This article has multiple issues. Please helpimprove it or discuss these issues on thetalk page.(Learn how and when to remove these messages) This articlemay containunverified orindiscriminate information inembedded lists. Please helpclean up the lists by removing items or incorporating them into the text of the article.(January 2015) This articlemay containoriginal research. Pleaseimprove it byverifying the claims made and addinginline citations. Statements consisting only of original research should be removed.(January 2015) (Learn how and when to remove this message) The examples and perspective in this articlemay not represent aworldwide view of the subject. You mayimprove this article, discuss the issue on thetalk page, orcreate a new article, as appropriate.(January 2015) (Learn how and when to remove this message) This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Conditional access" – news ·newspapers ·books ·scholar ·JSTOR(March 2008) (Learn how and when to remove this message) (Learn how and when to remove this message)

Conditional access (CA) is a term commonly used in relation tosoftware and todigital television systems. Conditional access is an evaluation to ensure the person who is seeking access to content is authorized to access the content. Access is managed by requiring certain criteria to be met before granting access to the content.

Conditional access is a function that lets an organization manage people's access to the software in question, such as email, applications, and documents. It is usually offered asSaaS (Software-as-a-Service) and deployed in organizations to keep company data safe. By setting conditions on the access to this data, the organization has more control over who accesses the data and where and in what way the information is accessed.

When setting up conditional access, access can be limited to or prevented based on the policy defined by the system administrator. For example, a policy might require that access is available from certain networks, or access is blocked when a specificweb browser is requesting the access.

Under theDigital Video Broadcasting (DVB) standard, conditional access system (CAS) standards are defined in the specification documents for DVB-CA (conditional access),DVB-CSA (the commonscrambling algorithm) andDVB-CI (theCommon Interface).^[1] These standards define a method by which one can obfuscate a digital-television stream, with access provided only to those with valid decryptionsmart-cards. The DVB specifications for conditional access are available from thestandards page on the DVB website.

This is achieved by a combination ofscrambling andencryption. The data stream is scrambled with a 48-bit secret key, called thecontrol word. Knowing the value of the control word at a given moment is of relatively little value, as under normal conditions, content providers will change the control word several times per minute. The control word is generated automatically in such a way that successive values are not usually predictable; the DVB specification recommends using a physical process for that.

In order for the receiver to unscramble the data stream, it must be permanently informed about the current value of the control word. In practice, it must be informed slightly in advance, so that no viewing interruption occurs.Encryption is used to protect the control word during transmission to the receiver: the control word is encrypted as anentitlement 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 anentitlement management message (EMM). The EMMs are specific to eachsubscriber, as identified by the smart card in his receiver, or to groups of subscribers, and are issued much less frequently than ECMs, usually at monthly intervals. This being apparently not sufficient to prevent unauthorized viewing,TPS has lowered this interval down to about 12 minutes. This can be different for every provider,BSkyB uses a term of 6 weeks. WhenNagravision 2 was hacked,Digital+ started sending a new EMM every three days to make unauthorized viewing more cumbersome.

The contents of ECMs and EMMs are not standardized and as such they depend on the conditional access system being used.^[2]

The control word can be transmitted through different ECMs at once. This allows the use of several conditional access systems at the same time, a DVB feature calledsimulcrypt, which saves bandwidth and encourages multiplex operators to cooperate.DVB Simulcrypt is widespread in Europe; some channels, like theCNN International Europe from theHot Bird satellites, can use seven different CA systems in parallel.

The decryption cards are read, and sometimes updated with specific access rights, either through aconditional-access module (CAM), aPC card-format card reader meeting DVB-CI standards, or through a built-inISO/IEC 7816 card reader, such as that in theSky Digibox.

Several companies provide competing CA systems; ABV,VideoGuard, Irdeto,Nagravision,Conax,Viaccess,Synamedia,Mediaguard (a.k.a.SECA) are among the most commonly used CA systems.

Due to the common usage of CA in DVB systems, many tools to aid in or evendirectly circumvent encryption exist. CAM emulators and multiple-format CAMs exist which can either read several card formats or even directly decrypt a compromised encryption scheme. Most multiple format CAMs and all CAMs that directly decrypt a signal are based onreverse engineering of the CA systems. A large proportion of the systems currently in use for DVB encryption have been opened to full decryption at some point, including Nagravision, Conax, Viaccess, Mediaguard (v1) as well as the first version of VideoGuard.

In Canada and the United States, the standard for conditional access is provided withCableCARDs whose specification was developed by the cable company consortiumCableLabs.

Cable companies in the United States are required by theFederal Communications Commission to support CableCARDs. Standards exist for two-way communication (M-card), butsatellite television has separate standards. Next-generation approaches in the United States eschew such physical cards and employ schemes using downloadable software for conditional access such asDCAS.

The main appeal of such approaches is that theaccess control may be upgraded dynamically in response to security breaches without requiring expensive exchanges of physical conditional-access modules.

Conditional access systems include:

• EuroCrypt
• Nagravision
• Videocipher
• VideoCrypt

• Access control, the same principle applied outside of television.
• B-CAS
• CableCARD
• Card sharing
• Compression Networks
• Conditional-access module
• DigiCipher 2
• Digital rights management
• Pirate decryption
• PowerVu
• Smart card
• Television encryption
• Viaccess
• Videocipher
• VideoGuard
• Pairing Smartcard

• CAS history in Spanish
• CA ID list on dvbservices.com

• Digital television
• Digital rights management
• Broadcast engineering
• Conditional-access television broadcasting

• Webarchive template wayback links
• Articles with short description
• Short description is different from Wikidata
• Articles needing cleanup from January 2015
• All pages needing cleanup
• Wikipedia list cleanup from January 2015
• Articles that may contain original research from January 2015
• All articles that may contain original research
• Articles with limited geographic scope from January 2015
• Articles needing additional references from March 2008
• All articles needing additional references
• Articles with multiple maintenance issues