Yuan-Yu Tsai

Reversible data hiding scheme based on neighboring pixel differences

In this paper, we propose a reversible data hiding algorithm for grayscale images. Specifically, our algorithm is based on the histogram modification technique. The premise of this algorithm is that a histogram is constructed from the differences between each pixel and its neighbors. In the data embedding process, a modified histogram shifting scheme is used to embed a secret message into the pixels whose pixel difference is located at the peak value within the histogram. Experimental results show that our algorithm can achieve higher embedding capacity and imperceptible distortion. Performance comparisons with other existing algorithms are also provided to demonstrate the feasibility of our proposed algorithm in reversible data hiding.

An adaptive steganographic algorithm for 3D polygonal models using vertex decimation

Most 3D steganographic algorithms emphasize high data capacity, low distortion, and correct data extraction. However, their disadvantage is in the existence of the same embedding capacity for each data-embedded vertex in the 3D models. Embedding the same capacity in the vertex located on the surface with different properties may cause obvious distortion, making it difficult to achieve the initial goal of information-hiding techniques. This study proposes a new and adaptive 3D steganographic algorithm that considers the surface complexity. To increase the accuracy of the complexity estimation for each embedding vertex, the proposed algorithm adopts a vertex decimation process to determine its referencing neighbors. Thereafter, different amounts of the secret messages are embedded according to the surface properties of each vertex. This approach preserves important shape features and produces a more imperceptible result. Experimental results show that the proposed adaptive algorithm can achieve more accurate estimation results with a higher data capacity and acceptable distortion. The proposed technique is feasible in 3D steganography.

A Generalized Image Interpolation-based Reversible Data Hiding Scheme with High Embedding Capacity and Image Quality

Jung and Yoo proposed the first image interpolation-based reversible data hiding algorithm. Although their algorithm achieved superior interpolation results, the embedding capacity was insufficient. Lee and Huang proposed an improved algorithm to enhance the embedding capacity and the interpolation results. However, these algorithms present limitations to magnify the original image to any resolution and pixels in the boundary region of the magnified image are poorly manipulated. Furthermore, the capacity and the image quality can be improved further. This study modifies the pixel mapping scheme and adopts a bilinear interpolation to solve boundary artifacts. The modified reference pixel determination and an optimal pixel adjustment process can effectively enhance the embedding capacity and the image quality. The experimental results show our proposed algorithm achieves a higher embedding capacity under acceptable visual distortions, and can be applied to a magnified image at any resolution. Our proposed technique is feasible in reversible data hiding.

An Image Hiding Scheme by Linking Pixels in the Circular Way

The proposed method in this paper is derived from Mielikainen’s hiding method. However, there exist some significant differences between two methods. In Mielikainen’s method, pixels are partitioned into pairs and a LSB matching function is applied to two pixels for hiding. On the contrary, the proposed method partitions pixels into groups with three pixels in each group. The bits of pixels in each group are linked by using an exclusive OR (XOR) operator in a circular way. If the number of different values between the calculated XOR values and the secret bits is smaller than or equal to 2 in a group, the proposed method can guarantee that at most one pixel is needed to be modified by adding/subtracting its value to/from one, and three secret bits can be embedded to three pixels. Through theoretical analysis, the amount of the embedded secret data in the proposed method is larger than those in other methods under the same amount of pixel modifications. Taking real images in our experiments, the quality of stego-images in the proposed method is higher than those in other methods.

An efficient 3D information hiding algorithm based on sampling concepts

This study proposes an efficient 3D information hiding algorithm based on sampling concepts. The total embedding capacity depends on the number of feature points obtained from an auxiliary polygonal model, instead of model complexity. We use sampling concepts to derive the feature points directly on each polygon of the auxiliary polygonal model. A stego model can be efficiently generated by slightly adjusting the position of each feature point with the help of the secret message and the embedding parameter. This approach has four characteristics. First, it preserves the features of high embedding capacity and flexibility. Second, this approach resolves the shortcomings of the holed effects and the dummy points in previous algorithm. Third, this approach is efficient with the time complexity O(n), where n is the number of feature points. Finally, the proposed algorithm supports point geometries as auxiliary models by adopting a surface reconstruction scheme. The above characteristics demonstrate the feasibility of the proposed algorithm.

A reversible steganographic algorithm for BTC-compressed images based on difference expansion and median edge detector

Abstract In this paper, we propose a reversible steganographic algorithm for compressed images. The algorithm firstly compresses the input image using block truncation coding. One binary map and two quantisation levels, called high and low levels, are then obtained for each block. Thereafter, we adopt a median edge detector to predict the high and low quantisation levels for neighbouring blocks. A secret message is then embedded into the predicted difference based on the difference expansion technique. Each block can be classified as embeddable and non-embeddable according to the order of two quantisation levels. Thus, the location map is unnecessary in our proposed algorithm. The experimental results show that our data-embedded compressed code can be the same file size compared with standard block truncation coding-compressed code. Our algorithm can also resist the RS steganalysis attack. Further, the embedding capacity can be varied according to the given embedding parameter. The feasibility of our proposed algorithm is validated by presenting comparisons with existing algorithms.

An Image Hiding Method by Linking Multiple Pixels with XOR Operator

In 2006, Mielikaines method partitioned pixels into pixel pairs. Two secret bits are embedded to a pixel pair through modifying only one pixel. After that, Chans method linked bits of two continuous pixels by using XOR operator to further reduce the pixel modifications. To generalize Chans method, in this paper, the concept of linking multiple pixels by using XOR operator is introduced. This way, Chans method becomes a special case of the proposed method. Moreover, through the proposed concept, modifying one pixel can further affect more results of XOR operator. That means the proposed method can embed more than two secret bits through modifying one pixel by adding/subtracting its pixel value to/from one. The procedures of secret embedding and extracting by linking three pixels are also represented in this paper. According to the experimental results, the pixel modifications in the proposed method are fewer than those in Mielikaines method and Chans method in most cases.

Dual Image Reversible Data Hiding by Modifying Least-Significant-Bit Matching Revisited Rules

The concept of dual image reversible data hiding (DIRDH) is the technique that can produce two camouflage images after embedding secret data into one original image. Moreover, not only can the secret data be extracted from two camouflage images but also the original image can be recovered. To achieve high image quality, Lu et al.’s method applied least-significant-bit (LSB) matching revisited to DIRDH. In order to further improve the image quality, the proposed method modifies LSB matching revisited rules and applies them to DIRDH. According to the experimental results, the image quality of the proposed method is better than that of Lu et al.’s method.

Access Control Mechanism for Blog Posts with Fine-grained Ability Using Simple Operations

Access control enables the owners to assign different users different permissions to see different views. The current blog system does not support fine-grained authorization. That is, the bloggers disallow to just assign partial contents of the blog posts (i.e., a paragraph or several paragraphs) to readers. The management cost is no doubt to be significantly increased while handling the authorizations on the huge amount of blog articles. In this paper, we propose a scheme for supporting a fine-grained access control mechanism on blog articles. The advantage is that bloggers are able to authorize partial contents of blog posts to different users or groups of users.

Embedding information on search-order codes of VQ indices by rearranging the indicators

The purpose of this paper is to embed information on codes when using search-order coding (SOC) to compress index table. The proposed method reassigned the shorter indicators to the indices that can be transformed to SOC codes and those that can not be transformed are assigned by the other indicators. If the cover image is a smooth image, the proposed method can significantly reduce the size of compression code. Moreover, the size of the compression code is only related to the cover image not to the information in the proposed method. This improves the security of the compression code. According to the experimental results, the proposed method has better performance comparing with the related methods.