Hierarchical access control to ensure multiple levels of access privilege for group members is required in many environments, such as hierarchically managed organizations and multimedia applications. In this paper, to efficiently and effectively achieve this goal, we propose a distributed key management scheme whereby each SG (Service Group) maintains an SG server. This server is utilized to manage the key tree and provide the related session keys for all the users in this SG. Compared with the already existing method employing an integrated key graph to the hierarchical access control problem, there is no complex merging key tree algorithm needed in the proposed scheme, and thus the communication overhead can be greatly reduced. Also the trust and communication burden on one centralized server, KDC (Key Distribution Center), is scattered, and thus better scalability when the number of users increases can be achieved.
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