VideoGuard

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VideoGuard (sometimes referred to simply as NDS), produced by NDS, is a digital encryption system for use with conditional access television broadcasting. It is used almost exclusively on digital satellite television (DVB-S) systems operated by News Corporation, which owns the majority of NDS. Its most widely used implementation is BSkyB's Sky Digital (popular in Britain and Ireland) which adopted the system in 1998. Several other broadcasters around the world use the VideoGuard system, including: Yes (Israel), Viasat (Scandinavia), Sky Italia, Sky Network Television (New Zealand), Foxtel (Australia), Tata Sky (India), TotalTV (Serbia) and ONO (Spain).

Since the majority of content provided by companies like BSkyB requires subscription, VideoGuard protects that content by encrypting both standard subscription channels and pay-per-view movies and events. Access flags can be downloaded to the subscriber's card either over the air (via 'hidden' channels) or by using the box's built in modem, thereby allowing rapid changing of channel packages and ordering of events.

The VideoGuard system was introduced by News Corporation to replace the analogue VideoCrypt system. To date, the current encryption method has remained secure, although various pay per view flaws have been identified. Even these flaws are related merely to the stb's circuitry, rather than the NDS card. It is suspected that the version initially used by Sky Digital was either insecure or close to being broken, as a software update rolled out to all boxes required replacement of the BSkyB subscriber's viewing card.

Despite being designed to protect pay-TV, VideoGuard is used by BSkyB to encrypt Channel 4, and Five (To prevent these channels being viewed outside the UK for copyright reasons). These channels are free-to-air in the UK, either using analogue PAL or digital terrestrial (DVB-T) receivers, and can also be viewed using any working VideoGuard card from the correct area, even if expired. Until November 2005, all of ITV's channels were also encrypted using VideoGuard, but switched to becoming unencrypted like the BBC's channels. All these channels can also be viewed using the Freesat from Sky product which, due to the availability of inexpensive cards, potentially increases the risk of VideoGuard becoming cracked through experimentation.

To greatly improve security of the Videoguard encryption, News Corporation's encrypted output can only be viewed using a designated Set-Top Box (STB) in which VideoGuard is embedded into the circuitry. Due to News Corporation's control of VideoGuard, it is impossible to get a licensed VideoGuard Conditional Access Module (CAM) for a third-party STB, or to obtain VideoGuard routines for a software CAM. This is seen by many as an example of vendor lock-in, often to protect NewsCorp's preferred suppliers of boxes, eg PACE. In contrast, CAMs and even software CAMs are available for all other encryption systems, including Irdeto, Nagravision and Viaccess. The CAM monopoly may be broken due to Italian inter-operability laws, which are forcing Sky Italia to allow other boxes to read their cards for legally acquired services.

Several groups managed to reverse-engineer VideoGuard to the point where a legitimate subscriber's card can be read and utilisted firmware to decrypt only those channels that subscriber is authorised to view. A software CAM emulator for the DreamBox & Triple-Dragon Linux-powered satellite receivers, along with the Diablo, Dragon and T-Rex Conditional Access modules. However, many broadcasters choose to pair their cards to a specific STB serial number, meaning that a paired (also called "married") card can only be used in a broadcaster-supplied STB, or by using the serial number from said receiver with one of the reverse-engineered solutions.