Bidirectional Private Policy Matching Based on Additively Homomorphic Encryption Systems

In a open pervasive environment, we want to define trust model for many kinds of services. Thus, a mechanism which can create trust model for each service dynamically and use it securely is required. Automated Trust Negotiation (ATN) is a mechanism to establish mutual trust between service providers and users in an open network environment like the Internet. In this paper, we propose Bidirectional Private Policy Matching based on Additively Homomorphic Encryption Systems (BPPM/AHES) as an ATN negotiation protocol where uni-directional private policy matching based on additively homomorphic encryption systems is repeated. In this protocol, there is no disclosure of credentials before the negotiation succeeds. Because there is no unnecessary disclosure of policies except for policies which can be inferred the negotiation outcome, the amount of the unnecessary disclosure of policies decreases compared to existing protocols.