QuantumShield: Design, Implementation, and Evaluation of a Hybrid Post-Quantum Secure Peer-to-Peer Communication System

This paper presents QuantumShield, a hybrid post-quantum secure file transfer and peer-to-peer communication system designed to address emerging quantum threats. The system integrates ML-KEM (FIPS 203) for secure key encapsulation, ML-DSA (FIPS 204) for digital signatures, and AES-256-GCM for efficient and authenticated data encryption. A full-stack implementation using FastAPI and React demonstrates secure file transfer, encrypted real-time chat, and protocol visualization. The system follows a KEM-DEM architecture and incorporates forward secrecy to mitigate “Harvest Now, Decrypt Later” attacks. Performance evaluation shows that the proposed approach provides strong security with practical latency, enabling a smooth transition from classical cryptography to quantum-resistant communication systems.