skill-10-identity-did

Identity (DID)

When to Use

Creating or resolving Decentralized Identifiers (DIDs)
Issuing/verifying Verifiable Credentials (VCs)
Registering or resolving ENS names
Implementing ZK-KYC (prove eligibility without revealing PII)
Working with on-chain attestations (EAS, Verax)

Prerequisites

MCP: blockchain-rpc-server, compliance-screening-server
Skill-09 for KYC/regulatory context

Workflow

1. DID Methods

Method	Format	Chain
`did:ethr`	`did:ethr:0x...`	Ethereum
`did:pkh`	`did:pkh:eip155:1:0x...`	Multi-chain
`did:ion`	Sidetree on Bitcoin	Bitcoin L2
`did:web`	HTTPS-hosted	Off-chain

Create DID document with verification methods (public keys) and service endpoints.

2. Verifiable Credentials

Issuer → signs VC → Holder stores → Verifier requests proof

Use W3C VC Data Model v2
Sign with EthereumEip712Signature2021 or Ed25519Signature2020
Verify: check signature, revocation status, schema compliance

3. ENS

Resolve: eth_resolver.resolve(name, data)
Register via ETH Registrar Controller
Set records: address, text (email, url, avatar), contenthash (IPFS)
Reverse resolution: set addr.reverse record

4. ZK-KYC

Prove attributes without revealing identity:

User completes KYC with issuer off-chain
Issuer provides signed credential or Semaphore identity
User generates ZK proof of membership/eligibility
Verifier checks proof on-chain (no PII exposed)

Protocols: Polygon ID, World ID, Semaphore, Sismo

5. On-Chain Attestations

Ethereum Attestation Service (EAS):

eas.attest(AttestationRequest({
  schema: schemaUID,
  data: AttestationRequestData({ recipient, expirationTime, revocable, refUID, data, value })
}));

Use for reputation, KYC status, guild membership, and compliance proofs.

Privacy Rules

Never store PII on-chain
Minimize credential disclosure (selective disclosure proofs)
Honor GDPR right-to-erasure for off-chain identity data

References

references/did-methods.md
references/eas-schemas.md