Secure Direct Communication Protocol Research Articles

On the generalization and improvement of QSDC efficiency achieved through a quantum channel compression

The paper presents a complete and general representation of the overall efficiency expression for the quantum secure direct communication (QSDC) protocol that relies on quantum channel compression (QCC). For this purpose, (i) the encoding technique, respectively, QCC is generalized—QCCs of higher order are introduced; (ii) the data statistics of the messages to be transferred are incorporated into the overall efficiency expression. An analysis is made concerning the behavior and the extent of the overall efficiency. It is justified that QSDC protocols, which are based on high order of QCC, could achieve efficiencies that have never been reached before.

Impersonation attack on a quantum secure direct communication and authentication protocol with improvement

We analyze the security of a quantum secure direct communication and authentication protocol based on single photons. We first give an impersonation attack on the protocol. The cryptanalysis shows that there is a gap in the authentication procedure of the protocol so that an opponent can reveal the secret information by an undetectable attempt. We then propose an improvement for the protocol and show it closes the gap by applying a mutual authentication procedure. In the improved protocol single photons are transmitted once in a session, so it is easy to implement as the primary protocol. Furthermore, we use a novel technique for secret order rearrangement of photons by which not only quantum storage is eliminated also a secret key can be reused securely. So the new protocol is applicable in practical approaches like embedded system devices.

Cryptanalysis of Controlled Quantum Secure Direct Communication and Authentication Protocol Based on Five-Particle Cluster State and Quantum One-Time Pad

A new attack strategy, the so-called intercept-selectively-measure-resend attack is put forward. It shows that there are some security issues in the controlled quantum secure direct communication (CQSDC) and authentication protocol based on five-particle cluster states and quantum one-time pad. Firstly, an eavesdropper (Eve) can use this attack to eavesdrop on 0.656 bit of every bit of the identity string of the receiver and 1.406 bits of every couple of the corresponding bits of the secret message without being detected. Also, she can eavesdrop on 0.311 bit of every bit of the identity string of the controller. Secondly, the receiver can also take this attack to obtain 1.311 bits of every couple of the corresponding bits of the secret message without the permission of the controller, which is not allowed in the CQSDC protocols. In fact, there is another security issue in this protocol, that is, one half of the information about the secret is leaked out unconsciously. In addition, an alternative attack strategy which is called as the selective-CNOT-operation attack strategy to attack this protocol is discussed.

Controlled quantum secure communication protocol with single photons in both polarization and spatial-mode degrees of freedom

In this paper, we propose a new controlled quantum secure direct communication (CQSDC) protocol with single photons in both polarization and spatial-mode degrees of freedom. Based on the defined local collective unitary operations, the sender’s secret messages can be transmitted directly to the receiver through encoding secret messages on the particles. Only with the help of the third side, the receiver can reconstruct the secret messages. Each single photon in two degrees of freedom can carry two bits of information, so the cost of our protocol is less than others using entangled qubits. Moreover, the security of our QSDC network protocol is discussed comprehensively. It is shown that our new CQSDC protocol cannot only defend the outsider eavesdroppers’ several sorts of attacks but also the inside attacks. Besides, our protocol is feasible since the preparation and the measurement of single photon quantum states in both the polarization and the spatial-mode degrees of freedom are available with current quantum techniques.

Cryptanalysis and improvement of three-particle deterministic secure and high bit-rate direct quantum communication protocol

The three-particle deterministic secure and high bit-rate direct quantum communication protocol and its improved version are analyzed. It shows that an eavesdropper can steal the sender's secret message by the intercept-resend attack and the entanglement attack. The original version is even fragile under denial-of-service attack. As a result, some suggestions to revise them are given.

A NEW DETECTION STRATEGY FOR TWO-STEP QSDC PROTOCOL BASED ON THE FIVE-PARTICLE CLUSTER STATE

Detection efficiency of a quantum secure direct communication (QSDC) protocol is crucial. Therefore, it is necessary to improve the security of these protocols on the basis of new detection strategies. In this paper, a new strategy based on the five-particle cluster state is proposed, and applied to the two-step QSDC protocol. Moreover, information theoretical method and numerical analysis is applied to analyze the security of the improved protocol. If Eve intends to eavesdrop all of the information, the probability of being detected reaches up to 7/8, whereas the same is 0.5 in the original protocol. It is concluded that using the new detection strategy in the two-step QSDC protocol is more secure than using the original protocol when the quantum key distribution (QKD) protocol is considered.

Security analysis of the “Ping–Pong” quantum communication protocol in the presence of collective-rotation noise

Environmental noise is inevitable in non-isolated systems. It is, therefore, necessary to analyze the security of the “Ping–Pong” protocol in a noisy environment. An excellent model for collective-rotation noise is introduced, and information theoretical methods are applied to analyze the security of this protocol. If noise level e is lower than 11%, an eavesdropper can gain some, but not all, information freely without being detected. Otherwise, the protocol becomes insecure. We conclude that the use of ‘Ping–Pong’ protocol as a quantum secure direct communication (QSDC) protocol is quasi-secure, as declared by the original author when e⩽11%.

Three-particle deterministic secure and high bit-rate direct quantum communication protocol

A scheme for deterministic secure and high bit-rate direct communication without resorting to a distinct control interval is proposed. It utilizes three entangled qubits, and presents higher bit transfer rate of information and higher security. The security of protocol is asserted by introducing a security control for each transferred bit. The protocol is investigated for a class of individual attacks and it is explicitly showed that the protocol has a high security even in the presence of channel loss.

Cryptanalysis and improvement of a quantum secret sharing scheme based on χ-type entangled states

In the paper [2010 Chin. Phys. B 19 050306], Yang et al. put forward a novel three-party quantum secret sharing protocol of secure direct communication based on χ-type entangled states, they claimed that the scheme is secure. However, in this paper, we study the security of the protocol and find that it is insecure. Applying intercept and resend attack, the agent Bob can obtain Alice's secret without the help from the other agent Charlie. In the end, we give our effective modification for its improvement.

QUANTUM SECURE DIRECT COMMUNICATION WITH A CONSTANT NUMBER OF EPR PAIRS

In this paper, we propose a quantum secure direct communication (QSDC) protocol based on Einstein–Podolsky–Rosen (EPR) pairs. Previous QSDC protocols usually consume one EPR pair to transmit a single qubit. If Alice wants to transmit an n-bit message, she needs at least n/2 EPR pairs when a dense coding scheme is used. In our protocol, if both Alice and Bob preshare 2c + 1 EPR pairs with the trusted server, where c is a constant, Alice can transmit an arbitrary number of qubits to Bob. The 2c EPR pairs are used by Alice and Bob to authenticate each other and the remaining EPR pair is used to encode and decode the message qubit. Thus the total number of EPR pairs used for one communication is a constant no matter how many bits will be transmitted. It is not necessary to transmit EPR pairs before transmitting the secret message except for the preshared constant number of EPR pairs. This reduces both the utilization of the quantum channel and the risk. In addition, after the authentication, the server is not involved in the message transmission. Thus we can prevent the server from knowing the message.

Three-party quantum secret sharing of secure direct communication based on χ-type entangled states

Based on χ-type entangled states and the two-step protocol [Deng F G, Long G L and Liu X S 2003 Phys. Rev. A 68 042317], a quantum secret sharing protocol of secure direct communication based on χ-type entangled states |χ00⟩3214 is proposed. Using some interesting entanglement properties of this state, the agent entirety can directly obtain the secret message from the message sender only if they collaborate together. The security of the scheme is also discussed.

Threshold Quantum Secret Sharing of Secure Direct Communication

We propose a (t, n)-threshold quantum secret sharing protocol of secure direct communication following some ideas of Zhang's protocol [Phys. Lett. A 342 (2005) 60] and Tokunaga et al.'s protocol [Phys. Rev. A 71 (2005) 012314]. The sender distributes the classical secret shares to his or her n agents and each agent owns a secret share in advance. The sender's secure direct communication message can be extracted by an agent subset by collaboration in such a way that at least t or more agents can obtain the secret message with the mutual assistances but any t - 1 or fewer agents cannot. In contrast to the previous multiparty quantum secret sharing protocols in which the sender's secret message can be recovered only if all the agents collaborate, our protocol is more practical and more flexible.

PERFECT CONTROLLED QUANTUM SECURE DIRECT COMMUNICATION

We present a complete controlled quantum secure direct communication (CQSDC) protocol using a nonsymmetric quantum channel. We point out that the roles of controllers in two recent works16,17 can be excluded due to their design. We also give a revised CQSDC protocol such that their original advantages are retained and the complete CQSDC can be realized. We then analyze the roles of the controllers in different CQSDC protocols with different purposes and these protocols' applicabilities.

Quantum secure direct communication via partially entangled states

We present in this paper a quantum secure direct communication (QSDC) protocol by using partially entangled states. In the scheme a third party (Trent) is introduced to authenticate the participants. After authentication, Alice can directly, deterministically and successfully send a secret message to Bob. The security of the scheme is also discussed and confirmed.

Multiparty quantum secret sharing of secure direct communication

Based on the two-step protocol [F.G. Deng, G.L. Long, X.S. Liu, Phys. Rev. A 68 (2003) 042317], we propose a ( n , n ) -threshold multiparty quantum secret sharing protocol of secure direct communication. In our protocol, the sender's secure direct communication message can be extracted only if all the sharers collaborate. We show a variant version of this protocol based on the variant two-step protocol. This variant version can considerably reduce the realization difficulty in experiment. In contrast to the use of multi-particle GHZ states in the case that the sharer number is larger than 3, the use and identification of Bell states are enough in our two protocols disregarding completely the sharer number, hence, our protocols are more feasible in technique.