DeltaShaper: Enabling Unobservable Censorship-resistant TCP Tunneling over Videoconferencing Streams

Authors: Diogo Barradas (INESC-ID, Instituto Superior Técnico, Universidade de Lisboa), Nuno Santos (INESC-ID, Instituto Superior Técnico, Universidade de Lisboa), Luís Rodrigues (INESC-ID, Instituto Superior Técnico, Universidade de Lisboa)

Volume: 2017
Issue: 4
Pages: 5–22
DOI: https://doi.org/10.1515/popets-2017-0037

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Abstract: This paper studies the possibility of using the encrypted video channel of widely used videoconferencing applications, such as Skype, as a carrier for unobservable covert TCP/IP communications. We propose and evaluate different alternatives to encode information in the video stream in order to increase available throughput while preserving the packetlevel characteristics of the video stream. We have built a censorship-resistant system, named DeltaShaper, which offers a data-link interface and supports TCP/IP applications that tolerate low throughput / high latency links. Our results show that it is possible to run standard protocols such as FTP, SMTP, or HTTP over Skype video streams.

Keywords: Censorship Circumvention, Traffic Analysis, Traffic Encapsulation, Video Stream Synthesis

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