### Examinando por Materia "CRIPTOGRAFIA"

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Artículo de Publicación Periódica Foundations and applications for secure triggers(2006-02) Futoransky, Ariel; Kargieman, Emiliano; Sarraute, Carlos; Waissbein, ArielMás... "Imagine there is certain content we want to maintain private until some particular event occurs, when we want to have it automatically disclosed. Suppose furthermore, that we want this done in a (possibly) malicious host. Say, the conﬁdential content is a piece of code belonging to a computer program that should remain ciphered and then “be triggered” (i.e., deciphered and executed) when the underlying system satisﬁes a preselected condition which must remain secret after code inspection. In this work we present diﬀerent solutions for problems of this sort, using diﬀerent “declassiﬁcation” criteria, based on a primitive we call secure triggers. We establish the notion of secure triggers in the universally-composable security framework of [Canetti 2001] and introduce several examples. Our examples demonstrate that a new sort of obfuscation is possible. Finally, we motivate its use with applications in realistic scenarios."Más... Artículo de Publicación Periódica A model and query language for temporal graph databases(2021-09) Debrouvier, Ariel; Parodi, Eliseo; Perazzo, Matías; Soliani, Valeria; Vaisman, Alejandro ArielMás... "Graph databases are becoming increasingly popular for modeling different kinds of networks for data analysis. They are built over the property graph data model, where nodes and edges are annotated with property-value pairs. Most existing work in the field is based on graphs were the temporal dimension is not considered. However, time is present in most real world problems. Many different kinds of changes may occur in a graph as the world it represents evolves across time. For instance, edges, nodes, and properties can be added and/or deleted, and property values can be updated. This paper addresses the problem of modeling, storing, and querying temporal property graphs, allowing keeping the history of a graph database. This paper introduces a temporal graph data model, where nodes and relationships contain attributes (properties) timestamped with a validity interval. Graphs in this model can be heterogeneous, that is, relationships may be of different kinds. Associated with the model, a high-level graph query language, denoted T-GQL, is presented, together with a collection of algorithms for computing different kinds of temporal paths in a graph, capturing different temporal path semantics. T-GQL can express queries like “Give me the friends of the friends of Mary, who lived in Brussels at the same time than her, and also give me the periods when this happened”. As a proof-of-concept, a Neo4j-based implementation of the above is also presented, and a client-side interface allows submitting queries in T-GQL to a Neo4j server. Finally, experiments were carried out over synthetic and real-world data sets, with a twofold goal: on the one hand, to show the plausibility of the approach; on the other hand, to analyze the factors that affect performance, like the length of the paths mentioned in the query, and the size of the graph."Más... Artículo de Publicación Periódica A simple linearization of the self-shrinking generator by means of cellular automata(2010) Fúster-Sabater, Amparo; Pazo-Robles, María Eugenia; Caballero-Gil, PinoMás... "In this work, it is shown that the output sequence of a well-known cryptographic generator, the so-called self-shrinking generator, can be obtained from a simple linear model based on cellular automata. In fact, such a cellular model is a linear version of a nonlinear keystream generator currently used in stream ciphers. The linearization procedure is immediate and is based on the concatenation of a basic structure. The obtained cellular automata can be easily implemented with FPGA logic. Linearity and symmetry properties in such automata can be advantageously exploited for the analysis and/or cryptanalysis of this particular type of sequence generator."Más... Tesis de doctorado Sistema de transmisión segura punto a punto y multipunto en medios compartidos(c2015) Ortega, Alfredo Adrián; Álvarez-Hamelin, Ignacio; Grosz, DiegoMás... "En esta tesis se presenta una técnica novedosa de transmisión de datos en redes del tipo difusión de manera criptográﬁcamente segura utilizando técnicas de espectro expandido y corrección de errores. Especíﬁcamente, el esquema propuesto implementa la multiplexación aleatoria de la información transmitida por clientes que comparten un medio de transmisión"Más... Artículo de Publicación Periódica Using linear difference equations to model nonlinear cryptographic sequences(2010-03) Caballero-Gil, Pino; Fúster-Sabater, Amparo; Pazo-Robles, María EugeniaMás... "A new class of linear sequence generators based on cellular automata is here introduced in order to model several nonlinear keystream generators with practical applications in symmetric cryptography. The output sequences are written as solutions of linear difference equations, and three basic properties (period, linear complexity and number of different output sequences) are analyzed."Más...