Freedom of speech is a founding principle of democratic society, and the Internet has become one of the most effective and common means of conveying expression that is likely to be controversial or suppressed. One threat to the freedom of speech online is the now widespread practice of Internet censorship by both private and state interests. These censors use a variety of social and technological means to limit availability or expression of information, stifling the democratic process.
This project is focused on developing overlay networks that promote freedom of speech by circumventing social and technological censorship measures. The project will develop new software and protocols for secure overlay networks that satisfy three distinct security goals: relationship privacy, membership hiding, and blocking resistance. A secondary focus of the project is on understanding these security goals and the relationships between them, and investigating the extent to which existing systems satisfy these properties.
The project will train undergraduate and graduate students to perform and apply research from a variety of disciplines (including cryptography, networking, algorithms, and coding theory). The project also develops new intellectual infrastructure by introducing the new notion of membership hiding as a security problem. Finally, the results of the project are expected to include the broad dissemination of free software that promotes freedom of expression on the Internet, against regimes that strongly oppose such expression.
Freedom of speech is a founding principle of democratic society, and the Internet has become one of the most effective and common means of conveying expression that is likely to be controversial or suppressed. One threat to the freedom of speech online is the now widespread practice of Internet censorship by both private and repressive state interests. These censors use a variety of social and technological means to limit availability or expression of information, stifling the democratic process. This project focused on developing "peer to peer" networks that enable users to quickly deploy and use systems that promote freedom of speech by circumventing social and technological censorship measures. The project developed several new advances in this area: We developed two software projects, Torsk and Shadow, that improve the free and open-source peer to peer network Tor, the "King" of censorship circumvention tools. These projects led to improvements that enabled the Tor servers to safely and quickly handle many more users. They also provide new tools to let other researchers safely experiment with ways to improve Tor without endangering the millions of users currently using the Tor network. Several other research groups have successfully used these tools in their own experiments, and Shadow was released as open-source software. We studied ways to incentivize people to contribute to peer to peer censorship circumvention systems. Our design, which we called BRAIDS, has influenced the work of several other research groups. We studied how social networks can be used to protect users of censorship circumvention systems from being discovered by oppressive regimes. We showed that in principle, using your network of friends to send and receive information around censors can be helpful, but that many ways of doing this are dangerous and can lead to identification. For example, we demonstrated how an attacker could discover who was using Tor to write critical blog posts or tweets through flaws in the design of Tor's "bridge" system. We also showed how to fix this problem and improve the privacy of the bridge system, which resulted in plans to adapt our improvements in the next year. The project directly impacted millions of users of the Tor network, and also contributed to the education of hundreds of undergraduate students through course lectures, as well as the research training of five Ph.D. students, one postdoctoral fellow, and four undergraduate students.
