Television encryption

Television encryption, often referred to as "scrambling", is encryption used to control access to pay television services, usually cable or satellite television services.


Pay television exists to make revenue from subscribers, and sometimes those subscribers do not pay. The prevention of piracy on cable and satellite networks has been one of the main factors in the development of Pay TV encryption systems.

The early cable-based Pay TV networks used no security. This led to problems with people connecting to the network without paying. 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 techniques 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 technology 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 a scrambled service in 1984. It was also claimed that it was an unbreakable system. Unfortunately for that company, 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 to the pirates.

Conditional access

Cable and early satellite television encryption

Scrambled cable channel
A scrambled channel featuring a Paramount Pictures film (Possibly VideoCipher II or Oak ORION. Horizontal and vertical synch signal have been replaced by digital data with the effect that the picture is not properly displayed on the TV screen.[1][2][3] ) as viewed without a decoder.

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 television 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 methods were used to control access to programming. In some of these systems, the necessary sync signal was on a separate subcarrier though sometimes the sync polarity is simply inverted, in which case, if used in conjunction with PAL, a SECAM L TV with a cable tuner can be used to partially descramble the signal though only in black and white and with inverted luminance and thus a multi standard TV which supports PAL L is preferred to decode the color as well. This, however will lead to a part of the video signal being received as audio as well and thus another TV with preferably no auto mute should be used for audio decoding. Analog set-top boxes have largely been replaced by digital set-top boxes that can directly control access to programming as well as digitally decrypt 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)

Digital cable and satellite television encryption

DigiCipher 2 is General Instrument's proprietary video distribution system. DigiCipher 2 is based upon MPEG-2. A 4DTV satellite receiver is required to decode DigiCipher 2 channels. In North America, most digital cable programming is accessed with DigiCipher 2-based set-top boxes. DigiCipher 2 may also be referred to as DCII.

PowerVu is another popular digital encryption technology used for non-residential usage. PowerVu was developed by Scientific Atlanta. Other commercial digital encryption systems are, Nagravision (by Kudelski), Viaccess (by France Telecom), and Wegener.

In the US, 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 (2 and 3) encryption.

In Canada, both Bell TV and Shaw Direct DBS systems use digital encryption standards. Bell TV, like Dish Network, uses Nagravision for encryption. Shaw Direct uses a DigiCipher 2-based system very similar to that of earlier 4DTV large dish satellite systems.

Older television encryption systems

Zenith Phonevision

Zenith Electronics developed an encryption scheme for their Phonevision system of the 1950s and 1960s.


Oak Orion was originally used for analog satellite television pay channel access in Canada. It was innovative for its time as it used digital audio. It has been completely replaced by digital encryption technologies. Oak Orion was used by Sky Channel in Europe between the years 1982 and 1987. Oak developed related encryption systems for cable TV and broadcast pay TV services such as ONTV.

Leitch Technology

Leitch Viewguard is an analog encryption standard used primarily by broadcast TV networks in North America. Its method of scrambling is by re-ordering the lines of video (Line Shuffle), but leaves the audio intact. 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.

There was also a version that encrypted the audio using a digital audio stream in the horizontal blanking interval like the VCII system. One US network used that for its affiliate feeds and would turn off the analog sub carriers on the satellite feed.


B-MAC has not been used for DTH applications since PrimeStar switched to an all-digital delivery system in the mid-1990s.


VideoCrypt was an analogue cut and rotate scrambling system with a smartcard based conditional access system. It was used in the 1990s by several European satellite broadcasters, mainly British Sky Broadcasting. It was also used by Sky New Zealand (Sky-NZ). One version of Videocrypt (VideoCrypt-S) had the capability of scrambling sound. A soft encryption option was also available where the encrypted video could be transmitted with a fixed key and any VideoCrypt decoder could decode it.

RITC Discret 1

RITC Discret 1 is a system based on horizontal video line delay and audio scrambling. The start point of each line of video was pseudorandomly delayed by either 0 ns, 902 ns, or 1804 ns. 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.


Used by European channel FilmNet, the SATPAC 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. It was one of the first smart card based systems to be compromised.

Nagravision analogue system

An older Nagravision system for scrambling analogue satellite and terrestrial television programs was used in the 1990s, for example by the German pay-TV broadcaster Premiere. In this line-shuffling system, 32 lines of the PAL TV signal are temporarily stored in both the encoder and decoder and read out in permuted order under the control of a pseudorandom number generator. A smartcard security microcontroller (in a key-shaped package) decrypts data that is transmitted during the blanking intervals of the TV signal and extracts the random seed value needed for controlling the random number generation. The system also permitted the audio signal to be scrambled by inverting its spectrum at 12.8 kHz using a frequency mixer.

See also


  1. ^ Frank Baylin; Richard Maddox; John Mac Cormac (1993). World Satellite TV and Scrambling Methods: The Technicians Handbook, 3rd Edition. Baylin/Gale Productions. p. 196. ISBN 978-0-917893-19-3.
  2. ^ Rudolf F. Graf; William Sheets (1998). Video Scrambling & Descrambling: For Satellite & Cable TV. p. 100. ISBN 978-0-7506-9997-6.
  3. ^ John McCormac (1996-01-01). European Scrambling Systems: Circuits, Tactics and Techniques : The Black Book. Waterford University Press. pp. 2–78, 2–51, 3–19. ISBN 978-1-873556-22-1.

External links

Cable television piracy

Cable television piracy, a form of copyright infringement, is the act of obtaining unauthorized access to cable television services. In older analog cable systems, most cable channels were not encrypted and cable theft was often as easy as plugging a coaxial cable attached to the user's television into an apartment house cable distribution box (which often were unsecured without locks to prevent unauthorized access). In some rural areas nonsubscribers would even run long cables to distribution boxes on nearby utility poles. Set-top boxes were required with some systems, but these were generic, and often in an unknowing violation of contract, former customers would donate them to thrift stores for sale or retain them indefinitely in storage when they ended their subscription to the service rather than return them to the provider.

To prevent this, cable providers built stronger protection against theft into new digital cable systems which were deployed beginning in the mid-1990s as part of the changeover to the new digital HDTV standard, along with assessing a large fine for the entire cost of a set-top box if the customer didn't return it upon the termination of services. This has greatly reduced cable theft, although pirate decryption continued on some DVB-C systems which are based on the same compromised encryption schemes formerly used in satellite television broadcasting. Most cable companies have also issued new secured outside distribution boxes which require certain keys only given out to their installers to access, making theft via outside split line more difficult.

As of 2017, many cable providers have switched to digital-only systems which require mandatory use of either their approved set top boxes or an approved CableCARD device. In many cases, no analog channels are available, and if they are, are usually just the provider's paid programming, Emergency Alert System and barker channels, or merely a one-channel signal which lets a customer or installer know the signal is viewable on a television set. Channels and programming may also be available through digital media player devices such as the Roku or Apple TV (along with tablets and smartphones) via provider apps, which confirm subscriber eligibility through a private internal IP network and require an on-network connection to the provider (including disallowing connections to outside virtual private network services to emulate a home network connection elsewhere), making any piracy through that venue virtually impossible.

Common Interface

In Digital Video Broadcasting, the Common Interface (also called DVB-CI) is a technology which allows decryption of pay TV channels. Pay TV stations want to choose which encryption method to use. The Common Interface allows TV manufacturers to support many different pay TV stations, by allowing to plug in exchangeable conditional-access modules (CAM) for various encryption schemes.

The Common Interface is the connection between the TV tuner (TV or set-top box) and the module that decrypts the TV signal (CAM). This module, in turn, then accepts the pay-to-view subscriber card, which contains the access keys and permissions.

The host (TV or set-top box) 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. All Common Interface equipment must comply with the EN 50221-1997 standard. This is a defined standard that enables the addition of a CAM in a DTV receiver to adapt it to different kinds of cryptography. The EN 50221 specification allows many types of modules but only the CAM has found popularity because of the pay TV market. 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, thus increasing their choice of anti-piracy options.


Conax develops television encryption, conditional access and content security for digital television. Conax provide CAS technology to pay TV operators in 85 countries. The company has offices in Norway (headquarters), Russia, Germany, Brazil, the United States, Canada, Mexico, Indonesia, Philippines, Thailand, China, Singapore, and India, with a 24/7 Global Support Center in India.

Conax stems from Telenor Research Labs in the 1980s. It was incorporated as a separate company Conax AS in 1994.In March 2014, the company was sold by Telenor Group to Swiss-based Kudelski Group for NOK 1.5 billion.A few pay TV operators using Conax conditional access are Canal Digital (Norway), Malivision (Mali), StarTimes Media (SSA), Dish TV (India), K-Vision (Indonesia), Joyne Netherlands, Focus Sat (operated by UPC Romania), AKTA Telecom Romania, TVR Romania, Mindig TV Hungary, 4TV Myanmar, SitiCable India, Digicable India. Conax is also used by MNC Media's free to air channels (RCTI, MNCTV, GTV, and iNews) to encrypt some programs for satellitte transmissions for prevent illegal redistribution by unlicensed local cable operators or others third parties.

Conditional-access module

A conditional access module (CAM) is an electronic device, usually incorporating a slot for a smart card, which equips an Integrated Digital Television or set-top box with the appropriate hardware facility to view conditional access content that has been encrypted using a conditional access system. They are normally used with direct-broadcast satellite (DBS) services, although digital terrestrial pay TV suppliers also use CAMs. PC Card form factor is used as the Common Interface form of Conditional Access Modules for DVB broadcasts.

Some encryption systems for which CAMs are available are Logiways, Nagravision, Viaccess, Mediaguard, Irdeto, KeyFly, Verimatrix, Cryptoworks, Mascom, Safeview, Diablo CAM and Conax. NDS VideoGuard encryption, the preferred choice of Sky Digital can only be externally emulated by a Dragon brand CAM. The NDS CAM which the Sky viewing card ordinarily uses is built into the Sky Digibox thus not visible. Dragon and Matrix, two popular cams with satellite television enthusiasts are multicrypt meaning each is capable of handling more than one encryption system. Matrix CAMs can be upgraded via the PC Card port in a laptop personal computer whereas a Dragon cam update is done via separate programmer hardware.

The primary purpose of the CAM is to derive control words, which are short-term decryption keys for video. The effectiveness of a CAM depends on the tamper resistance of the hardware; if the hardware is broken, the functionality of the CAM can be emulated, enabling the content to be decrypted by non-subscribers. CAMs are normally removable so that they can be replaced after the hardware security is breached. Replacement of the CAMs in a system is called a card swap-out.

The standard format for a CAM is a PC card which takes a smart card to authenticate, although CAMs with the 'smart card' burnt into memory can be found. In addition, CAM emulators exist for many systems, either providing an interface to allow the use of more than one type of card, or a card not designed for that receiver.

Conditional access

Conditional access (abbreviated CA) or conditional access system (abbreviated CAS) 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.


In television encryption, Cryptoworks is a DVB conditional access system, developed by Philips CryptoTec but now belonging to Irdeto.

Cryptoworks is used by OSN, Digiturk, the BFBS satellite service, UPC Direct, ITV Partner the ORF, JSTV, and other pay TV or free-to-view systems; mainly in Europe. It is also used to encrypt some feeds to cable television head-ends.

2006, Cryptoworks was transferred to Irdeto.Other conditional access systems include Irdeto, VideoGuard, Nagravision, Mediaguard


In cryptography, encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot. Encryption does not itself prevent interference, but denies the intelligible content to a would-be interceptor. In an encryption scheme, the intended information or message, referred to as plaintext, is encrypted using an encryption algorithm – a cipher – generating ciphertext that can be read only if decrypted. For technical reasons, an encryption scheme usually uses a pseudo-random encryption key generated by an algorithm. It is in principle possible to decrypt the message without possessing the key, but, for a well-designed encryption scheme, considerable computational resources and skills are required. An authorized recipient can easily decrypt the message with the key provided by the originator to recipients but not to unauthorized users.

History of television

The invention of the television was the work of many individuals in the late 19th century and early 20th century. Individuals and corporations competed in various parts of the world to deliver a device that superseded previous technology. Many were compelled to capitalize on the invention and make profit, while some wanted to change the world through visual and audio communication technology.

Northern Access Network

Northern Access Network was a Canadian unlicensed television system which broadcast videotaped programming to remote Canadian communities in the late 1970s. Although shortlived and often in conflict with the Canadian Radio-television and Telecommunications Commission over its lack of a broadcast license, the service did have the effect of forcing Canada's major commercial television networks to add rebroadcast transmitters in a number of communities they had previously ignored.The service's operator, David Brough, told The Globe and Mail in 1978 that his ultimate goal was to operate five transmitters in each community: two general entertainment channels to rebroadcast content from CTV and Global, a French channel to rebroadcast content from TVA (and Radio-Canada, where that service was not already available), an educational programming service and a local community channel. In actual practice, only one station was actually set up in each community, which aired either English-only or English and French programming depending on local market needs.In the Globe interview, Brough clarified that his position was that he was simply using a different technological method to deliver a service legally and ethically no different from a cable television provider. The networks, however, viewed his methods as copyright infringement.

Oak Orion

The Oak Orion scrambling system was a form of television encryption developed by Oak Industries in the early 1980s.

It was mainly used for encrypting the satellite feeds of American and Canadian television services transmitted by Cancom via the Anik satellites, first on Anik B, and later on Anik D1 and Anik E2, beginning in 1982. Virtually all services uplinked by Cancom were encrypted via this method, with the exception of one channel, First Choice, which chose to use the Videocipher system adopted by U.S. programmers during the late 1980s-early 1990s. First Choice later switched to Orion.

This encryption system was discontinued by the mid-1990s in favor of digital delivery.

Pirate decryption

Pirate decryption most often refers to the decryption, or decoding, of pay TV or pay radio signals without permission from the original broadcaster. The term "pirate" in this case is used in the sense of copyright infringement and has little or nothing to do with sea piracy, nor with pirate radio, which involved the operation of a small broadcast radio station without lawfully obtaining a license to transmit. The MPAA and other groups which lobby in favour of intellectual property (specifically copyright and trademark) regulations have labelled such decryption as "signal theft" even though there is no direct tangible loss on the part of the original broadcaster, arguing that losing out on a potential chance to profit from a consumer's subscription fees counts as a loss of actual profit.

Satellite television

Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna commonly referred to as a satellite dish and a low-noise block downconverter.

A satellite receiver then decodes the desired television programme for viewing on a television set. Receivers can be external set-top boxes, or a built-in television tuner. Satellite television provides a wide range of channels and services. It is usually the only television available in many remote geographic areas without terrestrial television or cable television service.

Modern systems signals are relayed from a communications satellite on the Ku band frequencies (12–18 GHz) requiring only a small dish less than a meter in diameter. The first satellite TV systems were an obsolete type now known as television receive-only. These systems received weaker analog signals transmitted in the C-band (4–8 GHz) from FSS type satellites, requiring the use of large 2–3-meter dishes. Consequently, these systems were nicknamed "big dish" systems, and were more expensive and less popular.Early systems used analog signals, but modern ones use digital signals which allow transmission of the modern television standard high-definition television, due to the significantly improved spectral efficiency of digital broadcasting. As of 2018, Star One C2 from Brazil is the only remaining satellite broadcasting in analog signals, as well as one channel (C-SPAN) on AMC-11 from the United States.Different receivers are required for the two types. Some transmissions and channels are unencrypted and therefore free-to-air or free-to-view, while many other channels are transmitted with encryption (pay television), requiring the viewer to subscribe and pay a monthly fee to receive the programming.


In telecommunications, a scrambler is a device that transposes or inverts signals or otherwise encodes a message at the sender's side to make the message unintelligible at a receiver not equipped with an appropriately set descrambling device. Whereas encryption usually refers to operations carried out in the digital domain, scrambling usually refers to operations carried out in the analog domain. Scrambling is accomplished by the addition of components to the original signal or the changing of some important component of the original signal in order to make extraction of the original signal difficult. Examples of the latter might include removing or changing vertical or horizontal sync pulses in television signals; televisions will not be able to display a picture from such a signal. Some modern scramblers are actually encryption devices, the name remaining due to the similarities in use, as opposed to internal operation.

In telecommunications and recording, a scrambler (also referred to as a randomizer) is a device that manipulates a data stream before transmitting. The manipulations are reversed by a descrambler at the receiving side. Scrambling is widely used in satellite, radio relay communications and PSTN modems. A scrambler can be placed just before a FEC coder, or it can be placed after the FEC, just before the modulation or line code. A scrambler in this context has nothing to do with encrypting, as the intent is not to render the message unintelligible, but to give the transmitted data useful engineering properties.

A scrambler replaces sequences (referred to as whitening sequences) into other sequences without removing undesirable sequences, and as a result it changes the probability of occurrence of vexatious sequences. Clearly it is not foolproof as there are input sequences that yield all-zeros, all-ones, or other undesirable periodic output sequences. A scrambler is therefore not a good substitute for a line code, which, through a coding step, removes unwanted sequences.


VideoCrypt is a cryptographic, smartcard-based conditional access television encryption system that scrambles analogue pay-TV signals. It was introduced in 1989 by News Datacom and was used initially by Sky TV and subsequently by several other broadcasters on SES' Astra satellites at 19.2° east.


VideoCipher is a brand name of analog scrambling and de-scrambling equipment for cable and satellite television invented primarily to enforce Television receive-only (TVRO) satellite equipment to only receive TV programming on a subscription basis.The second version of Videocipher, Videocipher II, was the primary encryption scheme used by major cable TV programmers to prevent TVRO owners from receiving free terrestrial television programming. It was especially notable due to the widespread compromise of its encryption scheme.

Broadcast encryption and digital rights management
Conditional access
Smart cards and encryption
Digital video disc
Data security
Analogue broadcast encoding

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