Coffee Trade Unlink

Coffee Trade is a private peer-to-peer marketplace built on Ethereum Sepolia. Traders can list and purchase commodities with fully shielded USDC balances powered by Unlink. Traditional on-chain trading exposes every transaction — who bought what, from whom, and for how much. This leaks pricing strategy and supplier relationships. Unlink solves this by shielding balances inside a privacy contract where buyer and seller addresses cannot be correlated on-chain. Users connect via Dynamic SDK, initialize a private Unlink account, and execute trades that settle privately on Ethereum Sepolia. This project was originally built at HackMoney 2026 and extended this weekend with Dynamic and Unlink integration.

Built with Next.js 16 App Router, TypeScript, and Tailwind CSS. Dynamic SDK handles wallet authentication supporting MetaMask, WalletConnect, and embedded wallets. Unlink SDK (@unlink-xyz/sdk@canary) powers private USDC transfers on Ethereum Sepolia. The backend exposes two Next.js API routes — /api/unlink/register and /api/unlink/authorization-token — which keep the Unlink API key server-side and handle user registration and session authorization. The browser client derives a private spending key from the user's wallet signature via account.fromMetaMask(), creates a shielded Unlink account, and calls client.transfer() to execute private trades. The original project used Yellow Network's Nitrolite SDK — I fixed the auth flow this weekend (it now reaches Certified status) but Yellow is geo-blocked in the US so I integrated Unlink as the privacy layer instead.