Finding a reputable .ru registrar / is Gandi.net reputable?
Why are you worried about a passport number? It's unique to that passport, it changes when that passport expires or is replaced. It's a reference to THE PASSPORT not to THE PERSON. What do you think could happen if someone knew that number?
If someone were to use it fraudulently they could pretend to be you, say for registering .ru domain names.
I'd worry more about Russia than I would most registrars.
Are you saying that the people in their government who have access to the database of registered domains can't be trusted?
I don't actually know if the information goes to their government or if it's only stored by the registrar in the event that they need it because of fraudulent activity. Is there anyone here who can answer that?
Sign up, when it asks for your passport number make a few, shall we say "typos" and see if they take it.
And then hope that there will never ever be any dispute with the domain in question, because if it does, and they see that the passport number is fake… well, at best they will just take your domain out of your control, so, if you like to take risks…
Once again, you can only get caught if they actually cross check the data - and do you really believe that a mere domain registrar has access to that type of info? That would be like GoDaddy have access to your SSN in the States (of course it is Russia, so who knows - give it a shot with a throw away domain and see what happens).
So why go with that route anyway when you can simply provide your real passport number and avoid any potential future hassle? It's not your SSN or anything THAT sensitive, and you also need to reveal the passport number whenever you cross the border anywhere in the world, so why all this paranoid stuff?