Access control research on data security in Cloud computing

Based on role-based access control, the conception of Hierarchical role is proposed. For the dynamics of Cloud computing environment, we divided the trusted level of the users and updated the trusted value of the users in real time. Then we allocated the corresponding role according to the trusted value. In the traditional access control model, system´s security control strength was fixed. Once the user´s role was determined, the corresponding permissions were fixed. In this paper, we adjusted the security control strength at real-time congestion level of the system. With the control of different security strength, the same role had different activated permissions. Thus we solved the problem of the protection of privacy of users´ permissions.