🔐 Private Salary Comparison - FHE dApp

A complete decentralized application (dApp) that demonstrates Fully Homomorphic Encryption (FHE) for private salary comparison. Users can submit their encrypted salaries and get comparison statistics without revealing their actual amounts.

dApp link - ( https://quantumpay-gamma.vercel.app/ )

🌟 Real-World Use Case

This dApp solves a real privacy problem: salary transparency without compromising individual privacy. Users can:

• Submit encrypted salary data
• Compare their salary with others in the same role
• Get statistical insights (average, min, max) without revealing actual amounts
• Maintain complete privacy of their salary information

🚀 Features

Smart Contract Features

• ✅ FHE Integration: Uses Zama's FHEVM for encrypted computations
• ✅ Private Salary Submission: Encrypted salary storage
• ✅ Role-based Statistics: Compare salaries within job roles
• ✅ Experience Level Filtering: Junior, Mid, Senior categories
• ✅ Privacy Protection: No salary amounts are ever decrypted on-chain

Frontend Features

• ✅ Modern UI: Beautiful, responsive React interface
• ✅ Wallet Integration: MetaMask connection
• ✅ Real-time Updates: Live contract interaction
• ✅ User-friendly: Intuitive form and feedback system
• ✅ Mobile Responsive: Works on all devices

🏗️ Architecture

┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   React Frontend│    │  FHEVM Contract │    │   Sepolia Testnet│
│                 │    │                 │    │                 │
│ • Wallet Connect│◄──►│ • Encrypted Data│◄──►│ • Blockchain    │
│ • Form Interface│    │ • FHE Operations│    │ • Gas Fees      │
│ • Real-time UI  │    │ • Statistics    │    │ • Transactions  │
└─────────────────┘    └─────────────────┘    └─────────────────┘

📋 Prerequisites

• Node.js >= 20
• npm >= 7.0.0
• MetaMask wallet
• Sepolia testnet ETH

🛠️ Installation & Setup

1. Clone and Install

git clone https://github.com/Pradeeppilotdev/PrivacyOnFHE
cd fhevmcontract
npm install

2. Environment Setup

# Set up your wallet mnemonic
npx hardhat vars set MNEMONIC

# Set up Infura API key
npx hardhat vars set INFURA_API_KEY

# Set up Etherscan API key (optional)
npx hardhat vars set ETHERSCAN_API_KEY

3. Compile Contracts

npx hardhat compile

4. Deploy to Sepolia

npx hardhat --network sepolia deploy --tags PrivateSalaryComparison

5. Start Frontend

npm run dev

The dApp will be available at http://localhost:3000

🔧 Contract Details

Deployed Contracts

• PrivateSalaryComparison: 0x116cE34B5255588260c2A79168849C7091658C03
• Network: Sepolia Testnet
• Etherscan: View Contract

Key Functions

// Submit encrypted salary
function submitSalary(
    externalEuint32 encryptedSalary,
    bytes calldata inputProof,
    string calldata role,
    string calldata experience
) external

// Remove salary entry for a role
function removeSalary(string calldata role) external

// Get encrypted statistics for a role
function getRoleStats(string calldata role)
    external view returns (euint32 sumSalary, euint32 minSalary, euint32 maxSalary, uint256 totalEntries)

// Recalculate and make min/max publicly decryptable for a role
function recalculateMinMax(string calldata role) external

// Check if a user has an active entry for a role
function hasActiveEntry(address user, string calldata role) external view returns (bool)

---

🔑 Main Smart Contract Functionality

The PrivateSalaryComparison contract enables privacy-preserving salary analytics using Fully Homomorphic Encryption (FHE) on-chain. Here are the core features and logic:

• Encrypted Salary Submission:
  Users submit their salary (encrypted with FHE) along with their job role and experience. The contract stores this encrypted data and updates role-based statistics.

• Role-Based Encrypted Statistics:
  For each role, the contract maintains encrypted statistics:

  • Sum of all submitted salaries (encrypted)
  • Min and Max salary (encrypted, updated via recalculateMinMax)
  • Total number of entries for the role

• Privacy-Preserving Computation:
  All arithmetic (sum, min, max) is performed directly on encrypted data using FHEVM. No individual salary is ever decrypted or exposed on-chain.

• Public Decryption of Aggregates:
  Only the aggregated statistics (sum, min, max) are made publicly decryptable. The average is computed in the frontend after decrypting the sum and reading the count.

• Manual Min/Max Update:
  To avoid expensive computation on every salary change, min and max are updated only when recalculateMinMax(role) is called (either by the user or the frontend).

• User Experience:

  • Users can submit, update, or remove their salary entry for a given role.
  • After each salary submission or removal, users (or the frontend) should call recalculateMinMax for their role to update public stats.
  • Anyone can view encrypted statistics and request public decryption for aggregate values.

Privacy Model

• No individual salary is ever decrypted on-chain.
• All computations are performed on encrypted data.
• Only aggregate statistics (sum, min, max) are made public for decryption.
• Average is computed in the frontend after decryption.

---

🎯 How FHE Works in This dApp

1. Client-Side Encryption

// User enters salary: $75,000
const salary = 75000;

// FHE encryption happens client-side
const encryptedSalary = await fhevm.encrypt(salary);

2. Encrypted Storage

// Contract stores encrypted value
userSalaries[msg.sender] = SalaryEntry({
    encryptedSalary: salary, // This is encrypted!
    role: "Software Engineer",
    experience: "Senior",
    timestamp: block.timestamp,
    isActive: true
});

3. Encrypted Computations

// Compare encrypted salaries without decryption
euint32 currentMin = FHE.select(
    FHE.lt(newSalary, stats.minSalary),
    newSalary,
    stats.minSalary
);

4. Privacy Preserved

• ✅ No salary amounts are ever decrypted on-chain
• ✅ Comparisons happen on encrypted data
• ✅ Only the user can decrypt their own data
• ✅ Statistical insights without individual exposure

🎨 Frontend Features

Modern UI Components

• Gradient Background: Beautiful visual design
• Glass Morphism: Modern card-based layout
• Responsive Design: Works on mobile and desktop
• Interactive Elements: Hover effects and animations

User Experience

• Wallet Connection: One-click MetaMask integration
• Form Validation: Real-time input validation
• Loading States: Clear feedback during transactions
• Success/Error Messages: User-friendly notifications

🔒 Privacy & Security

FHE Benefits

• Zero-Knowledge: No salary amounts revealed
• Computational Privacy: Operations on encrypted data
• User Control: Only users can decrypt their data
• Statistical Insights: Get market data without exposure

Security Features

• Input Validation: Prevents malicious inputs
• Access Control: Only authorized operations
• Event Logging: Transparent transaction history
• Gas Optimization: Efficient contract operations

🧪 Testing & CLI Tools

Smart Contract Tests

npx hardhat test

CLI Tasks (Inspired by CoinSweeper)

Our project includes comprehensive CLI tasks for testing and interacting with the contract:

Get Contract Address

npx hardhat --network sepolia task:address

Submit a Salary Entry

npx hardhat --network sepolia task:submit-salary --value 75000 --role "Software Engineer" --experience "Mid"

Get Role Statistics

npx hardhat --network sepolia task:get-role-stats --role "Software Engineer"

Request Decryption

npx hardhat --network sepolia task:request-decryption --role "Software Engineer"

Check Decrypted Average

npx hardhat --network sepolia task:get-decrypted-average --role "Software Engineer"

Get Total Entries

npx hardhat --network sepolia task:get-total-entries

Check User Entry

npx hardhat --network sepolia task:has-entry

Frontend Testing

npm run build
npm run preview

📊 Demo Walkthrough

1. Connect Wallet

• Click "Connect Wallet" button
• Approve MetaMask connection
• View connected account address

2. Submit Salary

• Enter your salary amount
• Select job role and experience level
• Click "Submit Salary" (encrypted)
• Confirm transaction in MetaMask

3. View Statistics

• Enter a job role to check
• Click "Get Role Statistics"
• View encrypted statistics (sum, min, max, total entries)
• Note: Min/Max values are updated by calling recalculateMinMax. The frontend automatically calls this after each salary submission, and also provides a manual "Recalculate Min/Max" button for users.

4. Privacy Verification

• Check Etherscan transaction
• Notice: No salary amounts visible
• Only encrypted data on blockchain

🚀 Deployment

Production Deployment

# Build frontend
npm run build

# Deploy to your preferred hosting
# (Vercel, Netlify, AWS, etc.)

Contract Verification

npx hardhat --network sepolia etherscan-verify

🤝 Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests if applicable
5. Submit a pull request

📄 License

This project is licensed under the MIT License.

🙏 Acknowledgments

• Zama: For FHEVM and technical guidance
• Hardhat: For the development framework
• Ethers.js: For blockchain interaction
• React: For the frontend framework

📞 Support

For questions or issues:

• Create an issue in this repository
• Check the Zama FHEVM documentation
• Review the Hardhat documentation

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🔐 Built with FHE for a more private future