| Summary: | 博士 === 朝陽科技大學 === 資訊管理系 === 102 === Data hiding is a technique that conceals data into a carrier for conveying the secret message confidentially. Digital images are widely transmitted over the internet and with large payload, so digital images often serve as a carrier. After embedding the secret message into the cover image, the cover image termed as stego image and distortion occur. Reduce the distortion is an important issue in data hiding. The measurement of data hiding has two requirements, payload and imperceptibility. The payload is determined by the number of secret message embedded in each pixel on the cover image. The imperceptibility is calculated by peak signal-to-noise ratio. High imperceptibility implies low distortion difference between cover image and stego image.
Data hiding has two types: reversible and irreversible. The reversible data hiding can restore the cover image without any distortion after the secret message has been extracted. Due to requirement of extra information of reversible data hiding, it has lower payload than most irreversible data hiding schemes. Despite the irreversible data hiding has a higher payload; it must comply with the human visual system which implies the stego image cannot be recognized by human eyes.
In this dissertation, we propose three methods of irreversible data hiding. First, we use the perfect square number divide the quantization range table on the pixel-value-differencing scheme. Second, we use a new hybrid edge detector increase the embedding capacity by least-significant-bit substitution scheme and use the minimal distortion method to improve the quality of the stego image. Finally, we try to use the geometry relation on the modulus function to replace the calculation complexity and extend the exploiting-modification-direction scheme and the fully-exploiting-modification-direction scheme to n-dimensional hypercube.
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