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Quantum key distribution (QKD) allows two users to exchange a provably secure key for cryptographic applications. In prepare-and-measure QKD protocols, the states must be indistinguishable to prevent information leakage to an eavesdropper…

An elementary derivation of best eavesdropping strategies for the 4 state BB84 quantum cryptography protocol is presented, for both incoherent and two--qubit coherent attacks. While coherent attacks do not help Eve to obtain more…

Quantum Physics · Physics 2009-10-30 J. I. Cirac , N. Gisin

The Ekert 91 quantum key distribution (QKD) protocol appears to be secure whatever devices legitimate users adopt for the protocol, as long as the devices give a result that violates Bell's inequality. However, this is not the case if they…

Quantum Physics · Physics 2009-11-11 W. -Y. Hwang

Quantum key distribution (QKD) is the most explored application of quantum information theory. A central problem in entanglement-based QKD (EB-QKD), is whether every entangled state can be used to extract a key. We observe that entanglement…

Quantum Physics · Physics 2026-03-09 Shubhayan Sarkar , Tushita Prasad , Karol Horodecki

Recently, Liu et al. [Commun. Theor. Phys. 57, 583, 2012] proposed a quantum private comparison protocol based on entanglement swapping of Bell states, which aims to securely compare the equality of two participants' information with the…

Quantum Physics · Physics 2024-04-30 Wen-Jie Liu , Chao Liu , Yu Zheng , Zheng-Fei Chen

In a Letter, Cabello proposed a quantum key distribution (QKD) Protocol which attended to Holevo limit. In this comment, we show that Eve could use a simple plan to distinguish among quantum keys, without being detected by Alice and Bob. In…

Quantum Physics · Physics 2009-11-13 A. Fahmi , M. Golshani

In this paper, we propose how to construct a reconciliation method for the BB84 Quantum Key Distribution (QKD) protocol. Theoretically, it is unconditionally secure because it is based on the quantum laws of physics, rather than the assumed…

Cryptography and Security · Computer Science 2020-02-13 Nedra Benletaief , Houria Rezig , Ammar Bouallegue

Security proofs of quantum key distribution (QKD) typically assume that the devices of the legitimate users are perfectly shielded from the eavesdropper. This assumption is, however, very hard to meet in practice, and thus the security of…

Quantum Physics · Physics 2018-09-05 Weilong Wang , Kiyoshi Tamaki , Marcos Curty

A quantum key distribution and identification protocol is proposed, which is based on entanglement swapping. Through choosing particles by twos from the sequence and performing Bell measurements, two communicators can detect eavesdropping,…

Quantum Physics · Physics 2007-05-23 Fei Gao , Fenzhuo Guo , Qiaoyan Wen , Fuchen Zhu

Counterfactual quantum key distribution (QKD) enables two parties to share a secret key using an interaction-free measurement. Here, we point out that the efficiency of counterfactual QKD protocols can be enhanced by including…

Quantum Physics · Physics 2021-09-07 Vinod N. Rao , R. Srikanth

We calculate eavesdropper's optimal information on raw bits in Bennett-Brassard 1984 quantum key distribution (BB84 QKD) and six-state scheme in coherent attacks, using a formula by Lo and Chau [Science 283 (1999) 2050] with single photon…

Quantum Physics · Physics 2009-11-06 W. Y. Hwang , D. Ahn , S. W. Hwang

Quantum key distribution (QKD) can share an unconditional secure key between two remote parties, but the deviation between theory and practice will break the security of the generated key. In this paper, we evaluate the security of QKD with…

Quantum Physics · Physics 2020-10-26 Shi-Hai Sun , Zhi-Yu Tian , Mei-Sheng Zhao , Yan Ma

The quantum key distribution protocol BB84, published by C. H. Bennett and G. Brassard in 1984, describes how two spatially separated parties can generate a random bit string fully known only to them by transmission of single-qubit quantum…

Quantum Physics · Physics 2007-12-28 Olli Ahonen

Quantum key distribution (QKD) permits information-theoretically secure transmission of digital encryption keys, assuming that the behaviour of the devices employed for the key exchange can be reliably modelled and predicted. Remarkably, no…

Optical fiber networks are part of important critical infrastructure and known to be prone to eavesdropping attacks. Hence cryptographic methods have to be used to protect communication. Quantum key distribution (QKD), at its core, offers…

Quantum Physics · Physics 2023-06-27 Alexandra Popp , Florian Sedlmeir , Birgit Stiller , Christoph Marquardt

Quantum key distribution (QKD) stands as a pioneering method for establishing information-theoretically secure communication channels by utilizing the principles of quantum mechanics. In the security proof of QKD, the phase error rate…

Quantum key distribution (QKD) promises provably secure cryptography, even to attacks from an all-powerful adversary. However, with quantum computing development lagging behind QKD, the assumption that there exists an adversary equipped…

Quantum Physics · Physics 2020-07-01 L. C. G. Govia , D. Bunandar , J. Lin , D. Englund , N. Lütkenhaus , H. Krovi

In a two-way deterministic quantum key distribution (DQKD) protocol, Bob randomly prepares qubits in one of four states and sends them to Alice. To encode a bit, Alice performs an operation on each received qubit and returns it to Bob. Bob…

Quantum Physics · Physics 2013-12-11 Hua Lu , Chi-Hang Fred Fung , Qing-yu Cai

Quantum key distribution (QKD) systems provide a method for two users to exchange a provably secure key. Synchronizing the users' clocks is an essential step before a secure key can be distilled. Qubit-based synchronization protocols…

Quantum Physics · Physics 2021-08-11 Roderick D. Cochran , Daniel J. Gauthier

Quantum cryptography shows that one can guarantee the secrecy of correlation on the sole basis of the laws of physics, that is without limiting the computational power of the eavesdropper. The usual security proofs suppose that the…

Quantum Physics · Physics 2009-11-13 Valerio Scarani , Nicolas Gisin , Nicolas Brunner , Lluis Masanes , Sergi Pino , Antonio Acin