Privacy-Preserving Interest-Casting in Opportunistic Networks

Message forwarding is a fundamental brick to spread information among users in opportunistic networks. In this paper, we consider the recently proposed interest-casting networking primitive for opportunistic networks, according to which a packet generated by a sender should be delivered to all users in the network ? potentially unknown to the sender ? sharing similar interests. However, the current implementation of interest-casting assume users exchange their interest profiles to take forwarding decisions, thus revealing very sensitive in- formation to strangers. In this work, we approach for the first time the problem of designing an interest-casting protocol while not revealing sensitive information during the forwarding and message delivery process. In particular, we present a privacy- preserving mechanism based on the well-known Millionaires? problem allowing users to discover whether they have simi- lar interests without disclosing private information. Based on this mechanism, we propose four different privacy-preserving forwarding protocols to realise interest-casting in opportunistic networks, and we compare their performance on a real-world mobility trace