Quantum cryptography, especially quantum key distribution (QKD), is significant for shielding communications against the dangers of quantum computing by providing information-theoretic security established in quantum mechanics. To securely generate and distribute cryptographic keys between two parties, several quantum safe protocols were proposed. Even though the BB84 protocol is a more trusted, widely implemented and standardized protocol for QKD, it suffers from 50% key loss during sifting. The next version B92 protocol is the lighter version of BB84, has critical issues such as: less tolerance to noise and photon loss and is specifically applicable for short range, lower security scenarios and as B92 has only two non-orthogonal states, it makes it more vulnerable to certain Unambiguous State Discrimination (USD) attacks. Hence, this work has taken the most widely adopted protocol BB84 as it has more advantages for underwater networks by proposing a novel hybrid approach to mitigate the fundamental efficiency challenge of key losses during the sifting phase due to basis mismatches. As this inefficiency is a significant barrier to practical deployment, particularly in resource-constrained environments like underwater networks, we propose a novel hybrid KEM-QKD protocol that eliminates the sifting process of BB84 entirely. Our primary contributions are: (i) integration of a post-quantum key encapsulation mechanism (KEM), CRYSTALS-Kyber, to securely transmit basis information prior to measurement which allows for 100% basis alignment between communicating parties, preserving the entire raw key; (ii) benchmarked our modified protocol against traditional BB84 using NetSquid, a quantum network simulator and (iii) optimized the proposed protocol’s parameters using Bayesian Optimization (BO) and Genetic Algorithms (GA). Our results demonstrate two major performance enhancements: (i) a 100% raw key generation rate, a significant improvement over BB84’s 50% efficiency and (ii) an increase in the maximum secure distance of up to 42% in existing optic fiber cables, with BO proving superior for parameter optimization. Further, our rigorous experimentation results showcase the potential of the proposed hybrid quantum-classical framework to enhance the practical efficiency of QKD, advancing its viability for robust, high-performance underwater quantum networks.
Quantum cryptography, especially quantum key distribution (QKD), is significant for shielding communications against the dangers of quantum computing by providing information-theoretic security established in quantum mechanics. To securely generate and distribute cryptographic keys between two parties, several quantum safe protocols were proposed. Even though the BB84 protocol is a more trusted, widely implemented and standardized protocol for QKD, it suffers from 50% key loss during sifting. The next version B92 protocol is the lighter version of BB84, has critical issues such as: less tolerance to noise and photon loss and is specifically applicable for short range, lower security scenarios and as B92 has only two non-orthogonal states, it makes it more vulnerable to certain Unambiguous State Discrimination (USD) attacks. Hence, this work has taken the most widely adopted protocol BB84 as it has more advantages for underwater networks by proposing a novel hybrid approach to mitigate the fundamental efficiency challenge of key losses during the sifting phase due to basis mismatches. As this inefficiency is a significant barrier to practical deployment, particularly in resource-constrained environments like underwater networks, we propose a novel hybrid KEM-QKD protocol that eliminates the sifting process of BB84 entirely. Our primary contributions are: (i) integration of a post-quantum key encapsulation mechanism (KEM), CRYSTALS-Kyber, to securely transmit basis information prior to measurement which allows for 100% basis alignment between communicating parties, preserving the entire raw key; (ii) benchmarked our modified protocol against traditional BB84 using NetSquid, a quantum network simulator and (iii) optimized the proposed protocol’s parameters using Bayesian Optimization (BO) and Genetic Algorithms (GA). Our results demonstrate two major performance enhancements: (i) a 100% raw key generation rate, a significant improvement over BB84’s 50% efficiency and (ii) an increase in the maximum secure distance of up to 42% in existing optic fiber cables, with BO proving superior for parameter optimization. Further, our rigorous experimentation results showcase the potential of the proposed hybrid quantum-classical framework to enhance the practical efficiency of QKD, advancing its viability for robust, high-performance underwater quantum networks.
The rapid advancement of quantum computing poses a serious threat to traditional cryptographic systems such as RSA and Elliptic Curve Cryptography (ECC), which rely on computational difficulty for security. Quantum algorithms like Shor’s and Grover’s have the potential to break or weaken these methods, putting modern communication systems at risk. To address this challenge, this work presents a quantum-safe com-munication framework that combines the BB84 Quantum Key Distribution (QKD) protocol with Post-Quantum Cryptography (PQC) techniques, aiming to ensure secure data exchange in the presence of quantum-capable adversaries. In this system, the BB84 protocol is simulated to enable secure key exchange between two parties over a virtual quantum channel. The generated key is refined through processes such as basis matching, error correction, and privacy amplification using SHA-256 to ensure reliability and secrecy. For secur-ing communication, One-Time Pad (OTP) encryption is used alongside HMAC-SHA3-256 to provide both confidentiality and message integrity. Additionally, file encryption is handled using the XChaCha20-Poly1305 algorithm, selected for its efficiency and strong protection against potential vulnerabilities like nonce reuse. To further enhance security, the framework integrates a hybrid key management approach using the Kyber-512 Key Encapsulation Mechanism (KEM) combined with a Key Deriva-tion Function (KDF), merging classical and quantum-resistant techniques. Experimental results demonstrate the effectiveness of the system, achieving a Quantum Bit Error Rate (QBER) of 2.5% and successful performance in both message and file en-cryption. Overall, this work contributes toward the development of practical and resilient communication systems designed for the emerging quantum era.
Quantum Key Distribution (QKD) provides secure communication by leveraging quantum mechanics, with the BB84 protocol being one of its most widely adopted implementations. However, the classical post-processing steps in BB84, such as sifting, error correction, and key verification, often result in significant communication overhead, limiting its efficiency and scalability. In this work, we propose three key optimizations for BB84: (1) PRNG-based predetermined key bit positioning, which eliminates redundant bit exchanges during sifting, (2) hash-based subsequence comparison, enabling lightweight and efficient key verification, and (3) adaptive basis reconciliation, which minimizes the communication costs associated with basis matching. The proposed optimizations achieve a 50% reduction in communication overhead for large key sizes compared to traditional QKD protocols, as demonstrated through rigorous performance analysis. While the focus of this work is on the BB84 protocol, these optimizations are also directly applicable to a broader class of Discrete-Variable QKD (DV-QKD) protocols, such as six-state, B92, and E91, which share a fundamentally similar post-processing structure. This generality highlights the modularity and adaptability of the proposed methods across diverse QKD implementations. The proposed optimizations enhance post-processing efficiency and scalability, enabling practical deployment in bandwidth-limited environments like IoT networks, secure financial systems, and defense communications, thereby supporting broader adoption of quantum communication systems.
Quantum Key Distribution (QKD) represents a revolutionary advancement in secure communication. It leverages principles of quantum mechanics to establish cryptographic keys between parties with theoretically unbreakable security. Among the various QKD protocols, BB84 (Bennett and Brassard, 1984) and Twin-Field QKD are prominent due to their foundational simplicity and advanced key generation efficiency, respectively. The BB84 protocol, as the first QKD protocol, uses quantum bits (qubits) in different bases to securely generate shared keys, while Twin-Field QKD enhances the key generation rate by exploiting quantum interference between distant entangled states, making it more suitable for long-distance communication. This work explores the integration of BB84 and Twin-Field QKD into a hybrid algorithm, aiming at combining the robustness of BB84 with the high key generation rate and entropy of Twin-Field QKD. The hybrid algorithm alternates between the two protocols, leveraging their individual strengths to optimize key generation performance. Simulation results indicate that the hybrid algorithm can effectively balance the robustness and simplicity of BB84 with the high efficiency and entropy of Twin-Field QKD. Specifically, the hybrid algorithm demonstrated an error rate of 8.9%, a key generation rate of 50%, and an entropy of 0.999 bits, which outperforms the compared algorithms.
As the limitations of classical cryptographic systems become increasingly evident in the face of advancing quantum algorithms, Quantum Key Distribution (QKD) emerges as a vital paradigm for securing information in next-generation networks. This paper explores the theoretical foundations and protocol architectures underpinning QKD, including BB84, E91, and newer hybrid approaches designed for scalable integration into existing infrastructures. Performance metrics such as key generation rate, error thresholds, and resistance to various attack models are critically examined across both fiber-optic and free-space implementations. Furthermore, the study delves into real-world deployment challenges—ranging from synchronization errors and quantum channel noise to cost-efficiency and interoperability with classical systems. By offering a comparative analysis and proposing optimization strategies, this work aims to pave the way for robust quantum-secure communication protocols suited for large-scale, heterogeneous network environments.
The emergence of quantum computing poses a significant threat to classical cryptographic systems, particularly those relying on mathematical hardness assumptions for key exchange. While symmetric algorithms such as the Advanced Encryption Standard (AES) remain efficient and widely deployed, their long-term security ultimately depends on the secrecy of keys. In this paper, we present a hybrid framework that integrates quantum key distribution (QKD) with AES and DES to enhance key security without altering cipher internals. Using the BB84 protocol as the quantum key generator, we implement a simulation-based system in Qiskit and evaluate it against classical pseudo-random key generation.Our methodology covers five phases: establishing AES/DES baselines, generating quantum random keys, implementing BB84 with basis reconciliation and error detection, integrating quantum keys with AES/DES, and benchmarking across varying key sizes and file sizes. Results demonstrate that AES encryption throughput remains stable (around 250–370 MB/s) regardless of key source, while QKD introduces measurable latency in key generation (around 40–110 seconds for 128–256 bits). Importantly, adversarial interference is reliably detected, with 97.3% accuracy in eavesdropper identification.The findings confirm that while classical systems excel in speed and scalability, QKD offers unmatched, physics-backed security assurances. Our study highlights the practicality of hybrid quantum-classical encryption, providing a foundation for secure communication in the post-quantum era.
Quantum key distribution (QKD) is a method that enables secure communication between two parties by applying the ideas of quantum physics. By minimizing information leakage that can happen during the key generation process, privacy amplification is a technique used to improve the security of QKD. The technique involves processing the raw key obtained from QKD through a randomization procedure to remove any residual information that may have been leaked during the quantum transmission. While privacy amplification can significantly improve the security of QKD, the effectiveness of the technique is limited by the quality of the initial raw key. The BB84 QKD protocol has been improved with the proposed En-BB84 protocol, which includes built-in authentication and integrity checks. The En-BB84 protocol ensures secure distribution of secret keys and protects against tampering by attackers. Key distillation and error correction techniques are employed to extract a shorter, more secure shared secret key and correct errors introduced during qubit transmission. The protocol utilizes a four-state QKD approach, expanding on the traditional two-state scheme of BB84. A simulation of the En-BB84 protocol is demonstrated using a quantum circuit implemented with Qiskit in Python. The circuit employs various gates and operations, including Hadamard, CX, controlled swap, and RZ gates, to achieve encoding and error correction. Furthermore, we have designed a better protocol with improved error rates by incorporating improvisations on the BB84 protocol. Experimental results indicate the successful integration of the B92 error correction scheme into the modified BB84 protocol, enhancing the security and performance of QKD systems.