Cloak

The Tor anonymity network is widely used by journalists and whistleblowers to safely share sensitive information in countries where they would otherwise endure retaliation. This has led repressive regimes to block access to Tor by employing extensive network-level interference techniques. This project aims to design and implement Cloak: a new technology that allows Internet users to circumvent Tor blocking and give users unrestricted access to Tor while, simultaneously, preventing these communications from being detected by government-controlled ISPs. Concretely, Cloak will consist of a new Tor pluggable transport (and surrounding ecosystem) that will establish covert channels between Tor browsers and Cloak bridges, which act as proxies to the free Tor network. Cloak will set up these covert channels by piggybacking Tor traffic on the video streams of widely-used web conferencing services based on WebRTC technology, e.g., meet.jit.si. Thus, under the guise of a regular video call, users will be able to freely and stealthily access services like SecureDrop without being blocked or detected. Cloak will thereby help to expand open access to information across the world.

The above figure presents Cloak's overview. In the depicted scenario, a user living inside a censored region, Alice, would like to access CNN's website despite it being blocked by the government. Alice will take advantage of the fact that Jitsi Meet is still available to her and use Cloak to access this otherwise restricted service. The sequence of events that must take place for Alice to be successful is as follows: 1) a Cloak Bridge operating in a free region registers its availability with a Broker; 2) Alice uses a browser configured to use the Tor Network (eg. Tor Browser) via the Cloak pluggable transport to request cnn.com; 3) the Cloak client running on Alice's machine generates a random chatroom ID to use with Jitsi Meet; 4) the chatroom ID is relayed to the Broker, who then finds an available Bridge and shares this ID with it; 5) a WebRTC video call is established between Alice and the Bridge via Jitsi Meet using Alice's chatroom; 6) all requests destined for cnn.com are forwarded to the Tor Network through the WebRTC gateway, allowing 7) Alice's access to CNN.