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This paper proposes a visually secure asymmetric image encryption scheme based on Rivest–Shamir–Adlemen (RSA) algorithm and hyperchaotic map. It combines the advantages of the RSA and chaos-based image encryption algorithms. First, to fully encrypt the image information, the plain image is encrypted into a cipher image by applying the row and column encryption algorithms. Second, the image secret key is converted into a ciphertext by utilizing the RSA algorithm to increase the security, and then the ciphertext is transformed into an image and permuted using the Arnold map to enhance the robustness of the embedded image. We then obtain the key cipher image. Finally, the cipher image and the key cipher image are embedded into a carrier image (CI) to obtain a visually secure image. It simultaneously achieves the image information security and image visually security. To further improve the security, the RSA keys management technique is applied and the initial conditions of the hyperchaotic map are updated in real time based on the plain image. In addition, the encryption scheme is suitable for multi-user image transmission with high security requirements and image transmission without the secure channel for key transmission. The simulation results and performance analysis validate the effectiveness, security and robustness of the proposed scheme.

In the test of cross span distance of transmission line, the estimation of cross span distance is not accurate, which leads to the increase of subsequent test error. Therefore, a test method of transmission line cross span distance based on a multi-objective ant colony algorithm is proposed. Statistics of the actual information of different crossovers including trees and forest areas. Considering the transmission line as a flexible cable, the objective function for estimating the cross span distance of the transmission line is constructed according to the catenary model of the flexible cable model. On this basis, the multi-objective ant colony algorithm is used to solve the function, and the optimization results of transmission line crossing distance are output. The experimental results show that the method has high accuracy, small error, short time and reliability.

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