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TrustSoC-V: An Heterogeneous SoC Architecture for RISC-V, Secure-by-Design
No full textInternational audienc
Les algorithmes des IA peuvent-ils comprendre notre monde ?
No full textInternational audienceLes modèles massifs de langage sont partout : outils bureautiques, moteurs de recherche, applications professionnelles… Ils sont pourtant incapables de comprendre le monde des humains. Les immerger dans des univers factices – mais physiquement réalistes – suffira-t-il à les doter de bon sens
Motoric engagement, but not decision-making, during encoding influences route memory
No full textInternational audienceNavigation aids limit the need for decision-making, possibly hindering memory for routes traveled. We manipulated type of navigation at encoding, within virtual-reality. In the Active condition participants self-initiated decision-making about routes, to find a target, and in the Guided condition followed a pre-defined path overlaid onto virtual streets. In both, they had volitional control using hand-held controllers, allowing head and body rotation in a swivel chair. In the Passive condition they viewed a pre-defined route, with no control of movement. At retrieval, participants were asked to reproduce their exact route from the initial starting point. Route memory was better following Active and Guided encoding than Passive. A visual navigation aid does not impair route memory if volitional movement is maintained
Efficient Adaptive Multi-Level Privilege Partitioning With RTrustSoC
No full textInternational audienceIn recent years, heterogeneous SoCs (comprised of multiple processor cores and programmable logic) have greatly progressed both complexity and performance. From a security point of view, this leads to an expansion of the attack surface exposed to adversaries. To address this issue, in this article, we propose a novel heterogeneous SoC architecture called RTrustSoC. Our proposal includes an innovative fully-reconfigurable post-deployment strategy for partitioning the SoC architecture into multiple exclusion levels (worlds) with customizable degrees of privilege. We aim to provide SoC designers with fine control over the security of the system by segregating trusted hardware components from third-party IPs with ``on-demand'' hardware isolation. Therefore, we expect that an RTrustSoC instance could evolve from a multi-world SoC to a fully trusted platform as IPs progressively develop. RTrustSoC also proposes a dynamic reconfigurable penalty system to monitor the third-party IPs and take measures in case of a detected abnormal behavior. Our experimental testing on an AMD-Xilinx Zynq-7000 SoC-FPGA showed the penalty of the proposed isolation strategy to be small, up to 1% in LUT and 0.7% Flip Flop utilization, thus enabling to an efficient security solution. RTrustSoC introduces a novel design paradigm, evolving from the binary notion of security (trusted vs untrusted) into a flexible set of worlds that can be adapted to any scenario. We demonstrate a real case scenario of RTrustSoC use on time-based cache memory attacks with implementation results
Construction de conditions transparentes pour les guides d'ondes électromagnétiques.
No full textInternational audienceWe are interested in the numerical resolution of diffraction problems in closed electromagnetic waveguides by means of finite elements methods. To proceed, we need to truncate the domain and design adapted transparent conditions on the artificial boundary to avoid spurious reflections.When the guide is homogeneous in the transverse section, this can be done by writing an Electric-to-Magnetic condition based on a modal decomposition of the field. The latter takes a rather simple form thanks to the orthogonality of transverse modes.For guides that are heterogeneous in the transverse section, the transverse modes are no longer orthogonal but satisfy bi-orthogonality relations linked to the Poynting energy flux. Modal decompositions are more delicate to derive and it may happen that certain modes have phase and group velocities of different sign, which prevents the use of Perfectly Matched Layers.Adapting techniques already developed in elasticity, we derive a new transparent condition based on a Poynting-to-Magnetic operator with overlap.To illustrate the method, we present numerical results obtained with Nédélec finite elements using the XLiFE++ library.Nous nous intéressons à la résolution numérique des problèmes de diffraction dans les guides d'ondes électromagnétiques fermés par des méthodes d'éléments finis. Pour ce faire, nous devons tronquer le domaine et concevoir des conditions de transparence adaptées sur la frontière artificielle afin d'éviter les réflexions parasites.Lorsque le guide est homogène en section transversale, cela peut être réalisé en écrivant une condition électrique-magnétique basée sur une décomposition modale du champ. Cette dernière prend une forme relativement simple grâce à l'orthogonalité des modes transversaux.Pour les guides hétérogènes en section transversale, les modes transversaux ne sont plus orthogonaux mais satisfont à des relations de bi-orthogonalité liées au flux d'énergie de Poynting. Les décompositions modales sont plus délicates à dériver et il peut arriver que certains modes aient des vitesses de phase et de groupe de signes différents, ce qui empêche l'utilisation de couches parfaitement appariées.En adaptant des techniques déjà développées en élasticité, nous dérivons une nouvelle condition de transparence basée sur un opérateur de Poynting-magnétique avec recouvrement.Pour illustrer la méthode, nous présentons des résultats numériques obtenus avec des éléments finis Nédélec en utilisant la bibliothèque XLiFE++
Evaluation of tropospheric estimates from CentipedeRTK, a collaborative network of low-cost GNSS stations
No full textInternational audienceAbstract The CentipedeRTK network is a collaborative Global Navigation Satellite System (GNSS) network launched in 2019, consisting mainly of low-cost GNSS receivers and antennas. This network enables free Real-Time Kinematic (RTK) positioning with centimeter accuracy for all users. The raw GNSS measurements from the CentipedeRTK network are routinely archived by the French scientific network RÉseau NAtional GNSS permanent, with the aim of exploiting raw GNSS measurements for geoscience applications. This paper presents a first assessment of the use of this dataset for tropospheric monitoring. We considered all the data provided in 2023 by more than 400 low-cost GNSS stations in mainland France. After selecting the stations with dual-frequency observations over the period, the data of 331 stations were analyzed using precise point positioning , resulting in a set of 265 stations satisfying our screening procedure and providing data covering more than 50% of the year 2023. A first indication of the quality of the analysis is given by the repeatability of the stations, of the order of 2.2 ± 1.1 , 2.1 ± 0.8 and 6.9 ± 2.6 mm respectively on the East, North and Up components. These values are slightly higher than those obtained for nearby conventional stations, especially for the vertical component (5.4 ± 0.8 mm). The tropospheric delays were compared with those retrieved from nearby GNSS reference stations (less than 30 km away) belonging to conventional networks (186 stations considered). The comparison shows a good agreement between low-cost and conventional stations, with a root mean square of differences of 7.4 ± 3.0 mm; a mean bias of 2.7 mm is highlighted and shown to be stable over time; its origin has not yet been determined but its magnitude seems related to the antenna type of the CentipedeRTK stations. In a second step, the integrated water vapor content were derived from the tropospheric delays and compared with those of the European Centre for Medium-range Weather Forecasts fifth reanalysis (ERA5). Only stations located at an altitude less than 100 m around the ERA5 orography were considered (240 stations). The differences between the two techniques are similar to those reported in the literature for traditional networks, with a mean bias of 0.06 ± 0.82 kg m and a mean standard deviation of .48 ± 0.18 kg m . This again confirms the quality of the dataset. Finally, the value of such low-cost stations for monitoring and describing meteorological phenomena is illustrated by the study of an atmospheric river affecting the central–western part of France in December 2023. All these results underline the considerable potential of low-cost GNSS networks in geoscience applications, especially in regions with limited instrumentation. Their role could be particularly important in meteorological or climatological contexts, where GNSS-based water vapor monitoring is widely used
Reconstruction of averaging indicators for highly heterogeneous media
No full textInternational audienceWe propose a new imaging algorithm capable of producing quantitative indicator functions for unknown and possibly highly oscillating media from multistatic far field measurements of scattered fields at a fixed frequency. The algorithm exploits the notion of modified transmission eigenvalues and their determination from measurements. We propose in particular the use of a new modified background obtained as the limit of a metamaterial background. It has the specificity of having a unique non trivial eigenvalue, which is particularly suited for the proposed imaging procedure. We show the efficiency of this new algorithm on some 2D experiments and emphasize its superiority with respect to some clasical approaches such as the Linear Sampling Method
A new class of uniformly stable time-domain Foldy-Lax models for scattering by small particles. Acoustic sound-soft scattering by circles. Extended version
No full textInternational audienceIn this work we study time-domain sound-soft scattering by small circles. Our goal is to derive an asymptotic model for this problem valid when the size of the particles tends to zero. We present a systematic approach to constructing such models, based on a well-chosen Galerkin discretization of a boundary integral equation. The convergence of the method is achieved by decreasing the asymptotic parameter rather than increasing the number of basis functions. For the case of circular obstacles, we prove the second-order convergence of the field error with respect to the particle size. Our findings are illustrated with numerical experiments
Nonlinear Optimization Filters for Stochastic Time-Varying Convex Optimization
No full text22 pagesInternational audienceWe look at a stochastic time-varying optimization problem and we formulate online algorithms to find and track its optimizers in expectation. The algorithms are derived from the intuition that standard prediction and correction steps can be seen as a nonlinear dynamical system and a measurement equation, respectively, yielding the notion of nonlinear filter design. The optimization algorithms are then based on an extended Kalman filter in the unconstrained case, and on a bilinear matrix inequality condition in the constrained case. Some special cases and variations are discussed, notably the case of parametric filters, yielding certificates based on LPV analysis and, if one wishes, matrix sum-of-squares relaxations. Supporting numerical results are presented from real data sets in ride-hailing scenarios. The results are encouraging, especially when predictions are accurate, a case which is often encountered in practice when historical data is abundant
On bounds of the effective behavior of particulate composites with imperfect interface
No full textInternational audienceParticulate composites are considered here as multiphase composite in which the interfaces are imperfect. When the interface mechanical properties are those of a linear elastic material, the minimum of potential and complementary energy is used in order to obtain bounds of effective elastic modulus of the composite. Test displacements or stress fields are build and characterized using Green’s functions of a comparison homogeneous body, polarization fields and extension of the classical Lippmann–Schwinger equations. Then when spatial distribution of phases are known, in particular for isotropic distribution of phases or patterns, a generalization of Hashin–Shtrikman principle is obtained and lower and upper boundsare proposed