Research On Encryption Algorithm Of Digital Image Related To Plaintext Based On Hyperchaotic Map

In recent years,with the rapid development of computer technology and modern communication technology,information communication based on multimedia data including audio,image,video as carrier has ushered in an exponential growth.As a way of information expression,digital image is widely used in business,military,finance,scientific research,medical treatment,politics and other fields because of its intuitive and rich characteristics.How to ensure the safe access and transmission of digital images in the open communication environment has become one of the hot spots in the field of information security.Digital image is different from text information in terms of inherent characteristics,such as large amount of data,high redundancy and strong correlation and so on.Traditional text information encryption technology,such as DES,IDEA,AES and RSA etc.is not suitable for image encryption.Due to the extreme sensitivity to initial value and parameters,ergodicity and long-term unpredictability,chaotic system has strong relation to cryptography,which is widely used in image encryption research.The outstanding chaotic image encryption algorithm proposed in recent years is analyzed and summarized in this paper.Aiming at the shortcomings of most existing chaotic systems,such as narrow chaotic parameter interval,periodic window,and uncomplicated nonlinear dynamic behavior,we propose four new hyperchaotic systems with different structures,which can generate safe and efficient pseudo-random sequences.In view of the defect of the existing algorithms,such as low computational efficiency,inability to resist the chosen plaintext attack,etc.,four image encryption algorithms with good performance in both security and efficiency are put forward based on the proposed hyperchaotic system.The main innovative work of this paper is as follows:1.Construction and analysis of Hyperchaotic mapsIn view of the narrow chaotic interval,periodic window and uncomplicated nonlinear dynamic behavior of most one-dimension and two-dimension chaotic map,four classes of hyperchaotic systems with different structures are proposed,namely,NMHMD,NCHMD,COTDCM and LCHM.All of these four systems belong to hyperchaotic system and have wide hyperchaotic ranges,no periodic windows and complex dynamic behavior.Hence,they are very suitable for chaotic image encryption.2.An image encryption algorithm based on the combination of bit and pixel plane scrambling via a nonlinear modulated hyperchaotic map with delayConsidering that block level encryption or pixel level image encryption algorithm has advantage in encryption speed and disadvantage in encryption security;while bit level image encryption algorithm has more advantage in encryption security,and disadvantage in encryption speed,based on the nonlinear time-delay modulated logistic map,this paper proposes a chaotic image encryption algorithm which combines the scrambling operation on both pixel plane and bit plane.According to different amounts of information contained in the bit planes at different positions,the algorithm scrambles four high bit planes and the pixel planes composed of four low bit planes.In the diffusion stage,the current pixel value in the two-dimensional plane is not only related to its left adjacent encrypted pixel,but also related to the upper adjacent encrypted pixel,which enhances the correlation among pixels.The performance analysis shows that the algorithm has a good balance between time complexity and security performance.3.A new hyperchaotic image encryption method based on scrambling with dynamic correlation to plaintext pixelsThe key stream used in most existing chaotic image encryption algorithms has no relations to the plaintext pixels,which is generated by the chaotic system for scrambling operation,so it can't resist the known plaintext attack and the chosen plaintext attack.Moreover,different chaotic sequences are usually utilized as the key streams in the scrambling and diffusion stage,which results in the low efficiency of chaotic state sequence.In view of these weaknesses,based on the nonlinear cross coupling hyperchaotic map,an ingenious image encryption method is designed where the scrambling is dynamically related to plaintext pixels.In the scrambling phase of the encryption algorithm,a chaotic state sequence with the same length to the amount of plaintext pixels is used to realize the dynamic transformation of the position of the plaintext image relating to a single pixel.The scrambling operation also has a certain diffusion effect,which enhances its ability of resisting known plaintext attacks and chosen plaintext attacks.The whole algorithm only needs one round of scrambling and diffusion operation,which dramatically reduces the complexity of the algorithm.Simulation results show that the algorithm not only has strong security,but also has good encryption efficiency.4.A novel chaotic encryption algorithm with the concurrence of scrambling and diffusion based on COTDCMIn the traditional chaotic image encryption,the key stream is only related to the key,but not to the plaintext pixels,so it is not easy to resist the chosen plaintext attack.Based on the COTDCM hyperchaotic map,a novel chaotic image encryption algorithm with dynamic selection of key stream is put forward.In this algorithm,only single chaotic state sequence can be used.Scrambling and diffusion operation are executed simultaneously,and the scrambling operation is dynamically related to the pixel value,thus reducing the computational complexity and time cost of the algorithm,and enhancing the ability of resisting the chosen plaintext attack.The whole algorithm only needs one round of scrambling and diffusion operation.Simulation results show that the algorithm has good performance in terms of encryption efficiency and security.5.NCHMD based-on fast image encryption algorithm with the concurrence of scrambling and diffusion in both rows and columnsConsidering both pixel level and bit level chaotic image encryption have low speed,based on NCHMD,a fast encryption algorithm with the concurrence of scrambling and diffusion in both rows and columns is proposed,which reduces the rounds of encryption.The method includes two steps: simultaneous row and column scrambling and diffusion.Both row and column scrambling is dynamically related to plaintext pixels,enhancing the ability of resisting the chosen plaintext attack.The scrambling and diffusion are executed simultaneously according to both rows and columns.The proposed method just needs one round operation and increases the efficiency of encryption because the operation object is row or column,but not pixels or bits.Simulation results demonstrate that the algorithm exhibits better performance in terms of speed on the premise of security guarantee.