Telex is the software developed by US computer scientists with the purpose to hide data from banned websites inside traffic from sites deemed safe.
In test mode, Telex managed to defeat Chinese web filters thanks to its ingenious software. Its development started in early 2010 and the four member team – one being Dr. Alex Halderman – did an amazing effort to make Telex work against other anti-censorship technologies.
Most of the existing anti-censorship systems connect to a server or network outside the country in which a user lives. Promoting these servers and networks just enough so that censors can’t hear about them is the key to their success. However, Telex turns this approach against itself, Dr. Halderman said.
“Instead of having some server outside the network that’s participating we are doing it in the core of the network,” he said.
What Telex does is to take advantage on the small number of net-censoring nations.
How does it work ? For example, if a user stumbles upon a banned website, as it connects Telex puts a tag or marker on the datastream being sent to a safe destination. Then the routing points outside the country recognise that the datastream has been marked and re-direct a request to a banned site. Finally it bounces back to the user just as if it were data from a safe site.
Speaking of safety, the data is locked through a cryptograpic key that can be used only by the owner. This technique helps Telex being safe from intereferece, said Dr. Halderman.
“You cannot see this marker unless you have a corresponding private key,” he said.
Telex’s spotting routers unlock the banned content by using the cryptographic key we mentioned earlier. When Telex is deployed, ISPs usually add marker-spotting software to their routers.
Tests were ran by the development team for several months which proved to overcome even sophisticated filtering systems.
“We’ve also tried it from within China bouncing it off computers there,” he said. “So far, we’ve had no problems with the censorship there.”
The team succesfuly viewed banned content like HD YouTube videos and sites tagged „subversive” by Chinese authorities.
One of the biggest concerns for Telex was to reach its users uncompromised by net censors who might add key loggers or spyware, said Dr. Halderman.
“The most difficult part is making sure the connections the user is making to an uncensored website that we use to disguise the censored content are convincing enough,” he said.
“But, that’s the parameter we would adjust as the censor becomes more sophisticated.”
A formal launch of the program is planned by the development team at the upcoming Usenix security confference. Hopefuly, this confference will become a promoter to the ever growing number of people working on anti-censorship tools, he said.
“We are all seeing how powerful information can be at helping citizens assert themselves and their human rights,” he said. “It’s a deeply interesting technical problem and a goal that’s worthy of any technologist’s attention.”