Browsing by Author "Chen, Lee Shu-Teng"

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AUTHENTICATION AND CROSS-RECOVERY OF MULTIPLE IMAGES
(2011-07-01)
Chen, Lee Shu-Teng
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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 work presents an authentication and cross-recovery scheme to protect a group of n JPEG images. Given n images, the images are scaled down and then encoded using JPEG to create n recovery data. Based on a pre-determined threshold t, 2 <= t < n, the n recovery data are shared to create n shadows. Next, n authentication data are generated to identify malicious attacks on the system. Additionally, the n shadows and the n authentication data are embedded in the n JPEG codes of the n original images to form n JPEG stego codes, which can be stored in a distributed storage system. Moreover, in the daily maintenance of the storage system, the authentication data concealed inside these n JPEG stego codes are used to verify which ones have been attacked. If some (up to n - t) of the n JPEG stego codes are corrupted, the corrupted JPEG images can be recovered approximately using any t survived JPEG stego codes. Experimental results demonstrate the effectiveness of the proposed method. Comparisons with other image recovery methods are also included.
Error Correction of Secret Images by Search Order Coding
(2009)
Su, Wei-Kai
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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
In this paper, an image recovery method based on search-order coding (SOC) is proposed. By using SOC, a SOC-image of the secret image can be generated. If the secret Image is damaged, people can still obtain a version of the secret image that looks not bad by referring to the SOC-image. Also, the information of the secret image cannot be retrieved from the SOC-image alone.
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]
Fault-tolerant VQ-style Secret Image Sharing
(2009)
Su, Wei-Kai
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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
In this paper, we propose a fault-tolerant secret image sharing scheme based on vector quantization (VQ). The proposed method uses some of the n host images to generate the codebooks for VQ, and compresses the secret image by VQ with the generated codebooks. The VQ indices are thus created and then shared among n shadows. After obtaining the n shadows, they are embedded together with the mixed information of the generated codebooks into the n host images to form the n stego-images. When collecting any r (r <= n) of the n stego-images, the VQ indices and codebooks can be retrieved to recover the secret image. However, no information about the secret image can be revealed if obtaining less than r stego-images. Because of using VQ, the secret image is compressed to the VQ indices, and thus easier to be hidden than the non-compressed one. The quality of the recovered image is the same as the one of the ordinary VQ.
Multithreshold progressive image sharing with compact shadows
(2010-01-01)
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
We propose a multithreshold progressive reconstruction method. The image is encoded three times using Joint Photographic Experts Group (JPEG): first with a low-quality factor, then with a medium-quality factor, and last with a high-quality factor. Huffman coding is employed to encode the difference between the important image and the high-quality JPEG decompressed image. The three JPEG codes and the Huffman code are shared, respectively, according to four prespecified thresholds. The n-generated equally important shadows can be stored or transmitted using n channels in parallel. Cooperation among these generated shadows can progressively reconstruct the important image. The reconstructed image is loss-free when the number of collected shadows reaches the largest threshold. Each shadow is very compact and so can be hidden successfully in the JPEG codes of cover images to reduce the probability of being attacked when transmitted in an unfriendly environment. Comparisons with other image sharing methods are made. The contributions, such as easiness to apply to scalable Moving Picture Experts Group (MPEG) video transmission or resistance to differential attack, are also included. (C) 2010 SPIE and IS&T. [DOI: 10.1117/1.3295710]
Progressive sharing of multiple images with sensitivity-controlled decoding
(2015-02-14)
Chang, Sheng-Yu
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Lee, Suiang-Shyan
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Yeh, Tzu-Min
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Chen, Lee Shu-Teng
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Lin, Ja-Chen
Secure sharing of digital images is becoming an important issue. Consequently, many schemes for ensuring image sharing security have been proposed. However, existing approaches focus on the sharing of a single image, rather than multiple images. We propose three kinds of sharing methods that progressively reveal n given secret images according to the sensitivity level of each image. Method 1 divides each secret image into n parts and then combines and hides the parts of the images to get n steganographic (stego) JPEG codes of equal importance. Method 2 is similar; however, it allocates different stego JPEG codes of different 'weights' to indicate their strength. Method 3 first applies traditional threshold-sharing to the n secret images, then progressively shares k keys, and finally combines the two sharing results to get n stego JPEG codes. In the recovery phase, various parameters are compared to a pre-specified low/middle/high (L/M/H) threshold and, according to the respective method, determine whether or not secret images are reconstructed and the quality of the images reconstructed. The results of experiments conducted verify the efficacy of our methods.
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.
Steganography scheme based on side match vector quantization
(2010-03-01)
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
We propose a steganographic method that is based on side match vector quantization (SMVQ). The secret data are encrypted and then embedded in an SMVQ-decompressed image. In the decoding process, both the hidden secret and the original SMVQ code can be reconstructed without any error. Experimental results demonstrate that the proposed method provides a high hiding capacity and acceptable stego-image quality, to an extent comparable to a well-known SMVQ-based reversible steganographic method. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3366654]