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In recent years, the growth of the Internet along with multimedia data delivery, have caused the misuse and even alteration of the original digital content. As a security mechanism, digital watermarking has been used to protect digital content, traditionally in copyright protection applications, and more recently digital watermarking has been used in content enhancement applications. Regardless of the application, digital watermarking schemes always cause some level of signal degradation. There are however, certain applications as in the military or medical fields, where loss of information cannot be tolerated during the reconstruction of host signals, therefore conventional watermarking schemes do not satisfy the quality requirements. In order to reconstruct signals without loss of data, reversible watermarking is employed. Recent research in reversible watermarking has focused on either, the improvement of embedding capacity or the reduction of perceptual impact of the schemes, but scarcely exploring the robustness of reversible schemes. In this survey, we provide a deep review of reversible watermarking schemes and propose a new classification outline based on the robustness point of view. Finally, some future directions for reversible watermarking research are presented and open problems in robust reversible watermarking are outlined.

Self-recovery schemes identify and restore tampering, using as a reference a compressed representation of a signal embedded into itself. In addition, audio self-recovery must comply with a transparency threshold, adequate for applications such as on-line music distribution or speech transmission. In this manuscript, an audio self-recovery scheme is proposed. Auditory masking properties of the signals are used to determine the frequencies that better mask the embedding distortion. Frequencies in the Fourier domain are mapped to the intDCT domain for embedding and extraction of reference bits for signal restoration. The contribution of this work is the use of auditory masking properties for the frequency selection and the mapping to the intDCT domain. Experimental results demonstrate that the proposed scheme satisfies a threshold of -2 ODG, suitable for audio applications. The efficacy of the scheme, in terms of its restoration capabilities, is also shown.

In recent years, Internet use has increased the unauthorized distribution of multimedia content and digital watermarking is a means to protect these contents from illegal actions. However, conventional watermarking produces distortions to the watermarked signals that cannot be counteracted, which are not acceptable for applications in the medical or military field. Reversible watermarking schemes (RWS) allow to counteract such distortions; although they are fragile, which means that any modification to the watermarked signals will cause the loss of the embedded watermarks as well as the original signal. In this doctoral research, a reversible watermarking scheme with watermark and signal robustness is proposed. It is a contribution to the state of the art because there are no such schemes in the literature. A framework is proposed to address this problem, that was validated through experimental results with images and audio signals, and it is an abstract construction to solve the research problem. It was assumed that since the framework proved to be effective for images, it could be followed in the same way to propose a solution for audio signals. The framework consists of two stages, namely a fragile reversible one and a selfrecovery one. The fragile reversible stage allows the insertion of the watermark and the self-recovery one inserts control information that allows the restoration after the watermarked signals have been attacked with content replacement. To implement the framework for audio signals, a reversible watermarking scheme and a self-recovery scheme had to be proposed. The self-recovery scheme is a contribution to the state of the art because, to the best of our knowledge, the scheme proposed is the first effort for this type of media. The reversible watermarking scheme for audio signals uses the auditory masking properties of the signals to determine the frequencies where embedding of the watermark will cause unnoticeable distortions. Moreover, the strategy from the reversible watermarking scheme proposed was also included in the self-recovery scheme proposed, and it allowed the insertion of the control information that was required for perfect restoration of the signals after content replacement was applied. With perfect restoration, the framework could be completed and tested for audio signals. En años recientes, el uso de Internet ha incrementado la distribución no autorizada de contenido multimedia y las marcas de agua digitales han sido utilizadas para proteger estos contenidos de acciones ilegales. Sin embargo, los esquemas convencionales producen distorsiones sobre las señales marcadas que no pueden ser contrarrestadas, lo cual no es aceptable para aplicaciones en los campos médicos y militares. Los esquemas de marcas de agua reversibles (RWS, por sus siglas en inglés) permiten contrarestar estas distortiones, aunque son frágiles, lo que significa que cualquier modificación a las señales marcadas causará la pérdida de las marcas insertadas así como de las señales originales. En esta investigación doctoral, se propone un esquema reversible de marcas de agua con robustez de la marca y de la señal. Es una contribución al estado del arte porque tales esquemas no existen en la literatura. Se propone un marco conceptual para abordar el problema, éste fue validado a través de resultados experimentales con imágenes y señales de audio, y éste es una abstracción para resolver el problema de investigación. Se partió de la suposición que, dado que el marco conceptual demostró ser efectivo para imágenes, éste podría utilizarse de la misma manera para una solución en señales de audio. El marco conceptual consiste en dos etapas, una frágil reversible y otra autorecuperable; la etapa frágil reversible permite insertar la marca de agua y la etapa autorecuperable inserta información de control que permite la restauración después que las señales marcadas han sido atacadas con reemplazo de contenido. Para implementar el marco para señales de audio, un esquema reversible de marcas agua y un esquema auto-recuperable para señales de audio tuvieron que ser propuestos. El esquema auto-recuperable es una contribución al estado del arte, dado que éste es el primer esquema de este tipo para señales de audio. El esquema reversible de marcas de agua para señales de audio utiliza las propiedades de enmascaramiento auditivo para determinar las frecuencias donde la inserción de la marca produce distorsiones que no son notorias. Aún más, la estrategia usada por el esquema reversible de marcas de agua también fue incluida en el esquema auto-recuperable propuesto, misma que permitió la inserción de la información de control requerida para la restauración perfecta de las señales después que el ataque de reemplazo de contenido.

Digital audio watermarking is a recent technique that assists with copyright protection. This technique inserts additional data of the owner or the purchaser of a work. The fundamental aim of digital watermarking is to insert additional data in an electronic _le (such as images, audio or video), in a way that a human observer cannot detect its presence. In this research project we develop an audio watermarking scheme that is robust against desynchronization attacks. These kinds of attacks are of great interest in the area, because they make most of the recent watermarking schemes to fail. The strategy used in the proposed scheme against these attacks is to take low frequency DWT coefficients in order to construct a histogram; adjacent groups of bins from this histogram are used to insert the watermark. The detection is performed in a similar manner, the histogram is reconstructed and the same groups of adjacent bins are interpreted as the inserted watermark. Las marcas de agua digitales son una técnica que ayuda a la protección de derechos de autor, agregando información del propietario de una obra o el comprador de la misma. El objetivo fundamental de las marcas de agua es insertar datos adicionales en un medio electrónico (imágenes, audio, video) de tal manera que no puedan ser percibidos por un observador humano. En este trabajo de investigación se desarrolla un esquema de marcas de agua para audio que presenta gran robustez ante ataques de desincronización. Este tipo de ataques son de gran interés en el área, porque causan que la mayoría de esquemas actuales de marcas de agua para audio fallen. La estrategia del esquema propuesto para combatir estos ataques es tomar las bajas frecuencias del dominio DWT para construir un histograma, del cual se toman grupos de bins adyacentes y realizar la inserción de la marca de agua. La detección de la misma se lleva a cabo reconstruyendo el histograma e interpretando los mismos grupos de bins adyacentes para construir la marca.

C1 inhibitor deficiency (hereditary angioedema [HAE]) is a rare disorder for which there is a lack of consensus concerning diagnosis, therapy, and management, particularly in Canada. European initiatives have driven the approach to managing HAE with 3 C1-INH Deficiency Workshops held every 2 years in Hungary starting in 1999, with the third Workshop having recently been held in May 2003. The European Contact Board has established a European HAE Registry that will hopefully advance our knowledge of this disorder. The Canadian Hereditary Angioedema Society/Société d'Angioédème Héréditaire du Canada organized a Canadian International Consensus Conference held in Toronto, Ontario, Canada, on October 24 to 26, 2003, to foster consensus between major European and North American HAE treatment centers. Papers were presented by investigators from Europe and North America, and this consensus algorithm approach was discussed. There is a paucity of double-blind placebo-controlled trials in the treatment of HAE, making levels of evidence to support the algorithm less than optimal. Enclosed is the consensus algorithm approach recommended for the diagnosis, therapy, and management of HAE and agreed to by the authors of this article. This document is only a consensus algorithm approach and requires validation. As such, participants agreed to make this a living 2003 algorithm (ie, a work in progress) and agreed to review its content at future international HAE meetings. The consensus, however, has strength in that it was arrived at by the meeting of patient-care providers along with patient group representatives and individual patients reviewing information available to date and reaching agreement on how to approach the diagnosis, therapy, and management of HAE circa 2003. Hopefully evidence to support approaches to the management of HAE will approach the level of meta-analysis of randomized controlled trials in the near future.