Diogo Miguel Barrinha Barradas
Unobservable Covert Streaming for Internet Censorship Circumvention
Tese submetida para provas de mestrado em Engenharia Informática e de Computadores
Instituto Superior Técnico, Universidade de Lisboa.
Repressive regimes are known to deploy large-scale surveillance and
censorship mechanisms in order to deter their citizens from accessing
or publishing rightful information in the Internet. To evade the
censors’ control over the access to information, recent systems
enable the creation of covert channels by tunneling data through
popular media streaming protocols. Unfortunately, the covert channel
may induce patterns in the resulting packet stream that distinguish
themselves from the packet patterns that characterize regular
streams. If the differences are statistically significant, the censor
may be able to un- veil, and subsequently block, the covert
channel. Therefore, one of the main challenges in implementing this
technique is to ensure that the covert channel remains unobservable
Considering this challenge, this thesis studies the encoding of
arbitrary data on the video channel of widely used video-conferencing
applications, such that the traffic characteristics of legitimate
video- conferencing calls are preserved. Particularly, the thesis
proposes and evaluates different alternatives to encode information
within a video-stream, in order to maximize the available throughput
while re- maining indistinguishable from legitimate video-conferencing
traffic. A prototype of the system, named DeltaShaper, establishes a
covert channel that offers a data-link interface and that can support
any pro- tocol that runs over TCP/IP. The experimental evaluation's
results show that it is possible to achieve a throughput of 0.4 KB/s
while maintaining unobservability, which allows to run standard
applications such as FTP, Telnet, or Wget.
- Unobservable Covert Streaming for Internet Censorship Circumvention
- Diogo Miguel Barrinha Barradas
- MSc Thesis. Instituto Superior Técnico,
Universidade de Lisboa.
- September, 2016.
- Available BibTeX, MSC Thesis, and extended abstract, and mid-term
- Síntese de Vídeo para
Evasão de Censura na Internet.
- D. Barradas,
L. Rodrigues e N. Santos
- Actas do oitavo Simpósio de
Informática (Inforum), Lisboa, Portugal, Sep. 2016.
- DeltaShaper: Enabling Unobservable
Censorship-resistant TCP Tunneling over Videoconferencing
- D. Barradas, N. Santos, and
- In Proceedings of the 17th Privacy Enhancing
Technologies Symposium, Minneapolis (MN), USA July 2017.