ZK Multi-Item Auction

A decentralized multi-item sealed-bid auction platform using Zero-Knowledge Proofs (ZKP) built with Noir and Solidity.

zkp.mp4

Features

• Multi-Item Auctions: Create unlimited auction items
• Zero-Knowledge Proofs: Bid amounts remain private until reveal phase
• Sealed-Bid System: Commit-reveal scheme prevents bid manipulation
• Phase Management: Automatic COMMIT → REVEAL → FINALIZED workflow
• Winner Declaration: Transparent winner display after auction ends

Tech Stack

• Solidity 0.8.24 - Smart contracts
• Noir - Zero-knowledge circuits
• Hardhat - Development environment
• ethers.js v5 - Ethereum library
• Vanilla JavaScript - Frontend

Quick Start

Prerequisites

• Node.js 18+
• MetaMask browser extension

1. Install Dependencies

npm install

2. Start Local Blockchain

npx hardhat node

3. Deploy Contracts (new terminal)

npx hardhat run scripts/deploy-multi-item.js --network localhost

4. Update Contract Addresses

Copy the deployed addresses from the terminal output and update them in frontend-simple/app.js:

const CONTRACT_ADDRESSES = {
    auction: '0x...', // MultiItemAuction address
    verifier: '0x...'  // UltraVerifier address
};

5. Open Frontend

Open frontend-simple/index.html in your browser.

6. Connect MetaMask

• Add Hardhat network: RPC URL http://127.0.0.1:8545, Chain ID 31337
• Import a test account using private key from Hardhat node output

How It Works

Auction Flow

1. Create Auction (Add Item tab)

   • Set item name, description, beneficiary
   • Configure bidding and reveal periods

2. Place Bids (Browse Items → Place Bid)

   • Enter bid amount and deposit
   • Bid is committed as a hash (hidden)

3. Advance to Reveal (My Items tab)

   • After commit deadline, click "Start Reveal Phase"

4. Reveal Bids (Reveal Bid tab)

   • Bidders reveal their committed bids

5. Finalize (My Items tab)

   • After reveal deadline, click "Finalize & Declare Winner"

For Sellers

1. Go to Add Item tab
2. Fill in auction details
3. Click "Use My Address" for beneficiary
4. Create auction
5. Monitor in My Items tab
6. Advance phases when deadlines pass

For Bidders

1. Browse items in Browse Items tab
2. Click "Place Bid" on an item
3. Enter bid amount and deposit
4. Wait for reveal phase
5. Reveal your bid in Reveal Bid tab
6. Withdraw deposit if you lose

Project Structure

├── contracts/
│   ├── MultiItemAuction.sol    # Main auction contract
│   ├── UltraVerifier.sol       # ZK proof verifier (mock)
│   └── interfaces/
│       └── IUltraVerifier.sol
├── circuits/
│   └── bid_proof/              # Noir ZK circuits
├── scripts/
│   └── deploy-multi-item.js    # Deployment script
├── frontend-simple/
│   ├── index.html              # Main UI
│   ├── app.js                  # Frontend logic
│   └── styles.css              # Styling
└── hardhat.config.ts           # Hardhat configuration

Security Notes

This is an MVP for testing/demonstration:

• Uses mock verifier (always returns true)
• Not audited for production use
• Bids stored in browser localStorage

For production:

• Replace mock verifier with real Noir-generated verifier
• Audit smart contracts
• Implement proper ZK proof verification

License

MIT