| With the intensive study of information hiding,so image information hiding tech-nology has been widely used.However,traditional steganography in spatial domain of images are easy to be detected by steganalysis methods.In recent years,some scholars have proposed a idea based on coverless image steganography without modifying image data.The propose of the idea is to establish the mapping relationship between the secret information and image features,such as color,brightness,texture,edge structure.The ability of resisting detection is improved and the idea has broad application.According to the definition of coverless information hiding,the following two algori-thms are proposed:A steganography using reversible texture synthesis based on seeded region growing and Least Significant Bit(LSB)and coverless image steganography without embedding based on complete grouped.The former is aimed to improve coverless image steganography based on texture synthesis.The seeded region growing and LSB mothed are proposed to solve the problems of the stego synthesis texture,such as large size,poor visual effect and extra parameters needed to be transmitted.The former is aimed to improve coverless image steganography based on mapping relation-ship.The complete grouped basis is proposed to solve the problems of the established image feature sequences cannot be mapped to all kinds of secret information,because the composition of natural images is affected by the law of nature.The main contributions of this thesis arc as follows:(1)A stcganography using reversible texture synthesis based on seeded region growing and LSB is designed.A secret information segmentation algorithm is proposed and the size of the stego texture is decreased effectively.Moreover,the capacity of emb-edded information remains invariant.The visual effect of the generated stego synthetic texture is refined using this method.Synthesizing texture with seeded region growing method ensures the similarity and continuity between embedded texture blocks,and the visual effect of stego texture is close to the original texture.Finally,based on LSB stega-nography and the characteristics of portable network graphics(PNG)format image,the extra parameters of extracting secret information are embedded in stego synthesis text-ure.No parameters are required to transmit in the process of transmitting stego texture.The security of parameters is increased.When extracting information,the necessary parameters are extracted from the stego texture,and the original texture is restored according to the parameters.Depending on the original texture,the process of synthesi-zing stego texture is re-executed to extract the secret information.(2)A coverless image steganography without embedding based on complete grouped basis is designed.Firstly,the image feature sequences are established by the improved method based on the mean of pixel values with thresholds.Threshold restriction ensures robustness of image features.Then,complete grouped basis and grouped basis comple-tion method are proposed.Any kind of mapping relationship can be established between unmodified digital images and secret information.The transmitted secret images are determined by the joint operation of the grouped basis and secret information.The secu-rity of secret information in transmittal greatly.When extracting information,received stego images only need to be matched with the original basis images by image features.The wrong image feature sequences avoid being extracted from attacked stego images,and the success rate of extracting secret information is increased. |
