Enhancing traffic analysis resistance for Tor hidden services with multipath routing

Hidden service is a very important feature of Tor, which supports server operators to provide a variety of Internet services without revealing their locations. A large number of users rely on Tor hidden services to protect their anonymity. Around 30,000 servers are running hidden services every day. However, hidden services are particularly vulnerable to traffic analysis attacks especially when an entry guard of a hidden server is compromised by an adversary. In this paper, we propose a multipath routing scheme for Tor hidden servers (mTorHS) to defend against traffic analysis attacks. By transferring data through multiple circuits between hidden server and a special server rendezvous point, mTorHS is able to exploit flow splitting and flow merging to eliminate inter-cell correlations of the original flow. Experiments on the Shadow simulator [1] show that our scheme can effectively mitigate the risk of traffic analysis even when the most robust watermarking technique is applied.