| Summary: | 碩士 === 國立彰化師範大學 === 統計資訊研究所 === 106 === Data hiding means that the sender embedded the secret bits into a digital media and transmits it to the receiver by an agreed method, and only the legal receiver can retrieve the secret bits according to the agreed method. In this study, we use grayscale images as the cover media. There are three requirements in the data hiding field: payload, imperceptibility (stego-image quality) and robustness. In general, it is a trade-off between the payload and the robustness to certain attacks while keeping an acceptable level of stego-image quality.
The least significant bit (LSB) substitution method and pixel-value differencing (PVD) method are two well-known irreversible data hiding methods. Both methods have the advantages of high payload and low distortion. LSB method directly replaces the bits of the cover pixel with secret bits for embedding. In PVD method, the difference of two pixels in the cover image is calculated to determine the number of bits to be embedded in these two pixels and a pre-defined range table. The technique can embed a large number of secret bits into the cover image with high imperceptibility.
In this study, we divide the cover image into different size of jigsaw puzzle pieces by using logistic map function to enhance robustness and security and embedding the secret bits by two different methods. The experimental results show that the one of proposed method achieves high payload and low distortion with strong robustness and security and the another one method increases a lot of payloads, the image quality slightly decreased, but the naked eye cannot be detected as it makes use of the characteristic of human vision sensitivity.
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