Journalists have been asking us for our thoughts about a recent pdf about a judge deciding that a defendant shouldn't get any more details about how the prosecutors decided to prosecute him. Here is the statement we wrote for them:
"We read with dismay the Western Washington District Court's Order on Defendant's Motion to Compel issued on February 23, 2016, in U.S. v. Farrell. The Court held "Tor users clearly lack a reasonable expectation of privacy in their IP addresses while using the Tor network." It is clear that the court does not understand how the Tor network works. The entire purpose of the network is to enable users to communicate privately and securely. While it is true that users "disclose information, including their IP addresses, to unknown individuals running Tor nodes," that information gets stripped from messages as they pass through Tor's private network pathways.
This separation of identity from routing is key to why the court needs to consider how exactly the attackers got this person's IP address. The problem is not simply that the attackers learned the user's IP address. The problem is that they appear to have also intercepted and tampered with the user's traffic elsewhere in the network, at a point where the traffic does not identify the user. They needed to attack both places in order to link the user to his destination. This separation is how Tor provides anonymity, and it is why the previous cases about IP addresses do not apply here.
The Tor network is secure and has only rarely been compromised. The Software Engineering Institute ("SEI") of Carnegie Mellon University (CMU) compromised the network in early 2014 by operating relays and tampering with user traffic. That vulnerability, like all other vulnerabilities, was patched as soon as we learned about it. The Tor network remains the best way for users to protect their privacy and security when communicating online."
IANAL but this reminds me of
IANAL but this reminds me of Kyllo v. United States, where the Supreme Court ruled that thermal imaging of a home was a search that, if performed without a warrant, was unreasonable and hence unconstitutional. The reasoning was that there is an expectation of privacy in a home, and a thermal imaging camera is not commonly available to the public.
The discovery of IP addresses of Tor users can't be done with publicly available equipment either. The attack carried out by CMU SEI was performed with software they designed specifically to conduct surveillance on the Tor network. Also, Tor is designed to prevent identifiable information from leaving a person's home, through its use of encryption. It seems therefore at least some of the reasoning from Kyllo v. US could be applied to this and similar cases.