Multilevel Security Policy Model Combined with User Permission

Aiming at the problem that BLP model's access rule of "no write down" destroy data integrity,subject has most privilege and object holds constant security level,this paper presents a multilevel security policy model combined with user permission. In the model,trusted label is used in subject writing to protect object integrity. User permission solves the problem that subject privilege in BLP model and trusted label has more rights to steal data. By importing arbitration for system administrator,confidential label and trusted label for the modified objects is adjusted dynamically. Theory analysis indicates that the model can assure system security.