MultiFlow: Cross-Connection Decoy Routing using TLS 1.3 Session Resumption

Most approaches to circumventing Internet censorship and monitoring use conventional proxies which are accessed directly by their IP addresses and so are easily blocked. Decoy routing is an alternative approach that deploys a proxy in association with a router, called a decoy router, that is only accessible indirectly when traffic traverses the router. In this work, we design MultiFlow, a new decoy routing protocol that re-uses the TLS protocol's session resumption mechanism to enable the decoy router itself to resume a client's session. As a consequence, MultiFlow is able to (1) authenticate a client without blocking traffic inline on the decoy router, and (2) use information provided by the client to bootstrap the establishment of additional secure connections for covert communication. The client and decoy router then use a message board-like tunnel to communicate across multiple connections in a way that mitigates probing and traffic analysis attacks.