Research On Image Encryption Algorithm Based On Hyperchaotic System

With the rapid development of communication technology in the 21st century,a global communication network has enriched people’s lives.This colorful era is made up of networks connecting isolated nodes together.Because image information contains a large amount of information and it is more vivid than text.Thence,using two-dimensional image data to carry out information interaction,which is one of the important ways of information exchange in the 21st century.There are often malicious attackers in the network who is trying to steal information in transit.If the original image is directly transmitted,it will have unpredictable consequences when it is intercepted by the attacker.Therefore,encrypting the images to be transmitted is a powerful means to ensure information security.With the development of chaos theory,it is found that chaotic systems and hyperchaotic systems have excellent random characteristics,and the system parameters of chaotic systems may be changed unpredictably due to slight changes in initial values.The image information has the characteristics of a large amount of information.The chaotic system also has good random characteristics,which is especially suitable for image encryption.Among the image encryption schemes proposed by many scholars before,there are many schemes that only use a single encryption sequence or only scrambling to encrypt the image when changing the position of the pixel value in the image matrix.Comparing the above scheme with the scheme using diffusion,there are certain disadvantages in resisting statistical attacks.There are also some encryption schemes that use low-dimensional chaotic systems,and these schemes are prone to brute-force cracking compared to encrypt using hyper-chaotic systems.Combined with the above analysis,this paper designs two image encryption schemes based on hyperchaotic systems,and gives two different processing methods on the scrambling method.The main research work of this paper is as follows:1)An image encryption scheme with good encryption effect is proposed.The scheme first scrambles the image sequence by alternating parity scrambling,then further scrambles the image with the use of the bit plane parity alternating scrambling method,and then generates the key through the chaotic sequence.The key stream is used to diffuse the bit plane scrambled image,this step can further improve the security of the encryption system.After the encryption is completed,the numerical simulation is carried out.The performance of the encryption system is analyzed from the statistical point of view,the key point of view,and the diffusion test.The simulation results show that the proposed chaotic image encryption scheme can pass the above security test,that is to say the proposed algorithm has good security.In addition,the parity alternation scrambling scheme is to be proved that it have better statistical properties than single-sequence encryption.2)A new encryption scheme combining block encryption and bit encryption is proposed.The encryption scheme first uses a high-dimensional hyperchaotic system to resist some shortcomings of low-dimensional chaotic mapping.Next,the image matrix is divided into two blocks:D₁ and D₂.The scheme that scrambling the D₁ block in descending order,and scrambling the D₂ block in ascending order use bit encryption scrambling to encrypt the combined matrix for the second time.Finally,the encryption is done by diffusion.After the encryption is completed,the numerical simulation is carried out.The performance of the encryption system is analyzed from the statistical point of view,the key point of view,and the diffusion test.The simulation results show that the proposed scheme combining block sequence scrambling and bit encryption can pass the above security test.This scheme adopts a combination of block encryption and bit encryption.Compared with only block encryption or bit encryption,the histogram of gray distribution of pixel value position of this scheme is more uniform before diffusion,and the encryption effect is better for the naked eye.