Anonymous voting

Hi

I am currently using voting_api + vote_up_down on the smartphone apps site. I'd like to let the anonymous users vote, but in such a way that each user (for example, each IP address) can vote only once per node.

Can it be somehow done with voting_api?
If it can almost be done, I am not afraid of some PHP programing to finalize it, but I'd like to get some guidance on where to start.

Best regards,
Artem.