Abstract: In this paper, an image encryption algorithm based on two-dimensional, two state and five neighbor reversible Cellular Automaton (CA) is proposed. First, this method is applied to analyze several X type neighbor structures of CA, and a partial X type structure of CA is put forwarded, which has obvious key confounding effect. Second, in each CA encryption iteration, the results are processed with matrix transpose operation; then the key image with one-dimensional four neighbor CA is generated, which has chaotic behavior at the rules of 9d62 (hex). Finally, the key information is put into the CA boundary conditions, so that the key is involved in each cellular automaton iteration. Experimental results show that using partial X2 type CA structure and new model of key design can improve the sensitivity of the key in the encryption system. Compared with traditional single XOR operation, the new method can also reduce the number of CA iterations, thus, possessing advantages in plaintext diffusion rate and obfuscation key, the diffusion rate is increased by 36.14%.

Key words: image processing technology, X2 structure CA, image encryption, diffusion rate