Performance analysis of a security architecture for active networks in Java

Internacional Association of Science and Technology for Development - IASTED, Benalmadena, Spain: 8-10 Septiembre, 2003.Active network technology supports the deployment and execution on the fly of new active services, without interrupting the network operation. Active networks are composed of special nodes (named Active Router) that are able to execute active code to offer the active services. This technology introduces some security threats that must be solved using a security architecture. We have developed a security architecture (ROSA) for an active network platform (SARA). Java has been used as programming language in order to provide portability, but it imposes some performance limitations. This paper analyses the penalty of using Java and proposes some mechanisms to improve the performance of cryptographic implementations in Java.Publicad

Health Support in the Palm of Your Hand: The Role of Technology in Achieving Health Goals

Smartphones have transformed how individuals engage with each other, their leisure time, their work, and even the way they take care of their health. With a qualitative study, we explore how Smartphone apps and social network sites (SNSs) are being used by individuals who want to take care of their health. Findings suggest that individuals are taking advantage of digital technologies to improve their wellbeing in several manners: they use wearable devices to monitor their health and track their physical activity, keep in touch with doctors and health coaches using instant mobile messaging applications, and join virtual communities seeking for advice and support. Being a member of these communities provides certain advantages and rewards that motivate individuals to act on their good intentions toward their health. Given the high rates of adoption of digital technologies, specific social marketing campaigns can be designed to influence health behavior, including health promotion and interventions to help individuals achieve personal goals and improve the quality of their life

DSL line tester using wideband frequency domain reflectometry

Digital subscriber line (DSL) technology is used to provide high speed Internet access and, more recently, video services over twisted pair lines. Telephone lines have impairments that hinder DSL transmission, and some examples are coils and bridge taps that were introduced to aid voice telephony. Other faults are caused by physical damage that results in open circuits, short circuits or water in the line. Telephone companies have to locate and repair these faults to enable high-speed data services. It is also useful to “qualify” lines for future DSL service so that a new customer can be promptly informed whether high-speed service can be supplied. This thesis proposes a novel technique called Wideband frequency domain reflectometry (W-FDR) to accurately locate impairments in telephone lines and estimate the reflection magnitude caused by faults. The measurement produces a result similar to the well-known time domain reflectometer (TDR), however, digital signal processing techniques are now applied to provide enhanced resolution and range. In addition to magnitude, the new technique is able to measure reflection angle which can help to determine the nature of the fault (wire in the cable, broken wires, etc). The measurement technique consists of energizing the line with a sinusoid that increases from 50 kHz to 1300 kHz in discrete frequency steps after coherent detection. The amplitude of the reflected signal is recorded as a function of frequency for 2500 equally spaced frequencies. The Fourier transform and some signal processing are then used to estimate the complex reflection coefficient location of the faults in the telephone line. Lines with up to 4 reflection points have been accurately analyzed. Results show distance measurement accuracy better than 1% and phase measurement accuracy better than 10 degrees for line lengths up to 5 km. These measurements exceed the performance of currently available TDR instruments

Weak convergence of varying measures and Hermite-Padé orthogonal polynomials

23 pages, no figures.-- MSC1991 codes: 42C05, 30E10.MR#: MR1702795 (2000j:42036)Zbl#: Zbl 1058.42503It is known that the common denominator of the Hermite-Padé approximants of a mixed Angelesco-Nikishin system shares orthogonality relations with respect to each function in the system. It is less well known that they also satisfy full orthogonality with respect to a varying measure. This problem motivates our interest in extending the class of varying measures with respect to which weak asymptotics of orthogonal polynomials takes place. In particular, for the case of a Nikishin system, we prove weak asymptotics of the corresponding varying measures.Research by second author (G.L.L.) was supported by Dirección General de Enseñanza Superior under grant PB 96-0120-C03-01 and by INTAS under grant 93-0219 EXT.Publicad

Strong asymptotics for orthogoal polynomials with varying measures and Hermite-Padé approximants

13 pages, no figures.-- MSC1991 codes: 42C05; 30E10.-- Issue title: "Proceedings of the VIIIth Symposium on Orthogonal Polynomials and Their Application" (Seville, Spain, Sep. 1997), edited by Antonio J. Durán.MR#: MR1662686 (99i:42035)Zbl#: Zbl 0933.42017The strong asymptotic behaviour of orthogonal polynomials with respect to a general class of varying measures is given for the case of the unit circle and the real line. These results are used to obtain certain asymptotic relations for the polynomials involved in the construction of Hermite-Padé approximants of a Nikishin system of functions.The research of the second author (G.L.L.) was partially supported by Dirección General de Enseñanza Superior under grant PB 96-0120-C03-01 and by INTAS under grant 93-0219 EXT.Publicad

Convergence of multipoint Padé-type approximants

22 pages, no figures.-- MSC2000 code: 41A21.MR#: MR1820896 (2002a:41014)Zbl#: Zbl 0982.41008Let μ be a finite positive Borel measure whose support is a compact subset K of the real line and let I be the convex hull of K. Let r denote a rational function with real coefficients whose poles lie in \bbfC\setminus I\$ and r(\infty)=0$. We consider multipoint rational interpolants of the function$$f(z)=\int {d\mu(x)\over z-x}+r(z)$$, where some poles are fixed and others are left free. We show that if the interpolation points and the fixed poles are chosen conveniently then the sequence of multipoint rational approximants converges geometrically to f in the chordal metric on compact subsets of$\bbfC\setminus I\$.The second author (G.L.L.) was supported by Dirección General de Enseñanza Superior under Grant PB 96-0120-C03-01 and by INTAS under Grant 93-0219 EXT.Publicad

Convergencia relativa de polinomios ortogonales variantes

12 pages, no figures.-- MSC2000 codes: Primary: 42C05, 30E15; Secondary: 30E10.We consider the relative asymptotic behaviour of orthogonal polynomials with respect to varying measures supported on the real line and the unit circle. The main feature of the results is the generality of the class of measures studied.El trabajo de los dos autores ha sido parcialmente financiado por la Dirección General de Investigación, Ministerio de Ciencia y Tecnología, a través del proyecto BFM2000-0206-C04-01 y además, en el caso de G. López, por el INTAS.Publicad

Mecanismos de Seguridad para una red ad hoc en un entorno urbano

Las redes ad-hoc representan un paradigma de comunicación\ud emergente cuya aplicación se ha propuesto en diversos entornos por su\ud capacidad de autoconfiguración y rápido despliegue. Sin embargo, siguen\ud planteados importantes desafíos relativos a problemas de seguridad. Uno\ud de estos problemas es la gestión y distribución de claves. Se propone la\ud aplicación del protocolo TESLA de distribución de claves a una red adhoc\ud de servicios en un entorno urbano como la alternativa más adecuada\ud frente a otras propuestas en el estado del arte. Finalmente, se realizan\ud pruebas de validación de un estadio preliminar del algoritmo propuesto