An Approach towards an Efficient Encryption-Decryption of Grayscale and Color Images

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Protecting images from unauthorized access and use is an important task in various areas. The problem of unauthorized use of images is solved at different levels: from the provisions on copyright, to methods of cryptography and steganography, digital watermarking etc. The paper considers a new, authors-developed approach to encryption-decryption of grayscale and color images, which is based on the RSA algorithm. We describe the algorithmic implementation of encrypting and decrypting procedures by one row of image matrix with and without use of additional noise-adding. We developed the procedures of encrypting-decrypting of images by one row of image matrix by combining elements of the RSA algorithm and bitwise binary operations. The effectiveness of the proposed approach is confirmed by conducting a series of experiments with grayscale and color images. We also study the influence of additional noise-adding functions applied to the source image as well as the various values of simple numbers of the RSA system on the results of the method. It was found that these parameters do not result in appearance of contours in the encrypted image, and the resulting image differs from the source one by a small change in the brightness level only. In addition to the high cryptographic strength of the RSA algorithm, the overall method’s cryptostrength is provided by the additional use of bitwise binary operations.