Browsing by Author "Lin, Sian-Jheng"

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Authentication and cross-recovery for multiple images
(2008-10-01)
Chang, Yu-Jie
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Lin, Sian-Jheng
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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
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.
Authentication and recovery of an image by sharing and lattice-embedding
(2010-10-01)
Lin, Sian-Jheng
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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
Based on sharing and lattice-embedding techniques, we present an authentication-recovery method for an image. The recovery data are shared among many shadows, then lattice-embedding is utilized to embed each shadow in the discrete cosine transform domain of an 8x8 block. The proposed method can resist certain content-preserving operations such as JPEG compression, Gaussian noise, and brightness adjustment, up to a tolerance level controlled by a quantization parameter value. The method can also resist certain security attacks such as a cut-and-paste attack, a collage attack, and a vector quantization attack. Compared with previous works, the proposed method has following major advantages and novelty: (1) the method does not require prediction of the tampering trace, and the tampered blocks are always recovered as long as the number of valid blocks reaches a threshold and (2) lattice-embedding yields smaller distortion than does parity-check quantization, and the latter was often used in reported works. (C) 2010 SPIE and IS&T. [DOI: 10.1117/1.3500799]
Fast-weighted secret image sharing
(2009-07-01)
Lin, Sian-Jheng
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Chen, Lee Shu-Teng
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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
Thien and Lin [Comput. and Graphics 26(5), 765-770 (2002)] proposed a threshold scheme to share a secret image among n shadows: any t of the n shadows can recover the secret, whereas t-1 or fewer shadows cannot. However, in real life, certain managers probably play key roles to run a company and thus need special authority to recover the secret in managers' meeting. (Each manager's shadow should be more powerful than an ordinary employee's shadow.) In Thien and Lin's scheme, if a company has less than t managers, then manager's meeting cannot recover the secret, unless some managers were given multiple shadows in advance. But this compromise causes managers inconvenience because too many shadows were to be kept daily and carried to the meeting. To solve this dilemma, a weighted sharing method is proposed: each of the shadows has a weight. The secret is recovered if and only if the total weights (rather than the number) of received shadows is at least t. The properties of GF(2(r)) are utilized to accelerate sharing speed. Besides, the method is also a more general approach to polynomial-based sharing. Moreover, for convenience, each person keeps only one shadow and only one shadow index. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3168644]
Flip visual cryptography (FVC) with perfect security, conditionally-optimal contrast, and no expansion
(2010-11-01)
Lin, Sian-Jheng
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Chen, Shang-Kuan
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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 flip visual cryptography (FVC) scheme with perfect security, conditionally optimal contrast, and no expansion of size. The proposed FVC scheme encodes two secret images into two dual-purpose transparencies. Stacking the two transparencies can reveal one secret image. Flipping one of the two transparencies and then stacking with the other transparency can reveal the second secret image. The proposed scheme is proved to have conditionally optimal contrast: its contrast is optimal if the double-secrets non-expanded FVC scheme is required to have perfect security. The perfect security is also proved. (c) 2010 Elsevier Inc. All rights reserved.
Flip visual cryptography (FVC) with perfect security, conditionally-optimal contrast, and no expansion
(2010-11-01)
Lin, Sian-Jheng
;
Chen, Shang-Kuan
;
Lin, Ja-Chen
;
資訊工程學系
;
Department of Computer Science
This paper proposes a flip visual cryptography (FVC) scheme with perfect security, conditionally optimal contrast, and no expansion of size. The proposed FVC scheme encodes two secret images into two dual-purpose transparencies. Stacking the two transparencies can reveal one secret image. Flipping one of the two transparencies and then stacking with the other transparency can reveal the second secret image. The proposed scheme is proved to have conditionally optimal contrast: its contrast is optimal if the double-secrets non-expanded FVC scheme is required to have perfect security. The perfect security is also proved. (c) 2010 Elsevier Inc. All rights reserved.
REVERSIBLE JPEG-BASED HIDING METHOD WITH HIGH HIDING-RATIO
(2010-05-01)
Chen, Lee Shu-Teng
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Lin, Sian-Jheng
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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
The stego-images generated by many existing hiding techniques are not economic in size, and hence need compression. Unfortunately, compression usually destroys the secret content hidden inside. To solve this dilemma, some hiding methods based on compression code (rather than the image itself) are reported. This paper proposes a high-capacity and high-hiding-ratio "reversible" steganography method based on JPEG-compression code. In the proposed method, the JPEG compression code of an image is used as the cover media. An 8 x 8 hiding-capacity table is firstly evaluated, which is then utilized to modify the quantization table attached to the given JPEG code. The two quantization tables (modified and original) together can map the DCT coefficients of each block to some larger DCT coefficients, with secret data hidden inside these larger DCT coefficients. In the decoding process, after lossless extraction of the hidden secret data, the proposed method can also recover the original JPEG-compression code. Experimental results show that our method outperforms other JPEG-based hiding methods (reversible or not) regarding both hiding-ratio and stego-image's quality.
VCPSS: A two-in-one two-decoding-options image sharing method combining visual cryptography (VC) and polynomial-style sharing (PSS) approaches
(2007-12-01)
Lin, Sian-Jheng
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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 presents a novel method to combine two major branches of image sharing: VC and PSS. n transparencies are created for a given gray-valued secret image. If the decoding computer is temporarily not available at (or, not connected to) the decoding scene, we can still physically stack any t received transparencies (t <= n is a threshold value) to get a vague black-and-white view of the secret image immediately. On the other hand, when the decoding computer is finally available, then we can get a much finer gray-valued view of the secret image using the information hidden in the transparencies. In summary, each transparency is a two-in-one carrier of the information, and the decoding has two options. (c) 2007 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.