Abstract

An anonymous network provides services to hide the correspondence
between its incoming and outgoing messages. Timing attack is a
significant challenge for anonymous networks that support interactive
and low-latency applications.  We introduce a novel metric that can
quantitatively measure the practical effectiveness (i.e.  anonymity)
of all anonymous networks in the presence of timing attack. Our metric
is based on a novel measurement of the distortion of the packet timing
between the incoming and the outgoing flows to and from the anonymous
network and it uses wavelet based analysis to measure the variability
of the distortion. To the best of our knowledge, our approach is the
first practical method that can quantitatively measure the packet
timing distortion between flows that may have gone through such
transformations as flow mixing/spliting/merging, adding chaff, packet
dropping.

To validate our anonymity metric, we have conducted real-time timing
attacks on various deployed anonymous networks such as Tor,
anonymizer.com and have used the timing attack results as the ground
truth for validating our anonymity metric. We have found strong
correlation between our anonymity metric and the timing attack
results.  Our metric measurements and timing attack results show that
the circuit rotation in Tor network could significantly increase its
resistance to timing attack at the cost of more timing disturbances to
the normal users. In addition, we have found that adding constant rate
chaff (i.e. cover traffic) has diminishing effect in anonymizing
packet flows.


Speaker Bio


Jing Jin is a Ph.D. student in Computer Science Department of George
Mason University. Her research interests include system and networking
security, software engineering.