Set-top box CA encryption

CA has conditional receiving system and scrambling and encrypting two parts. Scrambling is an image, sound, and data stream under the control of a CW (or a key) in a way that makes it impossible to watch, and encryption is the process of protecting the key. The encrypted key must be transmitted to the client along with the scrambling signal. On the client side, the solution CW is decrypted with the smart card, and the scrambling signal is disturbed by the CW control spoiler, which can obtain the image and sound which is undetectable to the damage. The encryption information associated with the CW becomes the Authorization control information (ecm:entitlement Control Message), and the information about the service content, time, and permissions that are authorized by the user becomes the authorization control management information (emm:entitlement Management Message). After the EMM is encrypted, it can also be transmitted to the client, decrypted by a smart card, and then controlled by the spoiler, so that the spoiler can run on different CA systems that are not the same encryption and scrambling methods. DVB provides the standard of "public encryption Algorithm", which has been adopted by more CA system, but the encryption method is different.

Due to the existence of different encryption algorithms for digital TV, the client must use the digital TV decryption receiver authorized by the digital TV operator to decrypt the data, if the user wants to receive other digital TV programs, the corresponding digital TV decryption receiver must be replaced. This kind of non-universality will affect and restrict the development of digital TV charge service.

Set-top box CA encryption