PIDGIN: privacy-preserving interest and content sharing in opportunistic networks.

Opportunistic networks have recently received considerable attention from both industry and researchers. These networks can be used for many applications without the need for a dedicated IT infrastructure. In the context of opportunistic networks, content sharing in particular has attracted significant attention. To support content sharing, opportunistic networks often implement a publish-subscribe system in which users may publish their own content and indicate interest in other content through subscriptions. Using a smartphone, any user can act as a broker by opportunistically forwarding both published content and interests within the network. Unfortunately, opportunistic networks are faced with serious privacy and security issues. Untrusted brokers can not only compromise the privacy of subscribers by learning their interests but also can gain unauthorised access to the disseminated content. This paper addresses the research challenges inherent to the exchange of content and interests without: (i) compromising the privacy of subscribers, and (ii) providing unauthorised access to untrusted brokers. Specifically, this paper presents an interest and content sharing solution that addresses these security challenges and preserves privacy in opportunistic networks. We demonstrate the feasibility and efficiency of the solution by implementing a prototype and analysing its performance on smart phones.