Tracking Anonymous Peer-to-Peer VoIP Calls on the Internet

Kurt Albershardt kurt at nv.net
Thu Aug 24 08:34:51 PDT 2006


ABSTRACT

Peer-to-peer VoIP calls are becoming increasingly popular due to their
advantages in cost and convenience. When these calls are encrypted from
end to end and anonymized by low latency anonymizing network, they are
considered by many people to be both secure and anonymous.

In this paper, we present a watermark technique that could be used for
effectively identifying and correlating encrypted, peer-to-peer VoIP
calls even if they are anonymized by low latency anonymizing networks.
This result is in contrast to many people's perception. The key idea is
to em- bed a unique watermark into the encrypted VoIP flow by slightly
adjusting the timing of selected packets. Our analysis shows that it
only takes several milliseconds time adjustment to make normal VoIP
flows highly unique and the embedded watermark could be preserved
across the low latency anonymizing network if appropriate redundancy is
applied. Our analytical results are backed up by the real-time
experiments performed on leading peer- to-peer VoIP client and on a
commercially deployed anonymizing network. Our results demonstrate that
(1) tracking anonymous peer-to- peer VoIP calls on the Internet is
feasible and (2) low latency anonymizing networks are susceptible to
timing attacks.

<http://ise.gmu.edu/%7exwangc/Publications/CCS05-VoIPTracking.pdf>


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