A public key cryptosystem based on block upper triangular matrices

We propose a public key cryptosystem based on block upper triangular matrices. This system is a variant of the Discrete Logarithm Problem with elements in a finite group, capable of increasing the difficulty of the problem while maintaining the key size. We also propose a key exchange protocol that guarantees that both parties share a secret element of this group and a digital signature scheme that provides data authenticity and integrity.

An integral security kernel

As the user base of the Internet has grown tremendously, the need for secure services has increased accordingly. Most secure protocols, in digital business and other fields, use a combination of symmetric and asymmetric cryptography, random generators and hash functions in order to achieve confidentiality, integrity, and authentication. Our proposal is an integral security kernel based on a powerful mathematical scheme from which all of these cryptographic facilities can be derived. The kernel requires very little resources and has the flexibility of being able to trade off speed, memory or security; therefore, it can be efficiently implemented in a wide spectrum of platforms and applications, either software, hardware or low cost devices. Additionally, the primitives are comparable in security and speed to well known standards.

A viability analysis of a secure VoIP and instant messaging system on a Pocket PC platform

We propose a secure full-duplex VoIP and instant messaging system on a Pocket PC platform, allowing for session key transport using a public-key protocol and encrypted text or voice communication using a private-key algorithm. The full-duplex VoIP scheme presents good performance for long duration communication over LAN networks.

A secret sharing scheme based on exponentiation in Galois fields

To provide more efficient and flexible alternatives for the applications of secret sharing schemes, this paper describes a threshold sharing scheme based on exponentiation of matrices in Galois fields. A significant characteristic of the proposed scheme is that each participant has to keep only one master secret share which can be used to reconstruct different group secrets according to the number of threshold values.

Costa Blanca: Public Space And Perceived Image as Key to Tourism Competitiveness

Los destinos turísticos tradicionales del litoral español se enfrentan a profundas transformaciones debidas a varios factores, entre los que se encuentran cambios notables en el comportamiento de la demanda y un intenso crecimiento de la competencia a todos los niveles, que puede poner en duda la pervivencia del modelo de desarrollo de estas áreas maduras. Lejos de ser una excepción, la situación que se describe para la Costa Blanca es extrapolable a otros destinos turísticos en otras regiones y en ámbitos urbanos, que se enfrentan al reto de incorporar nuevas estrategias de renovación, diversificación y reestructuración de su tejido urbano y turístico, como clave de reorientación de su ciclo de vida. A partir del estudio del caso de la Costa Blanca, pero con una vocación globalizadora, se tratan a continuación argumentos referidos a los cambios en la demanda turística y de ocio cotidiano, y cómo ello afecta a la necesidad de intervenir de un modo distinto en el diseño y gestión del tejido urbano que perciben los visitantes y residentes. Se percibe de forma clara que se ha de trabajar de un modo distinto tanto la escena urbana como el territorio turístico a partir de la potenciación de valores diferenciadores: por una adecuada intervención urbanística en los espacios públicos con acciones capaces de distinguir al destino de sus competidores, por la incorporación de nuevos elementos de atracción e innovación urbana, o por una gestión más eficiente de los servicios y las funciones urbanas de los destinos turísticos. A partir de varios indicadores se demuestra que la competitividad de los destinos tradicionales, sean áreas costeras o ciudades, ya no sólo reside en sus recursos patrimoniales, litorales o climáticos, sino que su valor diferenciador se vincula también a la calidad urbana percibida y a la capacidad de incorporar en las acciones de futuro las nuevas necesidades de residentes y visitantes, cada vez más exigentes e impredecibles.

A three-stage DEA model to evaluate learning-teaching technical efficiency: Key performance indicators and contextual variables

This study evaluates the technical efficiency of the learning-teaching process in higher education using a three-stage procedure that offers advances in comparison to previous studies and improves the quality of the results. First, it utilizes a multiple stage Data Envelopment Analysis (DEA) with contextual variables. Second, the levels of super efficiency are calculated in order to prioritize the efficiency units. And finally, through sensitivity analysis, the contribution of each key performance indicator (KPI) is established with respect to the efficiency levels without omission of variables. The analytical data was collected from a survey completed by 633 tourism students during the 2011/12, 2012/13 and 2013/14 academic course years. The results suggest that level of satisfaction with the course, diversity of materials and satisfaction with the teacher were the most important factors affecting teaching performance. Furthermore, the effect of the contextual variables was found to be significant.