This study proposes a quantum key distribution (QKD) method based on the BB84 protocol, enhanced with quantum entanglement to improve key integrity and eavesdropping detection. The protocol employs two complementary metrics: Quantum Bit Error Rate (QBER) and Entanglement Check Ratio (ECR). QBER measures errors in key bits when both parties use the same basis, serving as the primary intrusion detector, while ECR reflects the proportion of entangled qubit pairs maintaining correlation across cross-basis measurements, acting as an indicator of entanglement integrity. The Clauser-Horne-Shimony-Holt (CHSH) test further validates entanglement by confirming Bell inequality violations. Simulation results show that the protocol effectively detects eavesdropping and man-in-the-middle (MiTM) attacks, with QBER rising under attack and ECR/CHSH values reflecting statistical entanglement degradation. Evaluation under practical noise conditions, including photon loss and detector inefficiency, demonstrates that ECR reliably indicates entanglement integrity even when the number of sifted key bits is reduced, while QBER remains the primary indicator of intrusion. This dual-metric approach, reinforced by CHSH analysis, provides a robust framework for detecting external interference and validating quantum behavior internally. The proposed entangled BB84 protocol offers a secure and efficient QKD solution, with potential for extension to long-distance and more physically robust implementations.
This study proposes a quantum key distribution (QKD) method based on the BB84 protocol, enhanced with quantum entanglement to improve key integrity and eavesdropping detection. The protocol employs two complementary metrics: Quantum Bit Error Rate (QBER) and Entanglement Check Ratio (ECR). QBER measures errors in key bits when both parties use the same basis, serving as the primary intrusion detector, while ECR reflects the proportion of entangled qubit pairs maintaining correlation across cross-basis measurements, acting as an indicator of entanglement integrity. The Clauser-Horne-Shimony-Holt (CHSH) test further validates entanglement by confirming Bell inequality violations. Simulation results show that the protocol effectively detects eavesdropping and man-in-the-middle (MiTM) attacks, with QBER rising under attack and ECR/CHSH values reflecting statistical entanglement degradation. Evaluation under practical noise conditions, including photon loss and detector inefficiency, demonstrates that ECR reliably indicates entanglement integrity even when the number of sifted key bits is reduced, while QBER remains the primary indicator of intrusion. This dual-metric approach, reinforced by CHSH analysis, provides a robust framework for detecting external interference and validating quantum behavior internally. The proposed entangled BB84 protocol offers a secure and efficient QKD solution, with potential for extension to long-distance and more physically robust implementations.
Quantum Key Distribution (QKD) provides information-theoretic security by exploiting the principles of quantum mechanics. Among QKD protocols, the BB84 scheme remains the most widely adopted for both theoretical research and practical implementation. A critical parameter determining the reliability and security of BB84 is the Quantum Bit Error Rate (QBER), which quantifies errors in the sifted key arising from channel noise or potential eavesdropping. This paper presents a systematic review and analysis of QBER within the BB84 protocol, examining its calculation, statistical estimation methods, and role in detecting eavesdropping activity. Simulation results, corroborated by reported experimental observations, reveal a near-linear relationship between eavesdropping intensity and QBER, with values approaching 25% under full intercept-resend attacks. Four confidence interval estimation methods, Wald, Wilson, Clopper-Pearson, and Hoeffding's inequality, are compared for robust QBER analysis in finite-key scenarios. Protocol enhancements, including decoy-state methods, hybrid cryptographic models, and quantum-resistant authentication, are discussed as mechanisms to mitigate errors and strengthen resilience across fiber, free-space, underwater, and satellite QKD systems. Open challenges in distinguishing noise-induced errors from malicious eavesdropping, and the role of adaptive error correction and machine-learning-assisted QBER estimation in future quantum networks, are identified as key directions for further research.
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.
Quantum cryptography offers possibilities to distribute keys securely by relying on the principles of quantum mechanics. This paper presents repeatable simulations of two well-known quantum key distribution protocols, BB84 and E91, and examines how eavesdropping, noise, and transmission losses affect their security. The simulations are carried out using the Qiskit framework. A theoretical analysis of the expected quantum bit error rate (QBER) under ideal conditions and during an intercept–resend attack is included. The Clauser–Horne–Shimony–Holt (CHSH) parameter is also evaluated for the entanglement-based protocol. The results show error rates close to zero without attack, an increase to about 25\% under eavesdropping, and reduced correlations in the presence of attacks or losses. For the E91 protocol, the CHSH parameter exceeds the classical bound (S >2) in the entangled scenario and drops below the classical limit (S <= 2) in the attack case.
Quantum Key Distribution (QKD) provides an innovative approach for secure communication by utilizing the principles of quantum mechanics. Among various QKD protocols, the BB84 protocol remains the most widely studied and implemented due to its simplicity and theoretical security guarantees. However, practical implementations of BB84 are vulnerable to several eavesdropping attacks and channel imperfections. This paper presents a comprehensive study on the detection and analysis of eavesdropping attacks in the BB84 protocol. The work focuses on common attacks such as intercept-resend attack, photon-number splitting attack, Trojan horse attack, and phase-covariant cloning attack. The effect of these attacks on Quantum Bit Error Rate (QBER) is analyzed in detail. Simulation-based observations are discussed to demonstrate how QBER increases under malicious interference. The study further explores statistical methods for detecting eavesdropping and examines practical countermeasures including decoy states, privacy amplification, and error correction techniques. The paper concludes that BB84 remains robust against eavesdropping when proper detection and mitigation mechanisms are employed.
Quantum Key Distribution (QKD) is increasingly recognized as a robust solution to the vulnerabilities posed by quantum computing to classical encryption systems. This paper presents a comprehensive investigation of the BB84 protocol, the foundational QKD scheme, through simulated quantum communication using IBM’s Qiskit framework. The study models quantum key exchange under both ideal and adversarial conditions, including channel noise and intercept-resend attacks. The Quantum Bit Error Rate (QBER) was measured as a function of noise intensity and eavesdropping, confirming that QBER increases predictably in compromised channels. A threshold of 11% QBER was used to determine the viability of secure key generation. Final key retention rates were analyzed across multiple channel scenarios, revealing BB84’s sensitivity to both photon loss and adversarial interference.\n\nSecurity vulnerabilities such as photon-number-splitting and detector blinding were assessed, and countermeasures including decoy-state protocols and authenticated classical channels were proposed. Four key performance graphs were generated to visualize system behavior under realistic operational conditions. The results support BB84’s theoretical advantage in ensuring information-theoretic security while acknowledging real-world limitations in transmission range and hardware reliability. The paper concludes by addressing future improvements in QKD systems, including satellite-based distribution, quantum repeaters, and device-independent implementations. Through simulation-driven analysis, this study validates BB84 as a practical defense against quantum-enabled attacks and underscores the need for continued development and standardization in post-quantum cryptographic infrastructure.
Quantum key distribution (QKD) enables secure communication using the principles of quantum physics. The BB84 protocol is not only effective for secure key sharing but also for detecting eavesdropping. This study simulates a computational model of QKD and analyzes error rates under varying numbers of bits. Using Python-based simulations with n = 10, n = 100, and n = 1000 bits, and a fixed noise probability of 0.02, we evaluated scenarios both with and without eavesdropping over 1000 trials. The results show an average error rate of 2% without eavesdropping and over 26% with eavesdropping. Standard deviation increases with lower n, indicating higher variability. This study validates BB84’s robustness under noise and demonstrates its sensitivity to third-party interference.