Throwing Your Weight Around: Fixing Tor's Positional Weighting

We analyze deficiencies in Tor's positional weighting system, identifying cases which the system either fails to produce valid weights or properly load balance across positions. describe how an attacker can take advantage of these failures reduce performance, thereby also easing censorship and surveillance through a denial-of-service attack. Our attacks exploit incorrectly determined positional-weight equations by adding new capacity network or, for even more covertness, just minor changes status existing malicious relays. analysis past Tor consensuses shows that could have reduced throughput as much 45% due only their triggering flawed position weights. Rather than mere patch currently ad hoc scheme, we then propose new, systematic method deriving two goal sets generated using method. derive weights, prove they satisfy sets, give examples would change from current system. use our results quickly fix main its well adopt better approach long-term.