Research On Key Technologies Of Robust Secret Image Sharing

With the penetration of social networks in people’s daily life,photo sharing has become a popular activity for users’ communication.On one hand,the use of images on social networks to transmit or store information can realize the covert transmission and storage of secret information,meet the needs of convenient and safe communication of the state and society,and is of great value to ensure information security.On the other hand,more and more attackers try to adopt the model of covert communication in social networks.Studying covert transmission and storage from the perspective of defense can help understand the behavior of malicious covert communication.Secret image sharing(SIS)can realize multi-channel covert communication,access control and loss tolerance.However,there are still three main challenges in applying mature SIS to social networks:(1)The participants involved are virtual accounts.It is impossible to judge whether the participants are fake or honest.Shadow authentication mechanism needs to be introduced to identify and locate fake shadow images.(2)JPEG image is the most popular digital image format on the Internet,but there is little effective SIS research on JPEG image.(3)The recovery of SIS is based on mathematical operation,and the social network channel usually performs filtering,sampling,recompression and other operations on the image,resulting in changes in shared data and further failure of the recovered secret image.This dissertation focuses on these three challenges to carry out robust SIS research,and implements shadow authentication without steganography and pixel expansion,and looks for invariants in spatial or frequency domain to construct robust shadow images to resist some typical image processing attacks.The main research contents of this dissertation are summarized as follows:1.A robust secret image sharing scheme with shadow authentication capabilities(2,n+1)thredhold radom grid based visual secret sharing(RG-VSS)is fused into the secret image sharing process based on polynomials by using random screening operation,so that the generated results of visual secret sharing(VSS)can ”guide” the generation of shadow images in the secret image sharing process based on polynomials,and finally achieve the ability of mutual authentication between participants.For the case that there is a combiner or no combiner to participate in the authentication,the scheme realizes that only one binary authentication image needs to be disclosed,and all members authenticate each other by exchanging the lowest plane rather than the whole shadow.The security and effectiveness of the proposed scheme are verified by experiments and analysis.The scheme has the characteristics of low generation and authentication complexity,no pixel expansion,high detection rate and lossless recovery.2.A robust secret image sharing scheme resist to filteringFirstly,a model of meaningful SIS scheme resist to typical image processing of shadows is proposed.In this model,first,the shadows are generated by extended polynomialbased SIS; then,through pixel expansion,pixel assignment and fine adjustment,the intermediate shadows are obtained,where the intermediate shadows are consistent with the original shadows after image processing and extraction.Then,we derive three specific algorithms for(k,n)threshold lossless meaningful SIS resist to three kinds of image processing from the model respectively.Further,the analysis of shadows quality is given.Finally,three groups of experiments show the feasibility of the proposed method,and the general model is especially effective against downsampling and filtering.Besides,the scheme obtains better attributes,such as lossless recovery,(k,n)threshold and meaningful shares.3.A secret image sharing scheme for JPEG imagesAt present,the research on secret image sharing for JPEG images is only for JPEG images with compression factor of 100.In order to overcome its limitations and lay the foundation for the next research on robust secret image sharing resist to JPEG recompression.Starting with the study of JPEG image coding,this dissertation carries out the research on secret image sharing for JPEG images.Due to the particularity of JPEG image format(not directly storing pixel values),the mid-frequency and low-frequency coefficients of secret image and cover images are selected as the target and covers of SIS,and the meaningful shadow images are generated through translation and other operations.This dissertation analyzes the reasons for the loss of secret image in the process of sharing,and then analyzes the influence of the parameters(k,n,δ,num,P,QF)on the quality of shadow image and restored secret image.Besides,this dissertation analyzes the causes of losses in the process of sharing.The security and effectiveness of the proposed scheme are verified by experiments and analysis.The scheme has good characteristics,such as(k,n)threshold,understandable shadow image and arbitrary compression factor.4.A robust secret image sharing scheme resist to JPEG recompressionStarting with the analysis of the process of JPEG re compression,the error in the process of re compression is evaluated,and the error without truncation operation is analyzed by using the method of probability density and statistics.The elements that are stable before and after recompression are found,that is,when the pixel value of JPEG image decompressed to spatial domain(before translation)falls in the interval [-128,127],and when the compression factor of recompression is equal to the compression factor of original JPEG and its value is less than 93,the DCT coefficient before and after recompression will not change.Next,based on the stable block condition and the random numbers screening mechanism of polynomial secret image sharing,a understandable and robust shadow image is constructed.For the former scheme,the use of this method leads to the problem that several blocks of the finally recovered secret image can not be recovered obviously.A robust shadow images construction method based on overall scale and stable blocks is proposed,the adjustment factor is set to 0.5.The preconditions for the application of the two schemes are further clarified.The security,robustness and visual quality of the two schemes are analyzed.A series of experiments are carried out to verify the effectiveness of the scheme.The scheme based on the stable block condition realizes the(k,k)threshold,while the scheme based on overall scale and stable block realizes the(k,n)threshold.Both of them realize the understandability of shadow image,and both of them are white box robust schemes.