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:

1. User completes KYC with issuer off-chain
2. Issuer provides signed credential or Semaphore identity
3. User generates ZK proof of membership/eligibility
4. 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

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: vaquarkhan
• Source: vaquarkhan/web3-agent-skills
• License: MIT

Install and usage instructions live in the source repository linked above.