Self Protocol Integration

Self lets users prove identity attributes (age, nationality, humanity) from passports/ID cards using zero-knowledge proofs — no personal data exposed. Users scan their document's NFC chip in the Self mobile app and share a zk proof with your app.

Quick Start (Next.js Off-Chain)

1. Install

npm install @selfxyz/qrcode @selfxyz/core

2. Frontend — QR Code Component

"use client";
import { SelfQRcodeWrapper, SelfAppBuilder } from "@selfxyz/qrcode";

export default function VerifyIdentity({ userId }: { userId: string }) {
  const selfApp = new SelfAppBuilder({
    appName: "My App",
    scope: "my-app-scope",
    endpoint: "https://yourapp.com/api/verify",
    endpointType: "https",
    userId,
    userIdType: "hex",
    disclosures: {
      minimumAge: 18,
    },
  }).build();

  return (
    <SelfQRcodeWrapper
      selfApp={selfApp}
      onSuccess={() => console.log("Verified")}
      type="websocket"
      darkMode={false}
    />
  );
}

3. Backend — Verification Endpoint

// app/api/verify/route.ts
import { SelfBackendVerifier, DefaultConfigStore } from "@selfxyz/core";

export async function POST(req: Request) {
  const { proof, publicSignals } = await req.json();

  const verifier = new SelfBackendVerifier(
    "my-app-scope",                    // must match frontend scope
    "https://yourapp.com/api/verify",  // must match frontend endpoint
    true,                              // true = accept mock passports (dev only)
    null,                              // allowedIds (null = all)
    new DefaultConfigStore({           // must match frontend disclosures
      minimumAge: 18,
    })
  );

  const result = await verifier.verify(proof, publicSignals);

  return Response.json({
    verified: result.isValid,
    nationality: result.credentialSubject?.nationality,
  });
}

Integration Patterns

• Off-chain: Fastest to implement. Proof sent to your backend, verified server-side.
• On-chain: Proof verified by Celo smart contract. Inherit SelfVerificationRoot. Use for trustless/permissionless scenarios.
• Deep linking: For mobile users — opens Self app directly instead of QR scan. See references/frontend.md.

Critical Gotchas

1. Config matching is mandatory — Frontend disclosures must EXACTLY match backend/contract verification config. Mismatched age thresholds, country lists, or OFAC settings cause silent failures.

2. Contract addresses must be lowercase — Non-checksum format in frontend endpoint. Use .toLowerCase().

3. Country codes are ISO 3-letter — e.g., "USA", "IRN", "PRK". Max 40 countries in exclusion lists.

4. Mock passports = testnet only — Set mockPassport: true in backend / use "celo-staging" endpoint type. Real passports require mainnet. To create a mock passport: open Self app, tap the Passport button 5 times. Mock testing requires OFAC disabled.

5. Version requirement — @selfxyz/core >= 1.1.0-beta.1.

6. Attestation IDs — 1 = Passport, 2 = Biometric ID Card. Must explicitly allow via allowedIds map.

7. Scope uniqueness — On-chain, scope is Poseidon-hashed with contract address, preventing cross-contract proof replay.

8. Endpoint must be publicly accessible — Self app sends proof directly to your endpoint. Use ngrok for local development.

9. Common errors: ScopeMismatch = scope/address mismatch or non-lowercase address. Invalid 'to' Address = wrong endpointType (celo vs https). InvalidIdentityCommitmentRoot = real passport on testnet (use mainnet). Invalid Config ID = mock passport on mainnet (use testnet).

Deployed Contracts (Celo)

References

Load these for deeper integration details:

• references/frontend.md — SelfAppBuilder full config, SelfQRcodeWrapper props, deep linking with getUniversalLink, disclosure options
• references/backend.md — SelfBackendVerifier constructor details, DefaultConfigStore vs InMemoryConfigStore, verification result schema, dynamic configs
• references/contracts.md — SelfVerificationRoot inheritance pattern, Hub V2 interaction, setVerificationConfigV2, customVerificationHook, getConfigId, userDefinedData patterns