A Color Image Encryption Algorithm Based on One Time Key, Chaos Theory, and Concept of Rotor Machine

Abstract

An innovative method proposed for encrypting color images is comprised of one-time keys and chaos theory using a distinctive concept of rotor machine. The novelty of this scheme is that the rows and columns of 2-dimensional images are converted into circular object called rotor and can be rotated at 360 degrees in clockwise or anti clockwise direction. The rotation will change the existing rotor into new one and can be used in substitution process of plain image. This process can be repeated β times and each time a new rotor is created just by a simple rotation. The rotation is performed in terms of pixels so degree of angle is converted into number of pixels. Using this method, same object with new face (after rotation) is used for encryption. The pixels of color image are permuted using the sorted index of logistic sequence. Then, three pseudo-random images are created from Piecewise Linear Chaotic Map (PWLCM). For substitution, both the permuted color channels and pseudo-random images are transformed into rotors. The angle is obtained from Chen chaotic system. The one-time keys are for chaotic maps are generated by using 512-bits hash of plain image. The simulated outcomes demonstrate that the proposed system has high quality of results and requires only single round of encryption to achieve high encryption along with high robustness against the transmission noises.

Keywords

• Chaos theory
• color image encryption
• SHA-512
• rotor machine
• one time key