PriFi: A Low-Latency Local-Area Anonymous Communication Network

Organizational networks are highly vulnerable to traffic-analysis attacks that can infer information from their communications even if they are encrypted. We present PriFi, an anonymous communication protocol that is provably secure against traffic-analysis attacks, has low communication latency, and is application agnostic. PriFi builds on Dining Cryptographers networks and solves several issues of existing such networks. The communication latency is reduced via a client/relay/server architecture, where a set of servers assists the anonymization process without adding latency. Unlike mix networks and other DC-nets systems, client's packets remain on their usual network path, without additional hop. PriFi protects clients against equivocation attacks with minimal latency overhead, without requiring communication between clients. PriFi also detects disruption (jamming) attacks without costly consensus among servers. We evaluate the practicality of PriFi in the context of a large, at-risk organization. Our results show that the system can be used with minimal latency overhead ($\approx100$ms for $100$ clients) and is compatible with delay-sensitive applications such as VoIP. In short, PriFi provides organizations with robust traffic-analysis resistance and maintains the Quality of Service of the communications.