The research paper Conditional Access System Technical Seminars for CSE Students describes what a Conditional Access System (CA) is. It says that a conditional access (CA) system comprises a combination of scrambling and encryption to prevent unauthorized reception. Scrambling is the process of rendering the sound, pictures and data unintelligible. Encryption is the process of protecting the secret keys that have to be transmitted with the scrambled signal in order for the descrambler to work. After descrambling, any defects on the sound and pictures should be imperceptible, i.e. the CA system should be transparent.
Why CA: The research paper explains that the primary purpose of a CA system for broadcasting is to determine which individual receivers/ set-top decoders shall be able to deliver particular program services, or individual programs to the viewers.
How CA should be: The research paper explains how the CA system should be it posits that the CA system should impose a minimum of burden on the authorized viewer at any stage in the transaction. In particular it should not require special action when changing channels (e.g. swapping a smart card or keying in a Personal Identification Number) nor should it significantly delay presentation of picture and sound when “zapping” (a sensible upper limit on the “zapping” time is 1 second). Furthermore, it should be easy to gain initial access to the broadcasts, requiring the minimum of equipment, outlay and effort. Ideally, the complete system would be integrated into the television set which would be able to access any combination of program services to which individual viewers had subscribed.
The research abstract concludes on a note that the specification or evaluation of a practical CA system requires considerably more depth and detail than could be included in this outline. In particular, an evaluation of security issues requires a careful analysis of the overall system security. Some of the core concerns could include non-technical issues such as the theft of data.
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