• Challenging networks
• delay tolerant networks
• publish/subscribe networks
• secure cooperation
• underwater acoustic networks

A Challenging Network (CN) is a network paradigm adapting to the many issues of the environment in order to guarantee the communication among nodes. One of the most important issues of a CN is the problem of secure cooperation among nodes. In fact, an attacker, either internal or external, may constitute a threat for the network. In this work I investigate the problem of secure cooperation in three kinds of CNs: the Underwater Acoustic Net- works (UANs), the Delay Tolerant Networks (DTNs) and the Publish/Subscribe Networks (PSNs). A UAN is a network paradigm allowing communication among underwater nodes equipped with acoustic modems. Since the acoustic channel is an open medium, an attacker conveniently equipped could intercept the messages traversing the network. In this work I describe a cryptographic suite, aimed at protecting the communication among underwater acoustic nodes. A DTN is a network paradigm guaranteeing message delivery even in presence of network partitions. A DTN relies on the implicit assumption that nodes cooperate towards message forwarding. However, this assumption cannot be satisfied when there are malicious nodes acting as blackholes and voluntarily attracting and dropping messages. In this work I propose a reputation-based protocol for contrasting blackholes. A PSN is a network paradigm allowing communication from publishers to subscribers by means of an infrastructure, called Dispatcher. In this work I present a secure PSN conceived to support cooperation be- tween organizations. The service is based on the notion of security group, an overlay composed of brokers representing organizations that guarantees confidentiality and integrity in end-to-end delivery of messages and supports clients mobility.