D-Card: A distributed mobile phone based system for relaying verified friendships

Cyber-physical networking systems (CPNSs) closely bridge cyberspace and the physical world. Cyberspace includes not only the Internet, but also telephone networks and short-range communications. CPNSs arise in many application domains, including social networking. Social CPNSs connect people embodied in the physical world with cyber social networking services to facilitate social interactions, including friendship formation. These services can be characterized by their dependence on Internet connections to operate. An important class of social CPNSs are mobile phone based ones. However, there is a lack of friendship verification in mobile phone based social CPNSs that allow miscreants to masquerade as friends. In this paper, we present D-Card, a mobile phone based social CPNS that provides friendship verification. D-Card provides an electronic name card that encodes relationship information for a person with his contact information. The name card includes a public key and digital signature. Comparing this public key with one from a trusted source enables identity verification. D-Card leverages a Bluetooth SDP toolkit to exchange information without requiring connection establishment. D-Card is a purely distributed CPNS that requires no Internet access or infrastructure. We implement the D-Card CPNS in Java ME and Bluetooth. Our experiments with real-world mobile phones illustrate its potential for friendship verification in mobile phone based social CPNSs. To the best of our knowledge, D-Card is the first such CPNS designed for this purpose.