Conditional access

Encyclopedia : C : CO : CON : Conditional access

Conditional access ("CA") is the protection of content by requiring certain criteria to be met before granting access to the content. The term is commonly used in relation to digital television systems, most notable satellite television.

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.

Conditional access

See also