Paper 2012/494

Protocol Misidentification Made Easy with Format-Transforming Encryption

Kevin P. Dyer, Scott E. Coull, Thomas Ristenpart, and Thomas Shrimpton

Abstract

Deep packet inspection (DPI) technologies provide much-needed visibility and control of network traffic using port-independent protocol identification, where a network flow is labeled with its application-layer protocol based on packet contents. In this paper, we provide the first comprehensive evaluation of a large set of DPI systems from the point of view of protocol misidentification attacks, in which adversaries on the network attempt to force the DPI to mislabel connections. Our approach uses a new cryptographic primitive called format-transforming encryption (FTE), which extends conventional symmetric encryption with the ability to transform the ciphertext into a format of our choosing. We design an FTE-based record layer that can encrypt arbitrary application-layer traffic, and we experimentally show that this forces misidentification for all of the evaluated DPI systems. This set includes a proprietary, enterprise-class DPI system used by large corporations and nation-states. We also show that using FTE as a proxy system incurs no latency overhead and as little as 16\% bandwidth overhead compared to standard SSH tunnels. Finally, we integrate our FTE proxy into the Tor anonymity network and demonstrate that it evades real-world censorship by the Great Firewall of China.

Metadata
Available format(s)
PDF
Category
Applications
Publication info
Published elsewhere. Unknown status
Keywords
applicationscensorshipcensorship circumventiondeep-packet inspectionimplementationinformation hidingregular expressionssecret-key cryptographysteganography
Contact author(s)
kdyer @ cs pdx edu
History
2013-09-30: last of 5 revisions
2012-09-03: received
See all versions
Short URL
https://ia.cr/2012/494
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2012/494,
      author = {Kevin P.  Dyer and Scott E.  Coull and Thomas Ristenpart and Thomas Shrimpton},
      title = {Protocol Misidentification Made Easy with Format-Transforming Encryption},
      howpublished = {Cryptology {ePrint} Archive, Paper 2012/494},
      year = {2012},
      url = {https://eprint.iacr.org/2012/494}
}
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