Anti-censorship technology uses online video games to bypass Chinese internet restrictions
New technology developed by US researchers can transmit messages through popular multiplayer online games, making it very difficult for censors to detect and block.
One of the most difficult tasks faced by those attempting to subvert internet restrictions, such as those put in place by China's so-called Great Firewall, is doing so in a manner that doesn't provoke suspicion from censors.
"People who were using [anonymising tools] were fairly easily detected by censors and blocked," said Rishab Nithyanand, a researcher at Stony Brook University and one of the developers of The Castle.
The Castle uses video games as a "benign transport", transmitting and receiving data through the game itself in a manner that will just look like normal gameplay from the outside.
"You will construct a request for the webpage you want to get, encode it as a series of game moves and put it through the game," said Rob Johnson, another researcher.
A client outside of the firewalled region can then decode the request and transmit the desired information back via the same method.
"We can basically transmit any kind of information through the video game," said Nithyanad.
Games already transmit huge amounts of data between players and servers, and between players themselves. This data is usually encrypted to prevent cheating, making it hard for censors to spot anything suspicious.
"In theory it could run completely in the background as a user uses an ordinary web browser," said researcher Bridgar Hahn, though he pointed out that the bandwidth available would normally restrict users to only receiving text.
Johnson said using video games rather than other benign protocols (such as voice-over-internet, the protocol which powers Skype and other similar tools), is that the technology can work across multiple games and be quickly adapted if censors cotton on.
"We can design a framework that makes it easy for us to move the whole system from one video game to another," he said.
At present, the technology, which was published on the code repository GitHub last week, is built to use 0AD, an open-source, multiplayer real-time strategy game.
The technology could be adapted to a similar title, such as Starcraft or the hugely-popular Dota series, in "about six to seven hours", Nithyanad said.
The team hoped that in future the technology will be packaged as a Tor pluggable transport, an extension to the popular anti-censorship and anti-surveillance tool used by more than two million people worldwide.
"It would only be marginally more difficult than using Tor itself," said Johnson.
The Castle team are not the first to use video games as a way of bypassing government surveillance, though previous methods have had limited success.
Documents leaked by former NSA contractor Edward Snowden revealed that both the NSA and CIA have been spying on online video games since 2006. This was reportedly because a number of terrorist groups, including al-Qaeda, were using games, including World of Warcraft, to recruit new members and transmit messages.