In Digital Video Broadcasting, the Common Interface is a technology which allows separation of conditional access functionality from a digital TV receiver-decoder (Host) into a removable conditional access module (CAM). It is also referenced as DVB-CI for Digital Video Broadcast - Common Interface. The host is responsible for tuning to pay TV channels and demodulation of the RF signal, while CAM is responsible for CA descrambling. The Common Interface allows them to communicate with each other.
The Common Interface can be used for pay-to-view TV; A module is used to interface between the pay-to-view card and the TV or device. This allows manufacturers to install a single (common) interface into their devices rather than many. It is a similar concept to USB.
All Common Interface equipment must comply with the EN 50221-1997 standard. This is a defined standard that enables the addition of a conditional access module (CAM) in a DTV receiver to adapt it to different kinds of cryptography. Indeed, one of Digital Video Broadcasting's main strengths is the option of implementing the required conditional access capability on the Common Interface.
This allows broadcasters to use modules containing solutions from different suppliers in the same broadcast system, thus increasing their choice of anti-piracy options.
The interconnect is formed between a host and a module. Examples of a host are a digital television or digital set-top box. The EN 50221 specification allows many types of module but only the Conditional Access Module (CAM) has found popularity because of the pay TV market.
Mode of operation
A DVB receiver may have one or two slots implementing the Common Interface (CI). The CI uses the conditional access module(PCMCIA) connector and conforms to the Common Scrambling Algorithm (CSA), the normative that specifies that such a receiver must be able to accept DES (Data Encryption Standard) keys in intervals of some milliseconds, and use them to decode private channels according to a specific algorithm.
Those algorithms are proprietary to individual suppliers. Each one uses their own algorithms and there is no defined standard for them.
As the full MPEG-2 transport data stream comes out of the demodulator, and error correction units, the DTV Receiver sends it through the card plugged into the Common Interface, before it is processed by the MPEG demultiplexer in the receiver. If several CI cards are present, the MPEG transport data stream will be passed sequentially through all these cards.
An embedded CAM may not physically exist, as it may be in CPU software. In such a case, only the ISO card reader normally in the CAM is fitted and not the PCMCIA type CI slots.
Even if the Common Interface has been created to resolve cryptography issues, it can have other functions using other types of modules such as Web Browser, iDTV (Interactive Television), and so forth.
In Europe, DVB-CI is obligatory in all iDTV terminals.
Conditional Access Module (CAM)
The host sends an encrypted MPEG transport stream to the CAM and the CAM sends the decrypted transport stream back to the host. The CAM often contains a smart-card reader.
The normative DVB-CI standard EN 50221 was defined in 1997 by CENELEC, the European Committee for Electrotechnical Standardization.
According to the Common Interface scheme:
- host : A device where module(s) can be connected; for example, an Integrated receiver/decoder (IRD), a VCR, a PC ...
- module : A small device, not working by itself, designed to run specialised tasks in association with a host; for example, a conditional access sub system, an electronic program guide application module, or to provide resources required by an application but not provided directly by the host.
The specification only defines two aspects, two logical interfaces to be included on the same physical interface. The first interface is the MPEG-2 Transport Stream. The link and physical layers are defined in this specification and the higher layers are defined in the MPEG-2 specifications. The second interface, the command interface, carries commands between the host (receiver) and the module.
The specification does not define the operation or functionality of a conditional access system application on the module. The applications that may be performed by a module communicating across the interface are not limited to conditional access or to those described in this specification. More than one module may be supported concurrently.
The common interface shares many features of the PC Card Standard (PCMCIA). By reducing the widths of the address and data busses it has been possible to include a bi-directional parallel transport stream interface.
Transport Stream Interface (TSI)
The transport stream format is specified by IEC 13818-1 and is the MPEG 2 TS format.
In addition there is a command interface for communication between the host and module.
This communication is in the form of a layered protocol stack which allows the host and module to share resources. For example the module can request the current date and time from the host, or can make the host display messages on the TV screen and can then read keypresses from the host remote control. The resource-sharing feature allows the CAM to request and receive PIN numbers as well as allowing the module to implement an interactive TV service.
The Command Interface is extensible and there are several specification documents available which describe these extensions. For example the host could contain a modem for communication over a telephone line allowing the CAM to implement pay-per-view. However these extensions have often not proved popular with manufacturers.
CI+ is a specification that extends the Common Interface as found in the digital broadcasting standard. CI Plus or Common Interface Plus implements a form of copy protection between a Conditional Access Module (CAM) and the television receiver (Host). CI+ is backward compatible with CIv1. Old television receivers, which have CIv1 CI-slot, can be used with CI+ CAM and vice versa, but for viewing only those of TV programs which are not marked as CI+ protected.
A first draft of the specification was put up for review in January 2008 as V1.00 CI Plus Specification. The establishment of the Trusted Authority has been completed and an official security certification lab appointed.
In 2009, versions 1.1 and 1.2 were released. The V1.2 version became the first one which was massively deployed.
In 2011, version 1.3.1 was released.
With the development of CI+, the standard has now come under the umbrella of the DVB standards organisation.
How it works
By making use of certificates and a certification authority, a trusted channel is formed between the CAM and television receiver (Host), when scrambled content is being received (in the original CI standard, decrypted content could be sent over the PCMCIA interface unscrambled).
A CI+ compliant Host device must also implement MHEG-5 interactive TV engine to manage navigation of the user within an interactive TV application, using its device remote control. Support of MHP or HbbTV interactive TV engines is optional.
Operators (partial list)
The following operators have currently rolled out CI+ support or plan to do so:
- Canal+ – launched the "Canal Ready" label for devices able to receive Canal+ channel
- Kabel Deutschland, KBW, SkyD, Telecolumbus – NDS (now Cisco) conditional access and SMiT CAM modules are used
- United Kingdom
In July 2009 the largest Cable operator in the Netherlands, Ziggo, announced that it will support CI+ based Integrated Digital Television sets (IDTVs) actively. In September 2009 the first batch of 15,000 SMiT (Shenzhen State Micro Technology Co., Ltd.) CI+ CAMs was offered by various Dutch retailers, followed in October 2009 by the first batch of Neotion CAMs. Other supporters include Canal+, and conditional access companies Irdeto and Conax. NDS announced that it will support Kabel Deutschland to deploy CI+ to its customers.
Compatible TV sets (partial list)
- LG 2010 models all LD and LE series also MFT models MXX80D.
- Many of Samsung's new LCD, LCD LED and Plasma model variants with CI+ compatible motherboards.
- Many of Sony's new models including the Bravia W5500 series.
- Philips new 5000 and 9000 series LCD TVs (required firmware pending according to Ziggo).
- Some Panasonic models. It seems that even products with CI+ slots need a new firmware to be fully CI+ compatible. (Update 2010)
- "Cabot Communications Ltd. CI+ Technical Paper". Retrieved 2013-07-10.
- "Führende TV-Hersteller vertrauen bei der Umsetzung des CI Plus-Standards in Europa auf TC TrustCenter (German)" (PDF). Retrieved 2013-07-10.
- March 5, 2009 10.48 Europe/London (2009-03-05). "Digital TV Labs to test for CI Plus". Broadbandtvnews.com. Retrieved 2013-07-10.
- February 18, 2011 10.55 Europe/London (2011-02-18). "CI Plus back with the DVB". Broadbandtvnews.com. Retrieved 2013-07-10.
- "CI Plus Specification 1.1" (PDF). Retrieved 2013-07-10.
- [dead link]
- Caiway CI+ CAM (dutch)[dead link]
- October 16, 2009 08.54 Europe/London (2009-10-16). "Caiway introduces CI Plus modules". Broadbandtvnews.com. Retrieved 2013-07-10.
- "Digitale Televisie Module (Dutch)". Ziggo.nl. 1970-01-01. Retrieved 2013-07-10.
- Cablecom makes access to digital TV in HD quality and Internet easier and cheaper[dead link]
- "CI+ Landing". Top Up TV. 2012-07-31. Retrieved 2013-07-10.
- Ziggo claims “world first” with CI Plus (visited July 7th 2009)
- Ziggo Approved SMiT CI+ CAM[dead link]
- After initial pioneering, ZIGGO and NEOTION are now further unleashing CI Plus momentum in the Digital Pay TV ecosystem
- August 30, 2009 13.31 Europe/London (2009-08-30). "Ziggo starts supply of CI Plus CAMs". Broadbandtvnews.com. Retrieved 2013-07-10.
- April 27, 2009 18.06 Europe/London (2009-04-27). "Canal+ backs CI Plus with ‘Canal Ready’ label". Broadbandtvnews.com. Retrieved 2013-07-10.
- "Iredeto press release". Irdeto.com. Retrieved 2013-07-10.
- September 12, 2008 11.28 Europe/London (2008-09-12). "Conax announces CI+ support". Broadbandtvnews.com. Retrieved 2013-07-10.
- September 13, 2009 08.45 Europe/London (2009-09-13). "NDS to deliver CI+ to KDG". Broadbandtvnews.com. Retrieved 2013-07-10.
- LinuxTV entry for common interface
- EN 50221 Specification
- ETSI TS 101 699 - DVB Extensions to the Common Interface Specification
- R206-001:1998 - Guidelines for Implementation and Use of the Common Interface for DVB Decoder Applications
- Gerard O'Driscoll, The essential Guide to Digital Set-Boxes and Interactive TV, reprinted April 2000
- Jerry whitaker, Television Receivers, 2001
- Consortium DVB
- CI Plus official web site
- CI Plus Specification V1.2 (2009-04)
- CI Plus Specification V1.3.1 (2011-09)
- Official CI Plus TrustCenter
- Official CI Plus test lab