Security and efficiency are two key factors that affect whether a certificateless authenticated group key agreement protocol can be applied in Ad Hoc networks. To improve the security and efficiency of key management problems in securing group communications of Ad Hoc networks, a certificateless group key agreement protocol was proposed, which utilizes Elliptic Curves Cryptography (ECC) multiplication to achieve the group key agreement and authentication without pairing. Meanwhile, the Huffman key tree was used to optimize the rounds of key negotiation, decreasing the computation and communication overheads and improving the group key negotiation efficiency. Security analysis and performance comparison demonstrate that the proposed protocol has good efficiency and security in group key negotiation, which can satisfy group key establishment and rekeying for dynamic groups with restrained resources.

Android uses the permission-based access control method to protect the system resources, which has the problem of rough management. At the same time, some malicious applications can secretly access resources in a privacy scenario without the user's permission, bringing certain threats to user privacy and system resources. Based on the original permission management and control and with the introduction of Access Control List (ACL) mechanism, an Android fine-grained permission management and control system based on ACL mechanism was designed and implemented. The proposed system can dynamically set the access rights of the applications according to the user's policy, avoiding the access of malicious codes to protect system resources. Tests of compatibility and effectiveness show that the system provides a stable environment for applications.