A fine-grained access control scheme based on Attribute-Based Encryption (ABE) was proposed to satisfy the demands for the protection of personal privacy in social network. The scheme realized the description for different granularity of members in social network through the setting of the property, which is the basis for the fine-grained encryption and access control. In particular, a proxy server was introduced to judge the relationship between the unauthorized members and authorized members. If the unauthorized members were judged to have the access rights, the key generation center would generate private keys for them based on ABE. The scheme achieved the transitivity of the access rights. Compared with other privacy protection methods based on access control or encryption technique, the proposed scheme combined access control with encryption and realized encryption and fine-grained access control at the same time.

Synthesis problem of Variable Structure Control (VSC) for mismatched uncertain discrete-time systems with internal parameter perturbation and external disturbance was researched. The ideal reaching law with dynamic disturbance compensator of mismatched uncertain discretetime systems was designed to eliminate the restriction of the system uncertainty bounded and the satisfaction of matching conditions compared with VSC by conventional reaching law. Discrete variable structure controller was designed by applying this type of reaching law, which not only guaranteed the system to reach the switching surface in finite time and decreased the system chattering effectively, but also reduced the region of the switching belt and enhanced the dynamic quality of the control system. The simulation results illustrate the feasibility and validity of the proposed approach.