Roger Dingledine - The Tor Censorship Arms Race: The Next Chapter
Tor Project co-founder presents the ongoing arms race between Tor's traffic obfuscation and state-level deep packet inspection censorship systems.
Summary
Tor Censorship Arms Race
Roger Dingledine, co-founder and research director of the Tor Project, presents the ongoing technical arms race between Tor's traffic obfuscation techniques and state-level DPI-based censorship in China, Russia, Iran, and Belarus.
Current Censorship Landscape
National censorship infrastructure (GFW, SORM, IRGC filtering) has become sophisticated at identifying and blocking Tor traffic using deep packet inspection, flow correlation, and active probing. Standard Tor connections are blocked in multiple countries within hours of becoming operational.
Pluggable Transport Evolution
Dingledine traces the development of pluggable transports: obfs3, obfs4, ScrambleSuit, meek (domain fronting), Snowflake (WebRTC-based), and Conjure — each designed to evade the specific detection mechanism used against its predecessor.
Decentralized Bridge Distribution
The current challenge is distributing unlisted Tor bridge addresses to censored users without those addresses being harvested by censors. The talk covers the BridgeDB distribution system, Moat (reCAPTCHA-gated bridge distribution), and Tor's collaboration with major tech companies to provide meek domain fronting.
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