A challenging problem in dissent networking is that of circumventing large-scale communication blackouts imposed by oppressive governments. Although prior work has not focused on the need for user anonymity, we contend that it is essential. Without anonymity, governments can use communication networks to track and persecute users. A key challenge for decentralized networks is that of resource allocation and control. Network resources must be shared in a manner that deprioritizes unwanted traffic and abusive users. This task is typically addressed through reputation systems that conflict with anonymity. Our work addresses this paradox: We prioritize resources in a privacy-preserving manner to create an attack-resilient, anonymity-preserving, mobile ad-hoc network. Our prioritization mechanism exploits the properties of a social trust graph to promote messages relayed via trusted nodes. We present Rangzen, a microblogging solution that uses smartphones to opportunistically relay messages among citizens in a delay-tolerant network (DTN) that is independent of government or corporate-controlled infrastructure.




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