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Griffin CAS overview

Griffin CAS is a SimulCrypt DVB Conditional Access System from Nucleus Systems, Ltd. It comprises of a PC/Linux system running the Griffin CAS Server software, and smart-cards for use in the receiving Set-Top-Boxes (STBs).

At the head-end side, DVB stream in clear form enters a standalone SimulCrypt Scrambler, usually through standard ASI interface. Using the Common Scrambling Algorithm (CSA) and a random Crypto Word (CW), the SimulCrypt Scrambler does the bulk of encryption. This is the heart of all SimulCrypt conditional access systems. CW is sent to the CAS, which by turn encrypts it in a proprietary manner and returns Entitlement Control Message (ECM) for injecting into the output stream. CW is randomly generated in the Scrambler periodically, with Crypto Period of 10 seconds being common. Based on subscription and other information from a Subscriber Management System (SMS), CAS generates proprietary Entitlement Management Messages (EMMs) which are injected by the Scrambler in the output stream, too. Some additional DVB-SI tables are modified and/or generated by the Scrambler.

Griffin CAS Server provides ECM Generator (ECMG) and EMM Generator (EMMG) for every stream, as well as interface to the SMS.

Once the scrambled signal is received in the STB, the relevant ECMs and EMMs are sent to a Griffin smart-card. Depending on subscription and other criteria, CW and/or user data are returned to the STB, where the bulk of decryption for the entitled period is carried out by a hardware CSA descrambler.
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