QUANTUM CRYPTOGRAPHY: EMERGING PARADIGMS FOR SECURE COMMUNICATION

International Journal of Computer Science (IJCS) Published by SK Research Group of Companies (SKRGC)

Abstract

Quantum cryptography has evolved from a theoretical curiosity into a practically deployable technology for securing communication in an era increasingly threatened by the computational power of quantum computers. Classical public-key cryptosystems, such as RSA and elliptic-curve cryptography, derive their security from computational hardness assumptions that are vulnerable to Shor's algorithm once large-scale fault-tolerant quantum computers become available. Quantum cryptography, and in particular Quantum Key Distribution (QKD), offers information-theoretic security grounded in the laws of quantum mechanics rather than computational complexity. This paper presents a comprehensive review of the foundational principles of quantum cryptography, surveys established QKD protocols including BB84, B92, and E91, and examines emerging paradigms such as Measurement-Device-Independent QKD, Twin-Field QKD, Continuous-Variable QKD, Device-Independent QKD, satellite-based QKD, and quantum repeater networks that are shaping the future "quantum internet." The paper further discusses the complementary role of post-quantum cryptography, practical implementation challenges, real-world deployments, and open research problems. The objective is to provide researchers and practitioners with a structured understanding of how these emerging paradigms collectively advance the goal of provably secure, long-term communication infrastructure.

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Keywords

Quantum cryptography, Quantum Key Distribution (QKD), BB84 protocol, post-quantum cryptography, quantum repeaters, quantum internet, device-independent QKD, satellite QKD.