Refraction Networking

Internet freedom in the network’s core

What is refraction networking?

Most of today’s censorship circumvention tools use the same fundamental approach: they encrypt the user’s traffic to make it look innocuous, and channel it to a proxy server located outside the censored network. This leads to a fundamental problem: Once the censor discovers the proxy server, the proxy itself becomes just another site to block. If users can find the proxy servers, the censors can too.

In this race to find and use—or find and block—proxy servers, censoring governments enjoy natural, growing advantages over censored users. For example, they can examine all data flowing across their borders in search of disfavored activity. Strategies that rely on friendly servers are failing against increasingly sophisticated state-level censors who can see and control a country’s entire network.

Refraction networking* takes a different approach. Rather than trying to hide individual proxies from censors, refraction brings proxy functionality to the core of the network, through partnership with ISPs and other network operators. This makes censorship much more costly, because it prevents censors from selectively blocking only those servers used to provide Internet freedom. Instead, whole networks outside the censored country provide Internet freedom to users—and any encrypted data exchange between a censored nation’s Internet and a participating friendly network can become a conduit for the free flow of information.

What work is happening now?

Refraction networking was independently invented in 2011 by three engineering teams. Five protocols exist: Telex and TapDance at the University of Michigan, Cirripede at the University of Illinois, and Curveball and Rebound at Raytheon BBN Technologies. These designs share the same basic premise but represent a range of design choices and technical tradeoffs.

Today, researchers from Michigan, Illinois, and the University of Colorado have formed a coalition to make refraction networking a widely deployed and powerful tool for Internet freedom, with support from the U.S. State Department's Bureau of Democracy, Human Rights, and Labor. Since 2019, the coalition has been operating a real-world production deployment that provides refraction networking service to more than a million users globally.

What research has been published?

The papers are: