Researchers have developed a new means of circumventing state internet censorship – by hiding an illegal connection request within a legal one.
States such as China censor traffic by forcing domestic ISPs to operate blacklists. If a user tries to connect to a blacklisted site the ISP denies the request, acting as a barrier between the user and banned foreign websites.
Telex doesn’t bypass the censorship barrier but instead goes through it.
Users enter two web addresses into the Telex client. The first is the “decoy” address of a state-sanctioned site that is hosted outside of the country. The second is the banned site the user actually wants to visit, which is embedded in an encrypted tag attached to the header by the Telex client.
Foreign ISPs that support Telex can detect and decode this tag, and connect the user to the second site. The website data that is sent back to the user purports to come from the first “legitimate” website, thus beating the blacklist.
“Telex doesn’t require active participation from the censored websites, or from the non-censored sites that serve as the apparent connection destinations,” according to J Alex Alderman, in a post on Princeton University’s Center for Information Technology Policy blog.
“However, it does rely on ISPs to deploy Telex stations on network paths between the censor’s network and many popular internet destinations. Widespread ISP deployment might require incentives from governments.”
Getting the client into users’ hands also poses a problem. The developers suggest “downloading it from an intermittently available website”, or “making a copy from a friend”.
The researchers claim that because Telex “works like a proxy server” it can’t simply be added to a block list like pirate ISPs, making it “much more difficult” to block.
Currently working as a proof-of-concept, the developers have a mock ISP running in their office. They’ve so far managed to connect to YouTube from Beijing, where the site is blacklisted.
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