A simple payment application with server-side smart account wallets, USDC transfers, and gasless transactions on Arbitrum Sepolia. Earn interest on idle USDC balances with Aave integration.

git clone <your-repo-url> cd onchain-payments npm install

Copy .env.example to .env:

cp .env.example .env

Then fill in the required values:

• Get from: https://app.supabase.com/project/_/settings/api
• NEXT_PUBLIC_SUPABASE_URL - Your Supabase project URL
• NEXT_PUBLIC_SUPABASE_ANON_KEY - Your Supabase anonymous key

• Can be any PostgreSQL database, including Supabase
• For Supabase: https://app.supabase.com/project/_/settings/database
• DATABASE_URL - Full PostgreSQL connection string

• Get from: https://dashboard.alchemy.com/
• Create an app and a gas policy
• ALCHEMY_API_KEY - Your Alchemy API key
• ALCHEMY_POLICY_ID - Your Alchemy gas sponsorship policy ID
• ⚠️ These are server-side only and never exposed to the client

• Generate a new private key:

  node -e "console.log('0x' + require('crypto').randomBytes(32).toString('hex'))"

• MASTER_WALLET_PRIVATE_KEY - The generated private key

⚠️ Security Note: This master wallet approach is for demo purposes only. In production, use:

• Hardware Security Modules (HSM)
• Multi-Party Computation (MPC) services (e.g., Fireblocks, BitGo)
• Secure key management systems (e.g., AWS KMS, HashiCorp Vault)
• Multi-signature setups

Different institutions have different security practices for private key management. Choose the approach that fits your security requirements.

Push the database schema to your PostgreSQL database:

npm run db:push

This uses Drizzle Kit to read your schema from src/db/schema.ts and create the tables directly. For future schema changes, you can use Drizzle migrations to track changes over time.

npm run dev

Visit http://localhost:3000

Deploy to Vercel with one command:

npm run deploy

Or deploy to production:

npm run deploy:prod

After deploying, make sure to set up your environment variables in the Vercel dashboard:

1. Go to your project settings → Environment Variables
2. Add all variables from .env.example
3. Redeploy to apply changes

1. Sign Up - Users create an account with email/password
2. Smart Account - A smart account wallet is automatically created for each user
3. Get USDC - Users get testnet USDC from Circle's faucet
4. Send Payments - Send gasless USDC payments to other users
5. Earn Interest - Toggle on Aave to automatically earn interest on idle USDC balances
6. View Transactions - See all transactions on Arbitrum Sepolia

• Next.js 14 - App Router
• Supabase - Authentication and PostgreSQL database
• Alchemy - Smart account wallet infrastructure
• Aave - For earning interest on the USDC
• Arbitrum Sepolia - Testnet blockchain
• USDC - Real testnet USDC token
• Tailwind CSS + shadcn/ui - Styling and components

• ✅ No wallet installation required for users
• ✅ One-click gasless payments
• ✅ Server-side transaction signing
• ✅ Real USDC on Arbitrum Sepolia testnet
• ✅ Earn interest with Aave - simple toggle to start earning
• ✅ Transaction history and receipts