Offline UPI Payment — Mesh Network

Send encrypted UPI payments across a mesh of phones with no internet. Packets hop through 10 nodes using GPSR routing until they reach the bank.

Node-1 → Node-5 → Node-9 → Node-10 → Bank → ✅ SETTLED

Quick Start

docker compose up --build -d
python3 -m venv venv && source venv/bin/activate && pip install cryptography requests
python3 pay.py

Open http://localhost:5002 to watch hops animate.

How it works

• Mesh routing — Each phone forwards packets to the neighbor closest to the bank using GPSR
• Encryption — X25519 ECDH + AES-256-GCM, signed with Ed25519
• Security — 7-step pipeline: replay check, signature verify, decrypt, auth cross-check, freshness, idempotency, atomic transfer
• Docker — One command starts the bank (Spring Boot), database (PostgreSQL), 10 mesh nodes (Python), and visualizer (Flask + SSE)

Project Structure

docker-compose.yml     # 13 containers: bank + db + 10 nodes + visualizer
Dockerfile             # Spring Boot multi-stage build
phone-node/            # Python mesh node with GPSR routing
visualizer/            # Flask SSE server + HTML5 Canvas dashboard
src/                   # Spring Boot bank (Java 21)
pay.py                 # One-click payment demo
demo_mesh.py           # Routing visualization demo
mesh-topology.json     # 10-node grid positions and neighbors