In this paper a scheme for quantum secure direct communication (QSDC) network is proposed with a sequence of polarized single photons. The single photons are prepared originally in the same state |0〉 by the servers on the network, which will reduce the difficulty for the legitimate users to check eavesdropping largely. The users code the information on the single photons with two unitary operations which do not change their measuring bases. Some decoy photons, which are produced by operating the sample photons with a Hadamard, are used for preventing a potentially dishonest server from eavesdropping the quantum lines freely. This scheme is an economical one as it is the easiest way for QSDC network communication securely.
In this paper a scheme for quantum secure direct communication (QSDC) network is proposed with a sequence of polarized single photons. The single photons are prepared originally in the same state |0〉 by the servers on the network, which will reduce the difficulty for the legitimate users to check eavesdropping largely. The users code the information on the single photons with two unitary operations which do not change their measuring bases. Some decoy photons, which are produced by operating the sample photons with a Hadamard, are used for preventing a potentially dishonest server from eavesdropping the quantum lines freely. This scheme is an economical one as it is the easiest way for QSDC network communication securely.
A quantum secure direct communication network scheme is proposed with quantum superdense coding and decoy photons. The servers on a passive optical network prepare and measure the quantum signal, i.e. a sequence of the d -dimensional Bell states. After confirming the security of the photons received from the receiver, the sender codes his secret message on them directly. For preventing a dishonest server from eavesdropping, some decoy photons prepared by measuring one photon in the Bell states are used to replace some original photons. One of the users on the network can communicate to any other one. This scheme has the advantage of high capacity, and it is more convenient than others as only a sequence of photons is transmitted in quantum line.
Quantum secure direct communication (QSDC) can transmit secret messages directly from one user to another without first establishing a shared secret key, which is different from quantum key distribution. In this paper, we propose a novel quantum secure direct communication protocol based on signal photons and Bell states. Before the execution of the proposed protocol, two participants Alice and Bob exchange their corresponding identity IDA and IDB through quantum key distribution and keep them secret, respectively. Then the message sender, Alice, encodes each secret message bit into two single photons (| 01〉or|10〉) or a Bell state , and composes an ordered secret message sequence. To insure the security of communication, Alice also prepares the decoy photons and inserts them into secret message sequence on the basis of the values of IDA and IDB. By the secret identity IDA and IDB, both sides of the communication can check eavesdropping and identify each other. The proposed protocol not only completes secure direct communication, but also realizes the mutual authentication. The security analysis of the proposed protocol is presented in the paper. The analysis results show that this protocol is secure against some common attacks, and no secret message leaks even if the messages are broken. Compared with the two-way QSDC protocols, the presented protocol is a one-way quantum communication protocol which has the immunity to Trojan horse attack. Furthermore, our proposed protocol can be realized without quantum memory.
The proposed protocols of quantum secure direct communication based on single photons up-to-date are almost two-way communication protocols, in which the probability of Trojan horse attack reduces the security of the communication. The aim of photons transferred forward and backward is to let the receiver know the code bases and the initial states of the photons. One-way quantum secure direct communication protocol based on single photons is proposed, in which the XOR operation by bits of the information sequence and random sequence is taken before coding. Then the code bases and the random sequence can be published if the quantum channel is secure, so the receiver can measure in the correct basis to get the information; even there exists eavesdropper, the information sequence is still secure. This protocol has the advantages of higher security, longer communication distance compared with two-way scheme and easier implementation than others.
In this paper an efficient quantum secure direct communication (QSDC) scheme with authentication is presented, which is based on quantum entanglement and polarized single photons. The present protocol uses Einstein–Podolsky–Rosen (EPR) pairs and polarized single photons in batches. A particle of the EPR pairs is retained in the sender's station, and the other is transmitted forth and back between the sender and the receiver, similar to the ``ping–pong'' QSDC protocol. According to the shared information beforehand, these two kinds of quantum states are mixed and then transmitted via a quantum channel. The EPR pairs are used to transmit secret messages and the polarized single photons used for authentication and eavesdropping check. Consequently, because of the dual contributions of the polarized single photons, no classical information is needed. The intrinsic efficiency and total efficiency are both 1 in this scheme as almost all of the instances are useful and each EPR pair can be used to carry two bits of information.
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.
Quantum secure direct communication (QSDC) enables direct private message transmission over quantum channels without pre-shared keys. This paper proposes a QSDC protocol based on two-step line-based quantum walks (QWs), which involves sender Alice, receiver Bob and an untrusted third party Charlie, and three stages consisting of preparing, checking quantum channel and communicating secret messages. In the first stage, Bob generates entangled states as the desired quantum channel via one-step QW and prepares decoy photons for the subsequent security checking of the quantum channel; In the second stage, Bob first sends a sequence comprising the photons from the entangled states and Bob’s decoy photons to Alice, who forwards Bob’s decoy photons along with her own decoy photons to Charlie for measurement, with Alice and Bob verifying security by comparing the measurement outcomes; In the third stage, Alice prepares a sequence of photons as coin state for encoding messages to be communicated, which along with the prepared entangled states form a quantum teleportation system, which completes the transmission of the messages under the dominance of another-step QW. Security analyses show the suggested protocol can resist against intercept-and-resend and measure-and-resend attacks, promoting the QSDC’s practicality via QW-based entanglement generation, simplified measurement operations and security checking under the assistance of the third party Charlie.