Cryptography, Security, and Privacy (CrySP)

This speaker series is made possible by an anonymous charitable donation in memory of cypherpunks and privacy advocates Len Sassaman, Hugh Daniel, Hal Finney, and Caspar Bowden.

View the list of past and upcoming speakers

Secure Load Balancing in Tor with Peerflow

Nicholas Hopper, University of Minnesota

[Download (MP4)]

September 1, 2015 3:30pm, in DC 1331


The privacy provided by the Tor network requires that no adversary handles too much client traffic, but it also depends on the network utilizing resources efficiently, in order to attract enough users to provide anonymity. However, Tor relays are run by untrusted volunteers, and there currently exists no method to securely determine their bandwidth for accurate load balancing. In this talk, I will briefly discuss security and accuracy shortcomings of the TorFlow bandwidth-scanning algorithm and the EigenSpeed peer-measurement protocol, before presenting PeerFlow, a new design for secure, private, and accurate load balancing in Tor.

PeerFlow is the result of joint work with Aaron Johnson, Rob Jansen, Paul Syverson and Aaron Segal.


Nicholas Hopper is an Associate Professor of Computer Science & Engineering at the University of Minnesota. He received a B.A. from the University of Minnesota in 1999 and a Ph.D. in Computer Science from Carnegie Mellon University in 2004. His research interests include online privacy, applied cryptography, and computer security.