A multi-level blocks scrambling based chaotic image cipher

Abstract

In this paper, an image encryption scheme based on multi-level blocks scrambling is proposed. The image is first decomposed into non-overlapping blocks and scrambling of these blocks is done by using 2D Cat transform. Multi-level blocks scrambling (MLBS) is implemented by starting with a large block size and the size of blocks gets reduced iteratively at each level. The scrambling of blocks is performed at multiple levels to get cummulative effect. At each level, the control parameters of scrambling are randomly generated through 2D coupled Logistic map to make the process of scrambling key dependent. The scrambled image obtained after carrying out MLBS scrambling is encrypted using chaotic sequence generated by one-dimensional Logistic map. The experimental results show that the proposed encryption scheme can successfully encrypts/decrypts the images with same secret keys. The algorithm has large key space and high sensitivity to a small change in secret keys. The simulation analysis also demonstrates that the ciphered images have high information entropy, very low correlation coefficients and uniform gray level distribution. © 2010 Springer-Verlag Berlin Heidelberg.