New anti-censorship scheme could make it impossible to block individual sites
Here’s how Telex would work:
Users install Telex software. Halderman envisions they could download it from an intermittently available website or borrow a copy from a friend.
Internet Service Providers (ISPs) outside the censoring nation deploy equipment called Telex stations.
When a user wants to visit a blacklisted site, he or she would establish a secure connection to an HTTPS website, which could be any password-protected site that isn’t blocked. This is a decoy connection. The Telex software marks the connection as a Telex request by inserting a secret-coded tag into the page headers. The tag utilizes a cryptographic technique called “public-key steganography.”
“Steganography is hiding the fact that you’re sending a message at all,” Halderman said. “We’re able to hide it in the cryptographic protocol so that you can’t even tell that the message is there.”
The user’s request passes through routers at various ISPs, some of which would be Telex stations. These stations would hold a private key that lets them recognize tagged connections from Telex clients. The stations would divert the connections so that the user could get to any site on the Internet.
Under this system, large segments of the Internet would need to be involved through participating ISPs.
“It would likely require support from nations that are friendly to the cause of a free and open Internet,” Halderman said. “The problem with any one company doing this, for example, is they become a target. It’s a collective action problem. You want to do it on a wide scale that makes connecting to the Internet almost an all or nothing proposition for the repressive state.”
Here’s how Telex would work:
Users install Telex software. Halderman envisions they could download it from an intermittently available website or borrow a copy from a friend.
Internet Service Providers (ISPs) outside the censoring nation deploy equipment called Telex stations.
When a user wants to visit a blacklisted site, he or she would establish a secure connection to an HTTPS website, which could be any password-protected site that isn’t blocked. This is a decoy connection. The Telex software marks the connection as a Telex request by inserting a secret-coded tag into the page headers. The tag utilizes a cryptographic technique called “public-key steganography.”
“Steganography is hiding the fact that you’re sending a message at all,” Halderman said. “We’re able to hide it in the cryptographic protocol so that you can’t even tell that the message is there.”
The user’s request passes through routers at various ISPs, some of which would be Telex stations. These stations would hold a private key that lets them recognize tagged connections from Telex clients. The stations would divert the connections so that the user could get to any site on the Internet.
Under this system, large segments of the Internet would need to be involved through participating ISPs.
“It would likely require support from nations that are friendly to the cause of a free and open Internet,” Halderman said. “The problem with any one company doing this, for example, is they become a target. It’s a collective action problem. You want to do it on a wide scale that makes connecting to the Internet almost an all or nothing proposition for the repressive state.”
