  Open communication over the Internet poses a serious threat to countries with
repressive regimes, leading them to develop and deploy censorship mechanisms
within their networks. Unfortunately, existing censorship circumvention systems
do not provide high availability guarantees to their users, as censors can
identify, hence disrupt, the traffic belonging to these systems using today's
advanced censorship technologies. In this paper we propose SWEET, a highly
available censorship-resistant infrastructure. SWEET works by encapsulating a
censored user's traffic to a proxy server inside email messages that are
carried over by public email service providers, like Gmail and Yahoo Mail. As
the operation of SWEET is not bound to specific email providers we argue that a
censor will need to block all email communications in order to disrupt SWEET,
which is infeasible as email constitutes an important part of today's Internet.
Through experiments with a prototype of our system we find that SWEET's
performance is sufficient for web traffic. In particular, regular websites are
downloaded within couple of seconds.
