Autonomic and opportunistic communications require specific routing algorithms, like replication-based algorithms or context-based forwarding. In addition to confidentiality, privacy is a major concern for protocols which disseminate the context of their destination. In this paper, we focus on the confidentiality and privacy issue inherent to context-based protocols, in the framework of an original epidemic forwarding scheme, which uses context as a heuristic to limit the replication of messages. We define the achievable privacy level with respect to the trusted communities assumption, and the security implications. Indeed, privacy in such an environment raises challenging problems, which lead us to a solution based on refinements of two pairing-based encryption, namely searchable encryption and identity-based encryption. This new solution enables forwarding while preserving user privacy by allowing secure partial matches in the header and by enforcing payload confidentiality.