A decentralized review platform powered by zero-knowledge proofs for verified, trustworthy reviews.

ZKTrust is a trustless review platform similar to Trustpilot, but with enhanced trust mechanisms. The core innovation is using ZK Email to cryptographically verify that a reviewer actually had a specific interaction (like making a purchase) with the business they are reviewing, thus combating fake reviews.

This project uses a monorepo structure with the following organization:

zk-trust-src/
├── zktrust-backend/    # Express API for proof verification
├── zktrust-contracts/  # Smart contracts for Base integration
├── zktrust-frontend/   # Next.js frontend application
└── README.md           # This file

• Node.js (v18 or higher recommended)
• npm or yarn
• MetaMask browser extension (for blockchain interactions)

1. Clone this repository
2. Install dependencies for all projects:

# Install backend dependencies
cd zktrust-backend
npm install

# Install frontend dependencies
cd ../zktrust-frontend
npm install

# Install smart contract dependencies
cd ../zktrust-contracts
npm install

Start all components in separate terminal windows:

# Terminal 1: Start the backend
cd zktrust-backend
npm run dev

# Terminal 2: Start the frontend
cd zktrust-frontend
npm run dev

# Terminal 3: Start a local blockchain (optional)
cd zktrust-contracts
npm run node

The frontend allows users to:

• Upload Gumroad purchase confirmation emails (.eml)
• Generate ZK proofs using the ZK Email SDK
• Connect their Ethereum wallet (MetaMask)
• Submit verified reviews on-chain
• View verification results with extracted product information

Access the frontend at: http://localhost:3000

The backend provides API endpoints for:

• Verifying ZK proofs generated from Gumroad purchase emails
• Extracting product information from verified proofs
• Managing review submission and retrieval

API endpoints:

• Health check: http://localhost:3002/api/health
• Verify proof: http://localhost:3002/api/verify-gumroad-proof (POST)
• Submit review: http://localhost:3002/api/submit-review (POST)
• Get reviews: http://localhost:3002/api/reviews (GET)

The project includes smart contracts for the Base testnet (Sepolia):

• ReviewVerification: Verifies zero-knowledge proofs on-chain
• ReviewStorage: Stores verified reviews and their metadata
• ReviewRegistry: Manages products, reviewers, and services

To compile and deploy the contracts:

# Compile contracts
cd zktrust-contracts
npm run compile

# Deploy to local node
npm run deploy:local

# Deploy to Base Sepolia testnet
npm run deploy:base-sepolia

• Frontend: Next.js, React, Tailwind CSS, ZK Email SDK, ethers.js
• Backend: Express, TypeScript, SQLite, ZK Email SDK
• Smart Contracts: Solidity, Hardhat, Base (Layer 2)
• ZK Technology: ZK Email Blueprint SDK for DKIM signature verification

• Phase 1: Email proof generation ✅
• Phase 2: Backend proof verification ✅
• Phase 3: Smart contract implementation ✅
• Phase 4: On-chain review storage and verification ✅
• Phase 5: Decentralized review platform launch 🔜

This project integrates with Base, a Layer 2 Ethereum scaling solution developed by Coinbase. The Base integration enables:

1. On-chain verification of email proofs: Cryptographically verify that reviewers had legitimate interactions with businesses.
2. Trustless review storage: Store verified reviews on-chain for maximum transparency and censorship resistance.
3. Decentralized reputation system: Build a reputation system for both reviewers and businesses.

To use the Base integration, ensure you have:

• MetaMask installed with Base Sepolia testnet configured
• Base Sepolia ETH for gas (available from the Base Faucet)