Measuring Tor and Iran (Part two)

Two weeks ago we posted early measurements about the growth of Tor usage in Iran. Since then we have improved our math, and used more data sources. This work is part of our metrics project, where we're learning about the Tor network to improve its availability and performance while keeping our users safe.

The first graph shows the estimated number of new and returning Tor clients per day coming from China and Iran. So for example, there were around 7800 new and returning Iranian Tor users on June 24. By "returning", we mean Tor clients that were off for at least several days, so they didn't have cached directory information. We added China as a comparison for the Iran numbers: you can see the results of the recent Green Dam fiasco and attempts to block Google services. Many more details and math are here.

The second graph shows the growth in bridge users coming from Iran and China. Bridges are like normal relays except that they are not listed in a public directory and therefore they're harder to block. We show "growth compared to June 1" because we don't yet have a good estimate of the absolute number of bridge users. The number is probably an order of magnitude smaller than the number of "regular" Tor users. But still, we can say that bridge usage from Iran has boosted to 950% as compared to June 1. For more information on these numbers see this report.

While it is great to see that so many people in Iran find the Tor network useful, we should continue our attempts to make Tor even better. Your contribution could be to set up a bridge or relay as many others recently did. You might also consider setting up an exit relay, possibly with the help of these instructions. But middle nodes and bridges are helping as well!


July 01, 2009


hi there,
is it possible to have a special build only allowing my exit node for clients originating in china, iran etc.? unfortunately i don´t know very much about this software but am unwilling to hassle with problems from my isp. right now i´m running only in bridge mode.
i think there might be a lot more people out there like me that would install a special iran package without having to think about it anymore


It is not possible for an exit node to know the originator of requests, without sniffing the data (violating user privacy and legally endangering yourself).

This is false: there's no *technical* way for the exit node to know the client except with collusion with other nodes in the circuit. If only legal consequences be the stopper for the exit node to figure out the client then Tor would be dead before birth.


July 04, 2009


Tor is apparently blocked in Iran and nothing happens when you try to connect hrough Tor... the relays list is empty... even bridges do not work... disappointing... really disappointing.

Please keep everyone updated about the status of TOR connection in Iran. If demonstrations intensify again soon, it would be good to coordinate to provide them with more relays.

from now on tor doesnt work in iran...i there is no tor connection anymore and i used every bridge i could find..plz inform me what i have to do?
i have macosx and use tor network via vidalia
plz inform me

Because we don't produce torchat and no one has thoroughly analyzed the code. Feel free to submit a detailed security analysis.