| Summary: | 碩士 === 國立成功大學 === 電腦與通信工程研究所 === 95 === With the fast advent of internet, many of data are converted to digital format in order to accelerate communication. However, it leads more consideration on security. Therefore a lot of data hiding techniques are proposed. Unlike cryptography, the secret information is not encrypted to prevent malicious behavior, but it used the cover media to embed the secret information for the sake of the secret communication.
In this thesis, we proposed three different data hiding schemes. The first two are based on the spatial domain, they can be classified fixed and unfixed LSBs substitution methods. The first one utilizes the arrangement of the secret data to compensate distortion. And the second proposed technique uses OPAP [3] to improve Lie and Chang proposed scheme [11]. The last one is based on JPEG compression, it utilizes the characteristic of DCT quantization. Therefore we can hide our secret message by adjusting the zero coefficients corresponding to medium frequencies. Besides, we can obtain original JPEG file after retrieving the secret data. In addition, we can enhance the performance of compression by adopting NAF [22, 24]. Both of these methods are no need of referencing the original image when extracting the hided data form the stego-image. Our experimental results will show the proposed method can reach the high capacity with good image quality.
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