Though I dislike cryptocurrency, it seems like the most plausible route for this. I would try to use my wealth to setup some NGO that would offer a "Citizen ID

Though I dislike cryptocurrency, it seems like the most plausible route for this. I would try to use my wealth to setup some NGO that would offer a "Citizen ID" solution to replace something like SSNs with a modern equivalent system using symmetric key cryptography, a yubikey like thing, and biometrics for people who lose their key. Once we get a satisfactory solution designed we start convincing more and governments to use it so we can get every individual human id'd, or, at least, most of them. Once everyone has a unique ID we create a cryptocurrency stablecoin backed by cash hoard. We create a wallet for every individual person and give them a stablecoin that they can redeem for one dollar. At that point I would consider the challenge more or less complete.