SkillChain — Decentralized Skills & Credentials on Polygon

SkillChain lets you issue, verify, and share tamper-proof skill credentials anchored to the Polygon blockchain. Every credential gets a blockchain transaction hash, a shareable verify link, and a QR code.

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Tech Stack

Layer	Tech
Frontend	React 18, Vite, Tailwind CSS, Redux Toolkit, Framer Motion
Backend	Node.js, Express, Neon PostgreSQL (serverless), Drizzle ORM
Blockchain	Polygon Amoy Testnet, ethers.js, Hardhat
AI	OpenAI GPT-4

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Project Structure

skillchain/
├── backend/          # Express API server
│   ├── db/           # Neon PostgreSQL client + migrations
│   ├── middleware/   # JWT auth
│   ├── models/       # User, Credential, ChatHistory
│   ├── routes/       # auth, credentials, ai, notifications, transactions, stats, upload
│   └── utils/        # blockchain helpers
├── frontend/         # React + Vite app
│   ├── public/       # favicon.svg
│   └── src/
│       ├── components/  # Layout, Navbar, Sidebar, CredentialCard, Modals
│       ├── pages/       # All page components
│       ├── store/       # Redux slices
│       └── utils/       # api.js, helpers.js
└── contracts/        # Solidity smart contracts (Hardhat)

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Prerequisites

• Node.js 18+
• A Neon PostgreSQL database (free tier works)
• An OpenAI API key
• MetaMask browser extension (for wallet features)

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Setup & Run

1. Clone / unzip the project

cd skillchain

2. Backend setup

cd backend
npm install

Create .env (copy from .env.example):

DATABASE_URL=postgresql://user:pass@host/dbname?sslmode=require
JWT_SECRET=your_super_secret_jwt_key_min_32_chars
OPENAI_API_KEY=sk-...
PORT=5000
NODE_ENV=development
FRONTEND_URL=http://localhost:5173

Run the backend (auto-migrates DB on first start):

npm run dev

The API will be live at http://localhost:5000. You should see:

✅ Database ready
🚀 SkillChain API → http://localhost:5000

3. Frontend setup

cd ../frontend
npm install

Create .env:

VITE_API_URL=http://localhost:5000/api
VITE_POLYGON_RPC=https://rpc-amoy.polygon.technology
VITE_CONTRACT_ADDRESS=0x0000000000000000000000000000000000000000

Run the frontend:

npm run dev

App is live at http://localhost:5173.

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Features

✅ Credential Management

• Issue credentials with skill name, category, level, recipient wallet address
• Every credential gets a blockchain tx hash (simulated on Amoy testnet)
• Revoke credentials with a reason

✅ Transaction History (/transactions)

• Real on-chain operations stored in Neon DB
• Each credential issue automatically records a transaction
• Links to PolygonScan for every tx hash

✅ QR Code Verify

• Each credential card has a share link (/verify/<credential-id>)
• VerifyPage auto-verifies when opened via QR scan
• Profile page shows a QR code for your public profile URL

✅ Credential Share Link

• Each credential card has a copy-link button (🔗)
• Copies https://yourapp.com/verify/<id> to clipboard

✅ Public Profile Page (/public/:address)

• View any wallet address's public credentials
• Search by entering any 0x... Ethereum address
• No login required

✅ Notification Bell

• Real notifications stored in Neon DB
• Auto-polls every 30 seconds
• Mark all read, clear read notifications
• Notifications fire on credential issue

✅ Dashboard Stats

• Stats loaded from separate /api/stats/dashboard call
• Includes real monthly activity chart (6 months)
• Transaction count included

✅ Avatar Upload

• Click your avatar to upload a photo (JPEG/PNG/WebP, max 2MB)
• Stored as base64 in the database
• Remove photo option

✅ favicon.svg

• Gradient shield icon at frontend/public/favicon.svg

✅ Third-party API Embed

• Profile page shows copy-ready fetch() snippets for:
  • Fetching all public credentials for a wallet
  • Verifying a specific credential by ID

✅ Dependencies Fixed

• react-markdown ✓ in package.json
• qrcode.react ✓ in package.json

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API Endpoints

Method	Path	Auth	Description
POST	/api/auth/register	—	Register
POST	/api/auth/login	—	Login
GET	/api/auth/me	JWT	Get profile
PUT	/api/auth/profile	JWT	Update profile
GET	/api/credentials	JWT	My credentials
POST	/api/credentials/issue	JWT	Issue credential
GET	/api/credentials/verify/:id	—	Verify credential (public)
GET	/api/credentials/public/:address	—	Public credentials by wallet
PUT	/api/credentials/:id/revoke	JWT	Revoke credential
GET	/api/notifications	JWT	List notifications
POST	/api/notifications/mark-read	JWT	Mark read
GET	/api/transactions	JWT	Transaction history
GET	/api/stats/dashboard	JWT	Dashboard stats
POST	/api/upload/avatar	JWT	Upload avatar
DELETE	/api/upload/avatar	JWT	Remove avatar

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Smart Contract (optional)

The contracts directory contains the Solidity source. To deploy to Amoy testnet:

cd contracts
npm install
npx hardhat compile
npx hardhat run scripts/deploy.js --network amoy

Add the deployed address to your frontend .env as VITE_CONTRACT_ADDRESS.

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Build for Production

# Frontend
cd frontend && npm run build   # outputs to frontend/dist/

# Backend
cd backend && NODE_ENV=production node server.js