Research On Some Issues In Image Reversible Data Hiding

Reversible data hiding is one of the hot research areas of information hiding in recent years. Unlike the traditional techniques, by which the source data is distorted permanently due to data hiding, the reversible techniques can fully restore the source data after the hidden data being correctly extracted. It is high valuable in the cases which distortion is intolerable. This paper mainly focuses on the image reversible data hiding algorithms, the major contributions are as the followings:1. A reversible data hiding algorithm based on five-pixel block and prediction-error expansion is proposed. The image is divided into five-pixel blocks, the secret data can be embedded by using the relationship between three pairs of prediction-error. In the best situation, each pixel value is modified at most by1in each block to embed six bits, in this way the high capacity is achieved. At the same time by identifying the complexity of image blocks, only the ones of simple texture are selected to hide data and the others of complexity are dropped, the impact on image quality is minimized.2. A reversible data hiding algorithm base on interpolation prediction and blocking model is proposed. The analysis on the previous histogram shifting algorithms shows that the quality of the stego-image can be improved by reducing the number of shifting points and the number of "1" in the secrete data without having impact on reversibility. Therefore a block predictor is designed and the secret data is pre-processed to improve the quality. Furthermore, the interpolation-error histogram is generated using interpolation prediction in the cover image, the histogram is shifted in two directions to have the high capacity.3. A binary image reversilbe data hiding algorithm using interpolation computation and steganographic coding is proposed. Three problems are resolved:the first is to have reversibility. Based on the fact that in binary image each pixel is saved in one bit and the required space is not big, the image is expanded when embedding data and is shrinked when extracting the data. The stego-image is obtained by hiding secret data in the particular pixels of the interpolated image; the cover image can be restored by re-arranging the non-interpolated pixels. The second is to decrease image distoration. Only the pixels with less effect on human being visual system can be selected to hide the secret data by setting the rules of modification. The third is to improve the capacity. By using steganographic coding, r bits data can be hidden in one block with changing up to two pixels, r=log2(mn+1). For the image with size of M×N, the maximum capactity can reach to (M×N)/(m×n)×r bits.4. In practice, a combined technical image protection system of reversible data hiding and robust watermarking is designed and implemented. The system implements two levels of protection for the cover image and can communicate with other application systems based on REST network interface. It can be easily integrated to the existing systems like remote-medical or E-government. At the same time, an anti-dithering attack algorithm is proposed after studying the robust watermarking. The image is divided into units with nine adjacent blocks in DCT domain, then the watermark is embedded and extracted by adjusting the DC coefficient of the center block. The experimental results show that the algorithm is robust for dithering and other attacks.