| Summary: | 碩士 === 國立勤益科技大學 === 資訊工程系 === 102 === In the paperless applications world, the document contents protection becomes more and more important. And, many documents contain owners’ secret assets. In this thesis, we use the PNG (portable network graphics) format images to illustrate our scheme. PNG format image contains basic channel and heterogeneous channel, named alpha channel. Alpha channel is used to define the degree of image transparency. We can use alpha channel to hide important information. We use the transparently fuzzy cognitive of human eyes to achieve secret information hiding and retrieving. Accordingly, the usage of the alpha channel to hide secret is a non-visible watermark technology. When a part content of the document is marked as important, we will use three colors, black, gray, and white, to parse the marked content. After ternarization, three values of the attributes will be calculated from the marked document image. In our experimental results, we show that our methods can valid and meaningful hiding secrets using alpha channel.
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