Stanford EE Computer Systems Colloquium

4:15PM, Wednesday, February 20, 2013
Skilling Auditorium, Stanford Campus

JavaScript anticensorship proxies

David Fifield
Stanford University, The Tor Project
About the talk:

Censorship is an everyday reality for many of the world's Internet users. Users turn to circumvention systems like Tor; censors respond by blacklisting the addresses of those systems. This talk will cover the use of "flash proxies" to evade such blacklisting. Flash proxies—which despite the name, do not use Adobe Flash—are miniature proxies implemented in JavaScript running in web browsers. Browsers can become temporary circumvention proxies just by viewing a web page, and stop being a proxy just by closing a tab. Browsers provide a large, diverse pool of IP addresses, which change too quickly to be effectively blocked by blacklisting. The system, originally a research idea, is now deployed on the Internet. The talk will discuss the overall design of the flash proxy system, and how it fits into a larger circumvention scheme. It will include challenges in implementation and deployment, and highlight some future directions for development. Flash proxies were the subject of a research paper, "Evading Censorship with Browser-Based Proxies" by David Fifield, Nate Hardison, Jonathan Ellithorpe, Emily Stark, Roger Dingledine, Phil Porras, and Dan Boneh; and the system now has more contributors from the Tor Project.


The talk slides can be viewed on-line at

About the speaker:

David Fifield is a Master's student in computer science at Stanford, an aficionado of freedom and free software. Public software projects he is involved with include the Tor anonymity network and the Nmap security scanner.

Contact information:

David Fifield