Browsing by Author "Chang, Yu-Jie"

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A Sharing-Based Fragile Watermarking Method for Authentication and Self-Recovery of Image Tampering
(2008)
Chang, Yu-Jie
;
Wang, Ran-Zan
;
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.
Authentication and cross-recovery for multiple images
(2008-10-01)
Chang, Yu-Jie
;
Lin, Sian-Jheng
;
Lin, Ja-Chen
;
資訊工程學系
;
Department of Computer Science
We propose a system with image authentication and cross-recovery ability to protect a group of n given digital images. The system is a (r, n) threshold scheme (r is a prespecified threshold satisfying 2 <= r < n). Any r of these images can reconstruct the whole group of n images, but less than r images cannot. Therefore the system has cross-recovery ability because if some [up to (n-r)] images in the group are destroyed or lost in a distributed storage scheme or transmission mission, the destroyed or lost can be rebuilt vividly by the mutual support of r survived members. The design is composed of compression, a two-layer sharing, cryptographic hash function, and information hiding. (C) 2008 SPIE and IS&T.
Data hiding using VQ index file
(2008)
Chang, Yu-Jie
;
Lin, Ja-Chen
;
資訊工程學系
;
Department of Computer Science
This paper modifies an elegant data hiding method of Chang et al's [Pattern Recog. Lett. 2004, vol. 25, no. 11, 1253-1261]. The embedding employs a modified search-order coding (SOC) technique to hide binary secret data in the vector quantization (VQ) index file of a host image. The recovered host image is identical to the one recovered by traditional VQ; the compression rate is competitive to traditional VQ's (often better than traditional VQ's if we use t = 1 mode); while the hidden binary data is revealed in the decompression procedure as a bonus. The compression rate and hiding capacity are also better than those in Chang et al's.
HIDING IMAGES USING MODIFIED SEARCH-ORDER CODING AND MODULUS FUNCTION
(2008-09-01)
Chang, Yu-Jie
;
Wang, Ran-Zan
;
Lin, Ja-Chen
;
資訊工程學系
;
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.
Progressive sharing of an image
(2008-04-01)
Hung, Kuo-Hsien
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Chang, Yu-Jie
;
Lin, Ja-Chen
;
資訊工程學系
;
Department of Computer Science
We propose a sharing method to progressively reveal a given important image in the recovery phase. In the encoding phase, the distributor utilizes the three frequency bands (low, middle, and high) of the given image to generate shadows according to three prespecified thresholds. In the recovery phase, the secret image cannot be revealed if the number of shadows a team collects is less than the lowest threshold. However, when the number of collected shadows reaches the prespecified low (or middle- or high) threshold, the team can reconstruct a low- (or middle- or high-) quality version of the secret image. In other words, the quality of the reconstructed image depends only on the number of shadows being received, rather than on which of the generated shadows are received. Each noise-like shadow is so small that it can be hidden in an ordinary image that is still several times smaller than the original image. (C) 2008 Society of Photo-Optical Instrumentation Engineers.
Verifiable Visual Cryptography
(2012)
Hsu, Shuo-Fang
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Chang, Yu-Jie
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Wang, Ran-Zan
;
Lee, Yeuan-Kuen
;
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.