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

Pattern	When to Use	endpoint	endpointType
Off-chain (backend)	Web apps, APIs, most cases	Your API URL	"https" or "https-staging"
On-chain (contract)	DeFi, token gating, airdrops	Contract address (lowercase)	"celo" or "celo-staging"
Deep linking	Mobile-first flows	Your API URL	"https"

• 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)

Network	Address
Mainnet Hub V2	0xe57F4773bd9c9d8b6Cd70431117d353298B9f5BF
Sepolia Hub V2	0x16ECBA51e18a4a7e61fdC417f0d47AFEeDfbed74
Sepolia Staging Hub V2	0x68c931C9a534D37aa78094877F46fE46a49F1A51

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