Verifiable Credential Trust Triangle
Thankfully the promise of digital credentials was recognized several years ago by pioneers at the World Wide Web Consortium (W3C). They began the effort to standardize the file formats and digital signatures needed. The result was the Verifiable Credentials Data Model 1.0 specification, approved as a full W3C standard in September 2019. Below is a diagram showing how verifiable credentials work.
- First the issuer writes a Decentralized Identifier (DID) together with its public key (and any other cryptographic material needed for the issuer’s verifiable credentials) to a blockchain (or other sufficiently trusted public utility).
- Second, the issuer uses its private key to digitally sign a verifiable credential it issues to a qualified holder, who stores it in her own digital wallet. Note that for privacy preservation, this entire issuance process takes place off-chain.
- Third, a verifier requests a digital proof of one or more credentials from the holder. If the holder consents, the holder’s wallet generates and returns the proofs to the verifier. Since the proofs contain the issuer’s DID, the verifier uses it to read the issuer’s public key and other cryptographic data from the blockchain.
- In the final step, the verifier uses the issuer’s public key to verify that the proofs are valid and that the digital credential has not been tampered with.