Browsing by Author "Lee, I-Shi"

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A new approach to covert communication via PDF files
(2010-02-01)
Lee, I-Shi
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Tsai, Wen-Hsiang
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資訊工程學系
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Department of Computer Science
A new covert communication method via PDF files is proposed. A secret message, after being encoded by a special ASCII code and embedded at between-word and between-character locations in the text of a PDF file, becomes invisible in the window of a common PDF reader, creating a steganographic effect for secret transmission through the PDF file. Experimental results show the feasibility of the proposed method. (C) 2009 Elsevier B.V. All rights reserved.
Data hiding in binary images with distortion-minimizing capabilities by optimal block pattern coding and dynamic programming techniques
(2007-08-01)
Lee, I-Shi
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new method for data hiding in binary images based on block pattern coding and dynamic programming with distortion-minimizing capabilities is proposed. Up to three message data bits can be embedded into each 2 x 2 block in an input image by changing the block's pixel pattern into another, which represents the value of the message data bits as a code according to a block pattern encoding table. And extraction of hidden message data is accomplished by block pattern decoding. To minimize the resulting image distortion, two optimization techniques are proposed. The first is to use multiple block pattern encoding tables, from which an optimal one is selected specifically for each input image, and the second is to use a dynamic programming algorithm to divide the message data into bit segments for optimal embedding in a sense of minimizing the number of binary bit flippings. Accordingly, not only more data bits can be embedded in an image block on the average, but the resulting image distortion is also reduced in an optimal way. Experimental results are also included to show the effectiveness of the proposed approach.
Data hiding in grayscale images by dynamic programming based on a human visual model
(2009-07-01)
Lee, I-Shi
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new method for data hiding in grayscale images based on a human vision model with distortion-minimizing capabilities is proposed. Each of the eight bit planes of an input grayscale image is viewed as a binary image, into which message data are embedded horizontally. Two optimization techniques, namely, block pattern coding and dynamic programming, are proposed for image distortion minimization. Experimental results show good performs of the proposed method. (C) 2009 Elsevier Ltd. All rights reserved.