KR20090073485A - Conditional access system for digital data broadcasting - Google Patents

Abstract

A CAS(Conditional Access System) for digital data broadcast for remarkably reducing the burden of data transmission is provided to minimize bandwidth according to EMM. An EMMG(Entitlement Management Message Generator)(40) generates EMM data. An ECMG(Entitlement Control Message Generator)(80) produces ECM data. A CW generator produces a CW(Code Word). A scrambler scrambles broadcast data. The EMMG delivers EMM data to ECMG. The ECMG inserts EMM data within ECM data. The ECMG delivers ECM data in which EMM data is inserted to the scrambler.

Description

Reception restriction system for digital data broadcasting {CONDITIONAL ACCESS SYSTEM FOR DIGITAL DATA BROADCASTING}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to digital data broadcasting systems, and more particularly, to a reception restriction system of digital data broadcasting.

As digitalization of broadcasting has recently progressed, digital data broadcasting services such as digital video broadcasting (DVB) and digital audio broadcasting (Digital Audio Broadcasting) have been in the spotlight. A key technology in digital data broadcasting service is a conditional access system (CAS). CAS is a system that allows only authorized subscribers to use a broadcast service, and means a series of processes that allow each digital broadcast receiver to determine whether or not reception is possible. Restriction system controls the subscriber to access services, programs and events. In broadcast systems, services, programs and events consist of three elements: video, audio and data. These three elements combine to form an event. The combination of one or more events under the control of the broadcast device forms a program. A service is a series of programs that are broadcast according to a schedule under the control of a broadcasting device.

The CAS consists of a transmitting side (CAS server, also referred to as 'Head-End') for encrypting and transmitting a signal, and a receiving side (CAS client) for receiving and decrypting the encrypted signal. The CAS server encodes and transmits three elements of video, audio and data with the appropriate encryption algorithm. In general, a CAS server includes an ECM generator (ECMG), an EMM generator (EMMG), a subscriber management system (SMS), a traffic control system (TCS), and a MUX. The ECMG creates an Entitlement Control Message (ECM) section and carries a CW (Control Word) to the ECM section. The SMS stores detailed information about all subscribers and initiates the creation of an Entitlement Management Message (EMM) via EMMG. Upon request from the SimulCrypto Synchronizer (SCS), EMMG creates an EMM section and passes it to the MUX. The EMM includes a service key used for encryption of CW. The output data of EMMG and ECMG is encrypted. The scrambled A / V broadcast stream is sent to the client along with the EMM and ECM. The client uses the smart card to decrypt the EMM to extract the service key. Using the extracted service key, the ECM is decrypted and the CW in the ECM is extracted. Broadcast data is decoded using CW.

Conventionally, when sending a service key in an EMM, the EMM must be sent to the subscriber of each individual taking up a lot of bandwidth. Since the amount of EMM bandwidth is proportional to the number of subscribers, more bandwidth is required as the number of subscribers increases, which is a large burden on the transmitting side.

It is an object of the present invention to provide a system for limiting reception of digital data broadcasts which minimizes the bandwidth according to the EMM.

In order to achieve the above object, the present invention inserts the EMM in the ECM. The present invention encrypts CW instead of encrypting ECM and EMM.

 According to an aspect of the present invention, an EMM generator for generating EMM data, an ECM generator for generating ECM data, a CW generator for generating a control word (CW), and a scrambler for scrambled broadcast data, the EMM A generator delivers EMM data to the ECM generator, and the ECM generator is provided with a reception limitation system for digital data broadcasting that inserts the EMM data into ECM data and delivers the MM to the scrambler.

In the reception restriction system, the ECMG and the EMMG may be formed of the same module conforming to the TCP / IP protocol for control information and the UDP protocol for data information.

In the reception restriction system, the ECMG and EMMG may be formed as separate modules conforming to the TCP / IP protocol for control and data information.

In the conditional access system, the control word may be encrypted by an asymmetric encryption algorithm.

In the conditional access system, the control word can be decrypted by the same private key for all subscribers.

According to the configuration of the present invention can achieve all the objects of the present invention described above. Specifically, since the ECM data includes the EMM data, the burden of data transmission can be significantly reduced.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, the reception restriction system 10 is for a paid broadcasting system, and includes a subscriber management system (SMS) 20, a traffic control system (TCS) 50, and an entitlement control message generator (ECMG) 80. And an Entitlement Management Message Generator (EMMG) 40, an Event Information Scheduler (EIS) 60, a CAS database 70, a multiplexer 99, and a scrambler module 90. The scrambler module 90 includes a CW generator 92, a SimulCrypt Synchronizer (SCS) 94, and a scrambler 96.

The SMS 20 is a system for supervising subscriber management information such as subscriber registration information and billing information. The SMS 20 is a central system in a pay broadcast system with the functions of subscription, calculation and billing. In addition, the SMS 20 also has other functions such as group management, text message commands and security commands. SMS 20 is a client and EMMG 40 is a server. The command message is sent from the SMS 20 to the EMMG 40, and the confirmation message is sent from the EMMG 40 to the SMS 20.

EMMG 40 is a device for generating an EMM section according to the SMS command. The output of the EMMG 40 is in the form of an EMM block. EMM block has a unique tag. The EMMG 40 may designate one subscriber or group or all subscribers of the reception restriction system.

The TCS 50 is a system for managing a broadcast schedule of a broadcast system. The TCS 50 defines each service channel as an event with a predetermined time and determines the means of operation for the event. The TCS 50 must deliver the CAS-related event schedule of each service to the CAS server in order to create an ECM containing access criteria for a given time of each event. CAS related event schedule information is CAS control information (access criteria), Pay Per View (PPV) information, and Parental Control of a specific event. The TCS 50 organizes CAS-related event information in a Schedule Information Format (SIF) format.

The EIS 60 is a device that connects between the TCS 50 and the CAS database 70. EIS 60 parses the SIF formation file and stores the data in CAS database 70.

The ECMG 80 is an apparatus for generating an ECM for a specific service according to a request of the scrambler module 90. The ECMG 80 searches for a service event corresponding to the present time from the CAS database 70 including the event schedule information, and then generates an access criterion for the event. Together with the CW and the generated access criteria, the ECMG 80 generates the ECM and passes it to the scrambler module 90.

The scrambler module 90 is a device that scrambles and protects video / audio / data inputs. The scrambler module 90 supports various content types of video, audio, and data, and is able to integrate and cooperate with various encoding systems and multiplexers. The scrambler module 90 includes a CW generator 92, a synchronizer 94, and a scrambler 96. The scrambler module 90 also provides a shared scrambler function that conforms to the DVB Simulcrypt standard, integrating into one or more CASs to send and receive ECM and EMM of each CAS with scrambled video and audio data.

1 to 5, the operation of the above embodiment will be described in detail.

The SMS 20 creates an XML format command and delivers it to the EMMG 40 through an HTTP request. EMMG 40 processes the request and sends the result to SMS 20 via an HTTP response in XML format.

The TCS 50 organizes CAS-related event schedule information in SIF format. EIS 60 includes an internal buffer for downloading and uploading SIF files. The EIS 60 keeps checking the uploaded file, and upon successful execution, the EIS 60 records the SIF information as event schedule information in the CAS database 70. If an error occurs while checking the received file, the EIS 60 creates an error log file and stores it in the error folder.

The interface between the ECMG 80 and the scrambler module 90 is based on the DVB Simulcrypt protocol.

The client EMMG 40 and the server ECMG 80 use a connection-oriented TLV protocol as shown in FIG. The TCP protocol is used for data provision and control as used in the DVB Simul Crypt standard.

When the SMS request is forwarded to the EMMG 40, the EMMG 40 creates an EMM section and forwards it to the ECMG 80 using the control data protocol. Upon receipt of the data of the EMMG 40, the ECMG 80 stores the EMM section in a queue buffer, and as shown in FIG. 4, the initial receiving EMM block 150 at the request of the SCS 94. Is inserted into the ECM section. If there are two or more EMM blocks in the ECM queue buffer, the ECMG 80 inserts the EMM block 150a in the ECM sense as much as possible, as shown in FIG. The ECMG 80 maintains the dispatched / undelivered state of each EMM. Upon the next request of the SCS 94, the ECMG 80 deletes the outgoing EMM message from the queue buffer and sends an outgoing EMM message of the ECM section. Upon receipt of an error message, the ECMG 80 toggles the status of the message already sent.

The ECMG 80 and the EMMG 40 may be formed in the same module or in separate modules. When formed in the same module, the ECMG 80 and the EMMG 40 may follow the TCP / IP protocol for control information and the UDP protocol for data information. When formed, it follows the TCP / IP protocol for control and data information.

The present invention seeks to encrypt the control word (CW) instead of encrypting the EMM and ECM sections. To support this, the EMM block does not contain any key section and follows the TLV format, meaning that the EMM block is identified by a unique tag. The EMM block mainly contains two sections, the first being the target detail and the second being the message detail. When another structure is inserted into the ECM section as shown in Fig. 3, the EMM section can be inserted into the ECM section with each tag as shown in Figs. If there is no EMM block, the ECM section includes only the ECM information block, as shown in FIG.

An asymmetric encryption method is used to encrypt the control word. Each subscriber has the same private key to decrypt the encrypted control word. The CAS of this embodiment uses NTRU encryption, RSA and EIGamal as asymmetric encryption algorithms.

The present invention can be used in digital broadcasting systems that control, manage, and broadcast data according to the DVB and DAB standards.

Although the present invention has been described with reference to the above embodiments, the present invention is not limited thereto. Those skilled in the art will appreciate that modifications and variations can be made without departing from the spirit and scope of the present invention and that such modifications and variations also fall within the present invention.

1 is a block diagram showing the structure of a reception restriction system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a protocol interface between EMMG and ECMG of FIG.

3 shows a data structure of a general ECM.

4 shows a data structure of an ECM with an EMM.

5 illustrates a data structure of an ECM having multiple EMMs.

Claims (5)

An EMM generator that generates EMM data, An ECM generator for generating ECM data, A CW generator for generating a control word (CW), A scrambler for scrambled broadcast data, The EMM generator delivers EMM data to the ECM generator, And the ECM generator inserts the EMM data into ECM data and transmits the EMM data to the scrambler. The reception limitation system according to claim 1, wherein the ECMG and EMMG are formed of the same module conforming to the TCP / IP protocol for control information and the UDP protocol for data information. The reception limitation system according to claim 1, wherein the ECMG and EMMG are formed as separate modules conforming to the TCP / IP protocol for control and data information. The reception limitation system according to claim 1, wherein the control word is a control word encrypted by an asymmetric encryption algorithm. A system according to any one of claims 1 to 4, wherein the control word is decrypted by the same private key for all subscribers.

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