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Under the DVB , conditional access system standards are defined in the specification documents for DVB-CA (Conditional Access), DVB-CSA (the Common Scrambling Algorithm ) and DVB-CI (the Common Interface ). These standards define a method by which a digital television stream can be scrambled, with access provided only to those with valid decryption cards. These cards are read, and even sometimes rewritten with access rights, through a Conditional Access Module (CAM), a PCMCIA format card reader, or an onboard card reader meeting DVB-CI standards, such as that in the Sky Digibox .

Due to the common usage of CA in DVB systems, many tools to aid or even Directly Circuvment encryption exist. CAM emulators and multiple-format CAMs exist which can either read many formats of cards or even directly decrypt a compromised encryption scheme. Most multiple format CAMs, and all CAMs which directly decrypt a signal are based on Reverse Engineering of the CA system. A large proportion of the systems in use currently for DVB encryption have been opened to full decryption at some point, including Nagravision, Conax, Viaccess and Seca Mediaguard.

A large number of companies provide competing CA systems, and the DVB standard allows the encryption of a channel in more than one system at once ( Simulcryption ). VideoGuard , Irdeto Access , Conax , Nagravision and Viaccess are among the most commonly used CA systems.


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