This study identifies a participant attack vulnerability in Li et al.’s SQPC protocol. The participant attack allows a malicious participant, Bob, to obtain the participant Alice’s secret information by intercepting and measuring photons sent to Alice, and later decrypting Alice’s encrypted comparison result. An improved SQPC protocol is proposed to address this problem. The key enhancement is introducing a mutual eavesdropping check requiring the third party and participants to verify they obtain the same photon measurement results. This enables detecting participant attacks like the one identified. The SQPC protocol proposed in this study not only withstands attacks from internal participants but also achieves quantum efficiency almost equivalent to Li et al.’s SQPC protocol. Thus, this study presents a more secure SQPC protocol without compromising quantum efficiency.
This study identifies a participant attack vulnerability in Li et al.’s SQPC protocol. The participant attack allows a malicious participant, Bob, to obtain the participant Alice’s secret information by intercepting and measuring photons sent to Alice, and later decrypting Alice’s encrypted comparison result. An improved SQPC protocol is proposed to address this problem. The key enhancement is introducing a mutual eavesdropping check requiring the third party and participants to verify they obtain the same photon measurement results. This enables detecting participant attacks like the one identified. The SQPC protocol proposed in this study not only withstands attacks from internal participants but also achieves quantum efficiency almost equivalent to Li et al.’s SQPC protocol. Thus, this study presents a more secure SQPC protocol without compromising quantum efficiency.
This study focuses on semi-quantum private comparison (SQPC) protocols, where participants with limited quantum capabilities compare private information with the help of a quantum third party (TP). Yan et al. introduced an SQPC protocol in 2021, but Li et al. later found it vulnerable to double controlled NOT (CNOT) operation attacks and proposed improvements. However, this study identifies a different vulnerability in Yan et al.’s protocol — a reflecting attack that allows information leakage. Bob can intercept and reflect quantum states, avoiding detection and then use Alice’s measurement outcomes and pre-shared key to access her confidential information. The study also proposes an enhanced method to secure the protocol.
Many semi-quantum private comparison (SQPC) protocols have been proposed to compare the equality of participants, but they suffer from low qubit efficiency and require classical participants to perform quantum state measurement and preparation operations. We here propose a novel SQPC protocol based on d-dimensional Bell states. With the assistance of a semi-honest third party, classical participants can compare the sizes of their privacies merely through particle reflection and simple unitary operations, but they do not need to prepare and measure quantum states. Furthermore, participants can compare two bits of privacy just once with one qubit. By combining decoy state eavesdropping detection with pre-shared key encryption as dual security strategies, analysis shows that the proposed protocol is secure against internal and external attack in theory. The qubit efficiency of the protocol reaches 66.7 % , which is significantly superior to existing schemes.
The goal of semi-quantum privacy comparison (SQPC) is to use a small amount of quantum capabilities to compare private information for equality. In recent years, research on semi-quantum privacy comparison protocol has made some achievements. However, most of SQPC protocols can merely compare the private information of two parties, and the research of multi-party SQPC protocols are still scarce. If the number of participants is more than two, the protocol needs to be executed multiple times. Therefore, we proposed a multi-party semi-quantum private comparison protocol based on the maximally entangled GHZ-type state, which has the capability to compare the equality of n parties by executing the protocol once. What is more, the transmission of participant’s encrypted information is not through the classical channel, which improves the security of the protocol. Finally, the security analysis shows that outsider attacks, dishonest participants attacks and semi-honest TP attacks are all invalid for this protocol.
Abstract Semi-quantum private comparison (SQPC) is a quantum cryptographic protocol that allows two classical participants to securely determine whether their private inputs are equal, with the assistance of a semi-honest third party possessing full quantum capabilities. However, most existing SQPC protocols suffer from low qubit efficiency and high implementation costs, primarily due to their reliance on pre-shared keys and complex entangled state preparations. To address these limitations, we propose a novel SQPC protocol based on hybrid quantum states, which integrates Bell states and single-qubit states within a circular transmission architecture. The protocol eliminates the requirement for pre-shared keys and reduces consumption of quantum resources by introducing randomness in the placement of quantum states. Security analysis demonstrates that the proposed protocol is robust against measure–resend attacks, entanglement measurement attacks and internal threats from dishonest participants. Furthermore, performance evaluation shows that the proposed protocol achieves a high qubit efficiency, quantified as η = n 10 n + 1 , where n is the number of bits compared. This efficiency surpasses that of several previously proposed SQPC protocols.
Abstract In this paper, we propose a novel semiquantum private comparison (SQPC) protocol based on Bell states, which enables one quantum user and one classical user to compare the equality of their private inputs with the help of a semi-honest quantum third party (TP). TP is assumed to be semi-honest in the sense that she may take all possible attacks to steal users’ private inputs except conspiring with anyone. The security analysis validates that our protocol can resist not only the attacks from internal participants but also the attacks from an external eavesdropper. Besides, our protocol only asks TP to perform Bell basis measurements but does not need quantum entanglement swapping; and it releases the classical user from conducting quantum measurements and having a quantum memory. Moreover, our protocol can take advantage over previous SQPC protocols based on Bell states in qubit efficiency. Finally, our protocol can be generalized into its counterpart of the collective-dephasing noise quantum channel.
Abstract In this paper, we propose two multi-party quantum private comparison protocols based on the properties of the d-dimensional GHZ state. Protocol 1 is designed to compare the equality of multiple participants’ secrets with the help of a semi-honest third party TP. The semi-honest TP will follow the protocol honestly, but he may attempt to learn additional information from the protocol execution. In this protocol, multiple participants encode their secret information into the corresponding particles in turn through unitary operations, thereby achieving the comparison of the equality of their multiple secrets in a single execution. This protocol has a wide range of applications. For example, by combining the basic model framework of this protocol with the Chinese Remainder Theorem, we propose Protocol 2. In this protocol, multiple participants compare the size relationships of their multiple secrets with the help of a semi-honest third party TP. Therefore, based on the same basic model framework, the two protocols proposed in this paper can be applied respectively to the comparison of the equality and the size relationships of multiple participants’ secrets. Importantly, the two protocols do not require pre-shared keys. Security analysis shows that the proposed protocols can resist various attacks, including entangle-measure attack, intercept-resend attack, third party attacks, and participant attacks.