NO331328B1 - Mechanism for obtaining alignment between a receiver and a security module - Google Patents

Abstract

Equipment for regulating the transfer of information between a recipient and a security module, especially for pay-TV, and where the transmitted information is encrypted and decrypted using a unique encryption key stored on one side of the receiver and on the other side of the security module.

Description

TECHNICAL AREA

This invention relates to equipment for regulating the transmission of information between a receiver and a security module, especially for pay television, as well as a method for regulating the transmission of discarded information.

BACKGROUND OF THE INVENTION

Pay-TV recovery equipment is composed of a receiver and a security module. This module can be removable or fixed. The purpose of the receiver is to restore the received signals to their original state. The main purpose of the security module is to control the work operation by verifying the recovery authorization and, as necessary, producing the information necessary to operate the signal recovery module, e.g. by creating restoration vectors, which are also called regulation vectors.

In the article EBU Project Group B/CA: "Functional model of a conditional access system", EBU Technical Review, winter 1995, a general access system for pay television is described, in which an encryption key for decoding broadcast signals is distributed on, for example, a security module in the form of a smart card that can be inserted into a generic decoder. This encryption key gives access to the programs the subscriber has paid for. The article also describes other methods of distributing an encryption key for signal decoding, for example if the subscriber has ordered access to one program, and it is obviously impractical to send the encryption key on a separate card, e.g. a smart card.

Existing equipment uses receivers that interrogate their security modules, and these latter then respond by producing the information necessary for signal recovery. At a given time during one and the same broadcast, all security modules will respond with the same information. Due to the fact that the information flows between the security module and the receiver take place at a low rate (around 20-30 bytes/s), counterfeiters can exploit this information for extensive publication of it, e.g. over the internet.

Such a scheme is described in the document "DVD Conditional Access" authored by David Cutts in a journal called "Electronics & Communication Engineering Journal" for February 1997. It describes a standardized scheme for undoing the reversal of audio and video streams which comes from different service providers. The security module, which is called CA (Conditional Access) is responsible for issuing the control words CW. This module can also utilize a smart card (SM) for the signal generation function. Once the information is recovered in the CA module, the control words CW are returned to the decoder to derive the uncoded information.

In an earlier publication entitled "Conditional Access Broadcasting: Datacare 2, an Over-Air Enabled System for General Purpose Data Channels", published on 1 August 1988 in the journal "BBC Research and Development Report No. 10", an independent module (Conditional Access Module) whose task is to receive and decrypt the information necessary for signal recovery. This module controls the key assigned to the equipment and emits the control words necessary for signal recovery of broadcast video signals. In this type of module, as soon as they have been decrypted, the control words are transferred uncoded to the unit responsible for signal recovery.

A problem then arises with regard to how a receiver and a security module are to be made mutually dependent so that: the given security module can only be used in the receiver for which the relevant security module is intended,

the information flow exchanged between the security module and the receiver is idiosyncratic. This peculiarity then prevents any public broadcasting of this stream from enabling other receivers to work without the special security module produced for this purpose.

SUMMARY OF THE INVENTION

The proposed solution to the above-mentioned problem is stated in claim 1, and uses at least one encryption key that is special for the recipient in question. This (or these) key (or keys) is then called the adaptation key. At least one of these keys is different for each recipient. This (or these) key (or keys) is installed in the receiver's non-volatile data storage, either during the manufacture of said receiver or in a subsequent process step. The recipient does not provide any opportunities for access to this or these keys from the outside world.

One possible means of programming this key into the security module is to use the central information equipment that controls the receiver group and which can introduce into the video transmission stream information for programming this key into the secret non-volatile data store of the security modules. The formatting of this procedure is of course kept secret.

When transferring confidential information and/or information that is necessary for the equipment's operation from the security module to the recipient (usually control words, but other information can also be transferred), the security module that is encrypted in this information will use one or more of the distinctive adaptation keys that are common to the recipient/security module pair in question. Any encryption method can be used, provided that the security module knows it, and the recipient knows the corresponding method of decryption. As soon as this information has been received by the recipient, it is then decrypted by the recipient in question using a known encryption method, and the adaptation key is stored in the recipient's non-volatile data storage. Said information is then uncoded information and can be used by said recipient.

According to the invention, equipment is therefore proposed for regulating the transfer of information between a receiver and a security module, especially in connection with pay television, where the transmitted information is encrypted and decrypted using at least one unique stored encryption key, which is stored on the one hand in the receiver and on the other hand in the security module.

The invention also applies to equipment for the recovery of discarded information and equipment for pay television which includes means for transmission control.

The invention further relates to a method for controlling

the information transfer between a receiver and a security module, and especially intended for pay television, characterized in that at least one unique adaptation key is stored on the one hand in the receiver and on the other hand, in the security module, and in that the information transmitted between the receiver and the security module is encrypted and decrypted using at least one of the aforementioned unique encryption keys.

This solution according to the invention solves the problem stated above. This is because: a security module that is inserted into a receiver other than the one to which said security module is adapted will then supply this other receiver with a stream of confidential information and/or information that is necessary for its operation equipment that is encrypted with a key that does not correspond to the one used to decrypt the equipment. The result cannot therefore be used;

a flow of confidential information and/or information that is necessary for the operation of the equipment and that comes from a security module cannot then be distributed to several recipients. Only the receiver that is adapted to the card that produces this stream of confidential and/or necessary information will then be able to successfully decrypt the stream in question.

The equipment may include a mechanism to verify the fitting procedure. The central information equipment can enter a number, which is unique to the recipient, into the security module that is adapted to the recipient in question, e.g. a number randomly generated by the latter, or simply, use its serial number. One method open to the receiver is then to freely verify this unique number written into the security module and compare it with that stored in its non-volatile data store.

This mechanism has the advantage that it does not use unsuitable data. The encryption result is followed by a decryption using a different key and which usually produces a semi-random result. If this result cannot be recognized as incorrect and it is used as it is, this could lead to damage to the receiver or other equipment connected to it.

Certain receiver types have a detachable signal generation module. This module is responsible for a number of work operations, including the one that involves restoring the signals received. Confidential information is then transferred between the removable security module and this removable signal creation module. The mechanism described above for encrypting communications between a receiver and a security module is then transferred, as it exists, between the releasable security module and the releasable recovery module.

Likewise, the above-described method for creating adaptation between the security module and the receiver is then transferred, in the form it exists, between the releasable security module and the releasable recovery module.

The recovered signals are then transmitted between the detachable recovery module and the receiver. The mechanism that encrypts the communication together with the above-described mechanism for creating adaptation between the security module and the receiver is then transferred, in the form it exists, between the receiver and the releasable recovery module.

The work functions performed by the removable signal recovery module and the removable security module will be able to be performed by a single module, which is then called a removable recovery/security module. The adaptation mechanism described above is then transferred, as it exists, between the removable recovery/security module and the receiver.

In all the cases described above, the adaptation key or keys can be used to encrypt a stream of confidential data and/or data necessary for the operation of the equipment in the opposite direction of transmission, by respectively reversing:

the receiver and the removable security module,

the removable recovery module and the removable security module, the receiver and the removable recovery module,

the receiver and the removable recovery/security module.

In all cases where an adaptation key is specific to a unit in the equipment (a receiver or a removable module), the same principle can be used when using an adaptation key (or several adaptation keys) that is specific to a group of units in the equipment.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 shows a configuration that utilizes a receiver and a removable security module. Fig. 2 shows a configuration utilizing a receiver, a removable recovery module and a removable security module. Fig. 3 shows a configuration utilizing a receiver and a removable recovery/security module.

DETAILED DESCRIPTION

The receiver A in fig. 1 receives a stream of reverse video information 1 from such a source as a satellite receiver or over cable. This current, which will be of the order of several megabits per second, is formed in the receiver A and then transmitted to a regulator unit B whose task is to restore the signal and to control the authorization for access to the reversed video information. In order to do this, the regulator unit B will periodically interrogate the releasable security module C (channel 3) which will then respond to the latter with a stream of confidential data and/or data necessary for the operation of the regulator unit B (channel 4). These exchanges take place at a low rate and can be easily processed by smart card microprocessors available on the market. According to the invention, the releasable security module C comprises at least one encryption key K in a non-volatile data store which encrypts the confidential data and/or the data necessary for the operation of the control unit B (channel 4) in the direction of the receiver A. This key K is specific to the receiver A and is written into the removable security module C, which will make the information flow 4 specific to this equipment. Any public dissemination of this information 4 will no longer be able to be used by other recipients, as these will not have access to the same key K, and the information flow will then be completely incomprehensible. With the help of the information 4, however, the regulator unit B can recover the restored video signal 2, so that this can be processed and then transmitted in standard form (PAL, SECAM, NTSC) to the video monitor.

An embodiment variant of the invention uses encryption of the same kind as for the information 3 that is transmitted to the releasable security module C either by using the same key K or using a different key J, which is distinctive and specific for the equipment made up by the receiver A and the detachable security module C. Any attempt to extract the key K from the information stream 4 is thus made much more difficult.

Fig. 2 shows an embodiment that uses a removable recovery module D comprising the regulator unit B. In this case, the reversed video stream 1 is formed at the receiver A and sent to the removable recovery module D. The operating mode described in the case indicated in fig. 1 between the receiver A and the removable security module C is in this case applied to the conversation between the removable recovery module D and the removable security module C. The key K is written into a secret part of the removable recovery module D instead of in the receiver A. The information transmitted of the removable security module C to the removable recovery module D is thus encrypted and therefore has no value for any other removable recovery module D.

It can thus be realized that the information sent to the receiver A consists of a stream of recovered video information 6 which can be easily utilized, e.g. for illegal copies. In an embodiment variant of the invention, the stream 6 is encrypted in the removable recovery module D before it is sent to the receiver A for recovery by means of the decryption unit E'. This work operation is carried out using a key K' which is unique only to the assembly of receiver A and detachable recovery module D. The information flow 6 will thus no longer have any meaning, and it can then only be understood by the receiver A with the same key K'.

The receiver A can add to the reversed video stream 1 the regulation information intended for the detachable recovery module D. In order to prevent this information from being published and from opening a door to understanding the encryption mechanism, this information is encrypted by the encryption unit E with the purpose of deriving a reversed video stream 6 which contains encrypted regulation information.

Fig. 3 shows an embodiment of the invention where the removable security module is part of a removable recovery/security module F. The work function of this module is to restore and control the authorization of the video signals received by the receiver A. According to the invention this module includes a distinctive encryption key which is special for the receiver A and is written into this releasable recovery/security module F. Likewise, the restored video stream 6 is encrypted with this key and transmitted in this form to the receiver A. The latter will then, with the help of of the decryption unit E' and using the same special key be able to recover the unencoded video signal.

Analogous to the work operation described in connection with fig. 2, the control information contained in the recast video stream 1 may be encrypted using a unique encryption key from the device D before it is sent to the releasable recovery/security module F.

In all the design examples that are described in connection with fig. 1-3, the fit can be checked. In the case indicated in fig. 1, recipient A enters a specially assigned number, e.g. its serial number, in the removable security module C. The recipient will then be able to confirm at all times that the removable security module C is actually the one intended for this recipient. In the context of the example shown in fig. 2, this control can be carried out on two levels, namely on a first level between the removable recovery module D and the removable security module C, as well as on a second level between the removable recovery module D and the receiver A. This second level is particularly important in the event that non-reversed information 6 that is transmitted to the receiver A is encrypted.

In the solution shown in fig. 3, the fit between the receiver A and the removable recovery/security module F is checked.

In one embodiment of the invention, the receiver A is an MPEG decoder that uses control words (information necessary to restore the signal) to restore the video signal. These control words are produced by the detachable security module C. This module, e.g. a smart card, includes a non-volatile data store for storing the words.

In one embodiment of the invention, the removable recovery module D is a PCMCIA type card comprising an MPEG decoder (controller unit B).

In one embodiment of the invention, the detachable recovery/security module F is produced in the form of a smart card comprising an MPEG decoder and a security module C

In a certain embodiment of the invention, the special encryption key is K

common to a group of recipients. This option is advantageous e.g. in a school with several receivers, each of which is fitted with the same removable security module as required. Likewise, several removable security modules contain the same encryption key in order to be placed in any of the receivers in the group. In this case

the matching check is carried out in relation to a number that no longer fits a single recipient, but a group of recipients. A combination can be produced using a number consisting of two parts, namely one part indicating the group and the other part indicating the recipient. The peculiarity of the assigned number is then

respected, and the word matching test is then performed on more than just the group part of this number.

Claims (17)

1. Receiving system for pay television comprising several receivers (A) and several security modules (C, F), where one receiver (A) is connected to one security module (C, F), where this receiver (A) receives recovery information from the security module ( C, F), characterized in that at least part of the information (4, 6) is encrypted before it is sent to the receiver (A) by the security module (C, F). by means of a special encryption key which is stored in advance on one side of the receiver ( A) and on the other side in the security module (C, F), which unique encryption key forms a pair of the security module (C, F) and the receiver (A) so that a given security module (C, F) can only be used in the receiver (A ) where the security module (C, F) was predetermined by storing the encryption key in the security module (C, F) and the receiver (A), in that the receiver (A) comprises a uniquely assigned number which is also written into the given security module (C, F), whereby it is possible for the receiver (A) at any time to confirm the match with the assigned number written into the security module (C, F), and thereby the match for the pair. 2. Reception system for pay television according to requirement 1, characterized in that the unique encryption key is shared by a group of recipients. 3. Reception system for pay television according to requirements 1 or 2, characterized in that at least some of the information (3, 5) which is sent from the receiver (A) to the security module (C, D, F) is encrypted using a special encryption key. 4. Reception system for pay television according to claim 1, 2 or 3, characterized in that the assigned number includes a part that is specific for a group of receivers and another part that is specific for a specific receiver, and that the matching of the pair is confirmed by that part which is specific to the relevant group of recipients. 5. Reception system for pay television according to requirements 1-4, characterized in that the receiver (A) comprises a regulator unit (B), and in that the security module consists of a detachable security module (C) where the confidential information (4) and/or the information (4) that is necessary for the operation of the regulator unit (B) , is stored. 6. Receiving system for pay television and according to claims 1-4, characterized in that the security module is a detachable recovery/security module (F) comprising a regulator unit (B) and a security unit (C), where these units are designed to restore and authorize the video information. 7. Pay-TV reception system comprising several receivers (A) and several sets of security devices, where one receiver (A) is connected to one set of security devices (C, D), where each set of security devices (C, D) comprises a detachable security module ( C) and a detachable recovery module (D) comprising a regulator unit (B), which receiver (A) receives recovery information from the set of safety devices (C, D) characterized in that at least some of the confidential information (4) and/or the information (4) which is necessary for the operation of the control unit (B) is encrypted before it is sent to the releasable recovery module (D) by the releasable security module (C ) by means of a unique encryption key stored in advance on one side in the removable recovery module (D) and on the other side in the removable security module (C), which unique encryption key forms a pair of the removable security module (C ) and the removable recovery module (D) so that a given security module (C) can only be used with the recovery module (D) where the removable security module (C) was predetermined by storing the encryption key in the security module (C) and the recovery module (D), in which the removable recovery module (D) comprises a uniquely assigned number which is also written into the given removable security module (C), thereby enabling the removable recovery the authentication module (D) at all times to confirm the match with the assigned number written into the detachable security device (C), and thereby the match for the pair. 8. Reception system for pay television according to requirement 7, characterized in that at least some of the information (3) sent from the releasable recovery module (D) to the security module (C) is encrypted using a unique encryption key. 9. Reception system for pay television according to requirements 7 or 8, characterized in that the assigned number includes a part that is specific to a group of releasable recovery modules (D), and a part that is specific to a particular releasable recovery module (D), and in that the conformity of the adaptability can be confirmed from the part that is specific for the group of removable recovery modules (D). 10. Reception system for pay television in accordance with requirements 8 to 9, characterized in that at least some of the information (5) which is sent from the receiver (A) to the releasable recovery module (D) is encrypted using a unique encryption key. 11. Reception system for pay television according to requirements 7 to 10, characterized in that at least some of the information (6) sent from the releasable recovery module (D) to the receiver (A) is encrypted using a unique encryption key. 12. Receiving system for pay television according to claim 10 or 11, characterized in that the receiver (A) includes an assigned number that can be entered into the releasable recovery module (D) so that it becomes possible for the receiver (A) at any time to confirm compliance with this assigned number written into the removable recovery module (D). 13. Method for regulating the transfer of information in a reception system for pay television according to claim 1 between a receiver (A) and a security module (C, F), where this security module sends to the receiver (A) recovery information that enables the decryption of video and audio the signals, characterized in that at least one unique encryption key is pre-stored on the one hand in the receiver (A) and on the other hand in the security module (C, F), and in that the information transmitted between the receiver (A) and the security module (D, F ), is encrypted and decrypted using the unique encryption key, which unique encryption key forms a pair of the security module (C, F) and the receiver (A) so that a given security module (C, F) can only be used in the receiver (A) where the security module (C, F) was predetermined by storing the encryption key in the security module (C, F) and the receiver (A), in that the receiver (A) comprises a uniquely assigned number which is also written into the given security module (C, F) in an initial work operation, whereby it is possible for the receiver (A) at any time to confirm the match with the assigned number written in the security module (C, F), and thereby the match for the pair. 14. Detachable security module (C, F) intended to be connected to a receiver (A) as part of a reception system for pay television according to claim 1 comprising at least one non-volatile data storage device designed for storing confidential data and/or data that is necessary for operation of the recovery system, transmission means for exchange with the receiver (A), where the removable security module (C, F) comprises means for encrypting the transmission, characterized in that the data store also includes at least one encryption key that is pre-stored in the data store on one side and in the associated receiver (A) on the other side, where the unique encryption key acts on the means for encrypting the transmission and thus forms a pair with the associated receiver ( A) so that a given security module (C, F) can only be used in the receiver (A) where the security module (C, F) was predetermined by storing the encryption key in the security module (C, F) and the receiver (A), in which the receiver (A) includes an assigned number that is also written into the given security module (C, F), whereby it is possible for the receiver (A) at any time to confirm the correspondence with the assigned number written into the security module (C , F), and thereby the match for the pair. 15. Detachable recovery module (D) forming part of a pay-television receiving system according to claim 7, comprising a regulator unit (B), first transmission means (3, 4) for exchange with a detachable security module (C), second transmission means (5, 6) for exchange with a recipient (A), as well as a non-volatile data store, comprising a first encryption device, characterized in that the data storage contains at least one unique encryption key pre-stored in the data storage on one side and in the associated releasable security module (C) on the other side, where the encryption key acts on the first encryption device arranged for encryption of the transmission from the first transmission means (3, 4) and thereby forming a pair of the removable recovery module (D) and the removable security module (C) such that a removable recovery module (D) can only be used in a given removable security module (C) where the removable recovery module (D) was predetermined when storing the encryption key in the security module (C) and the recovery module (D), in that the removable recovery module (D) comprises a uniquely assigned number which is also written into the given removable security module (C), thereby enabling the removable recovery module (D) to at any time to confirm compliance with the assigned number entered into the detachable the safety device (C), and thereby the match for the couple. 16. Detachable recovery module (D) according to claim 15, characterized in that it comprises a second encryption device, and in that the data store comprises at least one encryption key which can affect this second encryption device which is designed to encrypt the transmission from the other transmission means (5, 6). 17. Recovery receiver (A) for pay television which is part of a receiving equipment for pay television according to claim 1, comprising means for transmission to the security module (C, F) as well as a non-volatile data store, comprising encryption equipment for transmission from and to the security module ( C, F), characterized in that the data store contains at least one unique encryption key which is pre-stored in the data store on one side and in the associated security module (C, F) on the other side, where the unique encryption key acts on the means for encrypting the transmission and forms a pair of the receiver (A) and the security module (C, F) so that the receiver (A) can only be used in a given security module (C, F) where the receiver (A) was predetermined by storing the encryption key in the security module (C , F) and the receiver (A), wherein the removable recovery module (D) further comprises an assigned number which is also written into the given security module (C, F), whereby it is mu lig for the detachable recovery module (D) to confirm at all times the match with the assigned number written in the security devices (C, F), and thereby the match for the pair.