An Efficient Quantum Private Comparison of Equality over Collective-Noise Channels

This article proposes a collective-noise resistant QPC protocol with the help of an almostdishonest third party (TP) who may try to perform any sort of attacks to derive participants’ private secrets except colluding with any participant. The proposed scheme has some considerable advantages over the state-of-the-art QPC protocols over collective-noise channels, where it does not require any pre-shared key between the participants (Alice and Bob). Nevertheless, the proposed scheme can resist Trojan horse attacks without consuming half of the transmitted qubits and any additional equipment (wavelength filter and PNS) support. As a consequence, the proposed QPC protocol can guarantee higher qubit efficiency as compared to the others over collective noise channels.     

New arbitrated quantum signature of classical messages against collective amplitude damping noise

Recently, Chong et al. [Opt. Comm. 284, (2011) 893-895] pointed out that a dishonest party in Yang and Wen's arbitrated quantum signature scheme [Opt. Comm. 283, (2010) 3198-3201] is able to reveal the other party's secret key without being detected by using the Trojan-horse attacks. However, the solution to avoid the attack still remains open. This work further points out that in Yang and Wen's scheme, the arbitrator is unable to arbitrate the dispute between two users. Consequently, a user can deny that he/she has signed or verified a signature without performing a Trojan-horse attack. A solution is proposed to solve this problem as well as the open problem mentioned earlier.     

Quantum key agreement protocol based on BB84

This work presents a quantum key agreement (QKA) based on the BB84 protocol. The newly proposed QKA protocol enables two involved parties to jointly establish a shared secret key in such a way that the shared secret key cannot be fully determined by one party alone. In contrast to the traditional key agreement protocols that must be based on some mathematical difficulties, the security of the newly proposed protocol is based on the quantum phenomena, which allows unconditional security as well as detection of eavesdroppers. With the technique of delayed measurement, the proposed protocol has 50% qubit efficiency. Therefore, it is very efficient and feasible for practical applications.     

Intercept-Resend Attacks on Semi-quantum Secret Sharing and the Improvements

Recently, Li et al. [Phys. Rev. A 82(2):022303, 2010] presented two semi-quantum secret sharing (SQSS) protocols using Greenberger-Horne-Zeilinger-like states. The proposed schemes are quite practical because only the secret dealer needs to be equipped with advanced quantum devices such as quantum memory, whereas the other agents can merely perform classical operations to complete the secret sharing. However, the present study demonstrates the existence of a security pitfall in the eavesdropping check phase of both the schemes, which can lead to an intercept-resend attack and a Trojan horse attack on the two schemes by a dishonest agent, to determine the other agent’s shadow and consequently derive the master key of the SQSS. This contradicts the security requirement of QSS. Fortunately, two possible solutions are proposed herein to eliminate this security pitfall.     

Multi-Party Quantum Private Comparison Protocol with an Almost-Dishonest Third Party using GHZ States

This article proposes an innovative quantum private comparison (QPC) protocol for n users using GHZ states, where an almost-dishonest third party (TP) is introduced to assist the participants for comparing their secrets. It is argued that as compared to the existing QPC protocols our proposed scheme has some considerable advantages. First, in the existing QPC protocols, the TP can only to determine whether all participants’ secrets are equal or not. Instead of that, in our proposed scheme a TP can even compare the secrets between any subsects of users. Second, since our proposed scheme is based on GHZ state; hence it can ensure higher efficiency as compared to other existing multi-party QPC protocols on d-dimension photons.     

Trojan Horse Attack Free Fault-Tolerant Quantum Key Distribution Protocols Using GHZ States

Recently, Yang and Hwang (Quantum Inf. Process. 13(3): 781–794, 19) proposed two fault-tolerant QKD protocols based on their proposed coding functions for resisting the collective noise, and their QKD protocols are free from Trojan horse attack without employing any specific detecting devices (e.g., photon number splitter (PNS) and wavelength filter). By using four-particle Greenberger-Horne-Zeilinger (GHZ) state and four-particle GHZ-like state in their proposed coding functions, Yang and Hwang’s QKD protocols can resist each kind of the collective noise–collective-dephasing noise, collective-rotation noise. However, their proposed coding function can be improved by the utilization of three-particle GHZ state (three-particle GHZ-like state) instead of four-particle GHZ state (four-particle GHZ-like state) that will eventually reduce the consumption of the qubits. As a result, this study proposed the improved version of Yang and Hwang’s coding functions to enhance the qubit efficiency of their schemes from 20 % to 22 %.     

Improvement on ‘Cryptanalysis and Improvement of a Multiparty Quantum Direct Secret Sharing of Classical Messages with Bell States and Bell Measurements’

Recently, Liu (Int J Theor Phys: pp.1–6, 2018) pointed out that Song et al.’s multiparty quantum direct secret sharing protocol (Int J Theor Phys: 57, 1559, 2018) suffers from several attacks and then an improved quantum direct secret sharing protocol was hence proposed. However, this study shows that Liu’s protocol still suffers from an intercept-resend attack. To solve this problem, a modification is proposed here.

     

Enhanced Multiparty Controlled QSDC Using GHZ State

Recently, Gao et al. [Opt. Commun. 283 (2010) 192] pointed out that Wang et al.'s multiparty controlled quantum secure directcommunication (CQSDC) protocol [Opt. Commun. 266 (2006)732] has the information leakage problem and proposed an improvedprotocol. However, in the improved protocol, due to the introductionof an additional random sampling to avoid the weakness, the qubitefficiency is decreased. By introducing the base changing techniqueto the random sampling in Wang et al.'s protocol, this study overcomesthe information leakage problem and provides a better qubit efficiency.     

One-Way Quantum Authenticated Secure Communication Using Rotation Operation

This study proposes a theoretical quantum authenticated secure communication (QASC) protocol using Einstein-Podolsky-Rosen (EPR) entangle state,
which enables a sender to send a secure as well as authenticated message to a receiver within only one step quantum transmission without having
the classical channels and the certification authority.     

Attacks and Improvement on “Quantum Direct Communication with Mutual Authentication”

In 2009, Yen et al. [Quantum Inf. Comput. 9(5–6):376–394, 2009] proposed a quantum direct communication along with an authentication protocol using Einstein-Podolsky-Rosen states. This study points out several attacks on Yen et al.’s protocol, in which a malicious Trent can launch either an intercept-resend attack to reveal the secret information of a sender or an impersonation attack to impersonate a sender to send forged secret information to a receiver. Furthermore, an outsider can launch a modification attack to modify the secret information of a sender. A possible solution is proposed herein to avoid these security attacks.