Tor Hidden Services… Aren’t

Still trust encryption? Add this one to your file. The well-studied Tor anonymizing software / network has an interesting and very useful feature: you can use it to host untraceable, anonymous websites called “hidden services.” At least, they were thought to be untraceable and anonymous.

Researchers at the University of Luxembourg have figured out how to trace and deanonymize those previously hidden services. The problems are serious enough that the researchers call for the system’s “careful redesign.”

I don’t know enough to say whether i2p — whose primary function is providing the equivalent of Tor’s hidden services — suffers from the same flaws. Anyone know?

“We have analyzed the security properties of Tor hidden
services and shown that attacks to deanonymize hidden
services at a large scale are practically possible with only a moderate amount of resources.

We have demonstrated
that collecting the descriptors of all Tor hidden services is possible in approximately 2 days by spending less than USD
100 in Amazon EC2 resources. Running one or more guard
nodes then allows an attacker to correlate hidden services
to IP addresses using a primitive traffic analysis attack.
Furthermore, we have shown that attackers can impact the
availability and sample the popularity of arbitrary hidden
services not under their control by selectively becoming their hidden service directories.

To address these vulnerabilities we have proposed coun-
termeasures. These prevent hidden service directories from
learning the content of any the descriptors unless they also know their corresponding onion address and significantly
increase the resources required to selectively become a
hidden service directory for a targeted hidden service.
However, note that the above suggestions are nothing
more than stop-gap measures. We believe that the problems
we have shown are grave enough to warrant a careful
redesign of Tors hidden services.”

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