Noob Guide to Encryption

**intelliGEORGE** · 16-11-08, 10:59 PM

Encryption of Pay TV relies on two mechanisms.

Scrambling or Encryption of the audio and video and secondly, management of commercial entitlements which have to be transmitted as secured messages to the satellite decoder box.

I have found encryption can easily be applied to a digital bitstream, all bits are encrypted by using a block cipher like DES. Scrambling is used for analogue broadcasting.

Using the scrambling method, the synchronisation signals are suppressed and separately transmitted in an encrypted form. Sometimes, the audio signal is converted to a digital signal and encrypted. This digital encrypted audio signal can be embedded in the video signal.

The data is encrypted using a control word or key. The key will change periodically. To send the new keys to the decoder ECM's (Entitlement Control Messages) and EMM's (Entitlement Management Messages) are used. These messages have a digital signature field which ensures the integrity of the message e.g. a HASH-code. This prevents users from modifying the context of the message.

ECM's are transmitted together with the encrypted signal. An ECM consists of three fields. The first field contains the access parameters. These parameters define if/what access to the program is allowed. The second field contains the control word in encrypted form and the last field contains a data integrity check.

EMM's on the other hand usually consist of four fields. EMM's start with an address field to select an individual decoder box. The second field contains the entitlement for the user. The third field contains the service keys in encrypted form and the last field contains a data integrity check.

To be sure that an EMM is received by the user, there is no other way than to repeat the message. EMM's are therefore organised in cycles for broadcasting.

Hope this helps in understanding EMM's and ECM's and other acronyms thrown around the forum

**raygbmw1** · 16-11-08, 11:48 PM

Thanks IG!

That is very informative. I have just got into this hobby and I am slow learning the ins and outs. I am at the card sharing chapter and have started experimenting and reading information about it. Thanks again.

**Godzilla** · 16-11-08, 11:59 PM

Good work George, nicely explained there.

**allstarnz** · 17-11-08, 03:58 PM

cheers mate, good write up.

**madmee** · 18-11-08, 05:55 AM

Good work George
thanks alot for info

16-11-08, 10:59 PM	#1 (permalink)
intelliGEORGE Premium Member iTrader: (2) Join Date: Jan 2008 Location: Antarctica Posts: 1,283 Spent time on board: 3 Weeks, 1 Day and 12:34:31	Noob Guide to Encryption Encryption of Pay TV relies on two mechanisms. Scrambling or Encryption of the audio and video and secondly, management of commercial entitlements which have to be transmitted as secured messages to the satellite decoder box. I have found encryption can easily be applied to a digital bitstream, all bits are encrypted by using a block cipher like DES. Scrambling is used for analogue broadcasting. Using the scrambling method, the synchronisation signals are suppressed and separately transmitted in an encrypted form. Sometimes, the audio signal is converted to a digital signal and encrypted. This digital encrypted audio signal can be embedded in the video signal. The data is encrypted using a control word or key. The key will change periodically. To send the new keys to the decoder ECM's (Entitlement Control Messages) and EMM's (Entitlement Management Messages) are used. These messages have a digital signature field which ensures the integrity of the message e.g. a HASH-code. This prevents users from modifying the context of the message. ECM's are transmitted together with the encrypted signal. An ECM consists of three fields. The first field contains the access parameters. These parameters define if/what access to the program is allowed. The second field contains the control word in encrypted form and the last field contains a data integrity check. EMM's on the other hand usually consist of four fields. EMM's start with an address field to select an individual decoder box. The second field contains the entitlement for the user. The third field contains the service keys in encrypted form and the last field contains a data integrity check. To be sure that an EMM is received by the user, there is no other way than to repeat the message. EMM's are therefore organised in cycles for broadcasting. Hope this helps in understanding EMM's and ECM's and other acronyms thrown around the forum

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16-11-08, 11:48 PM	#2 (permalink)
raygbmw1 Premium Member iTrader: (0) Join Date: Mar 2008 Posts: 16 Spent time on board: 2 Days and 20:00:03	Thanks IG! That is very informative. I have just got into this hobby and I am slow learning the ins and outs. I am at the card sharing chapter and have started experimenting and reading information about it. Thanks again.

16-11-08, 11:59 PM	#3 (permalink)
Godzilla Killer HKS GTR iTrader: (6) Join Date: Jul 2008 Location: Melbourne Posts: 1,339 Spent time on board: 1 Month, 1 Week, 4 Days and 6:32:02	Good work George, nicely explained there.

17-11-08, 03:58 PM	#4 (permalink)
allstarnz Premium Member iTrader: (0) Join Date: Jan 2008 Posts: 484 Spent time on board: 1 Week, 4 Days and 10:54:39	cheers mate, good write up.

18-11-08, 05:55 AM	#5 (permalink)
madmee Junior Member iTrader: (0) Join Date: May 2008 Posts: 29 Spent time on board: 3 Days and 3:15:35	Good work George thanks alot for info

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