The present paper is aimed at introducing a new algorithm for image encryption using chaotic tent maps and the desired key image. This algorithm consists of two parts, the first of which works in the frequency domain and the second, in the time domain. In the frequency domain, a desired key image is used, and a random number is generated, using the chaotic tent map, in order to change the phase of the plain image. This change in the frequency domain causes changes in the pixels value and shuffles the pixels location in the time domain. Finally, in the time domain, a pseudo random image is produced using a chaotic tent map, to be combined to the image generated through the first step, and thus the final encrypted image is created. A computer simulation is also utilized to evaluate the proposed algorithm and to compare its results to images encrypted by other methods. The criteria for these comparisons are chi-square test of histogram, correlation coefficients of pixels, NPCR (number of pixel change rate), UACI (unified average changing intensity), MSE (mean square error) and MAE (mean absolute error), key space, and sensitivity to initial condition. These comparisons reveal that the proposed chaotic image encryption method shows a higher performance, and is of more secure.
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