Application Research Of Novel Hyper-chaotic System In Image Encryption

With the rapid development of mobile Internet and multimedia technology,digital image has gradually become one of the main ways for people to obtain information.The application of digital images brings many conveniences to people.Meanwhile,it faces serious information security problems.The traditional encryption algorithms are mainly designed for text data and are not suitable for digital image with large data volume,a strong correlation between pixels and high information redundancy.The characteristics of chaotic systems including initial value sensitivity,pseudo-randomness and ergodicity are very agreed with the basic requirements of cryptography.Therefore,the application of chaotic systems in digital image encryption has broad research prospects.Based on chaos theory and digital image encryption technology,a novel hyper-chaotic system and its fractional order system are designed and analyzed,and two image encryption algorithms are proposed in this thesis.The main research contents are as follows:1.A novel type of hyper-chaotic system and its fractional order system are designed.In this thesis,the phase diagram,Lyapunov exponent spectrum and the bifurcation diagram of systems are used to analyze the dynamic characteristics of the system.The results show that:(1)According to the different parameter values,the system doesn't have equilibrium points or curve equilibrium;(2)There are coexisting attractors in the hyperchaotic system without equilibrium points and in the corresponding fractional system.2.A dual graph association encryption algorithm based on a hyper-chaotic system is proposed.Firstly,based on the novel hyper-chaotic system mentioned above,a chaotic sequence generator is designed,and the generated chaotic sequences are fully statistically analyzed and randomly tested.Then,a plaintext-related double-image association encryption algorithm is proposed.This algorithm uses plaintext-independent deep diffusion,plaintext-related scrambling and adaptive bit operations.Compared with other algorithms,the plaintext information is no longer used to control system parameters,so chaotic sequences can be safely and repeatedly utilized.The simulation results show that the overall efficiency of encryption is improved and the ability to resist plaintext attacks can be enhanced.3.A multi-image encryption algorithm based on chaotic synchronization is proposed.Firstly,a simple adaptive synchronization controller is designed based on the fractional hyper-chaotic system mentioned above.Then,a multi-image encryption algorithm based on chaotic synchronization is proposed.This algorithm introduces plaintext interference terms and involves bit-level rows and columns scrambling,the randomization of DNA,and fast scrambling and spreading operation of DNA.The interference term can be automatically retrieved during decryption with avoidance of the OTP mode,which makes chaotic random sequences safe and reusable.The simulation and analysis show that the iteration times of chaotic sequences are reduced,the high correlation between images is ensured and the distribution of bit information in plaintext is hidden.The algorithm has good security and can meet the basic requirements of image encryption.