Personhood Credentials (PHCs)

Semantic & Data Protocol

A verifiable credential type specifying claims that attest a credential holder is a real, unique person within an issuing ecosystem (e.g., a government, employer, university, or nonprofit community). PHCs add a credential-type semantic layer on top of the W3C Verifiable Credentials Data Model, defining what data a personhood credential carries and how its claims are structured for cross-ecosystem interpretation. Originally proposed in the August 2024 'Personhood Credentials' paper as a response to generative AI's ability to defeat CAPTCHAs and impersonate humans; being standardized by the Decentralized Trust Graph Working Group (DTGWG), a joint ToIP-DIF working group .

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Details

License N/A — specification document, not source code; reference implementations in OpenVTC (Apache-2.0) and other FPP-ecosystem projects are open source
Dev Status 📝 Draft
Dev Status Detail Draft / Standardization in progress (specification under development at DTGWG; multiple reference implementations underway including in the First Person Project ecosystem and OpenVTC)
Owner Specification origin: 27 multi-institutional authors of the August 2024 Personhood Credentials paper led by researchers from MIT, OpenAI, Microsoft, Harvard, UC Berkeley, and other institutions. Standardization: Decentralized Trust Graph Working Group (DTGWG) — joint ToIP-DIF Working Group
Owner - List
  • Trust Over IP Foundation
Governing Body Decentralized Trust Graph Working Group (joint ToIP–DIF working group) | None (originating multi-institutional author group spanning MIT, OpenAI, Microsoft, Harvard and UC Berkeley; not itself a governing body)
Country International (multi-institutional academic and industry collaboration)
Start Year 2024
Stack N/A — specification, not implementation
Funding Specification work supported by sponsoring organizations of the DTGWG (ToIP, DIF, Linux Foundation Decentralized Trust, Customer Commons, Ayra Association); original paper produced by academic and industry research collaboration
Funding - List
  • Decentralized Identity Foundation
  • Trust Over IP Foundation
Last Investigated Jul 1, 2026

Topology view

This tool in the centre and the things it is directly related to. Each line names the kind of relationship.

Topology view: Personhood Credentials (PHCs)This tool in the centre and the things it is directly related to. Each line names the kind of relationship.PersonhoodCredentials…DIDComm (Basis for)DIDCommFirst Person Project / Network (Basis for, Conforming implementations, Protocol spoken by)First PersonProject / Ne…OpenID for Verifiable Credentials (OpenID4VC) (Basis for)OpenID forVerifiable C…OpenVTC (Basis for, Conforming implementations)OpenVTCVCs (Based on, Built on, Conforms to, Speaks protocol)VCsVerifiable Relationship Credentials (VRCs) (Basis for)VerifiableRelationship…JSON-LD (Built on, Speaks protocol)JSON-LDDIDs (Conforms to)DIDsTrust Over IP Foundation (Developed by, Funded by)Trust OverIP FoundationDecentralized Identity Foundation (Funded by, Hosted at)DecentralizedIdentity Fou…

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Use Case Domains

Co-Creation & Knowledge

Affordances

Portable attestations Proof of humanity

Semantic & Data Protocol Attributes

Owner - List
  • Trust Over IP Foundation
Origins Proof of personhood / Decentralized identity (response to generative AI defeating CAPTCHAs and traditional bot-detection; alternative to centralized biometric solutions like Worldcoin)
Database N/A — credentials are stored in user-controlled digital wallets; no centralized database is part of the specification
Query Language N/A — credential exchange uses standard VC presentation/verification protocols rather than a query language
Data Formats W3C Verifiable Credentials Data Model (JSON-LD by default; JWT/SD-JWT serializations also possible per the underlying VC spec); zero-knowledge proof presentations for threshold-based unique-personhood proofs
Collaborative Live Editing N/A
Rich Text Editing N/A
Mobile Support N/A — credentials can be presented from any wallet on any platform; the specification is platform-agnostic
Web Support N/A — same as above
Native Apps N/A — same as above
Terms Free open standard (no licensing fees for adoption)
Funding - List
  • Decentralized Identity Foundation
  • Trust Over IP Foundation
Funds N/A — open standard, no funding round
Based On W3C Verifiable Credentials Data Model (the underlying credential framework PHCs extend); W3C Decentralized Identifiers (for issuer and holder identity); Personhood Credentials paper, August 2024 (originating specification); zero-knowledge proof cryptography (for threshold-based unique-personhood verification)
Semantic Web Compatibility Full (built on W3C Verifiable Credentials Data Model, which uses JSON-LD as its primary serialization; PHC claims are expressed as RDF-compatible structured data)
Protocol Maturity / Standardization W3C Draft / DTGWG standardization track (originating paper August 2024; specification work ongoing in the Decentralized Trust Graph Working Group, a joint ToIP-DIF participation Working Group; expected to produce a formal W3C-track specification)
Vocabulary / Ontology Type Identity attestation / Proof of personhood (specifies a credential-type vocabulary for attesting that the holder is a real, unique person within a given issuing ecosystem)
Usage Pattern Embedded in other protocols (PHCs are exchanged via standard VC issuance and presentation protocols such as OpenID4VC and DIDComm; the specification defines the semantic content of a particular credential type rather than its transport)

Relationships

How this tool connects to other tools and organizations, from relationships reviewed by the OpenHaven data steward. They describe how projects connect, not how good they are.

Based on
Built on
Conforms to
Developed by
  • Trust Over IP Foundation
Funded by
  • Decentralized Identity Foundation
  • Trust Over IP Foundation
Hosted at
  • Decentralized Identity Foundation
Speaks protocol
Basis for
Conforming implementations
Protocol spoken by