Decentralized, unique, human-usable identifiers, free and anonymous to legitimate humans (limited to only a few per) but unobtainable by non-humans. I can accep

Decentralized, unique, human-usable identifiers, free and anonymous to legitimate humans (limited to only a few per) but unobtainable by non-humans. I can accept humans giving/using up some of theirs for non-human purposes. Not really an idea, but seems impossible.