Image encryption based on fractional order lorenz system and wavelet Transform

Abbas Salman Hameed, Electronic Engineering Department, College of Engineering, University of Diyala
2017 Diyala Journal of Engineering Sciences  
To securely transmit data in open networks, encryption must be used. In this paper, cryptography technique of images is presented with chaos and Discrete Wavelet Transform (DWT). Fractional order Lorenz system that provides an expanded in key space is used to encrypt image. All properties of randomness and nonlinearity which are owned by this chaotic system are guarantee a highly secure and robustness for Encryption process. As well as DWT offers additional space and security by using wavelet
more » ... by using wavelet domain to shuffled image pixels after passing in DWT filters and sampling. The combination between Lorenz system and DWT have been taken to make the image more secure and thus make very hard to get back the original image without having its correct key and procedure which were used to encrypt. The results show a large sensitivity to a small change in the secret key or DWT family type. Therefore, high complicated image security is offered using this system. To meet expanded desire for secure image transmission through wireless networks and over the Internet, Image encryption schemes have been increasingly studied. Cryptography hides the contents of a secret message from an unauthorized people by scramble the structure of a message in such a way as to make it meaningless and unintelligible manner (1, 2, 3) . DWT is suggestions here to convert image to wavelet domain then encrypted by randomness sequences to produce highly secure cryptography scheme. To perform this encryption process, nonlinear dynamic systems as chaos is used. It is characterized by extremely sensitive to initial conditions and control parameters and mathematically is defined as randomness governed by simple deterministic rules (4) . Lorenz with high dimensional chaotic system and fractional order will give a more system variables, more structure complexity, and parameters. Then large key space for cryptosystem will be get by use integer orders and very greatest by use fractional order, and the time sequence for system variables will be more stray and unpredictable than using the low dimensional chaotic system (5, 3) . This paper demonstrates encryption of image using fractional order chaotic system to increase the security level of generated keys in Wavelet domain. The paper is organized as follows; section 2 describes main function of DWT and two-dimensional DWT components. In section 3, the Fraction Order Lorenz system, chaos permutation and the chaotic Mask Key generation will be illustrated. The proposed system model of the encrypted image is presented in section 4. In section 5, the simulation results that are computed by Matlab 2015a are shown. Finally, conclusions are clarified in section 6. WAVELET TRANSFORM: Variations in time-frequency resolutions will be provide by wavelet transform due to the variation in it basis function in terms of frequency and scale. The basis function of wavelet divides the data into different frequency components and chooses the component that
doi:10.24237/djes.2017.10108 fatcat:uijpatcvfvdkhpnygirsqpmyo4