Defense Event

Non-Hierarchical Networks for Censorship-Resistant Personal Communication

David R. Bild

Wednesday, April 02, 2014
2:00pm - 4:00pm
3725 BBB

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About the Event

The Internet promises widespread access to the world’s collective information and fast communication among people, but common government censorship and spying undermines this potential. This censorship is facilitated by the Internet’s hierarchical structure. Most traffic flows routers owned by a small number of ISPs, who can be secretly coerced into aiding such efforts. Traditional defenses use cryptographic means to provide security and anonymity at the cost of key management schemes that are confusing to common users. This thesis instead advocates non-hierarchical networks that lack such chokepoints, instead requiring would-be censors to control a substantial fraction of the participating devices—an expensive proposition. We take four steps towards the development of practical non-hierarchical networks. (1) We first describe Whisper, a non-hierarchical mobile ad hoc network (MANET) architecture for personal communication among friends and family that resists censorship and surveillance. At its core are two novel techniques, an efficient routing scheme based on the predictability of human locations and a variant of onion-routing suitable for decentralized MANETs. (2) We describe the design and implementation of Shout, a MANET architecture for censorship-resistant, Twitter-like public microblogging. (3) We describe the Mason test, a method to detect Sybil attacks in ad hoc networks in which trusted authorities are not available and used by Whisper. (5) We characterize and model the aggregate behavior of Twitter users to enable simulation-based studied of systems like Shout. We use our characterization of the retweet graph also study the retweet graph to analyze a novel spammer detection technique for Shout.

Additional Information

Sponsor(s): Robert Dick

Open to: Public