Television encryption
From Wikipedia, the free encyclopedia
Television encryption, often referred to as "scrambling", is encryption used to control access to pay television services, usually cable or satellite television services.
Contents |
[edit] History
Pay television has always emphasised the idea of making the subscriber pay. The early cable based Pay-TV networks used no security and had problems with people connecting to the network without bothering to pay. Consequently, some methods were developed to frustrate these self-connectors. The early Pay-TV systems for cable television were based on a number of simple measures. The most common of these was a channel based filter that would effectively stop the channel being received by those who had not subscribed. These filters would be added or removed according to the subscription. As the number of television channels on these cable networks grew, the filter based approach became increasingly impractical.
Other techiques such as adding an interfering signal to the video or audio began to be used as the simple filter solutions were easily bypassed. As the techology evolved, addressable set top boxes became common and more complex scrambling techniques such as digital encryption of the audio or video cut and rotate (where a line of video is cut at a particular point and the two parts are then reordered around this point) were applied to signals.
Encryption was used to protect satellite distributed feeds for cable television networks. Some of the systems used for cable feed distribution were expensive. As the DTH market grew, less secure systems began to be used. Many of these systems (such as OAK Orion) were variants of cable television scrambling systems that affected the synchronisation part of the video, inverted the video signal or added an interfering frequency to the video. All of these analogue scrambling techniques were easily defeated.
In France, Canal + launched an scrambled service in 1984. Unfortunately an electronics magazine, "Radio Plans", published a design for a pirate decoder within a month of the channel launching.
In the USA, HBO was one of the first services to encrypt its signal using the VideoCipher II system. In Europe, FilmNet scrambled its satellite service in September 1986 thus creating one of the biggest markets for pirate satellite tv decoders in the world because the system that FilmNet used was easily hacked. One of FilmNet's main attractions was that it would screen hard core porn films on various nights of the week. The VideoCipher II system proved somewhat more difficult to hack but it eventually fell prey.
[edit] Conditional access
[edit] Cable and early satellite television encryption
Analog and digital pay television have several conditional access systems that are used for pay per view (PPV) and other subscriber related services. Originally, analog-only cable TV systems relied on set-top boxes to control access to programming, as television sets originally were not "cable ready". Analog encryption was typically limited to "premium" channels such as HBO or channels with adult-oriented content. In those cases, various proprietary video synchronization suppression algorithms were used to control access to programming. Analog set-top boxes have largely been replaced by digital set-top boxes that can directly control access to programming as well as digitally encrypt signals.
VideoCipher II RS (VCII RS) is the scrambling system that C-Band satellite pay TV channels originally used. A VCII-capable satellite receiver is required to decode VCII channels. VCII has largely been replaced by DigiCipher 2 in North America. Originally, VCII-based receivers had a separate modem technology for pay-per-view access known as Videopal. This technology became fully-integrated in later generation analog satellite television receivers.
- VideoCipher I (deprecated)
- VideoCipher II (deprecated)
- VideoCipher II+
- VideoCipher II RS (Renewable Security)
[edit] Digital cable and satellite television encryption
DigiCipher 2 is General Instrument's proprietary video distribution system. DCII is based upon MPEG-2. A 4DTV satellite receiver is required to decode DCII channels. In North America, most digital cable programming is accessed with DigiCipher 2-based set-top boxes.
PowerVu is another popular digital encryption technology used for non-residential usage. PowerVu was developed by Scientific Atlanta. Other commercial digital encryption systems are Irdeto (by Irdeto Access), Nagravision (by Kudelski), Viaccess (by France Telecom), and Wegener.
In the United States, both DirecTV and Dish Network direct broadcast satellite systems use digital encryption standards for controlling access to programming. DirecTV uses VideoGuard, a system designed by NDS. DirecTV has been cracked in the past, which led to an abundance of cracked smartcards being available on the black market. However, a switch to a stronger form of smart card (the P4 card) wiped out DirectTV piracy soon after it was introduced. Since then, no public cracks have become available. Dish Network uses Nagravision (1 and 2) encryption.
In Canada, both Bell ExpressVu and StarChoice DBS systems use digital encryption standards. Bell ExpressVu, like Dish Network, uses Nagravision for encryption. StarChoice uses a DigiCipher 2-based system very similar to that of 4DTV large dish satellite systems.
[edit] Older television encryption systems
Oak Orion was originally used for analog satellite television pay channel access in Canada. Was innovative for its time as it used digital audio. It has been completely replaced by digital encryption technologies. Was used by Sky Channel in Europe between the years 1982 and 1987.
Leitch Viewguard is an analog encryption standard used primarily by broadcast TV networks in the North America. Its method of scrambling is by re-ordering the lines of video (Line Shuffle), but leaves the audio intact and listenable. Terrestrial broadcast CATV systems in Northern Canada used this conditional access system for many years. It is only occasionally used today on some satellite circuits because of its similarity to D2-MAC and B-MAC.
B-MAC has not been used for DTH applications since Primestar switched to an all-digital delivery system in the mid-1990s.
Analogue cut and rotate scrambling system with smartcard based conditional access system, used in 1990s by several European satellite broadcasters, mainly British Sky Broadcasting. Was also used by Sky New Zealand (Sky-NZ).No audio scrambling.
- RITC Discret 1
System based on horizontal line delay and audio scrambling. Each line of video was pseudorandomly delayed by either 0 nS, 902 nS or 1804 nS.(Line Delay) First used in 1984 by French channel Canal Plus, it was widely compromised after the December 1984 issue of "Radio Plans" magazine printed decoder plans.
- SATPAC
Used by European channel FilmNet the SATPAC system interfered with the horizontal and vertical synchronisation signals and transmitted a signal containing synchronisation and authorisation data on a separate subcarrier. The system was first used in September 1986 and saw many upgrades as it was easily compromised by pirates. By September 1992, FilmNet changed to D2-MAC EuroCrypt.
- Telease MAAST / Sat-Tel SAVE
Added an interfering sine wave of a frequency (circa 93.750 KHz) to the video signal. This interfering signal was approximately six times the frequency of the horizontal refresh. It had an optional sound scrambling using Spectrum Inversion. Used in the UK by BBC for its world service broadcasts and by the now defunct UK movie channel "Premiere".
- Payview III
Used by German/Swiss channel Teleclub in the early 1990s, this system employed various methods such as video inversion, modification of synchronisation signals and a pseudo line delay effect.
- D2-MAC EuroCrypt
Conditional Access system using the D2-MAC standard. Developed mainly by France Telecom, the system was smartcard based. The encryption algorithm in the smartcard was based on DES.
