Research On Content Protection Of Digital Television

With the development of digital technique, multimedia technique and network technique, broadcasting television is faced with a new opportunity. On the digital broadcasting television network, we could realize not only the traditional television service, but also a lot of new additional services, such as VOD, PPV, online games and data broadcasting. For implementing of these services, one key question is selecting a secure, open content protection system.We studied the key management of Conditional Access system and DRM solution fitting mobile TV on the basis of two major techniques of content protection——Digital Rights Management and Conditional Access, including the following aspects:First, we improved Lee's subscriber grouping scheme based on the three-level architecture of keys in DVB CAS and the characteristics of IPTV. This scheme would be more fitable to group the subscribers in the reality. Besides we adopted a new selective IP packets encryption scheme according to the reality of the TCP/IP network and feature of ECM and EMM. The corresponding analysis also was given which proved that our scheme could group the subscribers dynamicly and reduce the demand of amount of data needed to be transmitted and the amount of calculation during the encryption and decryption.Second, we proposed an improved key distribution scheme based on channel grouping according to Jiang's key distribution algorithm. Our scheme bases on the complexity of factoring large integer and realizes the partial order among the keys between upper level and lower level. We also give the specific solution to protecting the group key and realize the dynamic management function. The comparison shows that there are only small amounts of data need to be transmitted when subscribers frequently subscribe and delete services like in PPV service, by this way we could effectively reduce the amount of EMM.Third, OMA DRM 2.0 standard does not specify a complete DRM infrastructure which should include billing functionality, so we proposed a new architechure with a filling module by inserting a trusty third party between Rights Issuer and mobile device which could extract the subscribers'billing information and charge the subscribers together with the phone bill. Besides, we archived an efficient key distribution protocol by replacing the existing public key encryption scheme with a symmetric key encryption scheme which could make the scheme more competitive than the existing one.