Multiple-image encryption algorithm based on mixed image element and permutation

•We propose a new multiple-image encryption (MIE) algorithm based on the mixed image element and permutation.•This paper defines the conceptions of pure and mixed image elements;•This paper offers a method to generate a permutation and chaotic image with the chaotic system.•This paper introduces two similar algorithms and makes the comparison analyses.•Faster encryption speed than the similar schemes.

To improve encryption efficiency and facilitate the secure transmission of multiple digital images, by defining the pure image element and mixed image element, this paper presents a new multiple-image encryption (MIE) algorithm based on the mixed image element and permutation, which can simultaneously encrypt any number of images. Firstly, segment the original images into pure image elements; secondly, scramble all the pure image elements with the permutation generated by the piecewise linear chaotic map (PWLCM) system; thirdly, combine mixed image elements into scrambled images; finally, diffuse the content of mixed image elements by performing the exclusive OR (XOR) operation among scrambled images and the chaotic image generated by another PWLCM system. The comparison with two similar algorithms is made. Experimental results and algorithm analyses show that the proposed MIE algorithm is very simple and efficient, which is suitable for practical image encryption.