Self zkID verification

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name: self-xyz description: "Integrate Self (self.xyz) — a privacy-first identity protocol using zero-knowledge proofs to verify passports and ID cards. Use when the user mentions Self protocol, Self identity, self.xyz, passport verification, zero-knowledge identity verification, SelfAppBuilder, SelfBackendVerifier, SelfVerificationRoot, or wants to add privacy-preserving KYC, age verification, nationality checks, OFAC screening, or Sybil resistance using real-world identity documents. Covers frontend QR code integration, backend proof verification, and on-chain smart contract verification on Celo."

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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 (
     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