Obscura: Enabling Ephemeral Proxies for Traffic Encapsulation in WebRTC Media Streams Against Cost-Effective Censors#

Authors: Afonso Vilalonga (NOVA LINCS, NOVA School of Science, Technology), Kevin Gallagher (NOVA LINCS, NOVA School of Science, Technology), João S. Resende (Universidade do Porto), Henrique Domingos (NOVA LINCS, NOVA School of Science, Technology)

• Why: Post-domain-fronting, the circumvention field has moved to embedding traffic in legitimate-looking media protocols. Tunneling inside WebRTC media streams (DTLS/SRTP) is an engineering-heavy approach that treats the browser's real-time stack as cover traffic — relevant both to circumvention and to understanding what DPI can and can't classify cheaply.
• What: Apparently a proxy design that encapsulates arbitrary traffic inside WebRTC media streams, with proxies that are ephemeral — cheap to spin up and discard, so blocking by address is economically futile against "cost-effective" censors (title/author line only — no abstract in program).
• How: Inference: proxied connections are tunneled through WebRTC's media path so the observable traffic is indistinguishable from a video/audio session, plus orchestration for short-lived proxy instances.
• Where applicable: Browser-based circumvention; constraints are WebRTC's congestion control interacting with tunneled traffic (throughput/latency cost). The "cost-effective censor" threat model is explicitly budget-limited — results may not hold against well-resourced adversaries.