Cadence: A Simulator for Human Movement-based Communication Protocols

Unfettered access to the Internet is unfortunately not universal -- studies show that more than half of the world's population is subject to at least some censorship. Even in regions without censorship, Internet outages (e.g., during natural disasters) hinder the ability to communicate online. Avoiding censorship and communicating during Internet outages have inspired a number of proposals for communicating via a class of decentralized routing protocols based on sneakernets. In a sneakernet, messages are passed between human-carried devices (usually smartphones), completely avoiding the Internet. Importantly, the movement of messages in a sneakernet is dictated by the movements of the (human) device owners; these networks tend to be opportunistic in the sense that messages are exchanged between parties only when those parties encounter one another through happenstance. Understanding the security, performance, and privacy properties of various sneakernet protocols remains an open problem, with individual proposals inventing their own metrics and evaluation methodology, and is further challenged by a lack of unified evaluation and simulation frameworks. This paper presents Cadence, a simulator for decentralized human movement-based communication protocols that provides a unifying environment for evaluating sneakernet protocols under a variety of conditions. We describe the architecture of Cadence and argue its benefits to network and security researchers. Cadence is free open-source software.