  Deep packet inspection technology became a cornerstone of Internet censorship
by facilitating cheap and effective filtering of what censors consider
undesired information. Moreover, filtering is not limited to simple pattern
matching but makes use of sophisticated techniques such as active probing and
protocol classification to block access to popular circumvention tools such as
Tor.
  In this paper, we propose ScrambleSuit; a thin protocol layer above TCP whose
purpose is to obfuscate the transported application data. By using morphing
techniques and a secret exchanged out-of-band, we show that ScrambleSuit can
defend against active probing and other fingerprinting techniques such as
protocol classification and regular expressions.
  We finally demonstrate that our prototype exhibits little overhead and
enables effective and lightweight obfuscation for application layer protocols.
