Secure JPEG Bitstream Encryption Based On Histogram Shifting

With the rapid development of cloud computing,the privacy protection of cloud digital images has attracted wide attention of researchers.JPEG is a lossy compression standard for images.The image file size of JPEG format is small,which is more conducive to transmission and storage in the Internet.It is widely used in the field of Internet and digital cameras.Therefore,in the cloud computing and cloud storage environment,the research on JPEG bitstream encryption and reversible data hiding in encrypted JPEG bitstream algorithm has become a research hotspot.The main research contents of this dissertation are as follows:A JPEG bitstream reversible data hiding method based on entropy coding in full encryption is designed.In order to improve the security of JPEG bitstream encryption,a JPEG bitstream encryption method based on entropy coding in full encryption is designed.First,the last non-zero AC coefficient of the fixed image block entropy coding is unchanged,and the remaining AC coefficients are built into the block.Then,according to the encryption key,all the entropy coded extension bits of the DC and AC coefficients in the image block are encrypted,thereby not only encrypting the entropy coded extension bits,but also changing the Huffman coding in the original AC coefficient entropy coding.Content,improving the security of the encryption algorithm while preserving the size of the encrypted image.Since the data hiding capacity is positively correlated with the size of the encrypted image,the algorithm uses all the image block entropy encodes in the encrypted image as the data hiding carrier,which solves the contradiction between hidden capacity and security in the existing literatures,and effectively improves the hiding capacity of the algorithm.The experimental results show that the proposed algorithm can effectively resist ciphertext attacks and has high hidding capacity.In order to change the statistical characteristics of AC coefficients in the encrypted bitstream and improve the security of the encryption method,a JPEG bitstream encryption method based on histogram shifting is designed.The method extracts the last non-zeros AC coefficient entropy coding in the partial image block entropy coding according to the encryption key,and splices them into secret data.The data hiding method of the histogram shifting hides the secret data into the bitstream,and realizes the effective change of the statistical characteristics of the AC coefficients in the bitstream after encryption,which can improve the security of the encryption method.The experimental results show that the proposed method has a low file expansion and can effectively change the statistical characteristics of AC coefficients after encryption.In order to directly show the two algorithms in this dissertation,a GUI algorithm simulation system was designed by using MATLB,through which users can directly verify the experimental results.