Abstract: Most of existing access control models have been studied in centralized and static environment，and they don’t meet the requirements of some collaborative environments in which the subjects and objects vary dynamically.In this paper，the trust mechanism of P2P network is analyzed，a scheme is introduced for calculating the peer’s trust value by considering the transaction context factors，and a dynamic trust-based access control model is developed to address to the access security in P2P environments.This scheme constructs access control system based on trust degree of P2P members，and dynamically manages the access permission according to the trust values of subjects and objects.The concrete strategies are given for access control of different access services in P2P applications.

Key words: access control, P2P system, trust, access permission

摘要： 多数访问控制模型都针对集中式的和相对静态的系统，不适宜主客体动态变化的协同环境。文章分析了P2P系统的信任机制，介绍了考虑事务上下文因素的信任度计算方法，提出一种基于信任的动态访问控制模型dTBAC，以解决P2P环境的安全问题。该模型从网络个体信任的角度建立访问控制体制，根据主客体的信任值对访问权限进行动态管理。文章还就P2P应用中不同的访问服务类型给出了具体的访问授权策略。

关键词: 访问控制, P2P系统, 信任, 访问权限