Madoka Hasegawa

A study on a watermarking method for both copyright protection and tamper detection

Most of watermarking methods are either robust watermarking for copyright protection or fragile watermarking for tamper detection. We propose a watermarking method that has both robustness against image processing and ability of tamper detection. In the proposed method, three wavelet coefficients are treated as a vector and one bit of a watermark is embedded by using order relationships among the coefficients. The number of order relationships among three coefficients is six, while only two patterns of relationships are needed to represent one bit of a watermark. Order relationships that are not assigned to a watermark bit can be used for tamper detection.

A lossless coding method using shape information and rotation compensation for digital museum images

Studies of digital museum are making progress in the various fields. Especially, in case of preserving 3-D objects, it is necessary to take digital photographs from various viewpoints. Thus, the amount of data becomes huge and a data compression technique should be introduced for archiving them. Moreover, in order to represent art works faithfully, a lossless coding method is indispensable. This study aims to construct an encoding and a browsing scheme that enables free handling according to users demands for such images. In this paper, we propose a new lossless coding scheme for digital image sequences which were acquired from different perspectives. In such case, the neighboring frames have high correlation. Our proposed coding method is based on a predictive model with the shape information and the rotation compensation. Simulation results show that our proposed scheme is effective for coding of digital image sequences of convex objects.

Watermarking method for extracting embedded data without original image

In this paper, we propose a watermarking method that does not requires an original image to extract embedded data. In our proposal, watermark information data are embedded by using the differences between the neighboring wavelet coefficients of the lowest band in the wavelet domain. Though such a concept have been already proposed by H.S. Kim et al., the original image is needed for extracting embedded data in their method. We developed a new scheme which does not requires the original image to extract embedded data, by modifying the embedding algorithm. Simulation results show that our proposed scheme indicates good picture quality in the watermarked image and robustness to some types of image processing attacks including JPEG compression.

Data hiding method in adaptive lossless coding scheme

Data hiding method called steganography has bee studied. Steganography is a method to transmit noticeable data secretly by mixing them in carefree image data. In the steganography, an image is used only as the cloak to transmit noticeable information. In this summary, we propose a method to incorporate data hiding into an adaptive lossless coding method. An adaptive coding method is effective for data compression because image signals are usually not stationary. For example, it is possible to get better coding performance by dividing an image into some blocks and by using suitable coding parameter for each block. There are two types of adaptive coding schemes, one is the method to transmit suitable coding parameters, block by block, as an overhead information, and another is the method to estimate and use parameters from already transmitted data, so that the latter does not need to transmit the coding parameters. We propose the method for data hiding in the former adaptive coding method, i.e. adaptive method with overhead information. In our proposed method, coding parameters are controlled by the embedding data and the original image data are never changed.

Digital watermarking method using vector set of wavelet coefficients

In this paper, we propose a new watermarking method using vector sets of wavelet coefficients. In our proposal, unlawful attacks can be detected by finding invalid vector set caused by attacks and original watermark information is not required for extracting embedded data or detecting unlawful attacks. Though the watermarking method using a pair of wavelet coefficients has been already proposed by H.S. Kim et al, the original image is needed for extracting embedded data and unlawful attacks can be never detected in their method. Therefore, the author of contents cannot strongly claim a copyright to his contents when the embedded information is lost by the attack, because even if the attack is made, the watermark information is extracted without contradiction, rightly or wrongly. We propose a new watermarking method based on vector set of wavelet coefficients. The proposed scheme does not requires the original image to extract embedded data, and can detect unlawful attacks by detecting invalid vector set caused by attacks. Simulation results show that our proposed scheme indicates good picture quality in the watermarked image and robustness to some types of image processing attacks including JPEG compression.