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1

Three-Phase Lossless Data Hiding Method for the VQ Index Table

Chang C-C., Lin C-Y., Hsieh Y-P.

Fundamenta Informaticae

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2008

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Vol. 82, nr 1-2

1-13

EN

Hiding Data in a cover image often applies a steganographic technique that makes the stego image appear as similar to the original cover image as possible. Conventional VQ-based (vector quantization) steganographic methods typically involve codeword replacements to hide secret bits. Such replacements may cause serious distortion or a perceptible block effect on the stego image. In this paper, we propose a three-phase steganographic method for the VQ index table. Instead of applying codeword replacements, the proposed method uses different coding schemes-SOC, SMVQ, and VQ-to imply the secret bits. The quality of the stego image generated by the proposed method is completely equal to that of the original cover image (i.e., the VQ cover image). Experimental results have shown that the proposed method has the best stego image quality compared with other methods. In addition, the proposed method provides adaptive embedding capacity and compression bit rate according to predefined thresholds.

2

High-Performance Reversible Data Hiding

Lin C-C., Hsueh N-L., Shen W-H.

Fundamenta Informaticae

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2008

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Vol. 82, nr 1-2

155-169

EN

This paper proposes a high-performance reversible data hiding algorithm based on the block difference histogram of a cover image. If a message is to be embedded into an image, the difference of the block at the maximum point is increased by 1 or left unchanged if the message bit is 1" or 0", respectively. Experimental results show that the average payload capacity of the test images can be up to 1.52 bits per pixel (bpp). Average payload and pure payload capacities for PSNR ^(3) 30 dB can be up to 1.13 bpp and 1.06 bpp, respectively. Moreover, the original cover image can be recovered without any distortion and the implementation of the proposed algorithm is very easy.

3

High Capacity Data Hiding for Grayscale Images

Chang C-C., Chou Y-C., Kieu T.D.

Fundamenta Informaticae

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2008

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Vol. 86, nr 4

435-446

EN

High embedding capacity and low image distortion factors are main concerns of information hiding researchers. No scheme can achieve these two factors simultaneously. The purpose of achieving either high embedding capacity or low image distortion varies from application to application. This paper presents a high embedding capacity information hiding method for grayscale images. The proposed method converts binary secret data into secret digits in the base-5 numeral system first. Next, one secret digit in the base-5 numeral system is embedded into one cover pixel. The experimental results show that the proposed method can be used to embed two secret bits into one cover pixel with the imperceptible image distortion. Comparing with some other works, we found that our method indeed outperforms all others in terms of embedding capacity.

4

Generalizations of Pixel-Value Differencing Steganography for Data Hiding in Images

Liu J-C., Shih M-H.

Fundamenta Informaticae

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2008

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Vol. 83, nr 3

319-335

EN

Generalizations of the pixel-value differencing (PVD) method for data hiding in gray-level images are proposed. Two extensions of the PVD method are analyzed: the block-based approach and the Haar-based approach. For the block-based PVD, the cover image is divided into non-overlapping horizontal or square blocks of n pixels. In each block, n-1 differences are calculated between consecutive pixels. These differences are classified to embed the secret message. For the Haar-based PVD, the 2-D integer Haar wavelet is applied to decomposed the cover image. The high-frequency components are used to hide message. Higher level of Haar decomposition allows more bits to be embedded. For both proposed generalizations, the capacity of the embedded message is significantly increased. Moreover, both generalizations are invulnerable to the RS-diagram and histogram steganalysis.

5

Codebook Partition Based Steganography without Member Restriction

Chiang Y-K., Tsai P., Huang F-L.

Fundamenta Informaticae

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2008

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Vol. 82, nr 1-2

15-27

EN

The practice of concealing secret messages into index-based images has generally suffered from problems of image quality degradation and hiding capacity restriction. A steganographic scheme using an improved codebook partition is proposed in this paper. The proposed scheme partitions the codebook into different member sub-clusters in terms of their similarity between the codewords for increasing the hiding capacity and reducing the image distortion. Any size of a sub-cluster was allowed in the proposed scheme, so as to improve the traditional approaches in which the size of a sub-cluster was restricted to the power of two. As a result of this revised scheme, an increased hiding capacity and a reduction in image distortion are obtained, as indicated from experimental results. The average performance of the proposed scheme is superior to that of those standard methods.

6

Secret Image Hiding and Sharing Based on the (t,n)-Threshold

Chang C-C., Lin C-Y., Tseng C-S.

Fundamenta Informaticae

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2007

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Vol. 76, nr 4

399-411

EN

This study proposes a new secret image sharing method based on the ( t, n)-threshold. The sharing method is completed through three main steps: (1) quantizing the secret image, (2) generating n shadows from the quantized image, and (3) sharing the n shadows among n cover images. Our goal is both to attain good stego-image and secret image quality preservation effects and to limit the size of each shadow image down to 1/ t of that of the secret image for convenient transmission and storage. In the first step, the secret image is divided into non-overlapping 4 × 4 blocks that are quantized according to the results of block testing. Each block, after the block testing procedure, is judged to be either a smooth block or a non-smooth one. Smooth blocks can be neatly restored after being hidden into the cover image, while non-smooth blocks can be somewhat lossy, but such modification is perceptually invisible. The second step is to apply Shamir's ( t,n)-threshold, which uses a ( t-1)-degree polynomial to generate n shadows so that the secret image can be restored from any t out of n shadows. The last step involves a modulo operation to hide the n shadows in n cover images. According to our experimental results, the PSNR values of the reconstructed secret images by our method center around 39 dB, outperforming other recent methods.

7

Spatial Domain Image Hiding Scheme Using Pixel-Values Differencing

Chang C-C., Chuang J-C., Hu Y-C.

Fundamenta Informaticae

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2006

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Vol. 70, nr 3

171-184

EN

In this paper, we present a spatial domain Image hiding scheme that embeds secret data in a gray-level image. Our scheme is inspired from Wu and Tsai's scheme that embeds secret bits in the difference values of consecutive pixels. To improve the hiding capacity of their scheme, the overlapping concept is proposed to produce more difference values from the cover image in this paper. Experimental results show that our scheme provides an average hiding capacity gain of 84.16% over Wu and Tsai's scheme while maintaining satisfactory image quality.

8

Reversible Data Embedding Based on Prediction Approach for VQ and SMVQ Compressed Images

Chang C-C., Lin C-Y.

Fundamenta Informaticae

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2006

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Vol. 74, nr 2,3

189-207

EN

Reversible steganography allows an original image that has gone through the embedding process to be completely restored after the extraction of the embedded data. In this paper, we propose a reversible scheme with a high embedding capacity for VQ compressed images. Our reversible method is based on a prediction strategy and takes advantage of the local characteristics of the image. Since the location map is usually a necessary part of a reversible scheme, two methods, shifting and relocating, are also proposed to reduce the size of the location map. As the experimental results show later, our method outperforms previous schemes in terms of embedding capacity and image quality. To be more specific, with low distortion, the embedding capacity of the proposed methods can be higher than one bit per index value.

9

A Novel Color Image Hiding Scheme Using Block Truncation Coding

Hu Y-C., Lin M-H., Jiang J-H.

Fundamenta Informaticae

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2006

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Vol. 70, nr 4

317-331

EN

In this paper, a novel color image hiding scheme that is capable of hiding two color secret images into a color host image is proposed. The secret images to be embedded are first compressed by the single bit map block truncation coding. DES encryption is then conducted on the compressed message before the secret image is embedded into the rightmost 3, 2, 3 bits of the R, G, B channels of every pixel in the host image. The experimental results show that our scheme provides an average secret image quality of 29.220 dB. In addition to the improved quality of both host images and retrieved secret images, our scheme further strengthens the protection of the secret images by conducting image compression and DES encryption on the secret image in advance. Therefore, our scheme not only extends the hiding capability of host images, but also is practical and secure.

10

An Adaptive Steganographic Scheme for Color Images

Chang C.-C., Tsai P., Lin M.-H.

Fundamenta Informaticae

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2004

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Vol. 62, nr 3,4

275--289

EN

In this paper, a new palette-based image steganography is proposed. Palette-based images such as GIF files have been widely used on the Internet and web pages such that all browsers can recognize them. Palette-based images can be used as good carriers for transmitting secret messages. In this scheme, the Least Significant Bits (LSBs) of the palette-based image are utilized in order to hide the secret message by using the computational information hiding technique. The adaptive hiding capacity can be computed according to different sizes of the embedding block. Experimental results also show that existing artifacts in the traditional LSB-based method are unnoticeable. The number of modification pixels in the embedding process is decreased, while good stego-image quality is maintained, and the cover image is left unblemished by camouflaged information. Furthermore, the feature of adaptive hiding capacity provides the possibility of protecting different sizes of embedded secret messages.

11

A New Channel for Image Hiding Based on Interpolating polynomials

Chan C-W., Chang C-C.

Fundamenta Informaticae

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2003

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Vol. 58, nr 2

93--104

EN

More and more sensitive image data is generated and transmitted over the Internet. To protect them, a new image hiding scheme is proposed in this paper. The proposed scheme is based on steganography, the principle of human visibility, and interpolating polynomials. The scheme assumes the capacity of a cover image to its hypothetic upper bound size of a cover image in the general image hiding schemes. Moreover, the scheme introduces MSB channel of image hiding over which we can transmit secret information of text type.