In order to improve the eavesdropping detection efficiency in a two-step quantum direct communication protocol, an improved eavesdropping detection strategy using the four-particle cluster state is proposed, in which the four-particle cluster state is used to detect eavesdroppers. During the security analysis, the method of the entropy theory is introduced, and two detection strategies are compared quantitatively using the constraint between the information that the eavesdropper can obtain and the interference that has been introduced. If the eavesdroppers intend to obtain all information, the eavesdropping detection rate of the original two-step quantum direct communication protocol using EPR pair block as detection particles will be 50%; while the proposed strategy's detection rate will be 75%. In the end, the security of the proposed protocol is discussed. The analysis results show that the eavesdropping detection strategy presented is more secure. The goal of researching cryptography is to ensure that the secret message is only available to the two authorized parties of the communication and that the transmission will be altered. So far, it is trusted that the only proven secure cryptosystem is the one-time-pad scheme in which the secret key is as long as the message. The two parties staying far apart who want to transmit their secret message must distribute the secret key first. However it is difficult to distribute the secret key securely through a classical channel. The quantum key distribution (QKD), whose task is to create a secret key between two remote authorized users, is one of the most remarkable applications of quantum mechanics and the only proven protocol for secure key distribution. Since Bennett and Brassard presented the pioneer QKD protocol (BB84 protocol) [1] in 1984, a lot of quantum information security processing methods have been advanced, such as quantum teleportation [2][3][4][5][6][7], quantum dense coding [8][9][10], quantum secret sharing [11,12] and so on.In recent years, a novel concept, quantum secure direct communication (QSDC) [13,14] was put forward and studied by some groups. Different from the key distribution whose object is to establish a common random key between two parties, the secure direct communication is to transmit important message directly without establishing a random key to encrypt them first. Thus, the secure direct communication is more demanding on the security. As a secure direct communication, it must satisfy two requirements. First, the secure message should be read out directly by the legitimate user Bob when he receives the quantum states and no additional classical information is needed after the transmission of particles. Second, the secret message which has been encoded already in the quantum states should not leak even though an eavesdropper may get hold of the channel. That is to say, the eavesdropper cannot only be detected but also obtains blind results. As classical message can be copied fully, it is impossible to transmit secret message direct...
In order to transmit the secure message, a deterministic secure quantum direct communication protocol which was called "Ping-pong" protocol was proposed by Boström and Felbinger [Boström K, et al. Phys Rev Lett, 2002, 89: 187902]. But the protocol was proved very vulnerable, and can be attacked by an eavesdropper. An improved "Ping-pong" protocol is presented to overcome the problem. The GHZ state particles are used to detect eavesdroppers, and the classical XOR operation which serves as a one-time-pad is used to ensure the security of the protocol. During the security analysis, the method of the entropy theory is introduced, and three detection strategies are compared quantitatively by using the constraint between the information which an eavesdropper can obtain and the interference introduced. If the eavesdropper gets the full information, the detection rate of the original "Ping-pong" protocol is 50%; the detection rate of the second protocol which used two particles of EPR pair as detection particles is also 50%; and the detection rate of the presented protocol is 75%. In the end, the security of the proposed protocol is discussed. The analysis results show that the improved "Ping-pong" protocol in this paper is more secure than the other two."Ping-pong" protocol, XOR operation, GHZ state, eavesdropping detection, protocol security
Background: This study aimed to explore the independent risk factors for postherpetic neuralgia (PHN).Methods: Related studies of PHN risk factors were searched in PubMed for screening and meta-analysis.In this study, data from studies included were extracted and summarized, including odds ratio (OR) value, 95% confidence interval (CI), P value, sample size, and the number of patients with and without PHN. The chi-square test was used for heterogeneity test. Sensitivity analysis was conducted by excluding low-quality studies and using different model analysis.Results: A total of 14 studies were further screened for meta-analysis, including 4,192 patients with herpes zoster. Of these patients, 478 (11.40%) had neuralgia and 3,714 (88.60%) did not have neuralgia. Age [OR =1.59; 95% CI: (1.23, 2.04); Z=3.62; P<0.001], acute severe pain in the herpes stage [OR =1.49; 95% CI: (1.08, 2.08); Z=2.39; P=0.02], prodromal symptoms [OR =2.00; 95% CI: (1.16, 3.44); Z=2.48; P=0.01], and severe rash [OR =2.40; 95% CI: (1.83, 3.14); Z=6.38; P<0.001] were independent risk factors for PHN. The funnel chart shows that there is no publication bias or geographic bias in the above independent risk factors. Gender (Z=0.37; P=0.71) was not associated with PHN, and the funnel chart shows that there is no publication bias or geographic bias.Discussion: Age, acute pain, prodromal symptoms, and severe rash were independent risk factors for PHN.
A directional communication scheme, TRAC, is proposed in this paper to deal with issues in mobile directional communications. Directional communication can bring benefits in terms of spatial reuse, power consumption, and security. Using direction antennas implies that the transmitters must know the direction or location of the receiver. It is necessary to predict the receiver's location to keep the transmitter's antenna pointing in the right direction if nodes travel always. TRAC is composed of the location prediction and antenna adjustment. It predicts a possible circular region where the moving receiver may enter into in the near future. The transmitter points its antenna at the predicted circular region and adjusts the beam-width of its directional antenna to cover the predicted region. The authors validated the TRAC algorithm on some vehicles traces. The validation indicated that the algorithm efficiency of TRAC is larger than 96%. TRAC can be employed in mobile communications without nodes' history movement traces.
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