The novel use of Bridge Relays to provide persistent Tor connections for mobile devices

The number of wireless mobile devices connecting to the Internet, is predicted to surpass static connections by 2014. A desire for privacy will provide additional challenges in the future, for anonymity networks such as Tor, in supporting this increasing mobile user base. In this paper, we assess the potential performance impact to a mobile user accessing Tor while roaming from different Internet connections. An experiment was undertaken to simulate a mobile user at various mobility speeds (e.g. walking) alongside a range of Tor circuit build times. The results show that the impact to the mobile user (and potentially the overall Tor network) was significant when roaming between networks, and as expected, increased with higher mobility speeds and longer circuit build times. We also reviewed previous related research and, as one potential solution, considered whether Bridge Relays could additionally be used to provide a persistent connection to the Tor network, for roaming mobile users. Performance is critical for low latency anonymity networks, such as Tor, and understanding the potential impact of this increasing mobile user base, to both the mobile user and overall Tor network, is becoming critical.