With the rapid development of cable TV networks and the abundance of satellite TV programs, digital TV encryption technology has been widely used, and corresponding equipment companies have sprung up like mushrooms, corresponding to two different terminal devices. Series products: two series of products for teletext receiving cards for computer reception and set-top boxes for TV reception. However, despite the development of domestic companies over the past few years, the products have undergone several changes. However, in the face of huge market space and economic benefits, they continue to face the challenge of cracking and pirating products, which has caused great economic losses to manufacturers. Relatively speaking, foreign companies have decades of experience in the field of conditional access. They use the most popular dynamic encryption and smart card technology to make the whole system confidential and secure, and basically solve the problem of terminal equipment being pirated.
The following is an example of PHILIPS' Crypto WorksTM conditional access system, which illustrates the specific application of smart card technology in the digital TV add/descramble technology.
The system consists of 5 PC microcomputers and corresponding equipment. One of the microcomputers and corresponding equipment generates authorization control information (hereinafter referred to as ECM), and 4 microcomputers and corresponding equipments generate authorization management information (hereinafter referred to as EMM), and the decryption is performed by PHILIPS decoder. And smart card composition. The system uses a symmetric key mechanism, and the basic schematic is as follows:
At the transmitting end, the original data stream (TS) and the control word (CW) are modulo-added to form a scrambled data stream (TS'), and the control word is a set of random numbers, that is, an encryption key of the data stream. In this system, the control word consists of 3 digits, which is randomly changed every few seconds. At the receiving end, the same control word is used to control the same circuit for decryption.
While the control word is scrambling the data stream, the control word itself is also encrypted by the key ECMK1 in the ECM PC to form an Entitlement Control Message (ECM), that is, an encrypted control word, and the ECM information is transmitted through the Ethernet via the high speed. The data board is inserted into the transport stream and appears once in the transport stream approximately every few seconds.
At the same time, the user management information (Management Message) is also encrypted by the key EMMK1 to form an Entitlement Management Message (EMM). The user management information is formed by the user management system of the information provider, and the user management system is used to establish a name for all users. , address, smart card number, billing information, and currently authorized database. The EMM inserts the transport stream approximately every 8-10 seconds.
At the receiving end, the decryption is done by the smart card and the decoder. Corresponding to the decoder, there is also a very important data packet in the transport stream - MPEG-2 program specific information PSI. The PSI contains information about the packet ID of the transport stream packet and the relationship between the PIDs. The MPEG-2 decoder will use the PSI information to automatically set the parameters required by the decoder.
PSI information must be sent continuously at a certain frequency, at least 20 times per second. The PSI uses four tables to define the code stream structure. These four tables are the program correlation table PAT, and its PID is 0. The search program information must start from the PAT table. The table lists the program correspondence table PMT in the transport stream. The PID of the table; the basic code stream of the corresponding program can be found in the PMT table; the third table is the conditional access table CAT table, whose PID is 1, which will give the PID of the package where all EMMs are located; the fourth table is The network information table NIT, which gives the corresponding network information.
The principle of decryption at the receiving end is as follows: When the smart card is inserted, the decoder first searches for the PSI in the transport stream, finds the conditional access table CAT in the PSI, and finds the corresponding encryption according to the EMM packet identification code (PID) given in the CAT table. EMM information, the smart card contains the encryption system number and ECMK2, EMMK2 and other keys, the smart card first uses EMMK2, decrypts the encrypted EMM, and determines whether the smart card is authorized to watch the set according to the solved EMM information, if not Authorization will not be able to perform subsequent decryption, and will not be able to watch the program; if the card is authorized, ECMK2 will be enabled to decrypt the ECM, the control word CW will be obtained, and finally the encrypted transmission stream will be decrypted by CW to obtain normal MPEG-2. The transport stream is decoded by the decoder to obtain the desired television, broadcast or digital signal.
The smart card plays a very important role in the security of the entire system. Because the smart card has unparalleled security and anti-aggression, the key stored in it is absolutely safe. In addition, the smart card has its own COS operating system, which makes the file management. The key management is very safe and convenient, it is easy to implement many different applications, realize multi-layer authorization, multi-layer service, easy to manage and charge.
In the case where the charging and the service are relatively simple, for example, the method of selling the device at a time, the fee can be directly embedded in the device by encapsulating the smart card into a standard module, and the module is used to store important key information and the like.
The following is an example of PHILIPS' Crypto WorksTM conditional access system, which illustrates the specific application of smart card technology in the digital TV add/descramble technology.
The system consists of 5 PC microcomputers and corresponding equipment. One of the microcomputers and corresponding equipment generates authorization control information (hereinafter referred to as ECM), and 4 microcomputers and corresponding equipments generate authorization management information (hereinafter referred to as EMM), and the decryption is performed by PHILIPS decoder. And smart card composition. The system uses a symmetric key mechanism, and the basic schematic is as follows:
At the transmitting end, the original data stream (TS) and the control word (CW) are modulo-added to form a scrambled data stream (TS'), and the control word is a set of random numbers, that is, an encryption key of the data stream. In this system, the control word consists of 3 digits, which is randomly changed every few seconds. At the receiving end, the same control word is used to control the same circuit for decryption.
While the control word is scrambling the data stream, the control word itself is also encrypted by the key ECMK1 in the ECM PC to form an Entitlement Control Message (ECM), that is, an encrypted control word, and the ECM information is transmitted through the Ethernet via the high speed. The data board is inserted into the transport stream and appears once in the transport stream approximately every few seconds.
At the same time, the user management information (Management Message) is also encrypted by the key EMMK1 to form an Entitlement Management Message (EMM). The user management information is formed by the user management system of the information provider, and the user management system is used to establish a name for all users. , address, smart card number, billing information, and currently authorized database. The EMM inserts the transport stream approximately every 8-10 seconds.
At the receiving end, the decryption is done by the smart card and the decoder. Corresponding to the decoder, there is also a very important data packet in the transport stream - MPEG-2 program specific information PSI. The PSI contains information about the packet ID of the transport stream packet and the relationship between the PIDs. The MPEG-2 decoder will use the PSI information to automatically set the parameters required by the decoder.
PSI information must be sent continuously at a certain frequency, at least 20 times per second. The PSI uses four tables to define the code stream structure. These four tables are the program correlation table PAT, and its PID is 0. The search program information must start from the PAT table. The table lists the program correspondence table PMT in the transport stream. The PID of the table; the basic code stream of the corresponding program can be found in the PMT table; the third table is the conditional access table CAT table, whose PID is 1, which will give the PID of the package where all EMMs are located; the fourth table is The network information table NIT, which gives the corresponding network information.
The principle of decryption at the receiving end is as follows: When the smart card is inserted, the decoder first searches for the PSI in the transport stream, finds the conditional access table CAT in the PSI, and finds the corresponding encryption according to the EMM packet identification code (PID) given in the CAT table. EMM information, the smart card contains the encryption system number and ECMK2, EMMK2 and other keys, the smart card first uses EMMK2, decrypts the encrypted EMM, and determines whether the smart card is authorized to watch the set according to the solved EMM information, if not Authorization will not be able to perform subsequent decryption, and will not be able to watch the program; if the card is authorized, ECMK2 will be enabled to decrypt the ECM, the control word CW will be obtained, and finally the encrypted transmission stream will be decrypted by CW to obtain normal MPEG-2. The transport stream is decoded by the decoder to obtain the desired television, broadcast or digital signal.
The smart card plays a very important role in the security of the entire system. Because the smart card has unparalleled security and anti-aggression, the key stored in it is absolutely safe. In addition, the smart card has its own COS operating system, which makes the file management. The key management is very safe and convenient, it is easy to implement many different applications, realize multi-layer authorization, multi-layer service, easy to manage and charge.
In the case where the charging and the service are relatively simple, for example, the method of selling the device at a time, the fee can be directly embedded in the device by encapsulating the smart card into a standard module, and the module is used to store important key information and the like.
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