Cryptanalysis and Improvement of Ye et al’s Quantum Private Comparison Protocol

Recently, Ye et al. (Int. J. Theor. Phys. 56, 1517–1529, 2017) proposed a quantum private comparison (QPC) protocol based on five-qubit entanglement state. Two parties can verify that their secret information is equal or not with the help of the semi-honest third party (TP). However, in this paper we will point out the Ye et al.’s initial protocol is not safe under a special participant attack. That is a malicious participant can get the other party’s secret input information illegally under the forgery attack. Furthermore, we give two possible improvement protocols, which can perform this protocol secure against this kind of attack.

     

Bit-Oriented Quantum Public-Key Cryptosystem Based on Bell States

Quantum public key encryption system provides information confidentiality using quantum mechanics. This paper presents a quantum public key cryptosystem (QPKC) based on the Bell states. By Holevo’s theorem, the presented scheme provides the security of the secret key using one-wayness during the QPKC. While the QPKC scheme is information theoretic security under chosen plaintext attack (CPA). Finally some important features of presented QPKC scheme can be compared with other QPKC scheme.     

Cryptanalysis of Zhang et al’s Quantum Private Comparison and the Improvement

Based on EPR pairs, Zhang et al. analyzed the security of Yang and Tseng et al’s two QPC protocols, and proposed some new improvement strategies (Zhang and Zhang, Quantum Inform. Process. 12(5):1981–1990 2013). This paper points that Zhang et al’s protocol is insecure under a special attack, i.e. Trojan-horse attacks. To avoid this attack, we present an improved QPC protocol based on single particle encryption. Through security analysis of presented protocol, the improved protocol can resist Trojan horse attack (THA). We give a suggestion that non-orthogonal quantum states can be used to transmit information for reducing the leakage in a QPC protocol.