Anti-RAPTOR: Anti Routing Attack on Privacy for a Securer and Scalable Tor

Abstract

Regardless of Tor’s robustness against individual attackers thanks to its distributed characteristics, the network is still highly vulnerable to those very powerful adversaries, such as oppressive regimes which have control over a large proportion of the Internet. As recently confirmed by Edward Snowden, Autonomous-System level adversary is no longer theoretical, but poses a real danger to the Tor network. Therefore, through this research, we strive to propose an improved design in Tor to against the most contemporary de-anonymizing attack techniques, especially Raptor - Routing Attacks on Privacy in Tor. Different from most previous works, the scalability aspect of the overall Tor network is also taken into consideration in this study since the number of both end users and voluntary relays is foreseen to keep increasing in the next coming years. To against RAPTOR, we suggest that an Internet AS-level topology file should be periodically maintained and distributed by Directory Authorities. The file is only fetched by the guard and exit relays in addition to the conventional consensus network status document to preserve the scalability of the network. The user then decides to initiate her anonymous circuit based on the result of the intersection between two sets of ASes (1) the set of ASes between the user and the guard relay, and (2) the set of ASes between the exit relay and the final destination. The paper concludes by summarizing pros and cons of the proposed design from various points of view including the Directory Authorities, the voluntary relays and the end users; and suggesting future works that are necessary for a state-of-the-art anonymity technique.