Abstract. This paper2 presents a new approach for the secure and robust copyright protection of digital images. A system for generating digital watermarks and for trading watermarked images is described. The system is based on a new watermarking technique, which is robust against image transformation techniques such as compression, rotation, translation, scaling and cropping. It uses modulation of the magnitude components in Fourier space to embed a watermark and an accompanying template and, during watermark extraction, reads a template in the log polar transform of the frequency domain. The template is used for analyzing scaling and rotation suffered by the watermarked stego-image. The detection of the watermarks is also possible without any need for the original cover-image. In addition, the system applies asymmetric cryptographic protocols for different purposes, namely embedding/detecting the watermark and transferring watermarked data. The public key technique is applied for the construction of a one-way watermark embedding and the verification function to identify and prove the uniqueness of the watermark. Legal dispute resolution is supported for the multiple watermarking of a digital image without revealing the confidential keying information.

Abstract. This paper proposes a new approach for assessing the presence of a digital watermark in images and videos. This approach relies on a Bayesian formulation that allows to compute the probability that a watermark was generated using a given key. The watermarking itself relies on the discrete Fourier transform (DFT) of the image, of video frames or of three dimensional chunks of video scene. Two kinds of information are hidden in the digital data: a watermark and a template. Both are encoded using an owner key to ensure the system security and are embedded in the 2D or 3D DFT magnitude of the image or video. The watermark is encoded in the form of a spread spectrum signal. The template is a key based grid and is used to detect and invert the eect of an ane geometric transformation (rotations, scaling and/or aspect ratio change) or in the case of the video framerate changes, aspect-ratio modication and rescaling of frames. It is shown that, for the spread spectrum signal described in the paper, it is possible to positively detect the presence of a watermark without necessarily decoding it, given only the key used to generate it. To do that, the Bayesian approach allows the deduction of the relative logprobability of the presence of a watermark in an image given only the key. All that is required for positive watermark verication is the key. This approach also allows to infer the number of bits contained in the watermark. The performance of the presented techniques and the usefulness of the relative log-probability are shown through various applications and experimental results.

In this paper we present a new approach for the secure and robust copyright protection of digital images. We describe a system for generating digital watermarks and for trading watermarked images. The system is based on a new watermarking technique, which is robust against image transformation techniques such as compression, rotation, translation, scaling and cropping. It uses modulation of the magnitude components in Fourier space to embed a watermark and an accompanying template and, during watermark extraction, reads a template in the log polar transform of the frequency domain. The template is used for analyzing scaling and rotation suffered by the watermarked stego-image. The detection of the watermarks is also possible without any need for the original cover-image. In addition, the system applies asymmetric cryptographic protocols for different purposes, namely embedding/detecting the watermark and transferring watermarked data. The public key technique is applied for the construction of a one-way watermark embedding and the verification function to identify and prove the uniqueness of the watermark. Legal dispute resolution is supported for the multiple watermarking of a digital image without revealing the confidential keying information