Research Of Image Encryption Based On Dynamic Cat Mapping And Unix Stamp

Image encryption is a vital technology to solve the problem of image security.Compared with traditional text information,image information has the characteristics of large amount of data,high redundancy,and strong correlation between adjacent pixels,which make the existing text encryption algorithms are not able to be used directly for image encryption.The development of chaos theory has opened up a new route for image encryption technology.At present,there are some image encryption algorithms based on chaos theory have been widely used in the field of image encryption.But lots of them have a bad performance in dynamic encryption.In terms of the above problems,this paper does research the image encryption algorithm based on dynamic cat mapping and Unix time stamp.The principal work includes the following aspects:1.The research related image encryption,which includes mainly the storage structure of the image,the basic concept of image encryption and related algorithms are studied;two basic steps of image encryption are mastered: scramble and diffusion.Summarizes the security evaluation standard of the image encryption algorithm.It is difficult to resist the shortcomings of selecting plaintext attacks if an algorithm work without associating with plaintext,chaotic system is prone to be used to enhance the security of image encryption.2.Design an image encryption algorithm based on dynamic cat mapping to solve the period of standard cat mapping.Firstly,with a key is transformed by MD5,a hexadecimal string is obtained.Using the string,these block boundary parameters of the dynamic cat mapping are getted,and the S box which is needed in the diffusion stage is constructed through the randomness of MD5.Then at the scrambling stage,the scrambling parameters are combined with the plaintext image and the dynamic cat mapping is performed to obtain a scrambled image.In the diffusion phase,when each pixel value is diffused with the S box,the avalanche effect is formed in combination with the adjacent pixel values.Finally,the simulation experiment results show that the proposed encryption scheme can satisfy the security requirements of image encryption.It not only improves the periodic defects of traditional cat mapping,but also has better encryption effect.3.The dynamic cat mapping image encryption algorithm can not achieve the security standard of "one time one key",an image encryption scheme based on dynamic cat mapping and Unix time stamp is proposed.Firstly,the cat mapping algorithm is improved by another form to correlate the plaintext,and then the Unix timestamp is added to the chaotic sequence generating process.Since the Unix timestamp is constantly changing,different diffusion sequences can be generated each time when the encryption scheme is performed,so that the goal of "one-time-one-secret" is achieved.The theoretical research and simulation results show that the proposed algorithm can effectively resist the choice of plaintext attacks and has a better degree of security.