Proof of Personhood
Proof of personhood (PoP) is a system that verifies an account corresponds to a unique human being, without necessarily revealing that human's identity. It is the cryptographic answer to "how do you ensure one person, one account?"
✦ Key Insight
Many crypto applications — airdrops, governance, UBI experiments, anti-bot systems — break down when one person can create unlimited accounts. PoP enables Sybil resistance without giving up pseudonymity, which matters for the integrity of any economic distribution.
✕ Common Misconceptions
Trusting that a PoP system is fully Sybil-resistant — none is perfect.
Underestimating privacy concerns of biometric-based PoP.
Assuming PoP implies KYC; most designs intentionally separate uniqueness from identity.
Detailed Explanation
How It Works: Different systems use different approaches: biometric scanning (Worldcoin's iris scan), social-graph verification (web of trust), proof of unique device attestation, or zero-knowledge proofs over government IDs. The output is typically an on-chain attestation that an address belongs to a unique person.
FAQs:
Is biometric PoP safe? It depends on the implementation — local-only processing differs greatly from server-stored biometrics.
Can PoP attestations be sold? If the credential is transferable, yes — which undermines the design. Many systems use soulbound tokens to prevent this.
In Practice
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