CSIC - Institute of Applied Physics

Madrid, Spain

CSIC - Institute of Applied Physics

Madrid, Spain
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Bozzelli L.,Technical University of Madrid | Sanchez C.,IMDEA Madrid Institute for Advanced Studies | Sanchez C.,CSIC - Institute of Applied Physics
Journal of Automated Reasoning | Year: 2017

We introduce Visibly Linear Temporal Logic (VLTL), a linear-time temporal logic that captures the full class of Visibly Pushdown Languages over infinite words. The novel logic avoids fix points and instead provides natural temporal operators with simple and intuitive semantics. We prove that the complexities of the satisfiability and visibly pushdown model checking problems are the same as for other well known logics, like CaRet and the nested word temporal logic NWTL, which in contrast are strictly more limited in expressive power than VLTL. Moreover, formulas of CaRet and NWTL can be translated inductively and in linear-time into VLTL. © 2017 Springer Science+Business Media Dordrecht

Peinado A.,University of Malaga | Fuster-Sabater A.,CSIC - Institute of Applied Physics
Mathematical and Computer Modelling | Year: 2013

In 2002, Mita etal. [1] proposed a pseudorandom bit generator based on a dynamic linear feedback shift register (DLFSR) for cryptographic application. The particular topology there proposed is now analyzed, allowing us to extend the results to more general cases. Maximum period and linear span values are obtained for the generated sequences, while several estimations for autocorrelation and cross-correlation of such sequences are also presented. Furthermore, the sequences produced by DLFSRs can be considered as interleaved sequences. This fact allows us to apply the general interleaved sequence model proposed by Gong and consequently simplify their study. Finally, several remarks are stated regarding DLFSR utilization for cryptographic or code division multiple access (CDMA) applications. © 2011 Elsevier Ltd.

Fuster-Sabater A.,CSIC - Institute of Applied Physics | Caballero-Gil P.,University of La Laguna
Applied Soft Computing Journal | Year: 2011

In this paper, a method of obtaining cryptographic sequences based on discrete time chaotic dynamical systems is presented. The importance of the proposal is due to that such cryptographic sequences are also output sequences of a nonlinear keystream generator known as generalized self-shrinking generator, which is still considered secure for symmetric cryptography. It is remarkable that the linearity of the proposed chaotic model based on additive one-dimensional cellular automata might be used to launch a cryptanalysis against such nonlinear generators. © 2010 Elsevier B.V. All rights reserved.

Prieto J.L.,Technical University of Madrid | Munoz M.,CSIC - Institute of Applied Physics | Martinez E.,University of Salamanca
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The process of injection of a magnetic domain wall (DW) by means of a 25-100 ns current pulse flowing through an adjacent conductive track has been studied in detail. We find that the probability of creating a DW through this method is 100% for a wide range of amplitudes of the current pulse and of the external magnetic field, including zero external magnetic field. Micromagnetic simulations show that the DW is created in the first nanosecond of the pulse, and its movement is strongly influenced by the induced Oersted field, which can reach considerable values, especially in the perpendicular-to-plane direction. The edge roughness and temperature play also a crucial role in determining the type of DW that travels through the wire. Experimentally we show that a map of the probability of injection of a DW by a current pulse can be a very powerful method to check the structural quality of the nanostripe, which has very important practical consequences for research in this area. © 2011 American Physical Society.

Delgado-Mohatar O.,CSIC - Institute of Applied Physics | Fuster-Sabater A.,CSIC - Institute of Applied Physics | Sierra J.M.,Charles III University of Madrid
Ad Hoc Networks | Year: 2011

Sensor networks are ad hoc mobile networks that include sensor nodes with limited computational and communication capabilities. They have become an economically viable monitoring solution for a wide variety of applications. Obviously, security threats need to be addressed and, taking into account its limited resources, the use of symmetric cryptography is strongly recommended. In this paper, a light-weight authentication model for wireless sensor networks composed of a key management and an authentication protocol is presented. It is based on the use of simple symmetric cryptographic primitives with very low computational requirements, which obtains better results than other proposals in the literature. Compared to SPINS and BROSK protocols, the proposal can reduce energy consumption by up to 98% and 67%, respectively. It also scales well with the size of the network, due to it only requiring one interchanged message, independently of the total number of nodes in the network. © 2010 Elsevier B.V. All rights reserved.

Akerman J.,Technical University of Madrid | Munoz M.,CSIC - Institute of Applied Physics | Maicas M.,Technical University of Madrid | Prieto J.L.,Technical University of Madrid
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

This study explores experimentally the stochastic nature of the domain wall depinning in permalloy nanowires using notches of various shapes and depths. The presence of the domain wall in the notch is detected through its anisotropic magnetoresistance (AMR), which is measured with high precision in order to detect even small changes in the domain wall profile. These measurements showed that variations in the depinning field are related with changes, sometimes very small, in the AMR profile, which indicates that small changes in the pinned domain wall profile can affect largely the depinning process. As these small changes are many times unpredictable and uncontrollable, the stochastic nature of the depinning could have negative consequences for practical applications based on permalloy nanowires. © 2010 The American Physical Society.

Masque J.M.,CSIC - Institute of Applied Physics | Maria M.E.R.,Technical University of Madrid
Advances in Theoretical and Mathematical Physics | Year: 2012

Let M → N (resp. C → N) be the fibre bundle of pseudo-Riemannian metrics of a given signature (resp. the bundle of linear connections) on an orientable connected manifold N. A geometrically defined class of firstorder Ehresmann connections on the product fibre bundle M × N C is determined such that, for every connection γ belonging to this class and every DiffN-invariant Lagrangian density Λ on J1(M × N C), the corresponding covariant Hamiltonian Λγ is also DiffN-invariant. The case of DiffN-invariant second-order Lagrangian densities on J2M is also studied and the results obtained are then applied to Palatini and Einstein-Hilbert Lagrangians. © 2012 International Press.

Escuderos M.E.,IFAPA Centro del Llano | Garcia M.,CSIC - Institute of Applied Physics | Jimenez A.,IFAPA Centro del Llano | Horrillo M.C.,CSIC - Institute of Applied Physics
Food Chemistry | Year: 2013

An array of semiconductor sensors has been developed to discriminate virgin olive oil samples based on their organoleptic characteristics. The multisensor, developed at laboratory, is composed by 14 sensing elements of tin dioxide thin layers (doped with Cr and In, and undoped) deposited by the reactive sputtering technique. The sensors are stable and show good repeatability. Off-flavors and extra-virgin olive oil samples, taken at the outlet of the vertical centrifuge of a small experimental olive oil mill and sensory evaluated, have been used. A good discrimination of edible (extra-virgin and virgin) from non-edible (lampante) olive oils has been obtained through the statistical method of principal component analysis (PCA). © 2012 Elsevier Ltd. All rights reserved.

Martinez-Brdalo M.,CSIC - Institute of Applied Physics | Sanchis A.,CSIC - Institute of Applied Physics | Martin A.,CSIC - Institute of Applied Physics | Villar R.,CSIC - Institute of Applied Physics
Physics in Medicine and Biology | Year: 2010

Electronic article surveillance (EAS) devices are widely used in most stores as anti-theft systems. In this work, the compliance with international guidelines in the human exposure to these devices is analysed by using the finite-difference time-domain (FDTD) method. Two sets of high resolution numerical phantoms of different size (REMCOM/Hershey and Virtual Family), simulating adult and child bodies, are exposed to a 10 MHz pass-by panel-type EAS consisting of two overlapping current-carrying coils. Two different relative positions between the EAS and the body (frontal and lateral exposures), which imply the exposure of different parts of the body at different distances, have been considered. In all cases, induced current densities in tissues of the central nervous system and specific absorption rates (SARs) are calculated to be compared with the limits from the guidelines. Results show that induced current densities are lower in the case of adult models as compared with those of children in both lateral and frontal exposures. Maximum SAR values calculated in lateral exposure are significantly lower than those calculated in frontal exposure, where the EAS-body distance is shorter. Nevertheless, in all studied cases, with an EAS driving current of 4 A rms, maximum induced current and SAR values are below basic restrictions. © 2010 Institute of Physics and Engineering in Medicine.

Fuster-Sabater A.,CSIC - Institute of Applied Physics
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

In this paper, a procedure of decomposition of nonlinearly filtered sequences in primary characteristic sequences has been introduced. Such a procedure allows one to analyze structural properties of the filtered sequences e.g. period and linear complexity, which are essential features for their possible application in cryptography. As a consequence of the previous decomposition, a simple constructive method that enlarges the number of known filtered sequences with guaranteed cryptographic parameters has been developed. The procedure here introduced does not impose any constraint on the characteristics of the nonlinear filter. © 2011 Springer-Verlag.

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