cryptographic keys.

The solution according to the invention solves the indicated problem because:

a security module inserted into a receiver other than the one with which the security module conforms will send to the receiver a secret and / or information flow necessary for the system to be encrypted with a key that does not correspond to the key for decrypting it. The result will therefore be unusable;

the flow of secret information and / or information necessary for the operation of the system coming from the security module cannot be distributed among multiple receivers. Only the receiver in accordance with the card providing this stream of secret and / or necessary information is able to successfully decrypt the stream.

This system may include a mechanism for verifying the compliance procedure. The central information system may write the personal receiver number into a security module that is in conformity with said receiver, for example a receiver generated random number, or simply use its serial number. One way for the receiver is to freely verify this personal number written in the security module and compare it with the number stored in its nonvolatile memory.

This mechanism has the advantage that incorrect data are not used. The result of crypting followed by decrypting with another key usually gives a pseudo-random result. If it is not recognized that the result is erroneous and such result is used, it may result in damage to the receiver or equipment connected to it.

Certain types of receivers have a removable descrambling module. This module has several tasks, including descrambling of received signals. The secret information is then transmitted between the removable security module and the removable descrambling module. The communication encryption mechanism described above between the receiver and the security module is then transferred as such between the removable security module and the removable descrambling module.

Similarly, the match method described above between the security module and the receiver is then transferred as such between the removable security module and the removable descrambling module.

The descrambled signals are then transmitted between the removable descrambling module and the receiver. The encryption mechanism of the communication, together with the match mechanism described above, between the security module t and the receiver is then transferred as such to the other receiver and the removable descrambling module.

The functions provided by the removable descrambling module and the removable security module can be performed by a single module called the removable descrambling-security module. The compliance mechanism described above is then transferred as such between the removable descrambling-security module and the receiver.

In all the cases described above, the match key (s) may be used to encrypt the flow of secret data and / or data necessary for the system to operate in reverse:

- receiver and removable security module;

- a removable descrambling module and a removable security module

- receiver and detachable descrambling module

- receiver and removable descrambling-security module.

In all the cases described, where the match key is specific to one part of the device (receiver or detachable module), the same principles apply to the use of a match key (or several match keys) specific to a group of parts of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a configuration using a receiver and a removable security module.

Fig. 2 shows a configuration using a receiver, a removable descrambling module, and a removable security module.

Fig. 3 shows a configuration / using a receiver and a removable descrambling-security module.

DETAILED DESCRIPTION OF THE INVENTION

The receiver A in FIG. 1 receives a stream of scrambled video data 1 from a source such as e.g. satellite receiver or cable. This stream, of the order of several megabits per second, is shaped in receiver A and then transmitted to the control unit B, which is responsible for descrambling and managing the authority to access scrambled video data. To do so, the control unit B periodically asks the removable security module C (channel 3), which responds to it with a stream of secret data and / or information necessary for the operation of the control unit B (channel 4). These exchanges take place at a low speed and can be easily processed by the smart card microprocessors available on the market. According to the invention, the removable security module C comprises at least one encryption key K in non-volatile memory that encodes the secret data necessary for operation of the control unit B (channel 4) to the receiver A. This key K is unique to receiver A and is written to the removable security module C , and makes information stream 4 unique to this system. The public transmission of this information 4 is thus not applicable to other receivers as they do not possess the same key K and thus the information flow is completely unintelligible. Using information 4, the control unit B can restore the descrambled video signal 2, which is then transmitted in a standard manner (PAL, SECAM, NTSC) to the video monitor.

Another variant of the invention uses encryption, of the same kind, to send information 3 to removable security module C either using the same key K or another key J, which is unique and specific to the system comprised of receiver A and removable security module C. recovering the K key from the information flow.

Fig. 2 shows a variant using a removable descrambling module D connected to the control unit B. In this case, the scramble video signal i is shaped by the receiver A and sent to the removable descrambling module D. The operation mode described in case 1 between receiver A and the removable security module C this time it is applied to the communication between the removable descrambling module D and the removable security module C. The key K is written to the secret part of the removable descrambling module D instead of the receiver A. Thus the information provided by the removable security module C is not priced to the removable descrambling module D other removable desrambling module D.

Thus, it can be seen that the information sent to receiver A consists of a stream of descrambled video information 6 which can be used immediately, for example for illegal copies. In one variation of the invention, the stream 6 is encrypted in the removable descrambling module D before it is sent to the receiver A for descrambling by the decryption unit E '. Consequently, the information flow 6 has no meaning and can only be understood by the receiver A having the same key A '.

Receiver A may add control information for the removable descrambling module D to the scrambled video stream 1. In order to prevent this information from being published and thus the ability to understand the encryption mechanism, this information is encrypted in the encryption unit E to obtain a scrambled information stream 6 containing the encrypted control information. .

Fig. 3 illustrates a variant of the invention in which a removable security module is embedded in a removable descrambling-security module F. The purpose of this module is to descramble and manage the authorization for video signals received at receiver A. According to the invention, this module includes a unique encryption key characteristic of receiver A written in Similarly, the descrambled video information stream is encrypted with this key and sent in this form to receiver A. This, using the decryption unit E 'and using the same unique key, will be able to recover the uncoded video signal.

Analogous to the operation described in relation to FIG. 2, the control information contained in the video stream 1 can be encrypted with a unique encryption key by the unit E before being sent to the removable descrambling-security module F.

In all the examples described in relation to FIG. 1 to 3, it is possible to verify compliance. In the case of FIG. 1, receiver A writes the number assigned to it, for example its serial number, into the removable security module C.

Thus, the receiver can at any time verify that the removable security module C is indeed the one intended for it. Referring to the example shown in FIG. 2, this check can be done at two levels, the first level between the removable descrambling module D and the removable security module C and the second level between the removable descrambling module D and the receiver A. The second level is particularly important if the unscrambled information 6 sent to the receiver is encrypted .

In the solution shown in FIG. 3, compliance is tested between receiver A and removable descrambling-security module F.

In one embodiment, the receiver A is an MPEG decoder using control words (information necessary to descramble the signal) to descramble the video signal. These control words are provided by a removable security module C This module, such as a smart card, contains non-volatile memory for storing them.

In one embodiment of the invention, the PCMCIA card-type descrambling module D is removable and comprises an MPEG decoder (control unit B).

In one embodiment of the invention, the removable descrambling-security module F is implemented in the form of a smart card that includes an MPEG decoder and a security module C '.

In one embodiment, the unique encryption key K is common to t

group of receivers. This option is advantageous, for example, for a school having several receivers in which the same removable security module is used as needed. Similarly, several removable security modules contain the same encryption key to be placed in any receiver in a given group. In this case, the conformity test is performed for a number which is no longer specific to one receiver but to a group of receivers. It is possible to create a combination by a number composed of two parts, one defining a group and the other a receiver. The uniqueness of the personal number is respected, and the compliance test is then performed more than just on the group part of that number.

Claims (20)

A method for controlling the transmission of information in a pay-TV reception system between a receiver (A) and security means (C, D, F), wherein the security means (C, D, F) send descrambling information to the receiver (A) to decrypt video and audio signals, characterized in that at least one unique cryptographic key is stored both in the receiver (A) and in the security means, and the information transmitted between the receiver (A) and the security means is encrypted and decrypted using at least one of said unique cryptographic keys. Method according to claim 1, characterized in that the number belonging to the receiver (A) is entered into the security device during the initialization and that the receiver (A) can verify at any time that the personal number entered in said security device matches. A pay-TV reception system comprising a receiver (A) connected to security means (C, D, F), the receiver (A) receiving descrambling information from the security means (C, D, F), characterized in that at least some of the The information (4, 6) sent from the security means (C, D, F) of the receiver (A) is encrypted with a unique encryption key. 4. The pay-TV reception system of claim 1, wherein the unique encryption key is common to a plurality of receivers. The pay-TV reception system according to claim 1 or 2, characterized in that at least some of the information (3, 5) sent from the receiver (A) by the security means (C, D, F) is encrypted with a unique encryption key. Pay-TV reception system according to claims 1 to 3, characterized in that the receiver (A) contains a personal number which can be entered in the security means (C, D, F) and can at any time verify the conformity of this personal the numbers entered in the security devices (C, D, F). The pay-TV reception system of claim 4, wherein the personal number includes a group-specific portion and a single-receiver portion, and that the match is verified in a group-specific portion. Pay-TV reception system according to claims 1 to 5, characterized in that the receiver (A) comprises a control unit (B) and that the security means consist of a removable security module (C) in which the secret information (4) is stored and / or information (4) necessary for the operation of the control unit (B). The pay-TV reception system according to claims 1 to 5, characterized in that the security means comprise a removable descrambling security module (F) comprising a control unit (B) and a security unit (C ') for descrambling and authorizing the video information. A pay-TV reception system comprising a receiver (A) connected to security means (C, D, F), the receiver (A) receiving descrambling information from the security means (C, D, F), characterized in that the security means comprise: a removable security module (C) and a removable descrambling module (D) comprising a control unit (B), and wherein at least some of the secret information (4) and / or information (4) necessary for the operation of the control unit (B) is encrypted before being sent to the removable descrambling module (D) by the removable security module (C) using a unique encryption key. The pay-TV reception system according to claim 8, characterized in that at least some of the information (3) sent from the removable descrambling module (D) to the security module (C) is encrypted using a unique encryption key. A pay-TV reception system according to claim 8 or 9, characterized in that the removable descrambling module (D) comprises a personal number that can be written to the removable security module (C) to enable the removable descrambling module (D) to be verified at any time. the conformity of this personal number entered in the removable security module (C). Pay-TV reception system according to claim 10, characterized in that the personal number comprises a part specific for a group of removable descrambling modules (D) and a part specific for one removable descrambling module (D) and that the correspondence of this personal number is verified in the specific part for a group of removable descrambling modules (D). Pay-TV reception system according to claims 9 to 11, characterized in that at least some of the information (5) sent from the receiver (A) to the removable descrambling module (D) is encrypted using a unique encryption key. Pay-TV reception system according to claims 9 to 12, characterized in that at least some of the information (6) sent from the removable descrambling module (D) to the receiver (A) is encrypted using a unique cryptographic key. A pay-TV reception system according to any one of claims 12 and 13, characterized in that the receiver (A) comprises a personal number which can be written to the removable descrambling module (D) to enable said receiver (A) to be verified at any time. this personal number entered in said removable descrambling module (D). 17. A removable security module (C) intended to be connected to a receiver (A) as part of a pay-TV reception system, comprising at least one non-volatile memory for storing secret and / or information necessary for the operation of a descrambling system and means for transmission with the receiver ( A), characterized in that the removable security module (C) comprises a transmission encryption means and that the memory also comprises at least one cryptographic key acting on the transmission encryption means. A removable descrambling module (D) which is part of a pay-TV reception system comprising a control unit (B), a first transmission means (3, 4) with a removable security module (C), a second transmission means (5, 6) with a receiver ( A) and a non-volatile memory, characterized in that it comprises a first encryption means and that the memory comprises at least one encryption key acting on the first encryption means to encrypt the transmission of the first transmission means (3, 4). Removable descrambling module (D) according to claim 18, characterized in that it comprises a second encryption means and that the memory comprises at least one encryption key acting on the second encryption means to encrypt the transmission of the second transmission means (3,4). A pay-TV descrambling receiver (A) comprising means for transmitting to security means (C, D, F) as well as non-volatile memory, characterized in that it comprises means for encrypting / decrypting transmissions from and to the means of security (C, D, F) and that the memory comprises at least one cryptographic key that acts on the crypto / decrypt transmission means.