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) 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 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 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.
This thesis explores the critical advancements in quantum communication with a primary focus on the BB84 protocol, the foundation of Quantum Key Distribution (QKD). It delves into the theoretical principles, practical implementation using Qiskit, and performance evaluation through metrics like entropy, Quantum Bit Error Rate (QBER), and efficiency. Comparative analysis with alternative protocols, such as B92 and SARG04, highlights their advantages, limitations, and suitability for real-world applications. The work also addresses challenges like photon number splitting attacks and implementation imperfections, contributing to the development of robust quantum cryptographic systems. By bridging theory and practice, the thesis emphasizes the transformative potential of quantum cryptography in securing communication against both classical and quantum threats. This comprehensive study paves the way for advancements in secure, scalable quantum communication technologies.
Quantum Key Distribution (QKD) enables information-theoretic secure key exchange by exploiting fundamental quantum phenomena such as superposition and no-cloning. Classical QKD protocols (e.g., BB84) guarantee that any eavesdropping attempt introduces detectable disturbances, but they typically assume stable, high-quality channels and unconstrained devices. In contrast, Internet of Things (IoT) networks present a radically different environment: devices have limited processing power, minimal onboard memory, strict energy budgets, and communicate over highly variable wireless links subject to interference and rapid fading. These constraints lead to elevated quantum bit error rates (QBER), frequent key reconciliation failures, and prohibitive energy costs, all of which jeopardize practical QKD deployment. To address these challenges, we propose an AI-powered QKD protocol specifically optimized for IoT scenarios. Our approach integrates three AI modules: (1) a gradient-boosted regression channel estimator that predicts instantaneous link transmittance using lightweight sensor data and historical photon counts; (2) a reinforcement learning (RL) agent that adaptively tunes photon intensity, basis-selection probability, and reconciliation block size to balance key rate and error rate; and (3) a convolutional neural network (CNN) classifier that selects the optimal Low-Density Parity-Check (LDPC) code rate based on real-time noise characteristics. We simulate a star-topology IoT network of 50 battery-powered devices communicating over 5 km polarization-encoded links with realistic urban loss (0.1–0.3 dB/km) and environmental noise. Compared against a static BB84 baseline, our AI-enhanced protocol reduces average QBER from 4.5% to 2.9%, increases secure key rate from 12.5 kbps to 16.0 kbps, lowers latency by 22%, and reduces energy consumption per key bit by 18%. These improvements persist across channel conditions and device heterogeneity, demonstrating robustness.
Quantum Key Distribution (QKD) leverages quantum mechanical principles to establish information-theoretically secure cryptographic keys. The cornerstone BB84 protocol, however, suffers from key rate degradation due to the mandatory discarding of erroneous bits during post-processing. This paper presents an enhanced BB84 protocol incorporating a Tagging and Correction Method that systematically tracks, classifies, and corrects errors rather than discarding them. This approach maximizes the key material retained from the quantum transmission. The protocol integrates decoy state analysis for robust detection of photon-number-splitting (PNS) attacks and concludes with privacy amplification to ensure informationtheoretic security. Experimental validation using a high-fidelity Qiskit simulation with a realistic depolarizing channel model demonstrates a significant improvement in key rate efficiency. In a simulated environment with 15% eavesdropper intervention, our method achieved a 7.8% higher key rate than standard BB84, while successfully maintaining the Quantum Bit Error Rate (QBER) below the 11% security threshold. This work establishes a more robust and efficient framework for practical QKD implementations.
Secure communication has become essential due to the rapid increase in cyber-attacks and data security threats in modern networks. Traditional communication systems mainly rely on classical security methods, which may become vulnerable to advanced attacks. Quantum Key Distribution (QKD) improves secure communication by generating cryptographic keys using quantum principles, making key interception extremely difficult. In this work, a Quantum Random Number Generator (QRNG) is integrated with classical communication to develop a hybrid quantum-classical communication framework. The QRNG generates highly random bits that improve authentication, randomness, and key security. The proposed system compares three QKD protocols: BB84, B92, and E91 using different bit sizes of 8000, 10000, and 13000 bits. The protocols are evaluated using important metrics such as QBER, key rate, entropy, erasure rate, throughput, and correlation. Experimental results show that all protocols achieved entropy values close to 1 and correlation values near zero, indicating strong randomness and secure key generation. Among the evaluated protocols, E91 achieved lower QBER values and higher key rates, while BB84 showed stable and reliable performance. B92 produced comparatively higher error rates under similar conditions. The throughput remained nearly 278–281 bits/sec across all experiments. A ranking-based analysis confirmed that E91 provides the best balance between security, efficiency, and communication performance, making it suitable for future quantum-secure communication systems.