Add Drupal uid to the author field in nutch

So I still google the last weeks to find a solution, but I have nothing found.

I just want, if a user adds a domain after some verifications, that his site should get his uid thru the author field for example. This is because other users should search only in the registered domains of this special user or in all without his own domains. Any ideas or hints for me?

greetings
frank