Formal security analysis of registration protocols for interactive systems: a methodology and a case of study

In this work we present and formally analyze CHAT-SRP (CHAos based Tickets-Secure Registration Protocol), a protocol to provide interactive and collaborative platforms with a cryptographically robust solution to classical security issues. Namely, we focus on the secrecy and authenticity properties while keeping a high usability. In this sense, users are forced to blindly trust the system administrators and developers. Moreover, as far as we know, the use of formal methodologies for the verification of security properties of communication protocols isn't yet a common practice. We propose here a methodology to fill this gap, i.e., to analyse both the security of the proposed protocol and the pertinence of the underlying premises. In this concern, we propose the definition and formal evaluation of a protocol for the distribution of digital identities. Once distributed, these identities can be used to verify integrity and source of information. We base our security analysis on tools for automatic verification of security protocols widely accepted by the scientific community, and on the principles they are based upon. In addition, it is assumed perfect cryptographic primitives in order to focus the analysis on the exchange of protocol messages. The main property of our protocol is the incorporation of tickets, created using digests of chaos based nonces (numbers used only once) and users' personal data. Combined with a multichannel authentication scheme with some previous knowledge, these tickets provide security during the whole protocol by univocally linking each registering user with a single request. [..]Comment: 32 pages, 7 figures, 8 listings, 1 tabl

El desarollo rural en el contexto de la Unión Europea

Los espacios rurales de la Unión Europea se enfrentan a una importante encrucijada en los próximos años. La reciente aprobación del Reglamento (C.E.) 1698/2005 del Consejo, de 20 de septiembre de 2005, relativo a la ayuda al desarrollo rural a través del Fondo Europeo Agraria de Desarrollo Rural (FEADER) ha supuesto un importante punto de inflexión, apostando, de forma decidida, por los aspectos ambientales ligados a las actividades agrícola, ganadera y forestal, y por la diversificación de la actividad económica y la mejora de la calidad de vida en el conjunto de los espacios rurales. La agricultura, en este nuevo enfoque del desarrollo rural, es esencial, pero no suficiente, para lograr los objetivos y prioridades de una política de desarrollo global y ambiciosa. La participación de los actores del medio rural en la definición y gestión de las políticas es también reconocida en el Reglamento, que consolida definitivamente el enfoque LEADER. Sin embargo, el desarrollo rural sigue considerándose como una política alternativa, que necesita un mayor impulso económico, para el que la modulación de los pagos directos (y su utilización a través del FEADER) puede representar un importante acicate.The rural spaces of the European Union will be facing an important dilemma in the coming years. The recent approval of the Regulation (C.E.) 1698/2005 of the Council of December 30th 2005, relative to the help of the rural development through the Agrarian European Fund of Rural Development (FEADER) creates a key point, which is betting, ultimately, on the environmental as¬pects bound to agricultural activities, as well as on cattle raising and forest, and on the diversification of the economic activity and the improvement of the quality of life in the set of the rural spaces. Agriculture is not enough in this new approach of the rural development that seeks to achieve the goals and priorities of a global and ambitious development policy for itself. The participation of the actors of the rural environment in the definition and management of the policies is also recognized by the Regulation that definitively consolidates the approach of the program of Relations between Activities for the Development of the Rural Economy (LEADER). However, the rural development continues to be considered an alternative policy that needs a greater economic impulse, for which the modulation of the direct payments (and their utilization through Regulation of the Agrarian European Fund of Rural Development (FEADER) can represent an important incentive

Presencia de la literatura fantástica en el cine de David Lynch

Conferencias y Comunicaciones del primer Congreso Internacional de literatura fantástica y ciencia ficción, celebrado del 6 al 9 de mayo de 2008 en la Universidad Carlos III de Madri

Practice-oriented controversies and borrowed epistemic credibility in current evolutionary biology: phylogeography as a case study

Although there is increasing recognition that theory and practice in science are intimately intertwined, philosophy of science perspectives on scientific controversies have been historically focused on theory rather than practice. As a step in the construction of frameworks for understanding controversies linked to scientific practices, here we introduce the notion of borrowed epistemic credibility (BEC), to describe the situation in which scientists, in order to garner support for their own stances, exploit similarities between tenets in their own field and accepted statements or positions properly developed within other areas of expertise. We illustrate the scope of application of our proposal with the analysis of a heavily methods-grounded, recent controversy in phylogeography, a biological subdiscipline concerned with the study of the historical causes of biogeographical variation through population genetics- and phylogenetics-based computer analyses of diversity in DNA sequences, both within species and between closely related taxa. Toward this end, we briefly summarize the arguments proposed by selected authors representing each side of the controversy: the ‘nested clade analysis’ school versus the ‘statistical phylogeography’ orientation. We claim that whereas both phylogeographic ‘research styles’ borrow epistemic credibility from sources such as formal logic, the familiarity of results from other scientific areas, the authority of prominent scientists, or the presumed superiority of quantitative vs. verbal reasoning, ‘theory’ plays essentially no role as a foundation of the controversy. Besides underscoring the importance of strictly methodological and other non-theoretical aspects of controversies in current evolutionary biology, our analysis suggests a perspective with potential usefulness for the re-examination of more general philosophy of biology issues, such as the nature of historical inference, rationality, justification, and objectivity

Mean waiting time in the M/H2/s queue: application to mobile communications Systems

In this paper a procedure to approximately calculate the mean waiting time in the M/H2/s queue is presented. The approximation is heuristic although based in the intuitive symmetry between the deterministic and balanced hyperexponential-2 distributions. The three parameters which fully describe the H2 distribution are considered, so the approximation can also be used for the M/G/s queue when the first three moments are known. If only the first two moments of the holding time distribution are known, the estimation can also be applied accepting a lesser accuracy. The estimation proposed is a closed formula extremely easy to compute and the results are very accurate. This features makes it helpful in the design of mobile telecommunication systems with more than one channel and queueing allowed (like trunking Private Mobile Radio PMR systems), where holding time distributions with coefficients of variation higher than one may appear. As a second stage, the possibility of calls owning a certain level of priority is studied. Two service classes are considered according to a non-preemtive priority scheme (also known as Head Of the Line or HOL). This priority feature is often required in mobile telecommunications systems to improve the access delay of some special calls by degrading the delay suffered by the rest. If the proportion of calls owning priority is kept low, the degradation is shared by many calls and then kept small. In this paper a procedure to estimate the mean waiting time in queue for each priority class is presented. This procedure is also very easy to compute. The environment for which the results of this paper are intended suggests medium or heavy overall load and light priority load (priority proportion is kept low). This is the situation under which the accuracy of the proposed method is checked. Although simulations are necessary in the final phase of the design, the procedure presented here is helpful as a first quick insight into the system performance.Peer ReviewedPostprint (published version

Performance analysis of handoff resource allocation strategies through the state-dependent rejection scheme

The state-dependent rejection scheme (SRS) provides a common framework for analysing existing handoff schemes and for designing new ones easily. Designing new schemes is made simple by determining the appropriate set of state-dependent probabilities. The Markov analysis of SRS is simple and useful for drawing initial conclusions on handoff strategies. The analysis and simulations carried out here demonstrate the capability of SRS to adapt to different mobility and load scenarios and to achieve good performance while targeting quality of service performance metrics.Peer Reviewe

An engineering approximation for the mean waiting time in the M/H2b/s queue

Although the exact solution for the mean waiting time in the M/H2/s queue exists, it requires advanced programming skills and processing capacity. In most engineering problems the offered traffic and its features are known with a certain degree of uncertainty (e.g. traffic is predicted, traffic is not clearly Poisson, etc). In such environments where perfect accuracy is not required, approximations are often used to estimate the performance. For engineering applications, the easiness to compute the estimate is a key factor. The contribution of this paper is a new closed formula to estimate the mean waiting time in the M/H2 b/s queue. The formula is easy to compute and accurate. In contrast with the already existing approximations, the one presented here keeps its validity for mediumhigh coefficients of variation.Peer Reviewe