Traditional image permutation mechanisms like sort-based, Arnold-based, Baker-based, cyclic shift-based permutation mechanisms, etc., have disadvantages like weak permutation and high time complexity. Most of the researchers primarily focus on developing an efficient permutation strategy by devising a separate shifting algorithm that can effectively conceal the original image information. It is considered as the two basic steps in encryption. To enhance the security in all levels, the researchers use the concepts of DNA sequence operation, Cellular Automata, substitution-box, finite-state machine, fractal sorting matrix, bit-level permutation, compressive sensing, etc., along with chaos-based cryptography.Īs we explained earlier, the permutation-substitution process decides the level of security attained by the final cipher image. Various researchers use maps like Lorentz map, Arnold-Tent map, Cat map, etc., to generate random numbers so that they can be applied on the image to change the original pixel values (substitution or diffusion) and to shift the position of actual pixel values (permutation or confusion). The values of parameters or constants of the chaotic maps act as keys to the cryptosystem. Chaotic systems are mathematical functions with the property of being sensitive to primary values of parameters. It basically involves the processing of images with a sequence of random numbers produced by a chaotic system. The active area of research in designing encryption algorithms for images is chaos-based cryptography. It is observed that, due to the high correlation amongst pixels of the image, popular enciphering mechanisms like Data Encryption Standard (DES) and Advanced Encryption Standard (AES) are not effectively suitable for enciphering images. To achieve better security, we should mainly focus on four parameters: design of efficient confusion and diffusion strategy, reducing the correlation of neighboring pixels, enhancing the entropy value of the encrypted image, and huge key-space. An encryption algorithm, through its reversible set of operations, conceals the actual pixel values. In their concrete terminology, images are nothing but a matrix of numbers. Since the images are the inevitable source of digital data in today’s world, cryptosystem builders are focusing more on devising techniques that encipher the actual image information and in no way that the opponents must be able to disclose it. In the digital era of processing multimedia data by almost all of the electronic devices, technologists, researchers, and scientists are actively involved in the design and development of powerful cryptosystems. In order to save the data from exploitation by third parties, we need to build efficient encryption mechanisms so that they can be integrated with the cloud system for secure storage. Image data concerning the day to day activities of people are extremely sensitive and critical. The majority of the data take the form of images. The data of citizens include healthcare information, purchase behavior, weather conditions, environmental changes, and transport information. In smart cities environment, the data generated from various sources (smart city applications) are usually kept inside a cloud server and are manipulated by the concerned government officials and citizens of the city. The security analyses of the suggested approach prove that the encryption mechanism has good efficiency as well as lower encryption time compared with other related algorithms. Logistic-Sine map has been utilized to permute the plain image, and Logistic-Chebyshev map has been used to substitute the permuted image, while the cascading of both integrated maps has been utilized in performing XOR procedure on the substituted image. In this paper, we report an image cryptosystem for data transfer in cloud-based smart cities using the cascading of Logistic-Chebyshev and Logistic-Sine maps. To own the benefits of 1D chaotic maps and avoid their drawbacks, the cascading of two integrated 1D chaotic systems has been utilized. However, 1D chaotic maps suffer from different kinds of attacks because of their chaotic discontinuous ranges and small key-space. Chaotic maps are commonly used in designing modern cryptographic applications, in which one-dimensional (1D) chaotic systems are widely used due to their simple design and low computational complexity. Data security plays a significant role in data transfer in cloud-based smart cities.
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