Secure Chat Application Using BB84 Protocol

Abstract

As quantum computing continues to advance, many of the encryption methods used in today’s chat applications may no longer be secure. Techniques like RSA and Elliptic Curve Cryptography, which are currently reliable, could be broken by quantum algorithms such as Shor’s algorithm, creating risks for private communication. To address this issue, the project presents a Post-Quantum Secure Chat Application designed to remain secure even in the future. It uses Quantum Key Distribution(QKD), specifically the BB84 protocol, to generate and share encryption keys safely. Since measuring a quantum state changes it, any attempt to intercept the key can be detected. In this system, the key exchange process is simulated using quantum tools. If interference occurs, errors appear, alerting the system. Once a secure key is established, messages are encrypted using quantum-resistant methods to ensure privacy. The application includes a simple web interface for real-time messaging, a backend for handling users and messages, and a quantum module for secure key generation. The results show that the system enables secure communication and can detect eavesdropping attempts. Overall, this project demonstrated how quantum-based techniques can improve cybersecurity and provide a future-ready communication solution.

Introduction

This project presents a Post-Quantum Secure Chat Application designed to provide secure communication in the era of quantum computing. Traditional chat applications such as WhatsApp and Instagram rely on cryptographic techniques like RSA and Elliptic Curve Cryptography (ECC), which are secure against classical computers but vulnerable to quantum attacks, particularly through Shor’s Algorithm. To overcome this challenge, the proposed system adopts post-quantum cryptography using the CRYSTALS-Kyber algorithm for secure key exchange and integrates Quantum Key Distribution (QKD) through the BB84 protocol.

The literature review highlights the growing need for quantum-resistant security mechanisms and introduces a semi-open chat group model that combines the accessibility of open groups with the control and moderation of closed groups. The study emphasizes that quantum cryptography offers security based on the laws of quantum mechanics rather than computational complexity, making it significantly more resistant to future quantum threats.

The system uses the BB84 protocol to generate and distribute encryption keys securely. In this process, quantum states are used to transmit key information between users, and any interception attempt can be detected through changes in the quantum state and increased error rates. The protocol involves photon preparation, transmission, measurement, basis comparison, error detection, error correction, privacy amplification, and authentication to establish a secure shared secret key.

The proposed chat application follows a client-server architecture with end-to-end encryption, ensuring that only encrypted messages are transmitted and stored. The server handles ciphertext only, while decryption is performed exclusively by the intended recipient. Additional features include secure login, BB84-generated chat keys, deleted chat restoration, and screenshot protection.

Experimental results demonstrate that the system successfully supports secure real-time communication with acceptable latency. Comparative analysis shows that the combination of BB84 and CRYSTALS-Kyber achieves higher performance than traditional RSA and ECC-based systems, with improvements of approximately 3–5% in accuracy, precision, recall, and F1-score. Furthermore, the proposed approach offers enhanced security through quantum resistance, eavesdropper detection capabilities, and future-proof protection against quantum computing attacks.

Overall, the study concludes that the Post-Quantum Secure Chat Application provides a secure, scalable, and future-ready communication platform capable of protecting sensitive information in critical sectors such as banking, healthcare, defense, and government services.

Conclusion

The proposed Secure Chat Application Using Quantum presents a robust and future-ready communication system capable of defending against both classical and emerging quantum computing threats. Traditional encryption techniques such as RSA and ECC, which are vulnerable to quantum algorithms, are replaced with CRYSTALS-Kyber, a post-quantum cryptographic algorithm that ensures strong and reliable key encapsulation. In addition, the integration of the BB84 Quantum Key Distribution (QKD) protocol strengthens the system by enabling secure key exchange and providing the unique ability to detect any eavesdropping attempts during transmission.

References

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Copyright

Copyright © 2026 Ch. Jagadeesh, A. Eekshita, K. Jeswanth Sai, K. Vijayalakshmi, Ch. Rakesh. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.