Image Encryption through a Novel Permutation-Substitution Scheme Based on Chaotic Standard Map

A novel permutation-substitution scheme, which is based on chaotic standard map, for the image encryption is proposed. It is loss-less symmetric block cipher and specifically designed for the colour images. The initial condition & system parameter of the chaotic standard map, number of iterations and number of rounds constitute the secret key of the algorithm. Firstly we mix all three colour layers (3 D matrix) of the plain image and convert them into a 2D matrix. Each encryption round comprises of three stages: permutation rounds, substitution rounds and again permutation rounds. To increase the speed of encryption, the permutation and substitution are done row-by-row and column-by-column instead of pixel-by-pixel. The permutation process is controlled through the pseudo random number sequences (PRNS) generated from the discretization of chaotic standard map, however in the substitution, the properties of rows and column pixels of various layers are mixed with the PRNS generated from the standard map. The security of the proposed image encryption has been analyzed thoroughly using various statistical analysis, key sensitivity analysis, differential analysis, key space analysis, etc. Results suggest that the proposed image encryption technique can be used for the real time secure image and video communication applications.