| Summary: | 碩士 === 國立交通大學 === 電機資訊國際學程 === 107 === Nowadays, Internet usage for communication spread widely. A lot of issues such as data security become an important topic. Image hiding becomes one of many techniques to secure the data. Image hiding is a technique to secure secret data by embedding secret data into a cover image in a way that the secret data seems meaningless to the attacker during transmission. A good image hiding method fulfills three aspects, the first is capacity, the second is imperceptibility, and the third is robustness.
Adaptive pixel pair matching (APPM) is an image hiding method that produces stego image with good imperceptibility and large payload. However, this method embeds secret data uniformly without considering that the tolerance of the human visual system (HVS) toward changes occurred in the image is different between pixels in smooth area and in edge area. Therefore, here we propose a PVD – APPM method, which embeds different amount of secret data between smooth area and edge area. In order to make the secret data can be extracted correctly, we propose an adjustment step in our method. Based on our experiments, our PVD – APPM method has better PSNR result than other PVD – based methods.
APPM method is not robust against some image processing attacks. Therefore we propose a DWT – APPM method to improve its robustness. In this method, a cover image is transformed using discrete wavelet transform (DWT), then the secret data are embedded in the transformed image. In order to increase the robustness, we avoid embedding secret message in certain sub-band that is vulnerable to distortion. Based on our experiment, we found that our DWT – APPM method has better PSNR and better security result than many other DWT – based image hiding methods. Our stego images are more robust against some attacks.
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