Design And Implementation Of Hyperchaotic System With Wide Parameter Interval And Its Application In Image Encryption

With the rapid development of multimedia communication and network technology,digital image has been widely popularized in many fields,such as finance,agriculture,industry,commerce,services,education and military,for it has large amount of information,vivid detail and high transmission efficiency.Digital image brings convenience to people in life,and at the same time,how to ensure its information security and safe transmission on Internet has become one of research hotspots in the field of information security.In traditional encryption algorithm,plaintext information is operated as one dimensional binary data stream for encryption,but the digital image has the characteristics of large data volume,multi-dimensional distribution of pixels and high correlation between pixels.Therefore,the effect is not ideal for digital image encryption by traditional algorithm,for low efficiency and poor security performance.Chaotic system is highly sensitive to the initial conditions,besides,it has ergodicity and strong randomness.It coincides with the basic requirements of scrambling and diffusion in cryptography.Compared with low dimensional chaotic system,high-dimensional hyperchaotic system has more complex nonlinear dynamics characteristics,larger generated key space,and more complex key sequence,which are more suitable for image encryption,real-time encryption and transmission.In this paper,image encryption based on hyperchaotic system is studied.Firstly,two novel high dimensional hyperchaotic systems with hyperchaotic state in a wide parameter interval are constructed.Then,their dynamic characteristics are analyzed in detail,respectively.At last,based on such systems,a color image encryption scheme which is related to the region of interest is designed.The main work is as follows:1.Two novel high dimensional(four and five dimensional)hyperchaotic systems with hyperchaotic state in a wide parameter interval are proposed.And the dynamic characteristics of the systems are analyzed by the phase diagram,time domain waveform,Lyapunov exponent(spectrum),bifurcation diagram and Poincaré section,respectively.According to the basic principles of chaos circuit design and MULTISIM software,the analog circuit of the four-dimensional hyperchaotic system is designed and realized,and on this basis,the systemhardware platform is built.The results of the electric operation on the platform observed by the oscilloscope are in accordance with the ones of MATLAB simulation.2.Based on the above five dimensional hyperchaotic system,a hierarchical key encryption algorithm related to the region of interest for color image is designed.Because the chaotic system is sensitive to the initial value,the initial values of the chaotic system are set as the system secret keys.In the two level key system,the chaotic sequences generated from the first level hyperchaotic system are combined with the original image to produce the initial value keys of the second level system,and the sequence generated from the second level hyperchaotic system is applied to the scrambling and diffusion of the pixels of the plaintext image,then we get the final ciphertext image.Several image encryption evaluation criteria,such as key space,key sensitivity,statistical histogram,adjacent pixel correlation,differential attack,information entropy and anti-known \ selection attack are applied to algorithm validation.Experimental results show that the encryption algorithm designed in this paper has better security performance.