Information-sharing and privacy are fundamentally in tension, and it is important to study the trade-off from both technical and social-contextual perspectives. The emergence of ubiquitous computing opens up radical new possibilities for acquiring and sharing information, but today's methods cannot exploit the possibilites without grave privacy risks. This proposal explores a new methodology that provides much finer control over information exchange: only the information needed for the collaboration is shared, everything else is protected, and protection is provably strong. It is then possible to explore collaborative applications in ubiquitous computing settings that are exciting, but which would be otherwise impossible. Specifically, a class of collaborative applications called ``Ant Club Trails'' (ACT) will be developed. The idea behind Ant Club Trails is to combine information from the ``trails'' left by individual users, and to share it with other users by collaborative filtering in a way which protects individual privacy. The project draws on cryptography, probabilistic reasoning and computational geometry for the development of working ACT systems. It is also guided by sociology and critical theory toward design of socially realistic and desirable systems. The outcome should be better scientific understanding of the information-sharing privacy tradeoff, and a larger landscape of collaborative applications that protect privacy. The broader impacts of the work include: (i) empowerment of communities to share and possibly make a market in community knowledge; (ii) training of research graduate students; and (iii) involvement of undergraduates in developing ACT applications on smart phones.
