The .onion name can't exist without having the private key for it, that's kind of the point. There is already a private key needed to prove that who you're tal

The .onion name can't exist without having the private key for it, that's kind of the point. There is already a private key needed to prove that who you're talking to is the right person: otherwise the request can't be routed to it. That's pretty fundamental to how Tor hidden services work actually.