@inproceedings{11693a05e82e487fa98af1ec2d128f28,
title = "Cover your ACKs: Pitfalls of covert channel censorship circumvention",
abstract = "In response to increasingly sophisticated methods of blocking access to censorship circumvention schemes such as Tor, recently proposed systems such as Skypemorph, FreeWave, and CensorSpoofer have used voice and video conferencing protocols as {"}cover channels{"} to hide proxy connections. We demonstrate that even with perfect emulation of the cover channel, these systems can be vulnerable to attacks that detect or disrupt the covert communications while having no effect on legitimate cover traffic. Our attacks stem from differences in the channel requirements for the cover protocols, which are peer-to-peer and loss tolerant, and the covert traffic, which is client-proxy and loss intolerant. These differences represent significant limitations and suggest that such protocols are a poor choice of cover channel for general censorship circumvention schemes.",
keywords = "anonymity, censorship, censorspoofer, freewave, skypemorph",
author = "John Geddes and Max Schuchard and Nick Hopper",
year = "2013",
doi = "10.1145/2508859.2516742",
language = "English (US)",
isbn = "9781450324779",
series = "Proceedings of the ACM Conference on Computer and Communications Security",
pages = "361--372",
booktitle = "CCS 2013 - Proceedings of the 2013 ACM SIGSAC Conference on Computer and Communications Security",
note = "2013 ACM SIGSAC Conference on Computer and Communications Security, CCS 2013 ; Conference date: 04-11-2013 Through 08-11-2013",
}