NFTmarket

AI art marketplace with verifiable provenance, watermark-based authentication, and clear copyright licensing.

Problem

• NFTs don't convey ownership - buying an NFT doesn't transfer copyright or usage rights
• AI art has no provenance - anyone can generate similar images, no way to prove who created first
• Stolen art is rampant - images are re-minted without consequences

Solution

Combine invisible watermarking + NFT minting + legal licensing into a single transaction.

Artist uploads image
       ↓
Watermark embedded (unique ID)
       ↓
Image encrypted (original preserved)
       ↓
NFT minted with license terms
       ↓
Listed on marketplace
       ↓
Buyer purchases → gets NFT + clear legal rights
       ↓
Anyone can verify authenticity via watermark detection

Architecture

┌─────────────────────────────────────────────────────────────┐
│                     NFTmarket Platform                       │
├─────────────────────────────────────────────────────────────┤
│  Flutter Web    │    Node.js API    │    Watermark Engine   │
│   (Frontend)    │     (Backend)     │        (C++)          │
├─────────────────────────────────────────────────────────────┤
│     Polygon     │    Cloud KMS      │         IPFS          │
│   Blockchain    │     (Keys)        │   (Encrypted Blobs)   │
└─────────────────────────────────────────────────────────────┘

Project Structure

NFTmarket/
├── backend/          # Node.js Express API
│   └── src/
│       ├── commands/     # Command objects (mint)
│       ├── config/       # Centralized configuration
│       ├── events/       # Event system (types, dispatch, sinks)
│       ├── routes/       # mint, detect, verify, marketplace endpoints
│       ├── services/     # watermark, encryption, IPFS, blockchain/
│       ├── shared/       # EIP-712 type definitions
│       └── middleware/   # SIWE auth, request-id, auth-context
├── contracts/        # Solidity smart contracts
│   ├── NFTmarketNFT.sol  # ERC-721 with marketplace
│   ├── scripts/          # Deployment + upgrade scripts
│   └── test/             # Contract tests
└── flutter/          # Flutter web frontend
    └── lib/
        ├── pages/        # home, mint, gallery, verify, token detail
        ├── providers/    # wallet, mint, fee simulation state
        └── services/     # API client

Features

License Types

Type	Rights	Price
Display	Personal display, resale of NFT	$1
Commercial	Monetization, merchandise, derivatives	$5
Transfer	Full copyright transfer	$10

Smart Contract

• ERC-721 with integrated marketplace
• 2.5% platform fee on sales
• Duplicate prevention via image hash

Security

• Invisible DFT-based watermarking (survives print-and-scan)
• AES-256 encryption of originals
• Google Cloud KMS for key management
• Sign-In with Ethereum (SIWE) authentication

Setup

Prerequisites

• Node.js 18+
• Flutter 3.0+
• Polygon wallet funded with MATIC

Backend

cd backend
npm install
cp .env.example .env
# Configure environment variables
npm run dev

Required environment variables (see backend/.env.example):

• Firebase Admin SDK credentials
• Google Cloud KMS configuration
• Pinata API keys
• Contract addresses

Smart Contracts

cd contracts
npm install
cp .env.example .env
# Configure private key and RPC URLs

npm run compile
npm test
npm run deploy:amoy  # Testnet

Required environment variables (see contracts/.env.example):

• Private key for deployment
• RPC URLs for Polygon networks
• Polygonscan API key for verification

Flutter App

cd flutter
flutter pub get
flutter run -d chrome

Development

Running Tests

# Flutter
cd flutter && flutter test

# Backend
cd backend && npm test

# Contracts
cd contracts && npm test

CI/CD

GitHub Actions runs on push/PR to main and develop:

• Flutter: format, analyze, test
• Backend: npm test
• Contracts: compile, test

API Endpoints

Public

Method	Endpoint	Description
GET	/api/verify/:tokenId	Get token verification info
POST	/api/detect	Run watermark detection

Authenticated

Method	Endpoint	Description
POST	/api/mint	Watermark + encrypt + mint NFT
GET	/api/mint/price	Get minting prices

Tech Stack

Layer	Technology
Frontend	Flutter Web
Backend	Node.js, Express
Blockchain	Polygon (ERC-721)
Wallet	WalletConnect, MetaMask
Storage	IPFS (Pinata), Firestore
Key Management	Google Cloud KMS
Auth	Sign-In with Ethereum (SIWE)

License

MIT