Patent Grant
RE49394
This application claims priority under 35 U.S.C. § 120 to, European Application No. 13188147.913188117.9, filed Oct. 10, 2013, and further claims priority under 35 U.S.C. § 120 to European Application No. 14172364.3, filed Jun. 13, 2014.
The present invention relates to a method for processing messages intended to allow the access to conditional access content.
More particularly, this method concerns the management of priorities when several messages are received in a short period of time and must be processed according to a certain order for allowing the access to content.
This method is particularly adapted to the context of Pay-TV.
The present invention further concerns a security module provided for implementing this method.
The transmission of encrypted data or of conditional access content is well-known in the field of Pay-TV, where encrypted content is generally broadcast by terrestrial transmitters, via satellite or via a cable network to a number of subscribers, each subscriber having a multimedia unit, associated with or containing a security module to decrypt the encrypted content for its visualization.
The security module is in charge of the security operations and is associated with the multimedia unit or with a receiver. Such a security module comprises, on the one hand, a conditional access module referred to as CAK (Conditional Access Kernel), and on the other hand, a processing module. The conditional access module is in charge of the management of priorities of the messages that will be processed by the processing module. This processing module carries out the verification and/or the authentication steps, and is also responsible for processing the messages transmitted to it and for resending the results of this processing. Such a processing module can be made particularly in four different forms. One of these forms is a microprocessor card, a chip card, or more generally an electronic module (in a form of a key, a badge, . . . ). Such a module is usually removable and connectable to the receiver. The form with electric contacts is the most commonly used, but does not exclude a connection without contacts, for instance of the ISO 14443 type.
A second well-known form is that of an integrated circuit box, usually located in a definitive and irremovable way in the receiver box. A variant consists of a circuit mounted on a base or a connector such as a SIM module connector.
In a third form, the processing module is integrated in an integrated circuit box further having another function, for instance in a descrambling module of the decoder or the microprocessor of the decoder.
In a fourth embodiment, the processing module is not made in material form, but its function is only implemented as a software.
As in all four cases, even though the security level differs, the function is identical, we will refer to as a processing module regardless of the way in which its function is implemented or the form of this module. In the four above described forms, the processing module has means for executing a program (CPU) stored in its memory. The collaboration between the conditional access module (CAK) and the processing module allows the security module to perform the security operations, to verify rights, to perform a decryption or to activate a decryption module, etc.
In a system of the Pay-TV type, the scrambled or encrypted content can be descrambled or decrypted by a control word. In order to improve the security of the system, the control word is generally changed within a relatively short interval, called cryptoperiod, for example of ten-seconds. Every 10 seconds, or for each cryptoperiod, each subscriber receives, in an ECM control message (Entitlement Control Message), the control word required for decrypting the enciphered contents in order to allow the viewing or the access to the transmitted data. During the time of one cryptoperiod, a same control message or control messages containing the same control words are sent at regular intervals, for instance every 50 ms. This repetition of messages allows a user that switches on a specific channel to access control words that are required for decrypting the content of the specific channel without having to wait until the end of the cryptoperiod.
The control word itself is encrypted by a transmission key and is transmitted in an encrypted form in the ECM control message. The encrypted content and the encrypted control word are received by a multimedia unit which, if the subscriber is up-to-date with its subscription, or more generally, if he has the corresponding access rights, has access to the usage key stored in a security module. The encrypted control word is decrypted by the security module by means of the transmission key. The security module transmits the control word to the decoder. The encrypted content is decrypted by the decoder by means of the control word.
The transmission key is regularly changed, for instance, every month. A management message (EMM Entitlement Management Message) is received every month by the decoder and transmitted to the security module. The management message contains the transmission key in an encrypted form. A key assigned to the security module allows the latter to decrypt the encrypted transmission key.
The security modules currently used for processing the control messages mainly have a limited processing capacity. In particular, the processing module can only process one message at a time, which involves a storage and a sequential processing of the messages when several messages are received by a multimedia unit in a short period of time. Recently, the manufacturers of decoders intended to the Pay-TV or to conditional access TV have introduced broadband tuners that are able to receive a significant number of content and message streams, for instance, 8, 16, 32 or even more. This can be a problem. Indeed, when too many messages are received simultaneously or during a relatively short period, the security module might not be able to process all the messages received. This results in the risk that part of the content cannot be decrypted and that the user is presented with a blank screen. This might be the case, in particular, when the management of the processing order of the messages is not well done.
Presently, this problem is solved by assigning a priority to the messages, this priority being defined according to the real or possible use of the messages by a user. As an example, the message stream, corresponding to a content that is being viewed by a user, receives the highest priority, in order to avoid that a control message cannot be decrypted and that the user is presented with a blank screen.
The stream corresponding to a content being recorded also has a high priority level, otherwise, there is a risk that a part of the recording may not be performed.
The predictive stream or streams have a lower priority. These predictive streams correspond to the channels for which the probability that the user will view this channel is the highest. These channels may be the channels having a channel number immediately adjacent to the channel that is being viewed. They can also be defined according to the user's profile.
Usually, when the security module must process at the same time, a stream corresponding to the content displayed, a stream for a content that is currently recorded and predictive streams, the security module is strongly requested and the management of other streams can be a problem. In cases in which a patchwork is displayed for a user, with the current systems, the content forming this patchwork results from a specific channel. Indeed, in the current systems, it is not possible for instance, to decrypt enough messages for displaying a patchwork on the basis of the real content. For this reason, it is indispensable to use a specific channel. The priority for this kind of channels can be relatively low, and this may cause problems such as the impossibility to display the mosaic. Moreover, it is not possible to offer a customized patchwork to the users.
In the prior art systems, priorities are fixed. Thus, in certain situations, the user can find himself facing a blank screen. This could be the case, in particular, when the user frequently switches and when the security module cannot process all the control messages received.
This present invention aims to solve the drawbacks of the prior art by implementing a method for processing control messages, which allows to manage these messages in a more flexible and more effective way. These drawbacks are also solved by a security module used for the implementation of this method for processing messages.
The aim of the invention is reached by a method for processing messages intended to allow the access to conditional access content, characterized in that it comprises the following steps:
The aim of the invention is also reached by a security module comprising at least one conditional access module (CAK), means for receiving messages classified into at least two different categories and a processing module (SC) for these messages, a different priority level being assigned to the messages of each different category, one of said priority levels being defined as being high and another priority level, smaller than the high priority, being defined as standard priority level; a value being associated with the messages to which the standard priority level has been assigned, this value being assigned according to a predefined rule; a threshold value being assigned to the value associated with the messages having a standard priority level, this security module being characterized in that it further comprises means for comparing the threshold value for a specific message and the value associated with said specific message, and means for processing the messages according to their priority level, wherein:
According to the method of the invention, the processing of the control messages is carried out in a flexible and effective way so that the user does not have any inconvenience. This method is implemented in a security module comprising at least one processing unit and cooperating with at least one memory. This memory can be integrated in the security module or located into another device. The security module cooperates with a multimedia unit or is part of such multimedia unit. In the following description, we will assume that the multimedia unit is formed by a receiver-decoder and a security module cooperating with this receiver-decoder.
According to this invention, the method for processing control messages ensures an optimal processing that takes into account the limitations imposed by the processing capacities of the security module.
According to this method, the messages are not processed according to a fixed and pre-established priority, the message control is rather made in a flexible manner, depending on circumstances. In particular, the order for processing the messages depends on the moment when the multimedia unit will really need the content of the message to be processed.
According to one embodiment, it is possible, for instance, to provide that the first control message (ECM) received for each channel is associated with a high priority level, that the following control messages for the same channels have a priority level lower than the high level, that control messages for predictive channels are classified in an even lower priority level category and that the management messages EMM are associated with an even lower priority. This invention defines a “basic” management, according to which messages are processed starting with the messages having the highest priority, then pursuing the process with the messages of lower and lower priority level. This “basic” management can not be respected when certain conditions are met, these conditions usually involving a risk that a message corresponding to a content currently viewed or being recorded, cannot be deciphered in time in order to ensure a complete decryption of the event. The priority inversion remains valid as long as the conditions of this inversion are fulfilled. When these conditions are no more fulfilled, the processing order corresponding to the basic management is followed again.
The present invention and its advantages will be better understood with reference to the enclosed drawings and to the detailed description of particular embodiments, wherein:
The present invention relates to a method for processing messages intended for Pay-TV, in particular for control messages containing at least one control word (CW Control Word) allowing the decryption of encrypted content and accordingly, the visualization of conditional access content. The method of the invention also enables processing other types of messages such as management messages (EMM; Entitlement Management Messages), impulsive management messages (IEMM, Impulsive Entitlement Management Messages), used in particular for purchasing products, or even other types of messages.
This processing method is implemented in a security module comprising a conditional access module and a processing module, this security module being part of a multimedia unit. The multimedia unit or its receiver portion receives a stream of encrypted content. The security module receives a stream of control messages ECM from the receiver. This security module is in particular in charge of the processing of the control messages received, the process involving the verification of the access rights, and if the access rights are present and valid, the decryption of the message so as to extract the control word(s). When a control word is decrypted, it is transmitted to a descrambling module of the decoder that uses this control word to decrypt the content and to display it in order to be viewed.
In
In the example illustrated by
Three priority levels are associated with the control messages. These levels are referred to as 1st for the highest priority level, as 2nd for the medium priority level and as Std for the lowest priority level.
The lowest priority level, referred to as Std, is called standard level. The priority level referred to as 1st corresponds to a high priority and the priority level referred to as 2nd corresponds to a medium priority. The priority levels different from standard level, i.e., in this example, the high and medium levels, only receive first control messages for a specific channel. A first message is the first message that arrives when the conditions just change. Such a first message arrives in particular when the user has changed the channel.
In cases in which the system receives messages corresponding to predictive channels, a first message will be sent for the channel to which the user is connected to, as well as on predictive channels linked to this new channel viewed by the user. These first messages are all memorized in memories associated with the high (1st) and medium (2nd) security levels. More specifically, the first message corresponding to the channel to which the user has just switched is usually stored in the memory area associated with the high priority level and the first messages corresponding to the predictive channels are usually stored in the memory area associated with the medium priority level. When the security module receives following messages for these channels, these messages different from the first messages are memorized in a memory area corresponding to a standard priority level. In the embodiments illustrated by
The following description is made on the basis of the examples shown by
In these figures, the reference SC corresponds to the security module and more specifically to the processing module which is in charge of the processing of the control messages. The character found under the reference SC corresponds to the channel for which a message is being processed. The horizontal lines correspond to a priority level, a determined priority level can be associated with a memory area in which the messages are stored before processing. These messages are processed, for each horizontal line, according to the First In First Out principle, the first message stored, i.e., the one shown on the left in the figures, being processed first.
In the state shown in
The messages located in this memory area and corresponding to the standard priority level, are not first messages. The value of the message counter for channel B is 2, this value being defined as follows. A message (A) has been processed since the reception of the message B by the security module. The number of messages processed is equal to 1. The rank of the message B in the memory corresponding to the standard level is 1 as this is the first message of the queue corresponding to this priority level. The value associated with the message B is equal to the sum of these two values, 1+1=2.
The message of channel C is associated with the value 3 that corresponds to the sum of 1 (number of messages processed from the reception of message C) and 2 (rank of the message C in the standard level memory). The message of channel D is associated with the value 4 and the message E of channel E is associated with the value 5.
A counter threshold value is also set. The latter is for instance equal to 5 in the example used. This value is known to the security module and/or to the processing module.
Let us assume that the user switches from channel D to channel G. The first message from channel G is located in the memory corresponding to the high priority. The channel H being a predictive channel (on which the user is very likely to switch), the first message for this channel is stored in the memory corresponding to the medium priority level. Since messages referred to as D, that correspond to the channel previously viewed by the user, as well as E that was a predictive channel, are no more useful, the corresponding messages are deleted. This is shown by
In
In the situation corresponding to
In the step corresponding to
In the example disclosed by
In
The user thus switches on channel H and receives a message corresponding to the channel I as the predictive channel. This is illustrated by
In
The fact that a message from the standard priority level has a higher value than the threshold value results in initiating the processing of a standard priority level message, before processing a higher priority level message. It should be noted that the message having initiated the change of priority is not necessarily the message processed, but the first message of the queue or of the memory area corresponding to the standard level. In the example shown on
In the embodiment shown in
In the embodiment illustrated by
In the embodiment illustrated by
The security module contains means for determining a duration. These means can be a clock and means for determining the moment between the beginning and the end of a message processing. These means for determining a duration can further comprise a clock external to the security module, said clock transmitting time or durations to the security module. A way to determine a duration comprises adding a time stamp to each message.
In reference to
The threshold value is no longer, as in embodiments shown in
In the example of
As in the previous embodiments, the value associated with the messages stored in the memory of the security module is compared to the threshold value. According to an advantageous embodiment, the messages are stored in the form of a queue in an order corresponding to a decreasing AWT actual waiting time. It is therefore sufficient to compare the AWT value of the first message of the queue with the threshold value. According to a variant, it is also possible to compare the threshold value with the values associated with all the messages.
In the example disclosed in
The highest value, herein of 3020 ms, is compared to the threshold value, which has been set to 3000 ms. Since this threshold value has been exceeded, the message B1 is processed as a priority, before processing the message H which has a higher priority level. The processing for this message B1 is shown in
Let us assume that this process has lasted 200 ms. A value of 200 ms is then added to the value associated with each standard priority level message.
The new values associated with standard priority level messages are therefore 2420 for C1, 920 for B2 and 420 for C2. Since none of these values exceed the threshold value, the “normal” priority is respected, which means that the oldest message, having the highest priority level is processed. This message is the message referred to as H in the example shown in
In the embodiments previously described, the threshold value was common to all messages having the standard priority level. In the embodiment shown in
For this purpose, the memory of the security module comprises different memory areas. The security module comprises, as in the embodiment disclosed in
The security module further comprises a memory area intended to store an estimated waiting time EWT, another memory area for storing the threshold value and finally a memory for storing the remaining time RT, this remaining time being defined as the difference between the threshold value TV and the actual waiting time AWT.
As shown in
As it is disclosed in
The estimated waiting time EWT is equal to the actual waiting time AWT for the first message from the queue of messages of the standard priority level. For each following message from this queue, a duration corresponding to the theoretical processing time is added. The estimated processing time can be obtained by the following formula:
AWT=EWT+P′(Rk−1)
where Rk is the rank of the message in the queue.
In
Finally, a last value is associated with each message, this value corresponding to the remaining time RT before reaching the threshold value TV. This remaining time is calculated by the difference between the threshold value TV and the actual waiting time AWT. For the message E2, we have TR=3000−2420=580 ms; we have 3000−920=2080 ms for E3 and 3000−420=2580 ms for E4.
In the previous embodiments, the messages of a given priority level are processed according to the FIFO principle (First In First Out). A message of a given priority level received by the security module is stored at the end of the message queue of this priority level.
In the embodiment disclosed in
In the embodiment disclosed in
It is of course possible to set a threshold value to a positive number, for instance of 300 ms and to change the processing order when the remaining time falls below this threshold value of 300 ms. This avoids, in most situations, to manage a negative time value.
The remaining time RT is calculated as being the difference between the threshold value TV and the actual waiting time AWT in the embodiment of
According to a variant, it is also possible to calculate the waiting time, not using the actual waiting time, but rather the estimated waiting time. The result will be RT=TV−EWT. The estimated waiting time EWT value is calculated as in the embodiment of
The present invention allows to ensure that the standard messages, i.e., other messages than the first messages for a given channel, are processed sufficiently early in order to provide to the user the access to the conditional access content in a continuous way. It also allows to manage messages coming from sources using the different cryptoperiods.
The present invention has been described essentially with examples using two or three priority levels and the control messages ECM. It is possible to provide a much higher number of priority level, for instance until 256, and to process, according to the same method, a combination of control messages, management messages and other messages.
| Number | Date | Country | Kind |
|---|---|---|---|
| 13188117 | Oct 2013 | EP | regional |
| 14172364 | Jun 2014 | EP | regional |
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| Number | Date | Country | |
|---|---|---|---|
| Parent | 14501262 | Sep 2014 | US |
| Child | 15810465 | US |
