NAGUAL: A Novel Automated Trust Negotiation Model Based on Attribute Constraint

Automated trust negotiation (ATN) is a promising approach which establishes mutual trust between strangers through the iterative disclosure of digital credentials and access control policies of the two negotiation parties. Although many ATN systems are proposed, some issues still remain to be addressed: (1) their policy languages are coarse-grained; (2) they cannot generate all trust sequences and are short of the mechanism for evaluating trust sequences and selecting an optimal one. Therefore, we present a novel ATN, called NAGUAL. First, attribute constraint is introduced into NAGUAL in order to refine its policy language, which cannot only protect sensitive services and certificates effectively, but also enhance the flexibility of NAGUAL. Second, global access control policy is used to terminate impossible negotiation in advance, which can improve the negotiation efficiency of NAGUAL. Third, we describe the process of generating trust sequence using trust sequence search tree. Based on that tree, breadth-first can generate a trust sequence or all ones. Last, we evaluate trust sequences through disclosure cost and communication overhead for attribute certificates, which facilitates selecting an optimal one. This paper illuminates the usage of NAGUAL by using a typical example.