Abstract: In the Ubiquitous Computing Environment the user's contextual conditions of satisfaction, the user's level of trust and the permission's level of security risk arc fuzziness. Many of the existing access control model do not support for the inference of fuzzy information. This paper presented a fuzzy role-based access control model(FRBAC)，the roles assigned to users(UA) and role to the permissions assigned(PA) are divided into two parts in the FRABC model, the user can activate the role by contextual conditions of satisfaction, the user's level of trust, as well as the possible security risks of activating the role. This authorization process is completed through the fuzzy reasoning.FRBAC model achieves dynamic fuzzy authorization and automatic distribution of user roles, it simplifies the security management of the RBAC model. Finally, the paper gave the architecture of the model to achieve and the related fuzzy authorized reasoning algorithm.

Key words: Ubiquitous computing, Access control, Fuzzy reasoning, Authorization control