Paper 2026/2246 Original: eprint.iacr.org/2026/2246 ↗

Binding Humans to Keys: A Secure Decentralized Proof of Personhood Protocol

Abstract

Decentralised proof of personhood, cryptographically binding a digital identity to a unique living human without a trusted central authority, is a foundational problem in permissionless networks. We present a novel protocol, Secure-GYID (S-GYID), resilient to Identity Theft Attack (i.e., adversarial authorities substitute a victim's biometric fingerprint under a malicious public key) and Ghost Key Attack (i.e., colluding authorities fabricate a registration for a non-existent user). Our protocol closes both vulnerabilities by replacing raw biometric transmission with an encryption-based digital fingerprint derivation $F = E(pk_u, P_u)$ computed under a one-way, chosen-plaintext-secure, deterministic scheme, so that no authority can substitute or forge a binding pair without knowledge of the user's secret key. S-GYID further introduces a three-stratum generational authority hierarchy with bounded tenure and VRF-based session selection to limit long-term collusion structurally. We prove Identity Theft Resistance, Biometric Detectability, and Ghost Key Resistance under standard cryptographic assumptions, and provide a hypergeometric session-capture analysis that establishes concrete parameter design rules for both the key activation and authority promotion thresholds.