  We examine WebRTC's suitability as a means of Internet censorship
circumvention. WebRTC is a framework and suite of protocols for peer-to-peer
communication between web browsers. We analyze the implementation differences
in instantiations of WebRTC that make it possible to "fingerprint"
implementations--potentially distinguishing circumvention-related uses from
ordinary ones. This question is relevant to Snowflake, an upcoming
circumvention system that uses WebRTC to turn web browsers into temporary
peer-to-peer proxies. We conduct a manual analysis of WebRTC-using applications
in order to map the space of distinguishing implementation features. We run a
fingerprinting script on a day's worth of network traffic in order to quantify
WebRTC's prevalence and diversity. Throughout, we find pitfalls that indicate
that resisting fingerprinting in WebRTC is likely to be non-trivial.
