Design And Application Of Image Compression-encryption Algorithms

With the rapid development of the era of big data,the application and transmission of digital images on the Internet have become much more common than in the past.Therefore,image encryption and compression technology is very important for real-time transmission and storage via public networks.It can be divided into two stages,the first stage is to prevent information leakage,and the second stage is to reduce the amount of information and data.Traditional block ciphers DES and AES were originally designed for encrypting text data,and were found to be unsuitable for digital image encryption because of high pixel correlation and redundancy.Nowadays,researchers have noticed that the characteristics of chaotic systems have ideal cryptographic attributes,which can act on the image scrambling and diffusion process,so that the image can obtain good security.However,the above encryption results are not suitable for further compression processing,because the redundancy of plaintext has been eliminated in the encryption process,so that the ciphertext can not be further compressed.Then,the design of an effective synchronous image encryption and compression algorithm has become the focus of current research in this field.The main work of this paper is summarized as follows:1.Firstly,the research background of the topic is introduced,including two main stages of traditional image chaotic encryption and compressed sensing theory,JPEG2000 coding system and SPIHT coding theory.Then the innovations of this paper are elaborated.The characteristics of chaotic system and the basic structure of image encryption are described.Then,the current research status of image chaotic encryption based on compressed sensing,image encryption based on JPEG2000 and image encryption based on SPIHT are summarized briefly.Finally,the deficiencies in these three aspects are summarized and the improvement solutions are given.2.Based on compressive sensing theory,a new image compression-encryption scheme is proposed.The original image is decomposed into low-frequency component and high-frequency component by wavelet transform.Combining Chua's circuit,Logistic map and threshold processing based on LBP operator theory,a diffusion matrix is generated to diffuse low-frequency component.In addition,the asymptotic deterministic random sequence is generated by Lissajous mapping,and the measurement matrix CADRMM is generated under different compression ratios,and the high frequency components are measured respectively.Finally,the processed components are scrambled.The robustness of the system is greatly improved by retaining the low-frequency component and only compressing the high-frequency component.The experimental results show that the system has good robustness even under strong occlusion and noise attacks.At the same time,the performance analysis shows that the scheme owns the features of large key space,high key sensitivity,similar histogram distribution and weak correlation coefficient.3.An improved JPEG 2000 image encryption algorithm for codestream is proposed.In order to improve the performance of the original algorithm,skew tent map is used to encrypt all the bytes after 0xFFs.The lower 4 bits are diffused,the higher 4 bits are considered as one unit,and scrambled among these bytes.In this way,the security vulnerability of the original algorithm are eliminated.The experimental results show that the encrypted data volume increases by 0.3746% on average.Various security tests show that the encryption results are highly sensitive to the keys and the key space is large enough to resist exhaustive attack.By introducing this encryption scheme,the codestream format-compliance is ensured.4.An embedded compression-encryption algorithm for medical images is proposed.According to the characteristics of medical images,medical images are divided into ROI and RONI regions by using OTSU image segmentation.SPIHT coding is carried out for different regions,and codestreams are encrypted by using different encryption methods.This operation can improve the diversity of image encryption,thereby improving security.The chaotic system used in encryption is 2D-LSCM.In the process of encrypting ROI region,a new self-adaptive codestream encryption algorithm is adopted,which makes the bits in front and back position interact with each other,so as to achieve self-adaptability.A series of simulations and tests proved that the embedding compression-encryption algorithm has high plaintext and key sensitivity.At the same time,the cryptosystem can effectively resist common cryptographic attacks and provide a reliable solution to guarantee the compression performance and security of medical images.