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arXiv:1811.03190

Efficient semiquantum key distribution

Ming‐Ming Wang, Linming Gong, Lian-He Shao

Published Nov 7, 2018• 0 citations
arXivHTMLPDF

Abstract

Quantum cryptography has attracted much attention in recent years. In most existing quantum cryptographic protocols, players usually need the full quantum power of generating, manipulating or measuring quantum states. Semiquantum cryptography was proposed to deal with the issue that some players require only partial quantum power, such as preparing or measuring quantum states in the classical basis, which simplifies the implementations of quantum cryptography. However, the efficiency of the existing semiquantum cryptographic protocols was relatively low from a practical point of view. In this paper, we devise some new semiquantum key distribution (SQKD) protocols which highly improve the efficiency of the most well-known SQKD protocols [Phys. Rev. Lett. 99, 140501 (2007) & Phys. Rev. A 79, 052312 (2009)]. By letting players select their actions asymmetrically, the efficiency of our new protocols can be made asymptotically close to 100%. Besides, one of our proposed protocols also utilizes the discarded X-SIFT bits in the original SQKD protocol, which further improves the efficiency of SQKD. We prove that the proposed SQKD protocols are completely robust against the most general attack.

DOI
10.48550/arxiv.1811.03190

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Quantum cryptography has attracted much attention in recent years. In most existing quantum cryptographic protocols, players usually need the full quantum power of generating, manipulating or measuring quantum states. Semiquantum cryptography was proposed to deal with the issue that some players require only partial quantum power, such as preparing or measuring quantum states in the classical basis, which simplifies the implementations of quantum cryptography. However, the efficiency of the existing semiquantum cryptographic protocols was relatively low from a practical point of view. In this paper, we devise some new semiquantum key distribution (SQKD) protocols which highly improve the efficiency of the most well-known SQKD protocols [Phys. Rev. Lett. 99, 140501 (2007) & Phys. Rev. A 79, 052312 (2009)]. By letting players select their actions asymmetrically, the efficiency of our new protocols can be made asymptotically close to 100%. Besides, one of our proposed protocols also utilizes the discarded X-SIFT bits in the original SQKD protocol, which further improves the efficiency of SQKD. We prove that the proposed SQKD protocols are completely robust against the most general attack.
Recently Boyer et al. [Phys. Rev. Lett. 99, 140501 (2007)] suggested the idea of semiquantum key distribution (SQKD) in which Bob is classical and they also proposed a semiquantum key distribution protocol (BKM2007). To discuss the security of the BKM2007 protocol, they proved that their protocol is completely robust. This means that nonzero information acquired by Eve on the information string implies the nonzero probability that the legitimate participants can find errors on the bits tested by this protocol. The BKM2007 protocol uses four quantum states to distribute a secret key. In this paper, we simplify their protocol by using less than four quantum states. In detail, we present five different SQKD protocols in which Alice sends three quantum states, two quantum states, and one quantum state, respectively. Also, we prove that all the five protocols are completely robust. In particular, we invent two completely robust SQKD protocols in which Alice sends only one quantum state. Alice uses a register in one SQKD protocol, but she does not use any register in the other. The information bit proportion of the SQKD protocol in which Alice sends only one quantum state but uses a register is the double as that in the BKM2007 protocol. Furthermore, the information bit rate of the SQKD protocol in which Alice sends only one quantum state and does not use any register is not lower than that of the BKM2007 protocol.
Semiquantum key distribution protocols are designed to allow two parties to establish a shared secret key, secure against an all-powerful adversary, even when one of the users is restricted to measuring and preparing quantum states in one single basis. While interesting from a theoretical standpoint, these protocols have the disadvantage that a two-way quantum communication channel is necessary which generally limits their theoretical efficiency and noise tolerance. In this paper, we construct a semiquantum key distribution (SQKD) protocol which actually takes advantage of this necessary two-way channel, and, after performing an information theoretic security analysis against collective attacks, we show it is able to tolerate a channel noise level higher than any prior SQKD protocol to date. We also compare the noise tolerance of our protocol to other two-way fully quantum protocols, along with BB84 with classical advantage distillation. We also comment on some practical issues involving semiquantum key distribution (in particular, concerning the potential complexity in physical implementation of our protocol as compared with other standard QKD protocols). Finally, we develop techniques that can be applied to the security analysis of other (S)QKD protocols reliant on a two-way quantum communication channel.
A semiquantum key distribution (SQKD) protocol allows two users, one of whom is restricted in their quantum capabilities to being nearly classical, to establish a shared secret key, secure against an all-powerful adversary. The study of such protocols helps to answer the fundamental question of “how quantum” must a protocol be to gain an advantage over classical communication. In this article, we design a new SQKD protocol using high-dimensional quantum states and conduct an information theoretic security analysis. We show that, similar to the fully quantum key distribution case, high-dimensional systems can increase the noise tolerance in the semiquantum case. Furthermore, we prove several general security results which are applicable to other (S)QKD protocols (both high-dimensional ones and standard qubit-based protocols) utilizing a two-way quantum channel.
Abstract Semiquantum key distribution (SQKD) facilitates the establishment of secure keys even when one user (designated as the classical user) is constrained to performing quantum state preparation and measurement only within a fixed computational basis. From a resource-theoretic perspective, this approach presents both novelty and theoretical significance. Recently, a novel SQKD protocol based on Bell states, where the classical user’s REFLECT operations directly contribute to the generation of the final shared key was proposed [ Laser Physics Letters , 21 (9):095201, 2024]. However, our analysis reveals that this protocol is vulnerable to double CNOT attacks, posing security risks. To address this, we propose an improved SQKD protocol that maintains resistance to double CNOT attacks while preserving the classical user’s REFLECT operations as a functional component for key generation. Notably, we rigorously prove the unconditional security of the improved protocol and derive a maximum allowable error rate of 8.92% in depolarizing channels. This work serves two purposes: (1) it alerts SQKD protocol designers to the identified security vulnerability, and (2) it provides a foundational reference for establishing unconditional security proofs in SQKD protocols where REFLECT operations contribute to key generation.
Abstract In this paper, a novel semiquantum key distribution (SQKD) protocol is proposed by using Bell state, where quantum Alice can sharesecret bits with classical Bob via quantum channel. Classical Bob is required to measure particles with thebasis, produce fresh particles within thebasis and send particles via quantum channel. Security analysis turns out that this protocol is immune to various attacks launched by the outside eavesdropper. Compared with present SQKD protocols using Bell states without a third party, on one hand, this protocol has the highest qubit efficiency; and on the other hand, the reflecting operations of the classical user in this protocol contribute to the generation of final shared key.
Boyer et al put forward the first semi-quantum key distribution (BKM2007), which is completely robust while one side is limited. However, its efficiency is not satisfactory. In this paper, we present a high-efficient semi-quantum key distribution. The efficiency for qubits is approximately 50% while that is approximately 25% in the BKM2007 protocol, which means that the sifted key proportion of the SQKD protocol is double as that in the BKM2007 protocol. Furthermore, the proportion of information bits in our SQKD protocol is not lower than that of the BKM2007 protocol. Analysis shows that our protocol is still robust.