Centralized UPI Payment Gateway Backend

This is the backend implementation of a Centralized UPI Payment Gateway system integrating blockchain, lightweight cryptography (SPECK), and quantum cryptography simulations.

Overview

The backend is built with FastAPI and PostgreSQL, providing REST APIs for:

• Merchant management
• User accounts and authentication
• Transaction processing with UPI logic
• QR code scanning and decryption
• Blockchain-based transaction recording
• Lightweight cryptography for data encryption/decryption
• A simulation of Shor's algorithm (quantum cryptography) kept separate

Tech Stack (Backend)

• Python 3.10+
• FastAPI
• SQLAlchemy ORM
• PostgreSQL
• SPECK Lightweight Cryptography
• SHA256 hashing

Getting Started

1. Create a .env file in the root with your PostgreSQL connection string, e.g.:
   DATABASE_URL=postgresql://username:password@localhost:5432/yourdb

2. Install dependencies:
   pip install -r requirements.txt

3. Run the server locally:
   uvicorn main:app --reload

4. Access API docs at:
   http://localhost:8000/docs

Notes

• The Shor's algorithm quantum simulation is kept separate for demonstration and is not part of the live API.
• This backend is under active development and currently supports only core UPI transaction flows.