High Capacity Information Hiding Algorithm In Digital Images

Along with the rapid development of Internet and information science,which are providing great convenience for information transmission and processing,increasingly severe security problems have emerged gradually.Information hiding,as an important method to guarantee secure information transmission,has attracted great attention all over the world.By hiding the existence of information,hiding communication has solved the easily-being-attacked cryptographic problems in application.Its applications include copyright protection, digital fingerprinting,tamper authentication of multimedia,hiding communication,etc.of military or civil use;therefore,it is of great theoretical and practical importance.In the past decade,digital watermarking,as a branch of information hiding,has been developed rapidly.But achievements in hiding communication and tamper authentication are relatively insufficient because there exists some difficulties like inherent constraints among embedding capacity,security, perceptual distortion with the lack of objective measurement to both security and perceptual quality,especially embedding capacity of most present hiding algorithms can hardly reach the demands of hiding communication.The focus of this dissertation is on the study of evaluating the imperceptibility and security of hiding information and designing embedding algorithms with higher hiding capacity,mainly including imperceptibility evaluation of hiding information,encryption and scrambling of digital images,high capacity image information hiding algorithm,and so on.Some of the conclusions are listed as follows:(1) Based on the analysis of the drawbacks of commonly used visual imperceptibility criteria,such as PSNR(Peak Signal to Noise Ratio), PBED(Pixel-Block Error Distribution),a new criterion called VDSF (Vision Distortion Sensitivity Function) is proposed to evaluate the imperceptibility of hiding information algorithm according to human vision properties,which characterizes four aspects of human vision.First, human eyes are not sensitive to noise within violently varying visual signals(such as texture) but sensitive to noise in smoothing area.Second, human eyes are more sensitive to changes in horizontal direction than ones in diagonal direction.Third,brightness variances lower than perceptible limit are imperceptible to human.Fourth,adjacent pixels are correlated with each other,and the relativity depends on their distance. VDSF has lower computational complexity.Especially PSNR belongs to one of its specific cases.Experiments show that VDSF can overcome drawbacks of present visual imperceptibility criteria like PSNR and evaluate better the imperceptibility of hiding information.Moreover,the proposed algorithm is suitable for quality evaluation of binary images to solve the problem that the individual criterion can not be used for both grey image and binary image in the meantime.(2) On the basis of chaotic map information preprocessing,a logistic map based algorithm generating chaotic sequences is proposed,which avoids secure problems such as blank windows,stable window,etc. Moreover,the key space is greatly increased.A chaotic scrambling algorithm based on Arnold map is improved.In this scheme the periodicity of Arnold map is eliminated,it can effectively defend chosen plaintext attack.(3) Bit plane distribution property of an image in spatial domain is analyzed,and secure problems caused by damaging its bit plane texture characteristics due to replacing least significant bit(LSB) or multiple low bit plane with direct secret messages,is discussed.A bit plane decomposition method based on MSB(most significant bit) is proposed. Moreover,a conclusion that replacing certain low bit plane below MSB with random binary image doesn't damage its inherent texture property when original image is decomposed in fixed bit plane,is drawn.Based on image spatial domain,two adaptive information hiding algorithms are proposed by applying the above conclusion and the brightness masking effect of human visual system.The proposed schemes not only have high capacity but also are effective to protect against damaging texture property of low bit plane so as to improve the security.(4) DCT(Discrete Cosine Transform) domain based information hiding algorithm has merits of good robustness but weakness of low embeddable capacity.Based on spectrum analysis of natural images,high capacity DCT hiding information algorithms of both frequency spectrum homogenization and embedding information in high frequency coefficients are presented respectively.In frequency spectrum homogenization algorithm embeddable capacity is improved by using frequency spectrum homogenization processing on original image to obtain more DCT coefficients used for hiding information.Another algorithm uses JPEG invariance property,and information is embedded in high frequency coefficients under the conditions of imperceptibility in order to improve embeddable capacity.Moreover,this method has good robustness to lossy compression within default quality factors.(5) High capacity hiding information algorithms in binary host image is developed according to characteristics of binary image.The binary host image is first divided into blocks of size 2×2,and then each sub-block adaptively determines the embedded bits number and their positions according to the difference between its black pixel and white pixel number.Each sub-block in the transitional block between black pixel and white pixel can hide at least two bits messages.Therefore,its embeddable capacity is two times more than that of other presented blind algorithms.