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Quantization index modulation (QIM) watermarking has received a great deal of attention ever since the rediscovery of Costa's result on codes with host-interference rejecting properties. While such embedding scheme exhibit considerable improvement in watermark capacity over its earlier predecessors, (e.g. spread-spectrum), their fragility to even the… (More)
A digital image watermarking system that takes advantage of the Discrete Fourier Transform properties to embed a spread spectrum watermark in an image is presented in this paper. Watermark robustness to translation, rotation and scaling attacks is achieved with the proposed system. A description of the method is included and results are presented.
In this paper we study the effects of synchronization errors on the bit error rate performance of spatial domain image watermarking. For that, we introduce the concept of the Random Jitter Attack. This attack is characterized by the displacement of each pixel position by a random amount given by an arbitrary distribution, followed by interpolation over the… (More)
This paper presents a collaborative model for the development of learning content based on the Learning Objects and learning standards paradigm. In this model, development efforts and results are shared among companies, universities and new players in the education and training arena: the e-Learning content providers and integrators.
OBJECTIVES This study aimed to develop and test a tool for low bone mass pre-screening by combining periapical radiographs with clinical risk factors. METHODS The study sample consisted of 60 post-menopausal women over 40 years of age who were referred for dental radiographs. These patients also had their bone mineral density measured at the lumbar spine… (More)
Max Costa original results on dirty paper codes have given the foundation for Quantizatin Index Modulation (QIM) based for digital image watermarking. However, the standard QIM methods can be greatly degraded by simple amplitude scaling attacks. In order to overcome this limitation, Angle Quantization Index Modulation (AQIM) schemes have been recently… (More)
errors can lead to significant performance loss in image watermarking methods, as the geometric attacks in the Stirmark benchmark software show. The authors describe the most common types of geometric attacks and survey proposed solutions. A watermark's resistance to geometric attacksthat is, its ability to withstand an arbitrary displacement of all or… (More)