In a paper on Telex submitted to the Usenix Security Symposium this month, Halderman and others describe in detail how their system would resist attacks by censors.
“We’ve gotten a lot of comment from people who don’t understand the system, who are pointing out ways they believe the system could be defeated, but in almost every case, it’s something we’ve thought about and addressed in the paper,” he says, adding that the system was designed to adapt to increasingly sophisticated censorship methods.
“Censored users today have moderate success using normal proxy servers, but what we’re seeing is that major countries involved in censorship are adapting quite quickly to that,” Halderman says. “For example, China has gotten very effective in blocking Tor, and Iran has also made some quite sophisticated countermeasures against Tor.”
Bruce Schneier, a cryptography expert and chief security technology officer at BT, calls Telex “well-thought-out and designed,” but says the system would not work without widespread adoption by ISPs around the world.
“There are two ways to deploy this system: ask nicely, or make it a law [for ISPs to implement it],” Schneier says. “It would be great if the governments of the world backed this idea, because in general this sort of thing is why you don’t see these technologies widely adopted. No one is willing to pay for them, and no one is going to support them otherwise.”
The researchers are working to expand a test Telex network that they’ve been using for months to surf the Web, and even to watch YouTube videos. They note that the test system works with “acceptable stability and little noticeable performance degradation,” and that it performed well in the face of some unexpected stress testing. A researcher accidentally misconfigured one of the Telex stations to act as an open Internet proxy; it wasn’t long before the system was being used by outsiders hoping to hide their identities.