Trust Zone Model with the Mandatory Access Control Model

In order to protect internal networks of enterprises from any threats, a perimeter model has been widely used. Here, every access from subjects inside the perimeter is assumed to be trustworthy and the access is allowed without any conditions. Hence, a threat enters inside the perimeter once, the effect of the threat spreads inside the perimeter easily. In order to protect internal networks from any threats, a ZT (Zero Trust) model is proposed. Here, it is assumed that every access to an object is not trustworthy. Hence, every access is checked whether or not the access can be allowed to be performed. Although the ZT model makes the system secure, it is not easy to change the present system model to the ZT model for many enterprises. In order to make the shift to the ZT model smooth, a TZ (Trust Zone) model is proposed. In the TZ model, every object belongs to a trust zone. The authorization process in the TZ model is more simple than the ZT model. Hence, the TZ model is known as an intermediate stage of the shift to the ZT model. However, it is not discussed how to prevent illegal information flow in the TZ model. In this paper, we newly propose a TZMAC (Trust Zone with Mandatory Access Control) model to prevent illegal information flow in the TZ model. Here, the trust zones in the TZ model are used as the security classes of the MAC (Mandatory Access Control) model. Each subject also belongs to a security class. If a subject accesses an object, the relation between the security classes of the subject and object is also checked. Since the accesses implying illegal information flow are not allowed to be performed, the system is made more secure.