Research On Reversible Data Hiding Algorithm In Encrypted Images Base On Reconstruction Coding Of Difference

Information sharing in the internet era has become an indispensable and important part of social occasions and professional fields,among which multimedia data represented by digital images are widely used.Reversible data hiding in encrypted image(RDH-EI),a composite technology,emerges as security risks in the field of image become more and more serious.This technology can not only use image encryption technology to protect personal privacy and confidential secrets,but also embed management data and authentication watermarks in combination with information hiding technology to ensure effective and reliable information preservation,transmission and other practical needs.In recent years,some reversible information hiding algorithms for encrypted images make use of spatial redundancy to compress the encrypted images to free up available space for embedding secret information,which involves multi-angle applications of the difference between pixels,but most of them do not fully consider the distribution characteristics inside the difference.In order to ensure the complete reversibility of the algorithm and improve the information hiding capacity of the algorithm,two seperable algorithms are proposed to free up space after encryption by combining reconstruction coding of difference.According to the difference of texture complexity of different images,a reversible information hiding algorithm for encrypted images based on reconstruction coding of the difference of center neighborhood is proposed.In this algorithm,different pixels are classified according to coding requirements,and their transformation is saved in some pixels according to the value range of central neighborhood difference in the block.Pixel classification and difference transform make the reconstruction coding technology make full use of the image redundancy.For different texture feature images,the reconstruction coding algorithm of the difference in the central neighborhood can maximize the one-to-one embedding rate.Experimental simulation results show that the embedding rate of this algorithm for relatively smooth images can reach a maximum of about 3bpp.According to the difference of pixel correlation in different directions in the image block,a reversible information hiding algorithm for encrypted images based on reconstruction coding of neighborhood difference in variable direction is proposed.Instead of fixing the direction of the difference calculation,the algorithm selects the horizontal or vertical direction with stronger progressive correlation of adjacent pixels in the image block.The decrease of the overall difference makes the histogram distribution more inclined to zero,thus reducing the space occupied by saving the difference.The simulation results show that this algorithm can not only extract the secret information without error and recover the original image without loss,but also improve the information hiding capacity.In order to verify the feasibility and effectiveness of a reversible information hiding algorithm for encrypted images based on reconstruction coding of neighborhood difference in variable direction,a graphical user interface based on MATLAB was designed to visually demonstrate the algorithm's four processes: image encryption,information hiding,information extraction and image recovery.