Self Protocol + LayerZero (Celo → Base)

Build a cross-chain verification flow with Self Protocol on Celo Mainnet and forward results to Base Mainnet via LayerZero.

📁 Project Structure

self-layerzero-example/
├── app/                      # Frontend (Next.js)
│   └── app/
│       ├── page.tsx          # QR + Connect Wallet (no manual address input)
│       └── status/page.tsx   # Recent sends/receipts (polling)
└── contracts/                # Contracts + scripts (Foundry)
    ├── src/
    │   ├── ProofOfHumanOApp.sol      # Celo sender (Self + LZ OApp, has withdraw())
    │   └── ProofOfHumanReceiver.sol  # Base receiver
    ├── script/
    │   └── deploy-oapp-cross-chain.sh
    ├── Makefile              # make deploy, set-scope, fund-source, withdraw-source...
    └── .env(.example)

✅ Prerequisites

• Node.js 20
• Foundry toolchain
• Self App (iOS/Android)
• Wallet funded on Celo (deploy + funding) and Base (deploy)
• Note: Celo Alfajores is not supported by LZ v2

🚀 Quick Start

# 1) Install
cd contracts && npm install && forge install
cd ../app && npm install

# 2) Configure contracts/.env (edit PRIVATE_KEY, VERIFICATION_CONFIG_ID, SCOPE_SEED)
cd ../contracts && cp .env.example .env

# 3) Deploy (deploys + verifies + sets scope/peers + writes app/.env)
make deploy

# 4) Fund source (required for auto-forward; recommend ≥ 0.5 CELO)
make fund-source AMOUNT=0.5

# 5) Run frontend
cd ../app && npm run dev   # http://localhost:3000

On the homepage:

• Connect Wallet → scan QR with Self App → auto navigate to /status for delivery logs

🧠 How It Works

• Verification is initiated from the Self mobile app and executed inside a TEE server (trusted execution environment) that submits the proof to your on‑chain endpoint on Celo.
• Your endpoint is the OApp’s verifySelfProof (inherited from SelfVerificationRoot). It calls the Self Hub on Celo to validate the proof and your policy (e.g., minimum age, exclude country) and normalizes the result for retrieval.
• After success, your overridden onVerificationSuccess hook runs and calls _lzSend with a minimal payload. LayerZero V2 delivers it to Base (EID 30184), where the receiver persists the verification.

sequenceDiagram
    autonumber
    participant User as Self App (mobile)
    participant TEE as TEE server
    participant OApp as Celo OApp.verifySelfProof
    participant Hub as Self Hub (Celo)
    participant LZ as LayerZero Endpoint V2
    participant Base as Base Receiver Contract

    User->>TEE: Scan QR / deeplink
    TEE->>OApp: submit proof to verifySelfProof(userId, proof)
    Note right of OApp: inherited from SelfVerificationRoot
    OApp->>Hub: validate proof + policy checks
    Note right of Hub: minimum age, exclude country, etc.
    Hub-->>OApp: verification ok + attributes
    OApp->>OApp: normalize result for storage
    OApp->>OApp: onVerificationSuccess (override)
    OApp->>LZ: _lzSend(dst=Base EID 30184, gas=200k)
    LZ-->>Base: deliver message
    Base->>Base: _lzReceive() persist verification

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💡 Best Practices

• Keep cross-chain payload minimal (e.g., userAddress, verificationConfigId, small timestamp/flag)
• Avoid large strings/arrays; fees grow with bytes + dst gas
• Fund before testing; insufficient funds will skip sends silently

🔗 Network

• Celo Mainnet (EID 30125)
  • RPC: https://forno.celo.org, Explorer: https://celoscan.io
• Base Mainnet (EID 30184)
  • RPC: https://mainnet.base.org, Explorer: https://basescan.org

📚 References

• Self Docs: https://docs.self.xyz
• Self Tools: https://tools.self.xyz
• LayerZero OApp: https://docs.layerzero.network