Quantum Cyber Guardian for Securing Personal Data and Digital Communication

Abstract

Quantum computing poses a growing threat to conventional cryptographic schemes, particularly those based on Rivest-Shamir-Adleman (RSA) and Elliptic Curve Cryptography (ECC). These methods rely on computationally hard problems - such as integer factorization and discrete logarithm computation - that classical machines cannot solve efficiently, yet become vulnerable to quantum attacks via Shor's algorithm. This paper presents a mobile messaging application designed to remain secure against adversaries equipped with quantum computing capabilities. Rather than replacing individual components incrementally, the system integrates multiple defense layers: key exchange is performed using CRYSTALS-Kyber-1024, a lattice-based mechanism standardized by the National Institute of Standards and Technology (NIST) for its quantum resistance, while message confidentiality is ensured through AES-256-CBC encryption for its efficiency and proven strength. Message authenticity and non-repudiation are achieved through CRYSTALS-Dilithium3 digital signatures, which bind each transmitted data unit into a single verifiable package. Designed for cross-platform deployment, the application runs on Android using React Native and Expo. The backend, built with Node.js and Express, functions solely as a relay for encrypted data without accessing plaintext content. Performance evaluation conducted on a physical Android device confirms that all operations - from key generation to message decryption - complete within latency bounds suitable for real-time communication. These results demonstrate that post-quantum cryptographic methods can be effectively integrated into practical mobile applications without significant performance degradation.