Quantum Key Distribution (QKD) is a prominent solution to achieve proven secure data transmission between legitimate users despite any assumptions about the eavesdropper's computational power (given that the laws of quantum mechanics are correct). This remains true even under attacks by quantum computers. In recent years, there has been a great research interest in developing enhanced security constructions based on QKD. This is mainly driven by the envisioned threats of quantum computers to the traditional information security infrastructure based on public key cryptography. This research lies under the wide umbrella of the so-called post-quantum cryptography. However, for any QKD protocol, an accurate estimation of the Quantum Bit Error Rate (QBER) before the information reconciliation phase is crucial for both the efficiency and security perspectives. In spite of the importance of the QBER estimation step, the state-of-the-art literature still lacks a detailed investigation of the practical aspects of this issue. Therefore, this work aims to fill this research gap. An extension of the EnQuad simulator has been used to study the effect of QBER estimation on the efficiency and security of the BB84 QKD protocol for depolarizing quantum channels and individual Intercept/Resend Eve attacks. Various parameters affecting the QBER estimation process have been carefully investigated. Our evaluation has shown the significant importance of the QBER estimation step. Indeed, an empirical formula has been derived for calculating the required size of the sifted key subset (the so-called sharing rate) needed for the QBER estimation. This is a major contribution of the presented work.
Quantum Key Distribution (QKD) is a prominent solution to achieve proven secure data transmission between legitimate users despite any assumptions about the eavesdropper's computational power (given that the laws of quantum mechanics are correct). This remains true even under attacks by quantum computers. In recent years, there has been a great research interest in developing enhanced security constructions based on QKD. This is mainly driven by the envisioned threats of quantum computers to the traditional information security infrastructure based on public key cryptography. This research lies under the wide umbrella of the so-called post-quantum cryptography. However, for any QKD protocol, an accurate estimation of the Quantum Bit Error Rate (QBER) before the information reconciliation phase is crucial for both the efficiency and security perspectives. In spite of the importance of the QBER estimation step, the state-of-the-art literature still lacks a detailed investigation of the practical aspects of this issue. Therefore, this work aims to fill this research gap. An extension of the EnQuad simulator has been used to study the effect of QBER estimation on the efficiency and security of the BB84 QKD protocol for depolarizing quantum channels and individual Intercept/Resend Eve attacks. Various parameters affecting the QBER estimation process have been carefully investigated. Our evaluation has shown the significant importance of the QBER estimation step. Indeed, an empirical formula has been derived for calculating the required size of the sifted key subset (the so-called sharing rate) needed for the QBER estimation. This is a major contribution of the presented work.
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.
The rate at which a secure key can be generated in a quantum key distribution (QKD) protocol is limited by the channel loss and the quantum bit-error rate (QBER). Increases to the QBER can stem from detector noise, channel noise, or the presence of an eavesdropper, Eve. Eve is capable of obtaining information of the unsecure key by performing an attack on the quantum channel or by listening to all discussion performed via a noiseless public channel. Conventionally a QKD protocol will perform the information reconciliation over the authenticated public channel, revealing the parity bits used to correct for any quantum bit errors. In this invited paper, the possibility of limiting the information revealed to Eve during the information reconciliation is considered. Using a covert communication channel for the transmission of the parity bits, secure key rates are possible at much higher QBERs. This is demonstrated through the simulation of a polarization based QKD system implementing the BB84 protocol, showing significant improvement of the SKRs over the conventional QKD protocols.
The current public key infrastructure (pki) encryption/decryption methods are still vulnerable to attacks. The main issue is, the public key algorithm suffers no effective solutions which are natural within particular integer factorization, distinct logarithm and also elliptic curve interactions. It might be computationally possible for an individual to create public and private key set computationally for attacking purposes. The current single channel quantum key distribution (qkd) technique suffers high quantum bit error rates (qber) in the presence of eavesdropping attacks. Therefore this high error rate needs to be reduced for better security using two channels qkd. With the current emergence of quantum computers many security algorithm that could take classical computer years to break could now be broken in matter of seconds. Therefore stronger quantum cryptography is needed for high security networking. This paper is proposed to provide a way for solving the key transmission issues using qkd, as a new method, by providing two quantum channels to improve qber. In addition also to develop an algorithm for integrating pki and qkd in solving the secrete key sharing issues in grid environment. The research methodology will require the use of qkd devices to be placed at the end of the sender and the receiver nodes for quantum channel secrete key sharing. The outcome of the research shall provide highly enhanced network cryptography mechanism for cyber security.
Quantum computers have the potential to break the public-key cryptosystems widely used in key exchange and digital signature applications. To address this issue, quantum key distribution (QKD) offers a robust countermeasure against quantum computer attacks. Among various QKD schemes, BB84 is the most widely used and studied. However, BB84 implementations are inherently imperfect, resulting in quantum bit error rates (QBERs) even in the absence of eavesdroppers. Distinguishing between QBERs caused by eavesdropping and QBERs due to channel imperfections is fundamentally infeasible. In this context, this paper proposes and examines a practical method for detecting eavesdropping via partial intercept-and-resend attacks in the BB84 protocol. A key feature of the proposed method is its consideration of quantum system noise. The efficacy of this method is assessed by employing the Quantum Solver library in conjunction with backend simulators inspired by real quantum machines that model quantum system noise. The simulation outcomes demonstrate the method’s capacity to accurately estimate the eavesdropper’s interception density in the presence of system noise. Moreover, the results indicate that the estimation accuracy of the eavesdropper’s interception density in the presence of system noise is dependent on both the actual interception density value and the key length.
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) allows two spatially separated parties to securely generate a cryptographic key. The first QKD protocol, published by C. H. Bennett and G. Brassard in 1984 (BB84), describes how this is achieved by transmitting individual qubits and exchanging classical authenticated information. Any attempt to eavesdrop on the protocol introduces errors detectable by the legitimate parties. This Licentiate Thesis studies the recently introduced EEQKD protocol which builds on BB84. In EEQKD, the qubits sent individually in BB84 are entangled and thus not directly available to an eavesdropper who is, in this protocol, provided only one-by-one access to the transmission. The maximal information an eavesdropper can gain using a straightforward intercept-resend (IR) attack, is obtained for a given error rate. The secure key generation rate of EEQKD is estimated in practical scenarios including qubit loss and quantum channel noise. In addition, an exquisite vulnerability is exposed: For a particular setting of qubit entanglement, paradoxically proving most useful in the face of an IR attack, EEQKD reduces to BB84. Part of this research has been published in O. Ahonen et al., Physical Review A 78, 032314 (2008).