ProofPay

Secure peer-to-peer USDC escrow on Arc Testnet.

Live app · Smart contract · Deployment transaction

ProofPay is currently a public testnet MVP. It does not handle real funds and has not been audited.

Why ProofPay

Peer-to-peer online deals often force one side to take the risk first: the buyer pays before delivery, or the seller delivers before payment. ProofPay replaces that trust gap with a transparent escrow flow where test USDC is held by a smart contract and released only after the seller confirms delivery and the buyer approves payment.

Final-submission status

The public Arc Testnet MVP supports the complete escrow lifecycle:

1. A buyer creates an escrow request and shares a private review link.
2. The seller connects a wallet, verifies the deal, and accepts or rejects it.
3. After acceptance, the buyer deposits Arc Testnet USDC, EURC, or cirBTC into the matching escrow contract.
4. The seller confirms delivery.
5. The buyer releases the locked funds to the seller.

The web app also includes pending, active, completed, cancelled, and rejected order states; persistent off-chain order metadata; transaction links to Arcscan; Circle email wallets; and MetaMask and Rabby support. Developer-led testing is complete and public testnet testing is ongoing.

Live evidence

• Public application deployed at proofpay.online
• Escrow contract deployed on Arc Testnet
• Circle email wallet, MetaMask, and Rabby flows implemented and tested
• Three completed end-to-end escrow tests across three wallets
• Persistent order records stored in Neon Postgres
• Frontend and backend deployed together through Vercel Services
• Automated escrow lifecycle and authorization tests

Architecture

Buyer / Seller
      │
      ▼
React + Vite frontend
      │
      ├──────── ethers.js ────────► ProofPayEscrow.sol
      │                              │
      │                              └── Arc Testnet USDC
      │
      └──────── REST API ─────────► Express backend
                                     │
                                     └── Neon Postgres

Stack

• Frontend: React 19, Vite, Tailwind CSS, ethers.js
• Wallets: MetaMask and Rabby
• Backend: Express.js
• Database: Neon serverless Postgres
• Contracts: Solidity, OpenZeppelin, Hardhat and Foundry
• Network: Arc Testnet
• Hosting: Vercel Services

Contract details

Item	Value
Network	Arc Testnet
Chain ID	5042002
ProofPay escrow	0xCd0f43E573899809ff96C560439570A760698C9a
Test USDC	0x3600000000000000000000000000000000000000
EURC	0x89B50855Aa3bE2F677cD6303Cec089B5F319D72a
cirBTC	0xf0C4a4CE82A5746AbAAd9425360Ab04fbBA432BF
ProofPay USDC Escrow	0xCd0f43E573899809ff96C560439570A760698C9a
ProofPay EURC Escrow	0xa4322D8ba3E040A3028FD6ABaC3c6a5625ed4ca7
ProofPay cirBTC Escrow	0x8bfeD6F70Eb595946543b192b6E63d75A0bBEf4B

The contract uses SafeERC20, ReentrancyGuard, participant-only state transitions, and an owner-controlled dispute resolution path.

Repository structure

contracts/   Solidity escrow contract
scripts/     Hardhat deployment script
foundry/     Foundry deployment and test workspace
frontend/    React/Vite web application
backend/     Express API and database integration
vercel.json  Multi-service production configuration
docs/        Configuration and judge-testing guides
submission/  Final form copy and presentation artifacts

Deploy EURC and cirBTC escrow contracts

Use the same deployer account that owns the existing USDC escrow. Keep the private key in an encrypted Foundry keystore; do not commit it to the project.

cast wallet import proofpay-deployer --interactive
forge script script/DeployAssetEscrows.s.sol:DeployAssetEscrows \
  --root foundry \
  --rpc-url arc \
  --account proofpay-deployer \
  --broadcast

Copy the two resulting addresses into frontend/.env as VITE_EURC_ESCROW_ADDRESS and VITE_CIRBTC_ESCROW_ADDRESS.

Local setup

1. Install dependencies

npm install
npm --prefix frontend install
npm --prefix backend install

2. Configure the backend

cp backend/.env.example backend/.env

Set at minimum:

PORT=5001
FRONTEND_URL=http://localhost:5173
DATABASE_URL=your_neon_postgres_connection_string
CIRCLE_API_KEY=your_circle_standard_api_key

The Circle API key stays on the backend and is required for email OTP and user-controlled wallet creation.

3. Configure the frontend

cp frontend/.env.example frontend/.env

For local development:

VITE_API_URL=http://localhost:5001/api
VITE_CIRCLE_APP_ID=your_circle_user_controlled_wallet_app_id

Email authentication must also be enabled and configured under Wallets → User Controlled → Configurator → Email in the Circle Developer Console.

4. Run both services

npm --prefix backend run dev
npm --prefix frontend run dev

Validation

Run the complete local readiness check from the repository root:

npm run validate

This runs frontend lint, a production build, 12 ProofPay escrow contract tests, and backend syntax checks. See Testing and judge walkthrough for the public smoke-test flow.

Production configuration

Use Configuration to set Vercel, Circle, Neon, domain, and contract-deployment values in the correct service. Do not expose Circle API keys, database credentials, or deployer private keys in frontend variables.

Post-submission roadmap

• Expand public wallet and device testing
• Expand automated browser-level end-to-end coverage
• Complete an independent smart-contract security audit
• Add multi-signature or decentralized dispute administration
• Improve mobile onboarding and transaction guidance
• Complete security and operational reviews before any mainnet deployment

License

This repository is provided for hackathon evaluation and testnet experimentation.