Can you set hidden service to use specific HSdir?

Question

I am trying to understand what are possibilities of adversary running his own HSDir and few relays?

• Adversary cannot retrieve all the .onion addresses? Only the ones advertised on his HSDir? Are HSDirs that are advertising specific .onion addresses rotating over some time?
• Adversary can see how many connection attempts were made to specific .onion address?
• If adversary controls entry node(guard relay) and HSDir on the client side. He is able to retrieve the users IP by traffic correlation attack?
• If adversary controls entry node and HSDIR on hidden service side he can deanonymize location of hidden service?

Reffering to https://conference.hitb.org/hitbsecconf2015ams/wp-content/uploads/2015/02/D2T2-Filippo-Valsorda-and-George-Tankersly-Non-Hidden-Hidden-Services-Considered-Harmful.pdf

Slide 49 says:

• "You can trust an HSDir you run yourself."

• "Free detection: you will notice if someone competes with you for the HSDir positions"

These two quotes got me confused...

As a countermeasure client and person running hidden service can set their entry nodes or bridges also.

EntryNodes node,node,…

Adversary is than only in possibility (using positioning attack mentioned in slides) to see number of connection attempts but cannot deanonymize users or person running hidden-service.

Answer 1

I don't think it's possible to do this.

Your hidden service is advertised on 6 different HSDir nodes. The HSDir nodes to use are calculated from your hidden service's .onion address. The same calculation can then be used by a client who wants to visit the hidden service. This is the "rendezvous" protocol.

You couldn't configure your hidden service to use just any old HSDir because clients wouldn't be able to find it. The rendezvous wouldn't work. The most you could do would be to pick a subset (or one) of the 6 nodes it should be using, but I don't believe that's possible. (Have a look at the Hidden Service Options part of the Tor Manual for what can be configured.)

Have a read of this thread for more details of how the rendezvous works: How does Tor know which HSDir to connect to?