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Peinado A.,University of Malaga | Munilla J.,University of Malaga | Fuster-Sabater A.,Institute Tecnologias Fisicas Y Of La Informacion
Sensors (Switzerland) | Year: 2015

This letter is the reply to: Remarks on Peinado et al.’s Analysis of J3Gen by J. Garcia-Alfaro, J. Herrera-Joancomartí and J. Melià-Seguí published in Sensors 2015, 15, 6217–6220. Peinado et al. cryptanalyzed the pseudorandom number generator proposed by Melià-Seguí et al., describing two possible attacks. Later, Garcia-Alfaro claimed that one of this attack did not hold in practice because the assumptions made by Peinado et al. were not correct. This letter reviews those remarks, showing that J3Gen is anyway flawed and that, without further information, the interpretation made by Peinado et al. seems to be correct. © 2015 by the authors; licensee MDPI, Basel, Switzerland. Source

Cardell S.D.,University of Alicante | Fuster-Sabater A.,Institute Tecnologias Fisicas Y Of La Informacion
Procedia Computer Science | Year: 2015

In this work, we propose a cryptanalysis of the nonlinear sequence generator called the shrinking generator. The output sequence of this cryptographic generator, the shrunken sequence, can be modelled as one of the output sequences of linear cellular automata (CA). The shrunken sequence and the other sequences generated by the CA can be reduced to a combination of PN-sequences generated by the same characteristic polynomial. Therefore, all these PN-sequences are the same but shifted. We propose an efficient cryptanalysis that takes advantage of the linearity of these PN-sequences and the CA. © The Authors. Published by Elsevier B.V. Source

Peinado A.,University of Malaga | Munilla J.,University of Malaga | Fuster-Sabater A.,Institute Tecnologias Fisicas Y Of La Informacion
Sensors (Switzerland) | Year: 2014

This paper analyzes the cryptographic security of J3Gen, a promising pseudo random number generator for low-cost passive Radio Frequency Identification (RFID) tags. Although J3Gen has been shown to fulfill the randomness criteria set by the EPCglobal Gen2 standard and is intended for security applications, we describe here two cryptanalytic attacks that question its security claims: (i) a probabilistic attack based on solving linear equation systems; and (ii) a deterministic attack based on the decimation of the output sequence. Numerical results, supported by simulations, show that for the specific recommended values of the configurable parameters, a low number of intercepted output bits are enough to break J3Gen. We then make some recommendations that address these issues. © 2014 by the authors; licensee MDPI, Basel, Switzerland. Source

Martinez-Valdez R.,CINVESTAV | Ramos Fernandez A.,Institute Tecnologias Fisicas Y Of La Informacion | Vera Hernandez A.,CINVESTAV | Leija Salas L.,CINVESTAV
International Journal of Hyperthermia | Year: 2015

Purpose: The aim of this study was to design an applicator for haemostasis usage needing lower acoustic intensities (<880 W/cm2) than in previous devices intended for it, which is based on ultrasound propagation FEM modelling using a 2-MHz HIFU transducer. Materials and methods: Acoustic field characterisation and numerical simulations in water were performed with and without the proposed applicator. Parameters such as form factor, ellipsoidal shape ratio, and Euclidean distance were used (among others) to compare simulated data with transducer measurements without applicator. A low density polyethylene cone was manufactured from geometries validated from acoustic field modelling. The hollow cone was filled with 10% polyacrylamide gel as a coupling medium with liver phantom or chicken liver. Focal temperature was measured with a thermocouple embedded in the phantom for 1–20 W driving powers for 120 s. Standing wave ratios (SWR) were used as coupling indexes. Ex vivo experimentation in chicken liver was made at 10–20 W. Results: Simulated acoustic patterns showed good concordance with measurements. Experimental focal distance was 20.72 ± 0.24 mm, while the simulated was 19.79 mm (≈4% error). SWR at low power were: 2.01 with transducer emitting in air, 1.53 at applicator tip, and 1.35 after phantom placement. Average SWR at high power was 1.31. Similarity of percentages for data comparison in focal plane was over 60%. Maximum temperature measured at focus was 88.7 °C with 20 W after 85 s. Conclusions: Temperatures reached at focus suggest that this applicator has good efficiency, which notably reduces the power typically needed for haemostasis effect. © 2015 Taylor & Francis. Source

Rosado Maria E.,Technical University of Madrid | Munoz Masque J.,Institute Tecnologias Fisicas Y Of La Informacion
Differential Geometry and its Application | Year: 2014

Second-order Lagrangian densities admitting a first-order Hamiltonian formalism are studied; namely, i) necessary and sufficient conditions for the Poincaré-Cartan form of a second-order Lagrangian on an arbitrary fibred manifold p:E→N to be projectable onto J1E are explicitly determined; ii) for each of such Lagrangians, a first-order Hamiltonian formalism is developed and a new notion of regularity is introduced; iii) the variational problems of this class defined by regular Lagrangians are proved to be involutive. © 2014 Elsevier B.V.. Source

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