  Open communication over the Internet poses a serious threat to countries with
repressive regimes, leading them to develop and deploy network-based censorship
mechanisms within their networks. Existing censorship circumvention systems
face different difficulties in providing unobservable communication with their
clients; this limits their availability and poses threats to their users. To
provide the required unobservability, several recent circumvention systems
suggest modifying Internet routers running outside the censored region to
intercept and redirect packets to censored destinations. However, these
approaches require modifications to ISP networks, and hence requires
cooperation from ISP operators and/or network equipment vendors, presenting a
substantial deployment challenge. In this report we propose a deployable and
unobservable censorship-resistant infrastructure, called FreeWave. FreeWave
works by modulating a client's Internet connections into acoustic signals that
are carried over VoIP connections. Such VoIP connections are targeted to a
server, FreeWave server, that extracts the tunneled traffic of clients and
proxies them to the uncensored Internet. The use of actual VoIP connections, as
opposed to traffic morphing, allows FreeWave to relay its VoIP connections
through oblivious VoIP nodes, hence keeping itself unblockable from censors
that perform IP address blocking. Also, the use of end-to-end encryption
prevents censors from identifying FreeWave's VoIP connections using packet
content filtering technologies, like deep-packet inspection. We prototype the
designed FreeWave system over the popular VoIP system of Skype. We show that
FreeWave is able to reliably achieve communication bandwidths that are
sufficient for web browsing, even when clients are far distanced from the
FreeWave server.

Cryptography and Security