anti-censorship in network infrastructure

With AntiSec—and attendant censorship countermeasures—in full swing, Telex seemed like an appropriate subject.  In a nutshell, Telex offers a response to online censorship by placing anti-censorship technology into the Internet’s core network infrastructure, rendering it easy to distribute and difficult to detect and prevent. Governments tend to use firewalls in their network to block traffic or access to forbidden sites. Telex is different from previous anti-censorship systems in that it operates within the infrastructure at ISP points and non-blocked portions of the Internet, as opposed to network end points.

This “end-to-middle” proxying makes the system robust against censorship countermeasures. Furthermore, it emphasizes evading detection so that a censor may be circumvented without being alerted, complementing proxy and relay services like Tor. Telex employs and repurposes deep-packet inspection in its anti-censorship measures. Telex also does away with individual encryption keys or IP addresses that need to be communicated to users in advance, since the censor can block the system if it discovers this information. Telex is described, in short, as a “state-level response to state-level censorship” (

While most anti-censorship systems function by creating a “tunnel,” or encrypted connection, between an individual computer and a trusted proxy server outside the censor’s network, Telex creates a sort of proxy server that lacks an IP address. All the user has to do is install a Telex client app via download or file-sharing. When the user wants to access a blacklisted site, the server relays a request to censored site and returns responses through the tunnel, while the client marks the connection as a Telex request via a cryptographic, public-key steganography tag. In short, anyone can tag a connection, but only the Telex service can recognize a tagged connection. The connection—deployed as a decoy—looks normal, so the censor lets it pass.

Telex relies primarily on ISPs to deploy Telex “stations” between the censor network and censored sites. As of now, this system is more a concept than a ready-to-implement technology, although experimental software has been developed to allow researchers to toy with the idea.

I’m not as much of a techie as I’d like to believe, so instead I’ll conclude with this: “Telex illustrates how it is possible to shift the balance of power in the censorship arms race, by thinking big about the problem. We hope our work will inspire discussion and further research about the future of anticensorship technology” (

More information, the original paper, FAQs, and Q&As about Telex here.

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