In this paper a hybrid model of cellular automata and chaotic signal is proposed for image encryption. In this method, 8-bits mask is used for changing the pixel gray level of main image. Every bit content is 0 or 1. For changing each pixel gray level, value of each bit of the mask is selected by one of the 256 cellular automat standard rules. One of the 256 cellular automat standard rules is determined by chaotic signal. Studying the obtained results of the performed experiments, high resistance of the proposed method against brute-force and statistical invasions is obviously illustrated.

Keywords: Image encryption, cellular automata, chaotic function.