On Tue, Jul 01, 2014 at 08:31:00PM +0100, Mark McCarron wrote: > Paul, > [snip] > Eliminating this correlation attack is trivial.
So you keep saying. Everybody who has worked on this who has responded has said that they don't know how and that they find this a hard problem. But your response is simply to keep repeating that it is trivial to eliminate without telling us how. > The attack is dependent on having visibility at both ends. One at > the users end (perhaps ISP) and one near the hidden service (perhaps > exchange). It doesn't take much to match these two together (like > multiple nations sharing intelligence data). One simple attack is > just to flood the hidden service with connections and note where > traffic spikes. > > So, the simple solution is to distribute hidden services within Tor, > so that class of attack will fail. There are no servers in a data > center to expose because it is everywhere and no one can tell, just > by examining the flow of encrypted packets, who was looking at what. Lots of smart people have thought about hidden service design. E.g., Karsten did his dissertation on it and earlier guard nodes were introduced to Tor based on Lasse and my illustration of how easy attacks were on hidden services without guards. Our original design of hidden services in Tor harks back to notions of rendezvous services in earlier NRL onion routing work and earlier work by Ian Goldberg, I think in _his_ dissertation if memory serves. That HS design languished at times while other aspects of Tor were more urgently worked on and that they could use more attention has been acknowledged, and it is getting some. It could use still more and will hopefully be getting it soon. You may be way smarter than all of these people, but so smart that we can't infer how your simple solution works from these two sentence descriptions. As a kneejerk thought based on just even this brief description: a malicious active client is a trivial adversary to create. It can induce whatever signature it wants on its flow to the HS and can actively affect flows from the HS. What keeps the Tor relay adjacent to the HS or the ISP at the HS or between it and the adjacent relay from recognizing timing signals from malicious clients? For that matter, I don't understand why the system you mention would not be vulnerable to the attack you mention to motivate it. > > Now, I know there are a wide range of additional methods to expose > users and the majority are beyond your direct control, but this type > of attack is something within your control. Please illustrate how. Please give a design sketch with at least enough details and at a simple enough level of description that even the world's top hidden service design and analysis researchers can understand it since they keep telling you they don't understand these trivial fixes you keep mentioning. [snip] aloha, Paul -- tor-talk mailing list - tor-talk@lists.torproject.org To unsubscribe or change other settings go to https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk