Cisco Rfgw1d Manual
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Secure License Transfer 78-4025112-01 Rev H0 167 Result: The following email will be sent with the generated token. Note: The case is closed and you will now be able to use this license for another device. Refer to Obtaining a License File (on page 157).
78-4025112-01 Rev H0 169 Introduction This chapter describes how to integrate the RFGW-1 into scrambling applications. 13 Chapter 13 Encryption and Scrambling In This Chapter Introduction ......................................................................................... 170 Scrambling, Control Word, and Cryptoperiod ............................... 171 Access Criteria and Access Rights .................................................... 172 Entitlement Control Messages .......................................................... 173 Event Information Scheduler ............................................................ 174 Scrambling Levels ............................................................................... 175 Simulcrypt Scrambling ....................................................................... 177 Timing Parameters.............................................................................. 178 Steps To Take ....................................................................................... 180
Chapter 13 Encryption and Scrambling 170 78-4025112-01 Rev H0 Introduction The RF Gateway 1 is provided with a DVB Simulcrypt compliant scrambler designed to meet DVB Simulcrypt Conditional Access (CA) specifications ETSI TS 103 197. There are many CA Systems in use and the goal of the RF Gateway 1 is to integrate the devices in as many CA Systems as possible. To achieve this, a common set of protocols and interfaces between scramblers and CA Systems is required. The RF Gateway 1 scrambler works on a license basis. For more information concerning licenses, refer to Chapter 12: Licensing (see Licensing on page 155).
Scrambling, Control Word, and Cryptoperiod 78-4025112-01 Rev H0 171 Scrambling, Control Word, and Cryptoperiod At the transmission site of a CA System, services multiplexed into a Transport Stream can be scrambled using a DVB common scrambling algorithm with a scrambling/descrambling key called Control Word (CW). At the receiver site, the scrambled services can be descrambled by an appropriate descrambling algorithm using the same CW. To increase the security of a CA System, the CW used to scramble and descramble services changes periodically (typically every 10 seconds). The duration of scrambling by one CW is called Crypto Period. CWs, typically 64 bits long, are generated by a Control Word Generator (CWG) and requested by the Simulcrypt Synchronizer (SCS). CWs cannot be delivered from the transmitter to the receiver site in the clear. They need to be encrypted. The algorithm used to encrypt the CW is unique to each CA System and implemented in a secure device of the descrambler and uses the smart card of the customer’s Conditional Access Module (CAM).
Chapter 13 Encryption and Scrambling 172 78-4025112-01 Rev H0 Access Criteria and Access Rights When a subscriber is only interested in particular services, i.e. sports and nature, he only wants to pay for those services. Unpaid services must remain unintelligible. Therefore, two parameters are defined, Access Criteria (AC) and Access Rights. Access Criteria is vendor specified information and specifies service-related criteria applied to a package of services or elementary streams. These subscriptions (also called theme or product) are encapsulated into Entitlement Control Messages (ECMs). Refer to Entitlement Control Messages (on page 173). Access Rights are stored on the smart card of the descrambler and determines which services the subscriber can access. These Access Rights are periodically reconfirmed using Entitlement Management Messages (EMMs). When Access Rights for a particular subscriber are changed, EMMs are sent to the descrambler with the new Access Rights. Example: AC 1 subscription = Football ECM1 AC 2 subscription = Tennis ECM2 AC 3 subscription = Golf ECM3 A subscriber pays to view football and golf programs. His set top box receives all ECM packets that contain the appropriate CWs. The set top box also receives EMM packets that contain Access Rights for this box. These rights are compared with the AC and the set top box is only allowed to decipher the ciphered CWs of the ECMs for which the subscriber has Access Rights (ECM1 and ECM3).
Entitlement Control Messages 78-4025112-01 Rev H0 173 Entitlement Control Messages The SCS triggered from the EIS to start a CA event will get every Crypto Period a CW for this event from the CWG. For more information, refer to Event Information Scheduler (on page 174). The SCS extracts the AC from the Scrambling Control Group (SCG) information received from the EIS. The synchronizer sends this AC together with the CW for the corresponding Crypto Period to the Entitlement Control Message Generator (ECMG). The ECMG encrypts both the AC and the CW using a particular cryptographic algorithm with a specific Service Key. This encrypted data is encapsulated into an ECM and sent to the SCS. Before the first Crypto Period for this event begins, the SCS starts sending ECMs for this event to the multiplexer (typically every 200 msec). This start time is necessary to give the descrambler time to decrypt the encrypted CW and AC. The multiplexer multiplexes this stream of ECMs with the outgoing Transport Stream. When the event begins, the SCS sends the CW to the scrambler, which starts scrambling the service(s) associated with this event. Before the end of the Crypto Period, the SCS requests a new CW from the CWG, then sends it together with the AC to the ECMG, and receives a new ECM for this event from the ECMG. This new generated ECM is multiplexed in the outgoing Transport Stream. When the Crypto Period is ended, the new CW is sent to the scrambler, which starts scrambling the service(s) using the new CW. This occurs for every Crypto Period until the end of the event.
Chapter 13 Encryption and Scrambling 174 78-4025112-01 Rev H0 Event Information Scheduler The EIS is the functional unit in the CA System that holds the schedule, configuration, and other information required for the complete CA system. To start a scrambling event, the EIS provides the SCS with a SCG provisioning message. The message contains a list of services and/or elementary streams that must be scrambled at the same time with the same CW and a list with ECM groups for which ECMs must be generated. An ECM group contains the necessary information, like Super_Cas_ID, ECM_ID, and AC, to bind an ECM stream to a CA provider. To stop a scrambling event, the EIS sends a SCG provisioning message update to the SCS. The ECM group for the event of which scrambling must be stopped is removed from the SCG provisioning message. The following illustration shows a SCG provisioning message.
Scrambling Levels 78-4025112-01 Rev H0 175 Scrambling Levels Scrambling can be done on an elementary stream level or service level. The following list describes these scrambling levels. Elementary Stream Level Scrambling Each component of a service may be scrambled by a separate CW. For example, video and audio may be scrambled with a separate CW. This is useful in multilingual systems where a premium is charged for a second audio in a different language. In this case, each component or elementary stream is associated with its own stream of ECM messages. When scrambling at the elementary stream level, all elementary streams within the service are scrambled using different CWs. One ECM is required for each elementary stream. The CA descriptors are inserted after each elementary stream within the Program Map Table (PMT).
Chapter 13 Encryption and Scrambling 176 78-4025112-01 Rev H0 Service Level Scrambling The alternative to elementary stream level scrambling is to scramble all components that make up a service with the same CW. In this case, there is only one stream of ECM messages associated with the service as a whole. When scrambling at the service level, all elementary streams within the service are scrambled using the same CW. Only one ECM is required for each service. The CA descriptor is inserted near the top of the PMT. Note: Elementary stream level scrambling and service level scrambling can be mixed within the scrambler but not within the same service.