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W3C Verifiable Credentials

Definition

Verifiable Credentials (VCs) are a W3C standard for expressing credentials (identity claims) in a way that is cryptographically verifiable, tamper-evident, and privacy-respecting. VCs are the technical building block of digital identity wallets.

The Trust Triangle

graph LR
    A[Issuer<br/>Government, university, bank] -->|Issues credential| B[Holder<br/>Individual with wallet]
    B -->|Presents credential| C[Verifier<br/>Bank, employer, service]
    A -.->|Publishes public key| D[Verifiable Data Registry<br/>Blockchain, DNS, web]
    C -.->|Checks issuer's key| D

    style A fill:#1565C0,color:#fff
    style B fill:#2E7D32,color:#fff
    style C fill:#6A1B9A,color:#fff
  1. Issuer creates and signs a credential (e.g., government signs "Name: John, DOB: 1990-01-15, Citizen: India")
  2. Holder stores the credential in their wallet
  3. Verifier checks the issuer's cryptographic signature — if valid, the credential is trusted

VC Structure

{
  "@context": ["https://www.w3.org/2018/credentials/v1"],
  "type": ["VerifiableCredential", "IdentityCredential"],
  "issuer": "did:web:government.example.com",
  "issuanceDate": "2024-01-15T00:00:00Z",
  "credentialSubject": {
    "id": "did:key:z6Mkf5rG...",
    "givenName": "John",
    "familyName": "Doe",
    "dateOfBirth": "1990-01-15",
    "nationality": "IN"
  },
  "proof": {
    "type": "Ed25519Signature2020",
    "verificationMethod": "did:web:government.example.com#key-1",
    "proofValue": "z58DAdFfa9..."
  }
}

Selective Disclosure

VCs support Zero-Knowledge Proofs (ZKPs) and SD-JWT for selective disclosure:

Scenario What's Shared What's Hidden
Age verification at bar "Over 18: true" Name, DOB, address, everything else
Bank KYC Name, DOB, nationality, address Health info, education, employment
Employer check Degree, university, year GPA, other courses, personal info

Key Takeaways

Summary

  • VCs provide cryptographic proof of identity claims — tamper-evident, verifiable, portable
  • The Issuer → Holder → Verifier trust triangle enables decentralized identity
  • Selective disclosure allows sharing only what's needed — huge privacy improvement
  • VCs are the technical standard behind EUDI Wallet and other digital identity systems
  • For eKYC: verifying a VC is instant and mathematically certain — no OCR, no face matching needed