Dynamic Substitution and Diffusion Based Image Encryption Using Modified Logistic Map

Abstract

This paper presents a new image encryption scheme that employs an initial permutation for total shuffling of the positions of image pixels using randomly chosen prime numbers and then uses modified logistic map for the other operations. The logistic map and standard maps are modified for randomness and coupled together to increase the key length and used in the encryption process. A new substitution box is introduced and this substitution box changes dynamically during the iterations using the chaotic maps. The states combination of the chaotic systems are used to confuse the relationship between the plain-image and the cipher-image in a nonlinear fashion so as to resist against known plain-text and chosen plain-text attacks. The security and performance of the proposed image encryption technique have been analyzed using statistical analysis, key sensitivity analysis, key space analysis, differential analysis and entropy analysis. The simulation shows that a single pixel difference of the plain-image will change almost all the pixels in the cipher-image (NPCR>99%), and the unified average changing intensity is high (UACI>33%). The experimental results demonstrate that the new algorithm has a low time complexity and the suggested encryption algorithm has the advantages of large key space and high security, and moreover, the distribution of grey values of the encrypted image has a random-like behavior.