Proof of Personhood

Establishing that a unique, real human is behind an account — without necessarily revealing who they are — to resist Sybil attacks where one actor creates many fake identities. Approaches include biometrics (e.g. World), social graphs/webs of trust, and in-person events, each trading among scalable uniqueness, privacy, and decentralisation. It proves uniqueness, not identity or good behaviour, and is not perfectly Sybil-proof (verifications can be sold or coerced). Underpins fair airdrops, one-person-one-vote governance, and quadratic funding.