censorship

Experts in China tell us Tor is not being singled out, that all "circumvention" tools are being subjected to the censorship regime of the Great Firewall of China as politically sensitive anniversaries come about. We also hear people in China need their privacy too, even if they never leave the Chinese Internet.

However, it appears China is getting better at blocking Tor. Here's a graph of returning users to the Tor Network from China:

However, most Tor users in China switched to non-public relays, called bridges, over the past few months. Interestingly, the GFW has also started blocking some of the more popular bridges: read more »

Roger recently gave a talk at 26C3 about our experiences with various censorship technologies.

In the aftermath of the Iranian elections in June, and then the late September blockings in China, we've learned a lot about how circumvention tools work in reality for activists in tough situations. I'll give an overview of the Tor architecture, and summarize the variety of people who use it and what security it provides. Then we'll focus on the use of tools like Tor in countries like Iran and China: why anonymity is important for circumvention, why transparency in design and operation is critical for trust, the role of popular media in helping – and harming – the effectiveness of the tools, and tradeoffs between usability and security. After describing Tor's strategy for secure circumvention (what we thought would work), I'll talk about how the arms race actually seems to be going in practice.

The slides of the presentation can be found at the bottom of this post.

We've mirrored the full 700MB video of the presentation at http://media.torproject.org/video/26c3-3554-de-tor_and_censorship_lesson...

As reported, Tor was partially blocked by China on September 25th or so in anticipation of the CCP October 1, 2009 60th anniversary.

Here's what one directory mirror recorded for September,

And here's the growth of bridge users in response. Alas, like our graphs of bridge use in Iran in June 2009, we only have relative counts for bridge use, not absolute counts. But with a 70x increase in a week, we are talking about 10000+ bridge users: