Browsing by Author "Wang, Ran-Zan"

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A Sharing-Based Fragile Watermarking Method for Authentication and Self-Recovery of Image Tampering
(2008)
Chang, Yu-Jie
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Wang, Ran-Zan
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Lin, Ja-Chen
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資訊工程學系
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Department of Computer Science
This study presents an authentication method with self-recovery ability. The hidden watermark in the proposed method not only detects and locates the tampered portion of an image, but also self-recovers the tampered portion. To increase the ability to recover from tampering, the recovery data are shared by using an (r, n) threshold scheme and then scattered all over the image. Experimental results indicate that the visual quality of the watermarked image is acceptable, and that the positions of the tampered portions can be identified. Most importantly, the self-recovery result is very competitive. Copyright (C) 2008 Yu-Jie Chang et al.
HIDING IMAGES USING MODIFIED SEARCH-ORDER CODING AND MODULUS FUNCTION
(2008-09-01)
Chang, Yu-Jie
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Wang, Ran-Zan
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Lin, Ja-Chen
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資訊工程學系
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Department of Computer Science
This paper proposes a method for hiding an important image in a cover image whose size is limited. In this method, in order to save space, a modified search-order coding (MSOC) technique first transforms the important image, then, a randomization procedure permutes the transformed image to further increase the security. Finally, a modulus function embeds the permuted code in a cover image; notably, in the modules function, the modulus base used for a pixel is determined according to the variance of its neighboring pixels. Experimental results show that the images are of high quality. Comparisons with reported methods are provided.
Verifiable Visual Cryptography
(2012)
Hsu, Shuo-Fang
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Chang, Yu-Jie
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Wang, Ran-Zan
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Lee, Yeuan-Kuen
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Huang, Shih-Yu
The paper presents a verifiable visual cryptography (VC) scheme for checking the validness to the shares engaged in a VC decoding instance. The idea is to stamp a continuous pattern on the shares belonging to the same secret image, and a part of the pattern can be revealed through aligning and stacking half of two shares together. The visual coherent among the revealed patterns of all pair of shares provides evidence to the genuine of the shares engaged in the decoding process. Compare to the reported cheating prevention VC schemes, the proposed scheme maintains the original pixel expansion in VC scheme without cheating prevention ability, and the share verification process is done without resorting to any additional verification image. Besides, the proposed verification mechanism can easily be attached to any VC schemes in the literature to endow legitimate user with the ability to prevent cheating from malicious participants.