Evaluating Snowflake as an Indistinguishable Censorship Circumvention Tool
This work addresses the challenge of censorship circumvention for users in restricted regions, but it is incremental as it focuses on evaluating and improving an existing tool rather than proposing a new paradigm.
The paper tackled the problem of evaluating whether Snowflake, a Tor pluggable transport using WebRTC, is truly indistinguishable from other WebRTC services like Facebook Messenger and Google Hangouts, and found that it is identifiable with 100% accuracy based on features such as DTLS handshake extensions and packet counts.
Tor is the most well-known tool for circumventing censorship. Unfortunately, Tor traffic has been shown to be detectable using deep-packet inspection. WebRTC is a popular web frame-work that enables browser-to-browser connections. Snowflake is a novel pluggable transport that leverages WebRTC to connect Tor clients to the Tor network. In theory, Snowflake was created to be indistinguishable from other WebRTC services. In this paper, we evaluate the indistinguishability of Snowflake. We collect over 6,500 DTLS handshakes from Snowflake, Facebook Messenger, Google Hangouts, and Discord WebRTC connections and show that Snowflake is identifiable among these applications with 100% accuracy. We show that several features, including the extensions offered and the number of packets in the handshake, distinguish Snowflake among these services. Finally, we suggest recommendations for improving identification resistance in Snowflake. We have made the dataset publicly available.