Facade: High-Throughput, Deniable Censorship Circumvention Using Web Search

Censorship circumvention systems that use HTTP as cover traffic make tradeoffs between deniability and per-formance by offering either deniability at the expense of performance (e.g., Infranet) or performance at the expense of deniability (e.g., StegoTorus). These systems do so be-cause HTTP is typically very asymmetric, with very little capacity to carry covert data in each HTTP GET request; higher throughput channels achieve performance by gen-erating sequences of HTTP GET requests that do not mimic normal user traffic patterns. Fortunately, the emer-gence of new web services makes it increasingly common for any individual HTTP GET requests to contain more entropy. For example, site-specific search services cre-ate GET requests that contain sequences of search terms that can encode more bits than a single deniable HTTP request otherwise would. In this paper, we design a new encoding technique that uses web search terms to encode hidden messages in an upstream channel for censorship circumvention; implement the encoding technique in a system that resists fingerprinting attacks; and compare the security and performance of Facade to existing censorship circumvention systems that use HTTP as cover traffic.