A Selective Cross-Substitution Technique for Encrypting Color Images Using Chaos, DNA Rules and SHA-512

Abstract

An innovative approach of selective encryption for color images is proposed that utilizes SHA-512 hash of plain image to modify initial conditions and control parameters of 1-Dimensional (1D) chaotic maps. The three channels (red, green and blue) of a color image are combined into 1D array and permute using sorted index of a pseudo-random sequence. The 1D permuted array is split into three sub-arrays, DNA encoding is applied on every pixel of each channel chaotically and then separate each DNA encoded channel into its Least Significant Bits (LSB) and Most Significant Bits (MSB). The substitution is carried out in two phases using addition and exclusive-or operations on MSB of each channel only. In 1st phase, the DNA addition operation is applied on chaotically selected MSB of a pixel of one channel to LSB part of a pixel of other channel in a twisted fashioned named cross-substitution. The translated DNA bases from pseudo-random numbers are exclusive-or with cross substituted output to surge the complexity. The second substitution phase is accomplished by combining MSB part of a channel with randomly selecting LSB at pixel level. The novel algorithm is highly suitable for real time applications as it requires single round of permutation/substitution which can resist all possible statistical and differential attacks. The simulation results and analysis show that the proposed technique has the best quality output and highly efficient.