No Free Lunch in Data Privacy

Ashwin Machanavajjhala, Yahoo

Legal requirements and increase in public awareness due to egregious breaches of individual privacy have made data privacy an important field of research. Recent research, culminating in the development of a powerful notion called differential privacy, have transformed this field from a black art into a rigorous mathematical discipline.

In this talk, we critically analyze the trade-off between accuracy and privacy in the context of social advertising – recommending people, products or services to users based on their social neighborhood. We present a theoretical upper bound on the accuracy of performing recommendations that are solely based on a user’s social network, for a given level of (differential) privacy of sensitive links in the social graph. We also show using real networks that good private social recommendations are feasible only for a small subset of the users in the social network or for a lenient setting of privacy parameters.

I will conclude the talk with some exciting new research about a no free lunch theorem, which argues that privacy tools (including differential privacy) cannot simultaneously guarantee utility as well as privacy for all types of data.

Speaker Biography

Ashwin Machanavajjhala is a Senior Research Scientist in the Knowledge Management group at Yahoo! Research. His primary research interests lie in data privacy with a specific focus on formally reasoning about privacy under probabilistic adversary models. He is also interested in creating and curating structure knowledge bases from unstructured, noisy and time-varying web data using statistical methods. Ashwin graduated with a Ph.D. from the Department of Computer Science, Cornell University. His thesis work on defining and enforcing privacy was awarded the 2008 ACM SIGMOD Jim Gray Dissertation Award Honorable Mention. He has also received an M.S. from Cornell University and a B.Tech in Computer Science and Engineering from the Indian Institute of Technology, Madras.