Structure-Preserving Signatures on Equivalence Classes From Standard Assumptions

Structure-preserving signatures on equivalence classes (SPS-EQ) introduced at ASIACRYPT 2014 are a variant of SPS where a message is considered as a projective equivalence class, and a new representative of the same class can be obtained by multiplying a vector by a scalar. Given a message and corresponding signature, anyone can produce an updated and randomized signature on an arbitrary representative from the same equivalence class. SPS-EQ have proven to be a very versatile building block for many cryptographic applications. In this paper, we present the first EUF-CMA secure SPS-EQ scheme under standard assumptions. So far only constructions in the generic group model are known. One recent candidate under standard assumptions are the weakly secure equivalence class signatures by Fuchsbauer and Gay (PKC\u2718), a variant of SPS-EQ satisfying only a weaker unforgeability and adaption notion. Fuchsbauer and Gay show that this weaker unforgeability notion is sufficient for many known applications of SPS-EQ. Unfortunately, the weaker adaption notion is only proper for a semi-honest (passive) model and as we show in this paper, makes their scheme unusable in the current models for almost all of their advertised applications of SPS-EQ from the literature. We then present a new EUF-CMA secure SPS-EQ scheme with a tight security reduction under the SXDH assumption providing the notion of perfect adaption (under malicious keys). To achieve the strongest notion of perfect adaption under malicious keys, we require a common reference string (CRS), which seems inherent for constructions under standard assumptions. However, for most known applications of SPS-EQ we do not require a trusted CRS (as the CRS can be generated by the signer during key generation). Technically, our construction is inspired by a recent work of Gay et al. (EUROCRYPT\u2718), who construct a tightly secure message authentication code and translate it to an SPS scheme adapting techniques due to Bellare and Goldwasser (CRYPTO\u2789)

QDB: A new database of plasma chemistries and reactions

One of the most challenging and recurring problems when modeling plasmas is the lack of data on the key atomic and molecular reactions that drive plasma processes. Even when there are data for some reactions, complete and validated datasets of chemistries are rarely available. This hinders research on plasma processes and curbs development of industrial applications. The QDB project aims to address this problem by providing a platform for provision, exchange, and validation of chemistry datasets. A new data model developed for QDB is presented. QDB collates published data on both electron scattering and heavy-particle reactions. These data are formed into reaction sets, which are then validated against experimental data where possible. This process produces both complete chemistry sets and identifies key reactions that are currently unreported in the literature. Gaps in the datasets can be filled using established theoretical methods. Initial validated chemistry sets for SF 6 /CF 4 /O 2 and SF 6 /CF 4 /N 2 /H 2 are presented as examples

Sample-based Spectral Mapping around Landing Sites on the Moon—Lunar Timescale Part 1

Studying the geology of a terrestrial body and its evolution requires being able to set up a chronology. Crater statistics is a powerful tool to do so. However, calibration of this method, which is derived on the Moon, requires properly defined geological units, large enough for reliable crater statistics, and dated samples representative of these geological units. Yet, little effort has been put into choosing a representative set of lunar mission units and samples based on spectral information. Therefore, accuracy and precision of so-called cratering-chronology models remain limited. Here, we analyzed near-infrared orbital data to suggest a geological unit as a reference unit for Apollo 11, 12, 14–17 and Luna 16, 20, and 24 landing sites. We used near-infrared spectral information from orbital data and laboratory measurements to identify the set of samples that is the most representative of the landing-site reference units. We now provide spectrally constrained reference units, for which crater frequencies can be derived, and our sample recommendation will assign the reference age for updating the currently existing cratering-chronology models. We highlight that determining a reference geological unit in the highlands of the Moon is challenging because of the very nature of the terrain, while it is more straightforward for mare units. However, ejecta presence on these mare units comprises solvable challenges

First results on PEMFC diagnosis by electrochemical noise

This paper evaluates electrochemical noise (EN) technique as a possible tool for the diagnosis of Proton Exchange Membrane Fuel Cells (PEMFC) during operation. EN was employed to survey PEM single cell under various operating conditions at different humidification levels so as to focus on flooding or drying tendencies. Data was investigated in the frequency domain by means of power spectrum densities that showed to be sensitive to changes in the PEMFC operating conditions. EN seems an interesting way for an innovative and non-invasive on-line diagnosis tool. Keywords: PEMFC, Electrochemical noise, PSD, Diagnosi

Laser creation of aluminium plasma from a solid target: A model

International audienceSeveral phenomena are evolving at the same time in laser-induced plasmas. Modelling the creation phase of this kind of plasma implies to understand these phenomena and their interactions. A 1D model was elaborated with the purpose of providing a complete description of the ablation of an aluminium alloy target. Phenomena as solid heating, vaporisation step vapour excitation and ionisation processes, among others, were taken into account. The plasma was assumed to have stored energy in more than one hundred level of Al, Al + , Al ++ , Al +++ and free electrons interacting through five processes. In this paper we propose to describe influences of the multiphoton ionisation and target surface temperature from ambient to critical temperature

Cartographie du remplissage glaciaire passé de Valles Marineris, Mars

National audienc

Deep alteration between Hellas and Isidis Basins

Recent investigations of alteration of martian crustal outcrops suggest putative crustal hydrothermal systems, which are favorable environments for the emergence of life. In this study, we perform an analysis of the CRISM targeted observations covering crustal outcrops in the region between the Hellas and Isidis basins with the goal of investigating the alteration phases. Over the wide studied region, we detect the presence of possible serpentines, chlorites, smectites and carbonates. These detections occur within ejecta blankets, crater walls and central uplifts of impact craters. We investigate the relation between the observed associations of minerals and the ages of the impact craters assessed by crater count. No clear relation is observed. We also investigate the relationship between the group of detected mineral and the pre-impact depth of the studied outcrops assessed from the size of the impact craters. This method allows us to reconstruct the pre-impact cross-section. We suggest that alteration of the first 7 km of the crust between the Hellas and Isidis basins may have undergone alteration processes. (C) 2015 Elsevier Inc. All rights reserved

Diagnosis and modelling of proton-exchange-membrane fuel cell via electrochemical-impedance-spectroscopy and Acoustic-Emission measurements

International audienc