How to grant anonymous access

[EN] In this paper, we propose three protocols to share, among a set of N competing entities, the responsibility to grant anonymous access to a resource. The protocols we propose vary in their settings to take into account central or distributed registration. We prove that any subset of guardian authorities can neither tamper with, nor forge, new access-key tokens. Besides, two of the methods we propose are resistant to the eventual appearance of quantum computers. The protocols we propose permit new approaches for cryptographic applications such as electronic voting or blockchain access.Larriba, AM.; López Rodríguez, D. (2023). How to grant anonymous access. IEEE Transactions on Information Forensics and Security. 18:613-625. https://doi.org/10.1109/TIFS.2022.32265616136251

SUVS: Secure Unencrypted Voting Scheme

[EN] In this paper, we propose a light-weight electronic voting protocol. The approach used by our protocol to conceal the ballots does not imply encryption, and guarantees the privacy of the direction of the vote unless all the contestants (parties) agree to do so. Our method is based on the division of the ballot into different pieces of information, which separately reveal no information at all, and that can be latter aggregated to recover the original vote. We show that, despite its simplicity, this scheme is powerful, it does not sacrifice any of the security properties demanded in a formal electronic voting protocol, and, furthermore, even in post-quantum scenarios, neither the casted votes can be tampered with, nor the identity of any elector can be linked with the direction of her vote.Results related to Spanish Patent Application number P202131209.Larriba, AM.; López Rodríguez, D. (2022). SUVS: Secure Unencrypted Voting Scheme. Informatica. 33(4):749-769. https://doi.org/10.15388/22-INFOR50374976933

Efectos de la dolarización en América Latina

In this study we analyzed the performance of the main macroeconomic variables of Latin American dollarized countries compared to those countries in the regions that maintained their own currency as legal tender. With the inclusion of all dollarized economies in the region as the sample and 17 years of data (1995-2012), this research found that dollarized countries, compared to non-dollarized countries in Latin America: (1) are not significantly different in terms of growth (GDP); (2) are not significantly different in terms of inflation; (3) have a higher current account deficit; (4) their primary deficit is not significantly different; and finally (5) a higher level of gross debt-to-GDP.En este estudio analizamos el desempeño sobre las principales variables macroeconómicas de los países dolarizados de América Latina en comparación con los países de la región que han mantenido su moneda propia como moneda de curso legal. Con la inclusión de todas las economías dolarizadas de la región y un periodo de estudio de 17 años (1995-2012), esta investigación encontró que en Latinoamérica los países dolarizados en comparación con los países no dolarizados registran: (1) crecimiento del Producto Interno Bruto (PIB) no significativamente distinto; (2) un índice de inflación no significativamente distinto; (3) un mayor déficit de cuenta corriente; (4) un déficit primario no significativamente distinto; (5) un mayor nivel de deuda bruta con respecto al PIB

Grammatical inference of directed acyclic graph languages with polynomial time complexity

[EN] In this paper we study the learning of graph languages. We extend the well-known classes of k-testability and k-testability in the strict sense languages to directed graph languages. We propose a grammatical inference algorithm to learn the class of directed acyclic k- testable in the strict sense graph languages. The algorithm runs in polynomial time and identifies this class of languages from positive data. We study its efficiency under several criteria, and perform a comprehensive experimentation with four datasets to show the validity of the method. Many fields, from pattern recognition to data compression, can take advantage of these results.Gallego, A.; López Rodríguez, D.; Calera-Rubio, J. (2018). Grammatical inference of directed acyclic graph languages with polynomial time complexity. Journal of Computer and System Sciences. 95:19-34. https://doi.org/10.1016/j.jcss.2017.12.002S19349

A sufficient condition to polynomially compute a minimum separating DFA

This is the author’s version of a work that was accepted for publication in Information Sciences. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Information Sciences 370–371 (2016) 204–220. DOI 10.1016/j.ins.2016.07.053.The computation of a minimal separating automaton (MSA) for regular languages has been studied from many different points of view, from synthesis of automata or Grammatical Inference to the minimization of incompletely specified machines or Compositional Verification. In the general case, the problem is NP-complete, but this drawback does not prevent the problem from having a real application in the above-mentioned fields. In this paper, we propose a sufficient condition that guarantees that the computation of the MSA can be carried out with polynomial time complexity. © 2016 Elsevier Inc. All rights reserved.Vázquez-De-Parga Andrade, M.; García Gómez, P.; López Rodríguez, D. (2016). A sufficient condition to polynomially compute a minimum separating DFA. Information Sciences. 370-371:204-220. doi:10.1016/j.ins.2016.07.053S204220370-37

DFA minimization: Double reversal versus split minimization algorithms

“NOTICE: this is the author’s version of a work that was accepted for publication in Theoretical Computer Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published inTheoretical Computer Science, [Volume 583, 7 June 2015, Pages 78–85] DOI 10.1016/j.tcs.2015.04.002In this paper, we show the relationship between the two most widely used approaches for the minimization of deterministic finite automata: minimization by split of partitions and minimization by double reversal. Even though the double reversal approach has usually been considered to be unconventional with respect to the more common split approach, we show that any double reversal minimization algorithm can be related to a split minimization algorithm and vice versa.García Gómez, P.; López Rodríguez, D.; Vázquez-De-Parga Andrade, M. (2015). DFA minimization: Double reversal versus split minimization algorithms. Theoretical Computer Science. 583:78-85. doi:10.1016/j.tcs.2015.04.002788558

Experiencia de clase inversa en el grado de ingeniería informática

La amplia disponibilidad de herramientas de generación de contenido multimedia hace posible la incorporación de nuevos recursos que complementen la actividad habitual en el aula. En la experiencia que se expone, se analizaron los recursos que existían relacionados con la materia de Teoría de Autómatas del Grado de Informática de la Universidad Politécnica de Valencia. Este análisis permitió detectar algunos aspectos clave que no eran convenientemente asimilados por el alumnado. Para cada uno de estos se elaboró material audiovisual que presentaba el contenido así como ejercicios de autoevaluación a realizar antes de la clase presencial. Se comprobó que el efecto de facilitar de forma anticipada al estudiante de este material permite al alumno, si bien en principio no completamente, trabajar ciertos conceptos, permitiendo plantear las dudas de forma más orientada. Pese a que el grupo piloto de esta experiencia estaba formado exclusivamente por voluntarios, lo que puede suponer un sesgo en la valoración, la experiencia se considera muy positiva

Non-additive electronic polarizabilities of ionic liquids: charge delocalization effects

Electronic charge delocalization on the molecular backbones of ionic liquid-forming ions substantially impacts their molecular polarizabilities. Density functional theory calculations of polarizabilities and volumes of many cations and anions are reported and applied to yield refractive indices of 1216 ionic liquids. A novel expression for the precise estimation of the molecular volumes of the ionic liquids from simulation data is also introduced, adding quadratic corrections to the usual sum of atomic volumes. Our significant findings include i) that the usual assumption of uniform, additive atomic polarizabilities is challenged when highly mobile electrons in conjugated systems are present, and ii) that cations with conjugated large carbon chains can be used together with anions for the design of ionic liquids with very high refractive indices. A novel relation for the polarizability volume is reported together with a refractive index map made up of the studied ionic liquidsThis work was supported by Ministerio de Economia y Competitividad (MINECO) and FEDER Program through the project MAT2017-89239-C2-1-P; Xunta de Galicia and FEDER (ED431D 2017/06, ED431E2018/08, GRC 508 ED431C 2020/10). C. D. R. F. thanks the support of Xunta de Galicia through the grant ED481A-2018/032. We also thank the Centro de Supercomputacion de Galicia (CESGA) facility, Santiago de Compostela, Galicia, Spain, for providing the computational resources employed in this workS

Bibliografía [Cuadernos del Instituto Antonio de Nebrija de estudios sobre la Universidad. 2005, nº 8]

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Charge delocalization and hyperpolarizability in ionic liquids

In this work the role that charge delocalization plays in the non-linear optical response of ionic liquids is evaluated. The first hyperpolarizability for the non-linear process of second harmonic generation (SHG) and second hyperpolarizability for the non-linear process of electro-optical Kerr-Effect (EOKE) of a large number of ionic liquid forming ions were estimated by means of density functional theory calculations. The results point to that both charge delocalization and molecular geometry are the key features that govern their hyperpolarizabilities. Our findings show that some of the most commonly used anions in ionic liquids are expected to present strong non-linear responses while common cations present a much more limited performance. However, this limitation can be overcome by a proper tailoring of cations to present charge delocalization over large molecular regions. The hypothesis of additivity of hyperpolarizabilities in ionic liquids is tested and exploited to obtain a map of second and third order non-linear susceptibilities of 1496 ion combinations. This map is intended to be a guide for future works on the hyperpolarizability of ILsThis work was supported by Ministerio de Economia y Competitividad (MINECO) and FEDER 17 Program through the projects (MAT2017-89239-C2-1-P); Xunta de Galicia and FEDER (GRC ED431C 2016/001, ED431D 2017/06, ED431E2018/08). C. D. R. F. thanks the support of Xunta de Galicia through the grant ED481A-2018/032. We also thank the Centro de Supercomputacion de Galicia (CESGA) facility, Santiago de Compostela, Galicia, Spain, for providing the computational resources employed in this workS