CA - Conditional Access
By: Preethi Ramkumar
Meaning of CA – “Conditional Access” is a technology used to control access to digital television (DTV) services to authorized users by encrypting the transmitted programming. CA has been used for years for pay-TV services. There are numerous (ATSC) and (DVB)-compliant CA systems available for a broadcaster to choose from. The CA system provider provides the equipment and software to the broadcaster who then integrates the CA system into his equipment. CA is not designed solely for DTV. It can be used for digital radio broadcasts, digital data broadcasts, and non-broadcast information and interactive services.
A CA system consists of several basic components:
Subscriber Management System (SMS):
The SMS is a subsystem of the CA system that manages the subscriber's information and requests entitlement management messages (EMM) from the Subscriber Authorization System (SAS). An EMM provides general information about the subscriber and the status of the subscription. The EMM is sent with the (ECM) . The ECM is a data unit that contains the key for decrypting the transmitted programs.
Subscriber Authorization System (SAS):
The SAS is a subsystem of the CA system that translates the information about the subscriber into an EMM at the request of the SMS. The SAS also ensures that the subscriber's security module receives the authorization needed to view the programs, and the SAS acts as a backup system in case of failure.
Security module:
The security module, usually in the form of a smart card, extracts the EMM and ECM necessary for decrypting the transmitted programs. The security module is either embedded within the set-top box or in a (PC) Card that plugs into the set-top box.
Set-top box:
The set-top box houses the security module that gives authorization for decrypting the transmitted programs. The set-top box also converts the digital signal to an analogue signal so an older television can display the programs.
A typical CA process involves three basic elements: the broadcast equipment, the set-top box, and the security module. The broadcast equipment generates the encrypted programs that are transmitted to the subscriber. When these are transmitted, the set-top box filters out the signals and passes them to the security module. The security module then authorizes these programs for decryption. The programs are then descrypted in real time and sent back to the set-top box for display.
Other Related Definitions:
“…A conditional access system comprises a combination of scrambling and encryption to prevent unauthorised reception. Encryption is the process of protecting the secret keys that are transmitted with a scrambled signal to enable the descrambler to work. The scrambler key, called the control word must, of course, be sent to the receiver in encrypted form as an entitlement control message (ECM). The CA subsystem in the receiver will decrypt the control word only when authorised to do so; that authority is sent to the receiver in the form of an entitlement management message (EMM). This layered approach is fundamental to all proprietry CA systems in use today. ” [Digital TV Group]
“…Conditional Access (CA) system has been chosen for easy.TV, the new satellite pay-TV service in Germany. easy.TV is seen as a major breakthrough in today’s pay-TV market. When its CryptoWorks-encrypted channels go on air in September 2005, easy.TV is set to becomeGermany’s most flexible and easy-to-use pay-TV service. Users can purchase by program content, by specifying channels or individual programs, or even order a specific number of viewing hours. There is no regular subscription charge. ” [Philips’ CryptoWorks]
“…Conditional Access is not wholly specified in DVB, but a collection of tools enables users of DVB to come up with the most effective and efficient mechanisms for their market. Central to the whole "DVB CA package" is the DVB Common Scrambling Algorithm (CSA) which is available from ETSI.” [The Standard Of Digital world]
“…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 CAM's exist which can either read many formats of cards or even directly decrypt a compromised encryption scheme. Most multiple format CAM's, and all CAM's which directly decrypt a signal are based on reverse-engineering of the CA system 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. ” [ Wikipedia]
“…CA) - (May also be known as: Authentication, Access Control System,) - CA is an encryption/decryption management method (security system) where the broadcaster controls the subscriber's access to digital and ITV services. This can ensure that the person is who he/she says he/she is (authenticity). It also offers security in purchase and other transactions. The end-users (subscribers) have a receiver/Set-top Box that allows him or her "Conditional Access" to the services available through that service. "Smart cards" and/or a private PIN number are most often used to access the services, and/or premium services, by the end-user (subscriber.) The system is primarily made up of 3 parts: (1) signal scrambling, (2) encryption of electronic "keys" which the viewer will need, and the (3) Subscriber Management System - ensuring those who have bought the scrambled programming, are able to receive and watch it. ” [Common Interactive Television (ITV)]
Related Links:
Reference - Fundamentals of Conditional Access
DVB - CA interoperability
Mobile_solutions - mVideoGuard for Mobile Broadcast: Conditional Access
Functionality and architecture of a Conditional Access system - Minutes of the Conditional Access workshop
N. Helberger, N. A. N. M. van Eijk & P. B. Hugenholtz, Institute for Information Law (IViR), University of Amsterdam - Study on the use of conditional access systems
Pacemicro - Dynamic Switchable Conditional Access
Interactivetvweb - The Conditional Access API
Broadbandmag - Conditional Access - Revenues in; Racketeers out
Conax AS - CONAX CONDITIONAL ACCESS TECHNOLOGY
Cabledatacomnews - Downloadable Conditional Access Picks Up Steam
Drmwatch - NDS DRMizes Conditional Access
DTV - Different Conditional Access
Strategis - Determination of Interference for Equipment that defeats the conditional access system of Broadcast Satellite Receivers
Technical Resources:
Sky.com - Method for Establishing Conditional Access Charges
Products and Solutions:
Cedmagazine
Dtvprofessional
Git
VideoGuard
Myrio
Nagravision
Nds
Portal
Scmmicro
Blogs, News, feeds…
http://www.software.philips.com/cryptotec/article-14670.html
http://www.dvb.org/documents/press-releases/pr005_DVB%20agrees%20conditional%20access%20package.940927.pdf
http://www.cl.cam.ac.uk/~mgk25/ca-law/
Books:
A conditional access system for direct broadcasting by satellite (BBC RD 1986/11) by S. M Edwardson
Conditional access broadcasting: An over-air enabled system for general purpose data channels by Douglas T Wright
See Also:
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