Sorry the term of art is really soulbound identity right now, I use POS but it's less common. Definitions vary but I say a useful system must allow people to endorse statements with evidence they are a) alive b) not able to be represented by more than one identity (id is linked to your entire soul, not a persona or facet of your being) c) a kind of socially recognized person (human in the expected case)

and then layer on citizenship on top if you want to use this for polling, voting, etc.