Summary Quantum Key Distribution (QKD) is a secure key sharing technology with unconditional security. Certain well-known protocols for QKD have been presented, which claim their security by means of higher eavesdropping error-rates. A generalized quantum key distribution protocol that can be optimized for arbitrary number of bases and dimensions of photon states is presented in this paper. The protocol can provide higher eavesdropping error-rates than the well-known existing QKD protocols like BB-84 [4] and B-92 [5]. The higher error-rate makes it possible for Alice and Bob to share secure keys on relatively large distances.
Summary Quantum Key Distribution (QKD) is a secure key sharing technology with unconditional security. Certain well-known protocols for QKD have been presented, which claim their security by means of higher eavesdropping error-rates. A generalized quantum key distribution protocol that can be optimized for arbitrary number of bases and dimensions of photon states is presented in this paper. The protocol can provide higher eavesdropping error-rates than the well-known existing QKD protocols like BB-84 [4] and B-92 [5]. The higher error-rate makes it possible for Alice and Bob to share secure keys on relatively large distances.
Employing the fundamental laws of quantum physics, Quantum Key Distribution (QKD) promises the unconditionally secure distribution of cryptographic keys. However, in practical realisations, a QKD protocol is only secure, when the quantum bit error rate introduced by an eavesdropper unavoidably exceeds the system error rate. This condition guarantees that an eavesdropper cannot disguise his presence by simply replacing the original transmission line with a less faulty one. Unfortunately, this condition also limits the possible distance between the communicating parties, Alice and Bob, to a few hundred kilometers. To overcome this problem, we design a QKD protocol which allows Alice and Bob to distinguish system errors from eavesdropping errors. If they are able to identify the origin of their errors, they can detect eavesdropping even when the system error rate exceeds the eavesdropping error rate. To achieve this, the proposed protocol employs an alternative encoding of information in two-dimensional photon states. Errors manifest themselves as quantum bit and as index transmission errors with a distinct correlation between them in case of intercept-resend eavesdropping. As a result, Alice and Bob can tolerate lower eavesdropping and higher system error rates without compromising their privacy.
Quantum key distribution (QKD) allows two remote users to establish a secret key in the presence of an eavesdropper. The users share quantum states prepared in two mutually unbiased bases: one to generate the key while the other monitors the presence of the eavesdropper. Here, we show that a general d-dimension QKD system can be secured by transmitting only a subset of the monitoring states. In particular, we find that there is no loss in the secure key rate when dropping one of the monitoring states. Furthermore, it is possible to use only a single monitoring state if the quantum bit error rates are low enough. We apply our formalism to an experimental d=4 time-phase QKD system, where only one monitoring state is transmitted, and obtain a secret key rate of $17.4\ifmmode\pm\else\textpm\fi{}2.8$ Mbits/s at a 4 dB channel loss and with a quantum bit error rate of $0.045\ifmmode\pm\else\textpm\fi{}0.001$ and $0.037\ifmmode\pm\else\textpm\fi{}0.001$ in time and phase bases, respectively, which is 58.4% of the secret key rate that can be achieved with the full setup. This ratio can be increased, potentially up to 100%, if the error rates in time and phase basis are reduced. Our results demonstrate that it is possible to substantially simplify the design of high-dimensional QKD systems, including those that use the spatial or temporal degrees of freedom of the photon, and still outperform qubit-based (d=2) protocols.
Quantum key distribution (QKD) is one of the exciting applications of quantum mechanics. It allows the sharing of secret keys between two communicating parties with unconditional security. A variety of QKD protocols have been proposed since the inception of the BB84 protocol. Among different implementation techniques of QKD protocols, there is a category which exploits higher dimensions qubit states to encode classical bits. In this paper, we focus on such a QKD protocol called KXB10, which uses three bases with higher dimensions. Analysis of the generalized dimension quantum states is performed by evaluating it based on the index transmission error rate ITER. We find that there is a direct relationship between qubit dimensions and ITER for the KXB10 protocol.
Quantum Key Distribution (QKD) is a technique that enables secure communication between two parties by sharing a secret key. One of the most well-known QKD protocols is the BB84 protocol, proposed by Charles Bennett and Gilles Brassard in 1984. In this protocol, Alice and Bob use a quantum channel to exchange qubits, allowing them to generate a shared key that is resistant to eavesdropping. This paper presents a comparative study of existing QKD schemes, including the BB84 protocol, and highlights the advancements made in the BB84 protocol over the years. The study aims to provide a comprehensive overview of the different QKD schemes and their strengths and weaknesses and demonstrate QKDs working principles through existing simulations and implementations. Through this study, we show that the BB84 protocol is a highly secure QKD scheme that has been extensively studied and implemented in various settings. Furthermore, we discuss the improvements made to the BB84 protocol to enhance its security and practicality, including the use of decoy states and advanced error correction techniques. Overall, this paper provides a comprehensive analysis of QKD schemes, focusing on the BB84 protocol in secure communication technologies.
Quantum key distribution (QKD) is a secure communication protocol that uses quantum bits (qubits) to ensure the security of key exchange between two entities (Alice and Bob). Their shared qubits may suffer from errors due to noise and eavesdropping in the quantum channels. After the QKD key agreement phase, Alice's key may not be different from Bob's key. Therefore, we need key verification to deal with the inconsistent qubits (i.e. the wrong qubits at receiver end). This key verification process is also known as information reconciliation. Recently, Kurt et al. proposed a reconciliation in QKD (RQKD) by using the polynomial consistency property. In this paper, we propose an enhanced RQKD (ERQKD) to improve key verification. Our method is still based on polynomial consistency, but uses the properties of consistency in a different way to obtain better key verification efficiency.
The counter-intuitive features of quantum mechanics make it possible to solve problems and perform tasks that are beyond the abilities of non-quantum (classical) computers and communication devices. The field of quantum information processing studies how we can achieve such improvements by representing information as quantum states.One of the early achievements of quantum information processing is the development of quantum key distribution (QKD). QKD protocols allow two participants (Alice and Bob) to achieve the classically-impossible task of generating a secret shared key even if their adversary is computationally unlimited.Unfortunately, the security promises of QKD are true only in theory; practical implementations of QKD deviate from the theoretical protocols, and many of these deviations give rise to practical attacks. In this research thesis, we study the security properties of various QKD protocols in many practical settings:First, we study practical security of semiquantum key distribution (SQKD) protocols, where either Alice or Bob is non-quantum (classical). Following practical security problems in previous SQKD protocols, we suggest a new SQKD protocol (the "Mirror protocol") which can be securely implemented, and we prove it robust and secure against a wide range of attacks (the "uniform collective attacks").Then, we study "composable security" of the first QKD protocol created by Bennett and Brassard (BB84). BB84 has its unconditional security proved against adversaries performing the most general attacks in a theoretical (idealized) setting; however, some security approaches do not prove "composable security", which requires the secret key to remain secret even when Alice and Bob actually use it for cryptographic purposes. We generalize an algebraic security approach for BB84, making it prove composable security of BB84 (and many variants of BB84) against the most general attacks.Finally, we analyze an important practical attack (named "Bright Illumination"), showing how it can be modeled as a theoretical "Reversed-Space" attack.Overall, all results aim to enhance our understanding on how to bridge the gap between theory and practice in various sub-fields of QKD, and they may help solve a major open problem in the field of QKD: constructing a realistic QKD implementation that can be proved truly and unconditionally secure against any possible attack.