Research On Group Key Management Technology Of Multi-service Secure Multicast

A new multi-service multicast is springing up quickly. And it is to play a more and more important role in many areas such as HDTV, VoD and pay-per-viewed news broadcast service. For the sake of business and privacy, multicast content must be encrypted with a session key (SK), so as to assure that only legitimate ones can access it.It has been widely studied on single-service secure multicast. However there are quite difference between single-service secure multicast and multi-service one: a) multi-service secure multicast can provide several multicast service; b) multicast stream of each service is encrypted by different SK; c) each user can subscribe one or any services. This brings new challenges and pressures to group key management of multi-service secure multicast in the following issues:1. The complexity of group key distribution: the technology of key distribution affects the complexity of group rekeying, which is linear with size of addition or eviction of members, and all of number of rekeying, time cost and bandwidth cost are association with it.2. Cost of key storage: traditional technologies need to setup multicast groups for different services. A member who subscribes several services need join into different service group; as a result, the cost of key storage rises up doubly.3. Complexity of rekeying: former technologies need to renew different service groups respectively for applications of addition, eviction or service changing. They can't meet command of big dynamic multicast groups for the high cost of group rekeying. Research on efficient group key management for multi-service secure multicast is an urgent problem we should solve. To solve the above problems through assuring multicast secrecy in lowest complexity of group key distribution, this thesis addresses on group key management of multi-service secure multicast. The content of this thesis includes three issues: (1) technology of group key distribution based on minimum exact covering; (2) classification and integration of member group; (3) integrated management of multiple service groups. The works in this thesis has been supported by the Natural Science Foundation of China"Study on secure payments of electronic commerce"(No. 90104033).The contributions of this thesis include as follows:1) In order to reduce the complexity of group key distribution, technology of group key distribution based on minimum exact covering (MEC) is studied on this thesis. The minimum exact covering problem for group key distribution is put forward and studied, and two algorithms based on it are proposed to achieve fast distribution.2) In order to reduce the complexity of key storage and rekeying, a model of group management based on multi-dimension hierarchical tree (MHT) is presented. The model consists of three levels, namely: data stream secure level, hierarchical access control level and user group secrecy level. It can group all sub-groups into a multi-dimensional hierarchical tree, so as to reduce key storage greatly.3) Integrating above two achievements, an efficient algorithm for multi-service multicast is presented to solve the problem of group key management, which can meet the comments of scalability and robust.