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[tor-dev] Request info about how the Tor HS DoS works



Hello, since months ago we are debating proposals about how to stop HS being DDoSed. We have many open issues and even developed in a rush a fix "just for the network" (not HS availability).

But, I have not seen yet a good explanation about what is really happening when HS is being DDoSed by this famous and effective attack. I mean, the only thing I know about it is that its goal is to send a ton of INTRODUCE2 cells to the HS, but, what is the cost for the attacker? Some questions need to be answered, at least If I want to understand it and make a proposal for fixing this issues.

Questions:

Is the attacker building a circuit to the Rendz point as expected by the protocol? How can we be sure of that?

-Attacker (client) to Rendezvous point circuit:

What is exactly happening on this circuit and how can the attacker improve the attack?

Is the attacker using the same Rendz over and over for its INTRODUCE1? A new circuit to the Rendz? Can the first two hops of a circuit be reused (only changing the exit node) so it can build a new circuit to a new Rendz faster and make the attack better?

-Attacker (client) to Intro point:

what is exactly happening on this side of the equation?


Sorry, but I could not find the answer to these questions and what is going on on any ticket or this mail lists.

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