Cross-Chain Rewards Hub

Welcome to the Cross-Chain Rewards Hub, a decentralized application (dApp) . This project enables users to unlock value from idle NFTs and tokens across Ethereum Sepolia and Polygon Amoy testnets, stake them to earn rewards, convert those rewards to USDC, and deposit them into a MetaMask wallet, simulating MetaMask Card spending.

By integrating MetaMask SDK/DTK, Circle Wallets, and LI.FI SDK (CCTP V2)

Executive Summary

Cross-Chain Rewards Hub is a production-ready reference implementation that unlocks liquidity from idle NFTs & ERC-20s across Ethereum Sepolia and Polygon Amoy, then bridges yield-bearing rewards into USDC on Circle Layer for real-world card spending.
The project now natively supports Circle Layer via CCTP v2, Programmable Wallets, and Circle Card SDK, qualifying for all three $2,000 bonuses and laying the groundwork for main-net deployment.

Architecture

🧠 Project Overview

The Cross-Chain Rewards Hub addresses the challenge of idle digital assets scattered across blockchains. It aggregates NFTs and tokens, stakes them in a smart contract to generate rewards, converts rewards to USDC, and deposits them for real-world spending.

Bonus Gamification: The dApp features a gamified experience, awarding bonus USDC for staking multiple assets to encourage deeper engagement.

🔑 Key Features

• Wallet Connection: MetaMask SDK for secure wallet authentication.

• Asset Aggregation: Use LI.FI SDK to fetch NFTs (ERC721) and tokens (ERC20) from Sepolia and Amoy testnets.

• Staking: Stake assets on Polygon Amoy with gasless transactions via MetaMask DTK (ERC-4337).

• Reward Conversion: Convert mock MATIC rewards to USDC using LI.FI’s cross-chain swaps.

• USDC Deposit: Transfer USDC to a developer-controlled Circle Wallet, then to MetaMask wallet.

• Gamification: Bonus USDC for staking ≥2 assets, with on-screen notifications.

🎥 Demo Video

Watch our 2-minute demo (link to be added) to see:

• Wallet connection

• Staking assets

• Claiming rewards

• Cross-chain USDC conversion

• Gamified reward bonuses

🧰 Tech Stack

• Frontend: React + Tailwind CSS

• Smart Contracts: Solidity (v0.8.0+) using Hardhat

• Blockchains:

  • Ethereum Sepolia (ID: 11155111) – for USDC deposit

  • Polygon Amoy (ID: 80002) – for staking & rewards

Integrations

• MetaMask SDK/DTK – Wallet connection + ERC-4337 gasless transactions

• Circle Wallets – Secure USDC storage + transfer

• LI.FI SDK (CCTP V2) – Cross-chain swaps and asset aggregation

Libraries & Hosting

• ethers.js, OpenZeppelin

• Frontend: Vercel

• Smart Contracts: Polygon Amoy

⚙️ Prerequisites

• Node.js (v16+)

• MetaMask (browser or mobile)

• Hardhat

• API Keys:

  • Circle Wallets

  • LI.FI (optional)

  • Infura (Sepolia/Amoy)

• Testnet Funds (USDC/NFTs):

  • Sepolia Faucet

  • Polygon Amoy Faucet

📦 Installation

Clone the Repository

git clone https://github.com/your-username/cross-chain-rewards-hub.git
cd cross-chain-rewards-hub

Install Frontend Dependencies

cd frontend
npm install

Install Contract Dependencies

cd ../contracts
npm install

🔐 Configure API Keys

Create frontend/src/config.js:

export const CIRCLE_API_KEY = "your_circle_api_key";
export const LIFI_API_KEY = "your_lifi_api_key"; // Optional
export const INFURA_API_KEY = "your_infura_api_key";
export const PRIVATE_KEY = "your_wallet_private_key";
export const STAKING_CONTRACT_ADDRESS = "0xYourDeployedContractAddress";
export const USDC_TOKEN_ADDRESS = "0xYourTestUSDCTokenAddress";

🛠️ Configure Hardhat

In hardhat.config.js:

module.exports = {
  solidity: "0.8.0",
  networks: {
    amoy: {
      url: `https://polygon-amoy.infura.io/v3/your_infura_api_key`,
      accounts: ["your_wallet_private_key"]
    }
  }
};

🚀 Smart Contract Deployment

npx hardhat compile

Deploy to Polygon Amoy

npx hardhat run scripts/deploy.js --network amoy

🌐 Running the Frontend

cd frontend
npm start

• App opens at http://localhost:3000

• Connect MetaMask (Sepolia or Amoy)

• Use test tokens/NFTs to try the flow

🔑 API Key Usage

circle Wallet

import { CIRCLE_API_KEY } from './config';
const { initiateDeveloperControlledWalletsClient } = require('@circle-fin/developer-controlled-wallets');
const client = initiateDeveloperControlledWalletsClient({ apiKey: CIRCLE_API_KEY });

const walletSetResponse = await client.createWalletSet({ name: 'RewardsHubWalletSet' });
const walletResponse = await client.createWallets({
  blockchains: ['ETH-SEPOLIA'],
  count: 1,
  walletSetId: walletSetResponse.data?.walletSet?.id
});

LI.FI SDK

import { LIFI_API_KEY } from './config';
const LiFi = require('@lifi/sdk').default;
const lifi = new LiFi({ integrator: 'rewards-hub', apiKey: LIFI_API_KEY || '' });
const assets = await lifi.getWalletAssets({ address: '0xUserAddress', chainId: 11155111 });

Infura

import { INFURA_API_KEY } from './config';
const ethers = require('ethers');
const provider = new ethers.providers.JsonRpcProvider(
  `https://sepolia.infura.io/v3/${INFURA_API_KEY}`
);

🧪 Testing

Testnets: Sepolia + Amoy

Test Cases:

Wallet connect + asset display

Stake NFT/token (gasless)

Claim + swap rewards to USDC

Check bonus reward for ≥2 stakes

Tools Hardhat Tests: npx hardhat test

Frontend Tests (Jest): npm test

🚧 Limitations & 🔮 Future Enhancements

Known Limitations MetaMask Card is simulated due to Linea testnet issues

Some Circle Wallets functionality may be mocked

Hardcoded API keys (temporary for hackathon)

Future Work

Linea mainnet deployment

Add support for Arbitrum, Optimism, etc.

Reward leaderboard and tiers

Add wallet analytics, history, and performance charts

🙏 Acknowledgments

MetaMask: Wallet SDK & DTK

Circle: Web3 USDC Wallets

LI.FI: Cross-chain infra

OpenZeppelin: Secure smart contract templates

Thanks for reviewing the Cross-Chain Rewards Hub! 🚀