Log in
Register
Menu
Log in
Register
Home
What's new
Latest activity
Authors
Forums
New posts
Search forums
What's new
New posts
Latest activity
Members
Current visitors
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Satellite TV receivers & systems support forums
Satellite Systems - What to Buy - What to install
How is it possible to scramble channels with multiple encryptions?
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="kalamar" data-source="post: 51486"><p>A conditional access system comprises a combination of scrambling and encryption to prevent unauthorised reception. Encryption is the process of protecting the secret keys that are transmitted with a scrambled signal to enable the descrambler to work. The scrambler key, called the control word must, of course, be sent to the receiver in encrypted form as an entitlement 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 an entitlement management message (EMM). This layered approach is fundamental to all proprietry CA systems in use today.</p><p></p><p></p><p></p><p>The control word is changed at intervals of 10 seconds, typically. The ECM, sometimes called the multi-session key, is changed at perhaps monthly intervals to avoid hackers gaining ground.</p><p></p><p></p><p></p><p>2. The Development of Standards</p><p>Way back in 1988, an attempt was made by France Telecom and others to develop a standard encryption system for europe. The result was Eurocrypt. Unfortunately, in its early manifestations it was not particularly secure and multiplex operators went their own way. Thus, in 1992 when the DVB started their consideration of CA systems, they recognised that the time had passed when a single standard could realistically be agreed and settled for the still difficult task of seeking a common framework within which different systems could exist and compete.</p><p></p><p>They therefore defined an interface structure, the Common Interface, which would allow the set top box to receive signals from several service providers operating different CA systems. The common interface module contains the CA system, rather than the STB itself, if necessary allowing multiple modules to be plugged into a single STB. However, there were serious objections to the common interface from many CA suppliers on the grounds that the extra cost would be unacceptable so the DVB stopped short of mandating the Common Interface, instead recommending it, along with simulcrypt. The Common Interface was endorsed by CENELEC in May 1996 and the DTG unanimously adopted its use for digital terrestrial transmission in the UK at its meeting on 13th May 1996.</p><p></p><p>Since then the European Commission has required the use of a common interface mechanism for all integrated tv sets (excluding STBs which may employ embedded CA systems) and this is likely to be the eventual outcome - an embedded CA system in subsidised STBs and Common Interface slots in all other devices. It should be noted that the Common Interface connector allows plug-in cards for other functions besides CA; for example it is proposed to provide audio description for the visually impaired using a common interface card.</p><p></p><p>Simulcrypt allows two CA systems to work side by side, transmitting separate entitlement messages to two separate types of STU, with different CA systems. It also gives the multiplex provider the opportunity to increase his viewer base by cooperating with other multiplex operators. Technical simulcrypt is the same thing but within a single multiplex, thus giving the multiplex operator some leverage with the CA suppliers.</p><p></p><p>The simulcrypt system is shown diagramatically below. Note that it requires cooperation between CA suppliers - something which does not come naturally!</p><p></p><p></p><p></p><p>If a viewer wishes to receive services from different providers who do not simulcrypt each other's ECMs, the only option is to acquire separate decryption for each CA system. The Common Interface enables a multicrypt environment, allowing an additional CA system to be added as a module. This is not quite the panacea it seems, since it still requires the CA vendor to develop the module, something he is unlikely to be keen on if his best customer doesn't approve. In practice, the possibility of multicrypt encourages the parties to conclude a simulcrypt agreement.</p></blockquote><p></p>
[QUOTE="kalamar, post: 51486"] A conditional access system comprises a combination of scrambling and encryption to prevent unauthorised reception. Encryption is the process of protecting the secret keys that are transmitted with a scrambled signal to enable the descrambler to work. The scrambler key, called the control word must, of course, be sent to the receiver in encrypted form as an entitlement 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 an entitlement management message (EMM). This layered approach is fundamental to all proprietry CA systems in use today. The control word is changed at intervals of 10 seconds, typically. The ECM, sometimes called the multi-session key, is changed at perhaps monthly intervals to avoid hackers gaining ground. 2. The Development of Standards Way back in 1988, an attempt was made by France Telecom and others to develop a standard encryption system for europe. The result was Eurocrypt. Unfortunately, in its early manifestations it was not particularly secure and multiplex operators went their own way. Thus, in 1992 when the DVB started their consideration of CA systems, they recognised that the time had passed when a single standard could realistically be agreed and settled for the still difficult task of seeking a common framework within which different systems could exist and compete. They therefore defined an interface structure, the Common Interface, which would allow the set top box to receive signals from several service providers operating different CA systems. The common interface module contains the CA system, rather than the STB itself, if necessary allowing multiple modules to be plugged into a single STB. However, there were serious objections to the common interface from many CA suppliers on the grounds that the extra cost would be unacceptable so the DVB stopped short of mandating the Common Interface, instead recommending it, along with simulcrypt. The Common Interface was endorsed by CENELEC in May 1996 and the DTG unanimously adopted its use for digital terrestrial transmission in the UK at its meeting on 13th May 1996. Since then the European Commission has required the use of a common interface mechanism for all integrated tv sets (excluding STBs which may employ embedded CA systems) and this is likely to be the eventual outcome - an embedded CA system in subsidised STBs and Common Interface slots in all other devices. It should be noted that the Common Interface connector allows plug-in cards for other functions besides CA; for example it is proposed to provide audio description for the visually impaired using a common interface card. Simulcrypt allows two CA systems to work side by side, transmitting separate entitlement messages to two separate types of STU, with different CA systems. It also gives the multiplex provider the opportunity to increase his viewer base by cooperating with other multiplex operators. Technical simulcrypt is the same thing but within a single multiplex, thus giving the multiplex operator some leverage with the CA suppliers. The simulcrypt system is shown diagramatically below. Note that it requires cooperation between CA suppliers - something which does not come naturally! If a viewer wishes to receive services from different providers who do not simulcrypt each other's ECMs, the only option is to acquire separate decryption for each CA system. The Common Interface enables a multicrypt environment, allowing an additional CA system to be added as a module. This is not quite the panacea it seems, since it still requires the CA vendor to develop the module, something he is unlikely to be keen on if his best customer doesn't approve. In practice, the possibility of multicrypt encourages the parties to conclude a simulcrypt agreement. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Satellite TV receivers & systems support forums
Satellite Systems - What to Buy - What to install
How is it possible to scramble channels with multiple encryptions?
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
Accept
Learn more…
Top