Abstract: The mechanism of constraint in NIST standard of role-based access control (RBAC) is analyzed. To resolve the problem of shortages of constraints in the authorization process and accessing objects process, a novel RBAC model with enhanced constraints is proposed by extending the constraints and mapping true-life operation that has constrainted capability into RBAC model. The formalization definitions of the new model are presented and its security analyzed.

Key words: constraint, permission , rose-base access control (RBAC)