Conditional access module MSA-200
* A conditional access module MSA-200 provides TV program encryption of the DVB transport stream for a
conventional access system MSA and is intended for use as a part of CATV head-ends
A conditional access module (hereafter - encoder) "is turned on" before a modulator of any DVB-S, DVB-C or DVB-T standard.
After the operator's command the processor programs a PID-filtering device to search for packet data with PSI tables. The found tables are saved into a static RAM. The microprocessor analyses these tables and sends the information about the found programmes to the PC. The operator selects from the program-list those which should be sent to the output and those which should be encoded and sends a corresponding command to the encoder. The microprocessor puts into a register the PID of those video and audio packet data which belong to the selected programmes. The encoder begins encoding of packet data after having detected the packet data with the PID put into the register. This procedure is repeated for each encoder. The programmes allowed for encryption are detected by different encoders are put into a general list of encrypted programmes. The total quantity of programmes is not more than 128. The operator effects shaping of subscriber packet data afterwards. The total quantity of packet data is not more than 8. Each program can be included into several packet data. Afterwards the operator enters the information about registered subscribers and the packet data they subscribed to into a database. The PIDs of those audio and video streams which are allowed to be viewed by all the customers are transferred from the computer into a permanent memory of each encoder. The encoder microprocessor shapes service tables of subscriber status (EMM) on these data basis in a static RAM and inserts them into an input stream periodically. Each decoder has its unique number and will decode only those streams which are allowed for it to view.
Encoding of video and audio stream packets occurs in the following way. A key with the length of 64 bits (8 bytes) is used for information encoding. That is why the input DVB packet with the length of 188 bytes is split in 8 byte blocks (23 blocks with a total length of 184 bytes) and the rest which amounts to 4 bytes. Each block with the length of 8 bytes is encoded according to the CSA algorithm and the rest of 4 bytes passes without encryption. This rest is located at the beginning of the packet. That is why the packet title does not change (it is necessary to provide synchronization of modulator operation).
Except the status tables a table with a ciphering key is shaped and transmitted (ECM). The fact that the key is transmitted in the same program stream does not affect cryptographic robustness of the system because the table and the key are encrypted additionally with the AES algorithm (128) (Advanced Encryption Standard).
|Front-end interface type||Electrical, DVB ASI(C)|
|Output interface type||Electrical, DVB ASI(C)|
|Input stream rate||≤ 54 Mbps|
|Output stream rate||≤ 54 Mbps|
|Quantity of input streams||1|
|Quantity of subscribers||up to 300,000|
|Subscriber log-in/Tripping time||≤ 15 min|
|Quantity of Encrypted Programmes||20|
|Method of encryption||CSA algorithm|
|Length of ciphering keys||128 bits|
|Maximum quantity of subscriber packets||8|
|Maximum quantity of programmes||128|
|Voltage supply/Consumption current of an MSA-200||12V / 0.4A|
The company produces tuners with a built-in coding system for the standards DVB-C, T and S.