An authorization policy management framework for dynamic medical data sharing

In this paper, we propose a novel feature reduction approach to group words hierarchically into clusters which can then be used as new features for document classification. Initially, each word constitutes a cluster. We calculate the mutual confidence between any two different words. The pair of clusters containing the two words with the highest mutual confidence are combined into a new cluster. This process of merging is iterated until all the mutual confidences between the un-processed pair of words are smaller than a predefined threshold or only one cluster exists. In this way, a hierarchy of word clusters is obtained. The user can decide the clusters, from a certain level, to be used as new features for document classification. Experimental results have shown that our method can perform better than other methods.<br /

A Security Framework for JXTA-Overlay

En l'actualitat, la maduresa del camp de la investigació P2P empès a través de nous problemes, relacionats amb la seguretat. Per aquesta raó, la seguretat comença a convertir-se en una de les qüestions clau en l'avaluació d'un sistema P2P, i és important proporcionar mecanismes de seguretat per a sistemes P2P. El projecte JXTAOverlay fa un esforç per utilitzar la tecnologia JXTA per proporcionar un conjunt genèric de funcions que poden ser utilitzades pels desenvolupadors per desplegar aplicacions P2P. No obstant això, encara que el seu disseny es va centrar en qüestions com ara l'escalabilitat o el rendiment general, no va tenir en compte la seguretat. Aquest treball proposa un marc de seguretat, adaptat específicament a la idiosincràsia del JXTAOverlay.At present time, the maturity of P2P research field has pushed through new problems such us those related with security. For that reason, security starts to become one of the key issues when evaluating a P2P system and it is important to provide security mechanisms to P2P systems. The JXTAOverlay project is an effort to use JXTA technology to provide a generic set of functionalities that can be used by developers to deploy P2P applications. However, since its design focused on issues such as scalability or overall performance, it did not take security into account. This work proposes a security framework specifically suited to JXTAOverlay¿s idiosyncrasies.En la actualidad, la madurez del campo de la investigación P2P empujado a través de nuevos problemas, relacionados con la seguridad. Por esta razón, la seguridad comienza a convertirse en una de las cuestiones clave en la evaluación de un sistema P2P, y es importante proporcionar mecanismos de seguridad para sistemas P2P. El proyecto JXTAOverlay hace un esfuerzo por utilizar la tecnología JXTA para proporcionar un conjunto genérico de funciones que pueden ser utilizadas por los desarrolladores para desplegar aplicaciones P2P. Sin embargo, aunque su diseño se centró en cuestiones como la escalabilidad o el rendimiento general, no tuvo en cuenta la seguridad. Este trabajo propone un marco de seguridad, adaptado específicamente a la idiosincrasia del JXTAOverlay

Systematizing Decentralization and Privacy: Lessons from 15 Years of Research and Deployments

Decentralized systems are a subset of distributed systems where multiple authorities control different components and no authority is fully trusted by all. This implies that any component in a decentralized system is potentially adversarial. We revise fifteen years of research on decentralization and privacy, and provide an overview of key systems, as well as key insights for designers of future systems. We show that decentralized designs can enhance privacy, integrity, and availability but also require careful trade-offs in terms of system complexity, properties provided, and degree of decentralization. These trade-offs need to be understood and navigated by designers. We argue that a combination of insights from cryptography, distributed systems, and mechanism design, aligned with the development of adequate incentives, are necessary to build scalable and successful privacy-preserving decentralized systems