SkillChain (NCVET) — Python backend

FastAPI service for a blockchain-linked vocational certificate demo: IPFS (Pinata), Polygon Mumbai (web3.py), MongoDB (Beanie), JWT auth, optional fraud image scan (HuggingFace ViT), and mock DigiLocker hooks.

Prerequisites

• Python 3.10+
• MongoDB (local or Atlas)
• (Optional) Pinata API keys, deployed SkillCertificate contract + funded wallet for mint/revoke on Mumbai

Quick start

cd skillchain-backend
pip install -r requirements.txt
python seed.py
uvicorn main:app --reload --port 8000

Interactive docs: http://localhost:8000/docs

Environment

Copy .env and set real values for production:

• MONGODB_URI — e.g. mongodb://localhost:27017/skillchain
• JWT_SECRET — long random string
• PINATA_* — for PDF + JSON metadata uploads
• POLYGON_RPC_URL, PRIVATE_KEY, CONTRACT_ADDRESS — on-chain mint/revoke (owner wallet must match contract owner)
• FRONTEND_URL — used in QR codes ({FRONTEND_URL}/verify/{certificate_id})

Contract ABI is loaded from app/contracts/abi.json (update if you change the Solidity interface).

Smart contract

app/contracts/SkillCertificate.sol is written for OpenZeppelin ^0.8.20. Compile and deploy with your toolchain (Hardhat/Foundry), then paste the deployed address into CONTRACT_ADDRESS and refresh abi.json if needed.

Notes

• seed.py wipes users, certificates, and audit_logs in the configured database, then inserts demo data without calling the blockchain.
• The fraud endpoint uses google/vit-base-patch16-224 as a placeholder signal; it is not a trained forgery detector.
• Polygon Mumbai may be deprecated upstream; switch POLYGON_RPC_URL to your preferred test network if Mumbai RPCs fail.