Quantum Private Comparison without Classical Computation

Duan Ming-Yi

Haibin Wang, Daomeng Pan, Wenjie Liu

Chia‐Wei Tsai, Jason Lin, Han‐Chieh Chao +1 more

Ji et al. [Mod. Phys. Lett. A 34, 1950229 (2019)] and Fan et al. [Mod. Phys. Lett. A 37, 2250026 (2022)] proposed two-party quantum private comparison (QPC) protocols based on 7-qubit and 8-qubit states, respectively. However, these two QPC protocols did not consider third-party (TP) attacks. Therefore, this study focuses on TP attacks and demonstrates that the property of a 7-qubit or 8-qubit entanglement state is useless in this attack situation; that is, the participant wastes resources to maintain the qubits. For the same assumption environment proposed by Ji et al. and Fan et al., this study proposes an improvement and simplification protocol that allows participants to reach the goal of private comparison by using only classical computation and the classical communication channel without any entanglement state.

Min Hou, Yue Wu

Quantum private comparison (QPC) is a crucial component of quantum multiparty computing (QMPC), allowing parties to compare their private inputs while ensuring that no sensitive information is disclosed. Many existing QPC protocols that utilize Bell states encounter efficiency challenges. In this paper, we present a novel and efficient QPC protocol that capitalizes on the distinct characteristics of Bell states to enable secure comparisons. Our method transforms private inputs into unitary operations on shared Bell states, which are then returned to a third party to obtain the comparison results. This approach enhances efficiency and decreases the reliance on complex quantum resources. A single Bell state can compare two classical bits, achieving a qubit efficiency of 100%. We illustrate the feasibility of the protocol through a simulation on the IBM Quantum Cloud Platform. The security analysis confirms that our protocol is resistant to both eavesdropping and attacks from participants.

Yan‐Feng Lang

Kishore Thapliyal, Rishi Dutt Sharma, Anirban Pathak

Private comparison is a primitive for many cryptographic tasks, and recently several schemes for the quantum private comparison (QPC) have been proposed, where two users can compare the equality of their secrets with the help of a semi-honest third party (TP) without knowing each other’s secret and without disclosing the same to the TP. In the existing schemes, secrecy is obtained by using conjugate coding, and considering all participants as quantum users who can perform measurement(s) and/or create states in basis other than computational basis. In contrast, here we propose two new protocols for QPC, first of which does not use conjugate coding (uses orthogonal states only) and the second one allows the users other than TP to be classical whose activities are restricted to either reflecting a quantum state or measuring it in computational basis. Further, the performance of the protocols is evaluated under various noise models.