Update: The sites listed below to experiment with Blossom appear to be down. I’ve asked Roger and others for information on the status of the Blossom project and will post whatever I learn here. Sorry that I don’t have any more information at this point in time (6/21/07)
Roger Dingledine, one of the programmers behind the Tor anonymization service, has been spending some time around Berkman lately, and I’ve had the excellent chance to learn more about the architecture behind Tor. (Tor is “the onion router” and is a piece of software that allows you to access web pages with a very high degree of anonymity. I’ve written about it in the past, and hope to write a more detailed guide to using Tor in the near future.)
Roger has made the point that Tor is much more than a high security anonymization system – it’s a building block for other web tools as well. A great example is the Blossom tool being developed at Harvard by Geoff Goodell and others. Described as a “perspective access network”, Blossom is designed to let you look at the internet from the perspective of other nodes on the net. It does this by routing your request for a webpage through a Tor node located in another country.
What does Google.com look like from Poland? You could get on a plane to Warsaw, or you could use Blossom to pretend to be in Poland. A web interface to Blossom makes this pretty easy to accomplish – choose an URL to visit and a Tor node to connect from (in this case, one of the three Polish nodes available.) You should (eventually) get directed to the Polish version of the Google homepage, google.pl. (I’ve had better luck with the Blossom tool by setting my proxy to cassandra.eecs.harvard.edu:8119 and using this interface…)
This happens because you’re presenting a Polish IP address to Google – Google uses a geolocation service to determine where this IP is and presents a localized version of their homepage. If you browse a page that reports your IP – the frontpage of webmasterworld.com, for instance – you can see Blossom and Tor in action. Accessing this page via a browser not using Blossom, webmasterworld.com sees me coming from 188.8.131.52, an IP address associated with my ISP, Verizon. Accessing via the browser routed through the Tor network by Blossom, webmasterworld.com sees me coming from 184.108.40.206, an IP address associated with the Interdisciplinary Center for Nathematical and Computer Modeling at Warsaw University.
What’s fascinating about this, from my perspective, is that ICM in Warsaw never decided to run a service to let people browse the web from their servers. They decided to become part of Tor, and let one of their computers help route anonymized traffic through their machine, or through their machine onto the public Internet. Blossom borrows the ability of Tor “exit nodes” to route traffic, ignores most of Tor’s encryption capabilities and uses the growing Tor network to show a user in Massachusetts what the Internet looks like from Warsaw.
Other than being a nifty geek party trick, what’s this useful for? Well, it’s a fascinating way to check in on Internet filtering. There are at least three active Tor nodes in China – use Blossom to choose one of these computers as an exit node and you can surf the internet from China.
Accessed from 220.127.116.11, a computer controlled by China Unicom, google.com redirects to the Chinese language version of google.com (not google.cn, as many have speculated it someday will.) Try to go to zh.wikipedia.org, and you’re in for a long wait, followed by an error message from the proxy server, telling you the domain name is inaccessible. This is a great example of China’s non-transparent internet filtering at work – rather than presenting you with a page letting you know a URL is blocked, as the Saudis do, the great firewall simply blocks your request and lets you think the site is down, or simply doesn’t exist.
My friends over at the Open Net Initiative have lots of techniques for testing how the Internet is filtered in different countries – this sometimes involves visiting those nations and testing from within the country, and sometimes involves using proxy servers in those countries from the US, Canada or UK. Blossom gives you the chance to replicate some of this research at home… or merely check whether reports of a site being blocked in a particular country are true.
The limitation to Blossom’s usability to test filtering is the countries where Tor nodes exist. Playing with Blossom today, I saw a node available for a brief while in Pakistan… not long enough for me to check if Blogger.com was blocked there… Unless someone opens a Tor node in UAE, we can’t replicate BoingBoing’s reports of being blocked there.
Here’s an interesting sense where Tor and Blossom might be at cross purposes. Blossom is most interesting (in my opinion) where local authorities have constrained access to the Internet. But if Tor registers exit nodes in those countries (as in China, where we know the Internet is heavily filtered), it becomes less useful to Tor users trying to access Internet content while maintaining their anonymity… if your exit node from Tor is in China, you’re going to get a highly anonymized, filtered view of the Internet.
I made the argument a few weeks back that we’re dealing with a world where it’s less possible to talk about “the internet” and more correct to talk about “the internets” – Blossom’s a quick ticket to a world tour of these internets.