Research On Improved Chaotic Digital Image Encryption Algorithm

Confidentiality is an important issue when digital images are transmitted over public networks,and encryption is the most useful technique for this purpose.In view of the problems of pseudo-randomness,complexity,short period and limited precision of traditional digital image encryption technology,digital images have large data volume,low information entropy,high correlation between adjacent pixels and large redundancy of original data images.As a disadvantage,traditional digital image encryption methods are no longer suitable for encrypting digital images.Therefore,thesis presents a new and effective way to deal with the thorny problem of fast and efficient and secure image encryption,as well as expounds the research status and development trend of chaotic digital image.Firstly,according to the concept of chaos,the random sequence is generated from chaotic map,then according to the improved design flow of encryption algorithm,finally,the simulation experiment is carried out.The characteristics of chaotic dynamic systems,such as high sensitivity to initial conditions and statistical properties similar to white noise,apply to information encryption.They are similar to concepts such as password diffusion,encryption wheel,pseudo-random signal and key.Therefore,with the development of chaotic cryptography,chaotic-based digital image encryption algorithms have received extensive attention.Thesis focuses on two image encryption algorithms: one is based on the improved 3D cat image encryption algorithm;the other is image scrambling algorithm based on the three-dimensional Arnold transform.The new algorithm uses the Henon map of chaotic sequence to generate the rinsing control parameters,replaces the gray value with the improved two-dimensional Logistic mapping sequence,washes the array position with the Henon map,and alters the gray value of the image pixel by the improved two-dimensional Logistic map.In addition,the algorithm is highly secure against exhaustive attacks,statistical attacks and pure-text attacks,all of which will make it very difficult for potential attackers,even if attackers know the algorithm,but if they do not know the parameters of the algorithm,it is also not possible to obtain information about the image.From this point of view,scrambling can be regarded as the encryption of digital images with these parameters as keys.In thesis,the encryption algorithm of chaotic digital image has been improved,and the efficiency has been greatly improved.In addition,in order to further enhance the security of the cryptosystem,a chaotic mechanism related to plain text is introduced in the diffusion process by using the control parameters of the chaotic system used by the cryptographic pixel perturbation,using key analysis and key sensitivity analysis.The proposed scheme was extensively cryptanalyzed.The test results show that the new approach presented in thesis hasa satisfactory level of security and low computational complexity,making it a good candidate for real-time secure image transmission applications.