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Distinguished Seminar:  Characterizing and Mitigating AS-based Timing Attacks on the Tor Network

Date:October 3, 2016 
Talk Title:Characterizing and Mitigating AS-based Timing Attacks on the Tor Network
Speaker:Phillipa Gill, Assistant Professor, University of Massachusetts
Time & Location:12:00pm - 1:00pm
DEC, CIC Building, Pittsburgh


Traffic correlation attacks to de-anonymize Tor users are possible when an adversary is in a position to observe traffic entering and exiting the Tor network. Recent work has brought attention to the threat of these attacks by network-level adversaries (e.g., Autonomous Systems). We perform a historical analysis to understand how the threat from AS-level traffic correlation attacks has evolved over the past five years. We find that despite a large number of new relays added to the Tor network, the threat has grown. This points to the importance of increasing AS-level diversity in addition to capacity of the Tor network.

We identify and elaborate on common pitfalls of AS-aware Tor client design and construction. We find that succumbing to these pitfalls can negatively impact three major aspects of an AS-aware Tor client -- (1) security against AS-level adversaries, (2) security against relay-level adversaries, and (3) performance. Finally, we propose and evaluate a Tor client -- Cipollino -- which avoids these pitfalls using state-of-the-art in network-measurement. Our evaluation shows that Cipollino is able to achieve better security against network-level adversaries while maintaining security against relay-level adversaries and performance characteristics comparable to the current Tor client.

Speaker Bio

Phillipa Gill is an assistant professor in the Computer Science Department at the University of Massachusetts -- Amherst. Her work focuses on many aspects of computer networking and security with a focus on designing novel network measurement techniques to understand online information controls, network interference, and interdomain routing. She currently leads the ICLab project which is working to develop a network measurement platform specifically for online information controls. She was recently included on N2Women’s list of 10 women in networking to watch. She has received the NSF CAREER award, Google Faculty Research Award and best paper awards at the ACM Internet Measurement Conference (characterizing online aggregators), and Passive and Active Measurement Conference (characterizing interconnectivity of large content providers).