Homework #14 - Anonymity - Due Monday April 6, 1PM

Turn in this assignment via email (vern@berkeley.edu) by the due date, with the term Homework in the Subject.

Read the paper Tor: The Second-Generation Onion Router, Roger Dingledine, Nick Mathewson, Paul Syverson, USENIX Security 2004.

Note that this paper is dense and on the long side. Feel free to read Section 2 (Related Work) lightly, and to skip Sections 4.5 and 4.6 on Rate Limiting and Congestion Control.

Briefly write up your views of:

  1. What are the main contributions of this paper?
    (Frame these in terms of the paper itself from a stand-alone perspective. You don't need to worry about considering its differences from its predecessor system, nor should you incorporate post facto knowledge about Tor's subsequent influence.)

  2. What parts of the paper do you find unclear? (optional)

  3. What parts of the paper are questionable? (That is, you think a conclusion may be wrong, an approach or evaluation technically flawed, or data ill-presented.)

  4. Without using any external resources, analyze a potential attack on Tor:
    1. Sketch an attack on the system other than those presented in the paper.
    2. How you would evaluate how effectively it works?
    3. What countermeasures could defend against it?
    4. How serious is the attack in practical terms? (Or, if this isn't clear for your attack, how you could figure this out?)