Xinjiang, home of the China's muslim Uighur minority, has long been the world's laboratory for Internet repression. Faced with widespread local unrest, and online debate, China has done everything it can to enforce its vision of the Net in the region, from imprisoning bloggers and online publishers, to quarantining the entire Xinjiang network from the rest of the Internet for over ten months in 2009. Nonetheless, Xinjiang residents still circumvent censorship and surveillance in the pursuit of privacy and free expression. They use virtual private networks and other methods to get around the Great Firewall. They use popular messaging apps that they have heard could defend them against surveillance, like WhatsApp and Telegram.

Now China has taken the next step. In November, a select group of Xinjiang residents found their mobile phone service abruptly terminated. Their phone service providers told them to visit their local police station to have the service restored. When contacted, the police told them that they had been detected using a VPN, or downloading foreign messaging software. Remove the software, the police said, and you'll get your connection back.

Faced with being unable to spy on every conversation, China has set upon outlawing not just the content of particular communications, but the use of particular general purpose applications. Censorship has expanded from certain speech acts, to any software that enables free speech. In Xinjiang, there are no innocent users of certain programs, because that software is itself a crime.

It may not be just Xinjiang where ordinary users are being punished for their use of particular software. Last year, EFF spoke to a Chinese Internet user from outside Xinjiang who had a similar experience. They too were contacted by the authorities shortly after using a VPN for the first time on their family's broadband connection. A telephone call, from an unknown source, called and instructed them to stop using the software. It was unclear whether the call was from the local Internet provider, or one of China's multiple Internet security services.

Back in Xinjiang, China has now started using other elements of state control to police software use. At road checkpoints, the New York Times' outgoing China correspondent Andew Jacobs noted, ethnic Uighurs are asked to hand over their cellphones. There, local police have indicated that apps like Skype and WhatsApp are indicators of subversive behavior.

We've understood for a long time that Internet censorship requires pervasive surveillance. A centralized censor needs to know everything that you're looking at, so that it can block what it does not want you to see. What China's new strategies demonstrates is that relationship works the other way. Pervasive surveillance requires censorship of software and services. Mandating backdoors or outlawing encryption can't stop anyone from using secure tools or working encryption. So to achieve that policy goal, governments will also need to censor the kinds of software computer users can download or execute. Backdoors lead to checkpoints and software censorship.

"Are we going to allow a means of communication which it simply isn't possible to read?" asked David Cameron a year ago. He answered his own question, "No we must not." But has he, and have the other policymakers considering a backdoor policy, considered all the consequences? Are they all intent on walking blindly into Xinjiang?