With Tor members may send an email and instant messages, surf the web, and post content online without anybody knowing who or where exactly they are located. Subsequently, it is greatly acknowledged as a crucial tool for bypassing internet restrictions and thereby supporting freedom of expression.
Apparently, this is a great worry for countries that practice authoritarianism and wanted full control and censorship. The notable and most powerful of these countries is China, and the government works with a firewall that shields their citizens from accessing blocked websites.
Not too long ago, Philipp Winter and Stefan Lindskog at Karlstad University situated in Sweden have found a remedy. They have devised a means to circumvent the so-called Great Firewall of China that blocks Tor.
How is Tor blocked
One seemingly obvious means for China to block access to Tor is by preventing access from within the country towards the entry relays. It is entirely easy as the entry relays are publicly listed, and thus, the firewall can effectively do this. Nonetheless, in expectation of the action, the Tor network will surely operate a couple of entry relays without publishing their details conspicuously to the public. Hence, it is made tougher to block and may easily be changed. The main issue is that the China firewall has found a means to find and effectively block these secret relays as well.
Recently, Winter and Lindskog found out a way to cloak the secret relays even further and unblock Tor. The trick is done by setting their very own secret relay and to attempt to connect to it from within China. Winter and Lindskog commented that the firewall utilizes deep pattern inspection to find the code in every outgoing communications or traffic. Once it locates it, it takes on a potential Tor connection. Thereafter, it attempts to make its very own connection. Once this occurs, the firewall will then block the future access to the IP address. Furthermore, they have devised means to deep packet inspection this.
Not contented, these guys even went to the extent of using Google’s reverse DNS lookup to track down who is working behind all the restrictions. The evidence pointed clearly to the direction of China: China Telecom and China Unicom.
So, how to unblock Tor network?
One good move is to use packet fragmentation. This is accomplished by dividing up the packets so as to deceive the deep packet inspection system. There is one great tool being developed, the so-called Obfsproxy. This will effectively mask the Tor traffic, which makes it look like something else like Skype traffic, for instance.
China is alarmed by the approach, so they actively blocked all published relays designed to make use of Obfsproxy. Nevertheless, the two wiz guys from Sweden have set up a private Obfsproxy relay in Sweden and have successfully connected to it from within China. It only goes to show that the deep packet inspection system cannot spot private Obfsproxy relays and therefore appears like a promising route onward. The sole reason that the China firewall is capable of detecting Tor Traffic is that it is easily distinguishable from other types of web traffic.
The subject of a great debate
Since Tor is an open and transparent organization, these talks about how to unblock Tor are undeniably occurring in public, and Chinese authorities know each and every plan of attack. The publication of the Winter and Lindskog’s white paper regarding their techniques are wide open to Chinese authorities’ full view and scrutiny.
These talks are highly susceptible of becoming blocked and forestalled by the Chinese authorities long before Tor’s people can even implement them.
We are one with Tor in this fight, free people from the shackles of Internet censorship, spread the word about this and support Tor all the way!