The Tor Censorship Arms Race: The Next Chapter

Tor is a free-software anonymizing network that helps people around the world use the Internet in safety. But who cares how good Tor's privacy is, if your government prevents you from reaching the Tor network?

In the beginning, some countries filtered by DNS (so we made website mirrors and an email autoresponder for downloading Tor), and then some countries blocked Tor relays by IP address (so we developed bridges, which are essentially unlisted relays), and then some countries blocked Tor traffic by Deep Packet Inspection (so we developed pluggable transports to transform Tor flows into benign-looking traffic).

Then things got weird, with China's nationwide active probing infrastructure to enumerate bridges, with Amazon rolling over to Russia's threats when Telegram used "domain fronting" to get around blocking, with Turkey blocking Tor traffic by DPI in more subtle ways, with Venezuela and Ethiopia and Iran trying new tricks, and more.

In this talk I'll get you up to speed on all the ways governments have tried to block Tor, walk through our upcoming steps to stay ahead of the arms race, and give you some new—easier—ways that let you help censored users reach the internet safely.

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