Ting: Measuring and Exploiting Latencies Between All Tor Nodes

摘要

Tor is a peer-to-peer overlay routing network that achieves unlinkable communication between source and destination. Unlike traditional mix-nets, Tor seeks to balance anonymity and performance, particularly with respect to providing low-latency communication. As a result, understanding the latencies between peers in the Tor network could be an extremely powerful tool in understanding and improving Tor's performance and anonymity properties. Unfortunately, there are no practical techniques for inferring accurate latencies between two arbitrary hosts on the Internet, and Tor clients are not instrumented to collect and report on these measurements. In this paper, we present Ting, a technique for measuring latencies between arbitrary Tor nodes from a single vantage point. Through a ground-truth validation, we show that Ting is accurate, even with few samples, and does not require modifications to existing clients. We also apply Ting to the live Tor network, and show that its measurements are stable over time. We demonstrate that the all-pairs latency datasets that Ting permits can be applied in disparate ways, including faster methods of deanonymizing Tor circuits and efficiently finding long circuits with low end-to-end latency.