According to the characteristics of a class of three-particle W-states and the quantum dense coding,a new quantum secure direct communication scheme is presented.All particles,which are transmitted,are used to encode secret information except for the particles for testing security,which can greatly improve the communication efficiency.In order to ensure the security of the scheme,the channel is tested two times using the entanglement correlation between particles of W-states in particle distribution phase.It can improve the detection rate for eavesdropper and the reduce information leakage by inserting decoy photons into particles and rearranging the order of particles in information transfer phase.Security analysis shows that the scheme can ensure information transfer security and improve communication efficiency.
According to the characteristics of a class of three-particle W-states and the quantum dense coding,a new quantum secure direct communication scheme is presented.All particles,which are transmitted,are used to encode secret information except for the particles for testing security,which can greatly improve the communication efficiency.In order to ensure the security of the scheme,the channel is tested two times using the entanglement correlation between particles of W-states in particle distribution phase.It can improve the detection rate for eavesdropper and the reduce information leakage by inserting decoy photons into particles and rearranging the order of particles in information transfer phase.Security analysis shows that the scheme can ensure information transfer security and improve communication efficiency.
In order to improve the communication efficiency and security of Quantum Secure Direct Communication, a new Quantum Secure Direct Communication scheme based on d-dimension Bell entangled state is proposed. In the scheme, the receiver and the sender transport the d-dimensional Bell particles as secure test particles to ensure the security of communication. The receiver can calculate the security of the channel according to the measurement of d-dimensional Bell state particles, which is based on the entanglement properties of the d-dimensional Bell state. Secret information is transmitted through the other d-dimensional Bell state particles by dense coding technique. Then, the receiver can determine the security of the channel by comparing the measurements of the particles and makes a joint measurement of the transmitted particles to obtain secret information. Finally, the entropy theory is used to analyze the security of the protocol. Under the four dimensional Bell state, the transmission efficiency of the protocol is 90.90% and the efficiency of the quantum bit is 45.45%. The results show that the proposed scheme is safe and reliable and has high transmission efficiency.
Three-particle W state decoy is introduced in controlled quantum secure direct communication to improve the eavesdropping detection probability and prevent the double-CNOT attack. Each particle of three-particle W state decoy is inserted into sending particles to detect eavesdroppers. The decoy particles inserted randomly can prevent the receiver from obtaining the correct correlation between particle 1 and particle 2 before sender coding on them, so that he can not get any secret information without controller's permission. In the security analysis, the maximum amount of information in a qubit is obtained by introducing the entropy theory method, and two decoy strategies are compared quantitatively. If eavesdroppers intend to eavesdrop on secret information, the per qubit detection rate can reach 64% by using three-particle W state as decoy, but 58% by using extended three-particle GHZ state as decoy.
A novel quantum secure direct communication protocol based on four-particle genuine entangled state and quantum dense coding is proposed. In this protocol, the four-particle genuine entangled state is used to detect eavesdroppers, and quantum dense coding is used to encode the message. Finally, the security of the proposed protocol is discussed. During the security analysis, the method of entropy theory is introduced, and two detection strategies are compared quantitatively by comparing the relationship between the maximal information that the eavesdroppers (Eve) can obtain, and the probability of being detected. Through the analysis we can state that our scheme is feasible and secure.
A quantum secure direct communication scheme using dense coding is proposed. At first, the sender (Alice) prepares four-particle genuine entangled states and shares them with the receiver (Bob) by sending two particles in each entangled state to him. Secondly, Alice encodes secret information by performing the unitary transformations on her particles and transmits them to Bob. Finally, Bob performs the joint measurements on his particles to decode the secret information. The two-step security test guarantees the security of communication.
By studying the properties of the mixture of Bell state particles and single photons,in the paper we design a quantum code scheme with high coding capacity,and propose a novel quantum secure direct communication protocol with high transmission efficiency.Alice prepares Bell state particles and single photons,and divides Bell state particles into two sequences SA and SB.SB is sent to Bob for the first security check through using quantum correlation properties of particles.When the check result shows that the quantum channel is safe,by using the designed quantum code scheme, Alice encodes her classical message on the mixed quantum state sequence of Bell sequence SA and single photon sequence SS.Then,some single photons that are used for security check are re-inserted randomly into the encoded sequence,and the order of particles is rearranged to ensure checking Eve's attack.Alice sends the new sequence to Bob.Bob delays and receives it.And then,the quantum channel conducts the second-time security check.The transmission error rate is calculated,and if the error rate is lower than the tolerance threshold,the channel is safe.Bob decodes and reads Alice's message.The first security check is to determine whether quantum channel is safe.The second security check is to test whether there are eavesdroppers during information transmission.Safety analysis is done by applying the quantum information theory for the proposed protocol.The error rate introduced by Eve and the amount of information by Eve are calculated.It is shown that this pro-tocol can effectively resist measurement-resend attack,intercept-resend attack, auxiliary particle attack,denial of service attack and Trojan attack.Among them,auxiliary particle attack is analyzed in detail.The transmission efficiency and coding capacity are also analyzed.The transmission efficiency is 2,the quantum bit rate is 1,and the coding capacity is that a quantum state can encode three bits of classical messages.We also compare the proposed protocol with many existing popular protocols in the sense of efficiency,e.g.,Ping-Pong protocol, Deng F G et al.'s two-step and one-pad-time quantum secure direct communication protocol,Wang J et al.'s quantum secure direct communication protocol based on entanglement swapping and Quan D X et al.'s one-way quantum secure direct communication protocol based on single photon.It is proved that this proposed protocol has higher transmission efficiency.In addition,neither complex U operation nor entanglement swapping is used,and implementation process is simplified.However,this protocol is devoted to theoretical research of quantum secure direct communication.There are still some difficulties in the practical application.For example,the storage technology of quantum states is not mature at present.It is not easy to prepare and measure Bell state particles nor to combine them with single photons,and so on.The implementation of this protocol depends on the development of quantum technology in the future.
In the paper, a protocol of quantum secure direct communication (QSDC) based on EPR entangled state and a quantum state of one particle is presented. The proposed protocol of QSDC uses the idea of one time pad of classical cryptology. The concept of data block and the method of split-step transmission are introduced into the proposed protocol of QSDC. According to the property of quantum, the eavesdropper can get nothing from quantum communication system, so the security of whole QSDC system is ensured. A part of secret message which will be transmitted is loaded on entangled states by processing quantum dense encoding operation on entangled particles. A nonorthogonal mixed state of single particle is introduced into the proposed protocol in order to improve the transmission efficiency, hence another part of secret message which will be transmitted is loaded on states of single particle. The private key and secret message are transmitted directly at the same time on quantum channel. So the proposed scheme of QSDC shall gain higher efficiency as well as complexity increase, and the system be proved the security by performance analysis.