Combinatorial group theory and public key cryptography

After some excitement generated by recently suggested public key exchange protocols due to Anshel-Anshel-Goldfeld and Ko-Lee et al., it is a prevalent opinion now that the conjugacy search problem is unlikely to provide sufficient level of security if a braid group is used as the platform. In this paper we address the following questions: (1) whether choosing a different group, or a class of groups, can remedy the situation; (2) whether some other "hard" problem from combinatorial group theory can be used, instead of the conjugacy search problem, in a public key exchange protocol. Another question that we address here, although somewhat vague, is likely to become a focus of the future research in public key cryptography based on symbolic computation: (3) whether one can efficiently disguise an element of a given group (or a semigroup) by using defining relations.Comment: 12 page

Using decision problems in public key cryptography

There are several public key establishment protocols as well as complete public key cryptosystems based on allegedly hard problems from combinatorial (semi)group theory known by now. Most of these problems are search problems, i.e., they are of the following nature: given a property P and the information that there are objects with the property P, find at least one particular object with the property P. So far, no cryptographic protocol based on a search problem in a non-commutative (semi)group has been recognized as secure enough to be a viable alternative to established protocols (such as RSA) based on commutative (semi)groups, although most of these protocols are more efficient than RSA is. In this paper, we suggest to use decision problems from combinatorial group theory as the core of a public key establishment protocol or a public key cryptosystem. By using a popular decision problem, the word problem, we design a cryptosystem with the following features: (1) Bob transmits to Alice an encrypted binary sequence which Alice decrypts correctly with probability "very close" to 1; (2) the adversary, Eve, who is granted arbitrarily high (but fixed) computational speed, cannot positively identify (at least, in theory), by using a "brute force attack", the "1" or "0" bits in Bob's binary sequence. In other words: no matter what computational speed we grant Eve at the outset, there is no guarantee that her "brute force attack" program will give a conclusive answer (or an answer which is correct with overwhelming probability) about any bit in Bob's sequence.Comment: 12 page

Rewriting Methods in Groups with Applications to Cryptography

In this thesis we describe how various rewriting methods in combinatorial group theory can be used to diffuse information about group elements, which makes it possible to use these techniques as an important constituent in cryptographic primitives. We also show that, while most group-based cryptographic primitives employ the complexity of search versions of algorithmic problems in group theory, it is also possible to use the complexity of decision problems, in particular the word problem, to claim security of relevant protocols

El amor por las tinieblas : Diseño de una secuencia didáctica para el fortalecimiento de la comprensión de el texto narrativo

Se pretende fortalecer la comprensión lectora de los estudiantes de grado quinto de básica primaria, al diseñar una secuencia didáctica con el texto narrativo “El amor por las tinieblas”, los referentes teóricos que serán abordados tienen como referencia: la lectura, la comprensión lectora, los textos narrativos, el cuento, y la secuencia didáctica; dichos tópicos serán tomados desde varios autores, principalmente desde las teorías de ,Delia Lerner ,Anna Camps, Vigotsky, entre otros, los cuales son una base fundamental para el desarrollo de la presente investigación

Percepciones de los residentes acerca de los impactos del turismo de cruceros en la comunidad: un análisis factorial y de clústeres

This paper explores how residents in the Caribbean city of Cartagena de India regard cruise tourism as affecting their community. Local attitudes and perceptions allowed it to segment the sample into four different opinion groups using a hierarchical cluster analysis. The overall results indicate that the respondents perceive the cruise activity as positive from the economic, social and cultural viewpoint, but results of the research also suggested that the resident population should not be viewed as homogenous in its support for cruise tourism development. Indeed, its opinions regarding cruise tourism and its management were significantly diverse across a variety of socio-economic and demographic indicators. This information has serious implications for the management of tourism in the city and other cruise destinations.Este trabajo explora cómo los residentes de Cartagena de Indias perciben los efectos del turismo de cruceros. Las percepciones y actitudes de los residentes se usaron para segmentar la población en grupos de opinión bien diferenciados a partir de un análisis jerárquico de clústeres. Los resultados generales muestran que los encuestados perciben la actividad de los cruceros positivamente, aunque la investigación también sugiere que la población no debe ser vista homogéneamente en relación al apoyo de dicha actividad. Esta información tiene implicaciones para la gestión del turismo en la ciudad

Angular and polarization trails from effective interactions of Majorana neutrinos at the LHeC

We study the possibility of the LHeC facility to disentangle different new physics contributionsto the production of heavy sterile Majorana neutrinos in the lepton number violating channele−p → l+j + 3jets (lj ≡ e, µ). This is done investigating the angular and polarization trails ofeffective operators with distinct Dirac-Lorentz structure contributing to the Majorana neutrinoproduction, which parameterize new physics from a higher energy scale. We study an asymmetryin the angular distribution of the final anti-lepton and the initial electron polarization effect on thenumber of signal events produced by the vectorial and scalar effective interactions, finding bothanalyses could well separate their contributions.Fil: Duarte, Lucia. UNIVERSIDAD DE LA REPUBLICA (UDELAR);Fil: Zapata, Gabriel Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; ArgentinaFil: Sampayo, Oscar Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; Argentin

Impactos del turismo sobre el crecimiento económico y el desarrollo. El caso de los principales destinos turísticos de Colombia

This paper analyses the effects of tourism on the economic growth and development, focusing on the main tourism regions of Colombia: Antioquia, Bolivar, Bogotá, Magdalena and San Andrés-Providencia of Colombia. For the analysis, the study uses annual data from 1990 to 2006. Firstly, the work presents a quantitative exercise describing the evolution of the participation of the tourism sector in the different regions and its contribution to economic growth. The analysis shows an increasing participation of tourism in the economic growth of each region during the periods 1990-1999 and 2003-2006 and a decresing in the intermediate period. Secondly, the study uses cointegration analysis to evaluate the existence of VEC among real GDP per capita, tourism expenditures and real exchange rates. We show that the causality relationship is positive and unidirectional for all the regions but the values of elasticities are considerable different. This implies that a change in tourism expenditure will produce different effects on the economic growth of the regions

Determinants of Visitor’s Satisfaction to a Cultural Attraction: The Case of the Museum of Antioquia, Colombia

Los museos pueden llegar a competir directamente con otros atractivos culturales dentro de las alternativas de uso del tiempo libre de los visitantes, y de esto han sido conscientes sus gestores. Aunque los museos son principalmente organizaciones sin ánimo de lucro, en las últimas dos décadas éstos se han visto presionados a captar un amplia y diversa audiencia. Características demográficas, actitudes, percepciones y expectativas son aspectos que hacen parte de las dimensiones del conocimiento que se debe tener de los visitantes. El objetivo del presente trabajo consiste en analizar los determinantes del grado de satisfacción de los visitantes de un museo, considerando el caso particular del museo de Antioquia (Colombia). Para ello, se realiza un análisis empírico empleando un modelo logit ordenado, a partir de 410 encuestas realizadas a turistas y residentes que visitan este museo, considerando entre los determinantes características socioeconómicas, de la visita y experiencias de los visitantes. Los resultados muestran que el hecho de ser extranjero, tener mayoría de edad y haber pagado para entrar al museo eleva la probabilidad de caer en una categoría de satisfacción mayor. Por otro lado, una mejor señalización y un mejor trato por parte del personal de las salas elevan la satisfacción del individuo; a la vez que el trato del personal en taquilla no resulta tan relevante.Museums may compete directly with other cultural attractions in the race for capturing the leisure time of visitors and, museums managers have been aware of it. Although museums are primarily non-profit organizations, in the past two decades they have been pressured to capture a wide and diverse audience. Demographic characteristics, attitudes, perceptions and expectations are part of the knowledge that museums must obtain from their visitors. The aim of this paper is to analyze the determinants of the level of satisfaction of visitors in a museum, being the Museum of Antioquia (Colombia) the study case. For it, an empirical analysis is applied using an ordered logit model from 533 surveys of residents and tourists who visit this museum. Socioeconomic characteristics and visitor experience are considered as determinants. The results show that being a foreigner, being older and having paid for entrance increase the likelihood of being in a greater satisfaction category. Likewise, a better signage and treatment by the staff of exhibition rooms influence visitor satisfaction.Fil: Brida, Juan Gabriel. Libre Universidad de Bolzano; Italia;Fil: Monterubbianesi, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahia Blanca. Instituto de Investigaciones Económicas y Sociales del Sur; Argentina;Fil: Zapata Aguirre, Sandra. Institución Universitaria Colegio Mayor de Antioquia; Colombia