Breaking the t<n/3t< n/3 Consensus Bound: Asynchronous Dynamic Proactive Secret Sharing under Honest Majority

A proactive secret sharing scheme (PSS), expressed in the dynamic-membership setting, enables a committee of n holders of secret-shares, dubbed as players, to securely hand-over new shares of the same secret to a new committee. We dub such a sub-protocol as a Refresh. All existing PSS under an honest majority, require the use of a broadcast (BC) in each refresh. BC is costly to implement, and its security relies on timing assumptions on the network. So the privacy of the secret and/or its guaranteed delivery, either depend on network assumptions, or, on the reliability of a public ledger. By contrast, PSS over asynchronous channels do not have these constraints. However, all of them (but one, with exponential complexity) use asynchronous verifiable secret sharing (AVSS) and consensus (MVBA and/or ACS), which are impossible under asynchrony beyond t<n/3 corruptions, whatever the setup. We present a PSS, named asynchronous-proactive secret sharing (APSS), which is the first PSS under honest majority with guaranteed output delivery in a completely asynchronous network. More generally, APSS allows any flexible threshold $t<n$, such that privacy and correctness are guaranteed up to t corruptions, and liveness as soon as $t+1$ players behave honestly. Correctness can be lifted to any number of corruptions, provided a linearly homomorphic commitment scheme. Moreover, each refresh completes at the record speed of $2\delta$, where $\delta$ is the actual message delivery delay. APSS demonstrates that proactive refreshes are possible as long as players of the initial committee only, have a common view on a set of (publicly committed or encrypted) shares. Despite not providing consensus on a unique set of shares, APSS surprisingly enables the opening of any linear map over secrets { non-interactively, without consensus }. This, in turn, applies to threshold signing, decryption and randomness generation. APSS can also be directly integrated into the asynchronous Schnorr threshold signing scheme Roast [CCS\u2722]. Of independent interest, we: - provide the first UC formalization (and proof) of proactive AVSS, furthermore for arbitrary thresholds; - provide additional mechanisms enabling players of a committee to start a refresh then erase their old shares, synchronously up to $\delta$ from each other; - improve by 50x the verification speed of the NIZKs of encrypted re-sharing of [Cascudo et al, Asiacrypt\u2722], by using novel optimizations of batch Schnorr proofs of knowledge. We demonstrate efficiency of APSS with an implementation which uses this optimization as baseline

Reassessment of cell to module gains and losses: Accounting for the current boost specific to cells located on the edges

The power produced by a photovoltaic module is not simply the sum of the powers of its constituents cells. The difference stems from a number of so-called “cell-to-module” (CTM) gain or loss mechanisms. These are getting more and more attention as improvements in cell efficiency are becoming harder to achieve. This work focuses on two CTM mechanisms: the gain due to the recapture of light hitting the apparent backsheet in the “empty” spaces around the cells and the loss from the serial connection of “mismatched” cells i.e. with different maximum power points. In general, for insulation purposes, the spaces on the edges of modules are larger than the spacing between cells. This study reveals that, when reflective backsheets are used, these “edge spaces” provide an additional current boost to the cells placed at the edges that can lead to a 0.5% gain in the output power of modules (with 60 or 72 cells). This location-dependent current boost adds to the usual variations in cell characteristics dictated by the binning size and results in larger “cell-to-cell mismatch losses”. However, the simulations reveal that for short-circuit current bin size smaller than 5%, this additional mismatch loss is lower than 0.05%. All considered, this study demonstrates that the spaces at the edges of PV modules have a significant impact on the cell to module ratios (≈+0.5%abs or ≈16% of the CTM gains) when reflective backsheets are used

The Exploration of Effects of Chinese Cultural Values on the Attitudes and Behaviors of Chinese Restaurateurs Toward Food Safety Training

Citation: Liu, P., & Kwon, J. (2013). The exploration of effects of Chinese cultural values on the attitudes and behaviors of Chinese restaurateurs toward food safety training. Journal of Environmental Health, 75(10), 38-46.Foodborne illness is a challenge in the production and service of ethnic foods. The purpose of the study described in this article was to explore variables influencing the behaviors of U.S. Chinese restaurant owners/operators regarding the provision of food safety training in their restaurants. Seventeen major Chinese cultural values were identified through individual interviews with 20 Chinese restaurant owners/operators. Most participants felt satisfied with their previous health inspections. Several expressed having difficulty, however, following the health inspectors’ instructions and in understanding the health inspection report. A few participants provided food safety training to their employees due to state law. Lack of money, time, labor/energy, and a perceived need for food safety training were recognized as major challenges to providing food safety training in Chinese restaurants. Videos, case studies, and food safety training handbooks were the most preferred food safety training methods of Chinese restaurant owners/operators, and Chinese was the preferred language in which to conduct the training

Genetic and phenotypic spectrum associated with IFIH1 gain-of-function

IFIH1 gain-of-function has been reported as a cause of a type I interferonopathy encompassing a spectrum of autoinflammatory phenotypes including Aicardi–Goutières syndrome and Singleton Merten syndrome. Ascertaining patients through a European and North American collaboration, we set out to describe the molecular, clinical and interferon status of a cohort of individuals with pathogenic heterozygous mutations in IFIH1. We identified 74 individuals from 51 families segregating a total of 27 likely pathogenic mutations in IFIH1. Ten adult individuals, 13.5% of all mutation carriers, were clinically asymptomatic (with seven of these aged over 50 years). All mutations were associated with enhanced type I interferon signaling, including six variants (22%) which were predicted as benign according to multiple in silico pathogenicity programs. The identified mutations cluster close to the ATP binding region of the protein. These data confirm variable expression and nonpenetrance as important characteristics of the IFIH1 genotype, a consistent association with enhanced type I interferon signaling, and a common mutational mechanism involving increased RNA binding affinity or decreased efficiency of ATP hydrolysis and filament disassembly rate

Calcul effectif de la cohomologie des faisceaux constructibles sur le site étale d'une courbe

This thesis deals with the algorithmic representation of constructible sheaves of abelian groups on the étale site of a variety over an algebraically closed field, as well as the explicit computation of their cohomology. We describe three representations of these sheaves on curves with at worst nodal singularities, as well as algorithms performing various operations (kernels and cokernels of morphisms, pullback and pushforward, internal Hom and tensor product) on these sheaves. We present an algorithm computing the cohomology complex of a locally constant constructible sheaf on a smooth or nodal curve, which in turn allows us to give an explicit description of the functor RGamma(X,-): D^b_c(X,Z/nZ) -> D^b_c(Z/nZ). This description is functorial in the scheme X and the given complex of constructible sheaves. In particular, if X and the sheaf F are obtained by base change from a subfield, we describe the Galois action on the complex RGamma(X,F). We give precise bounds on the number of operations performed by the algorithm computing RGamma(X,F). We also give an explicit description of cup-products in the cohomology of locally constant sheaves over smooth projective curves. Finally, we show how to use these algorithms in order to compute the cohomology groups of a constant sheaf on a smooth surface fibered over the projective line.Cette thèse porte sur la représentation algorithmique des faisceaux constructibles de groupes abéliens sur le site étale d'une variété sur un corps algébriquement clos, ainsi que sur le calcul effectif de leur cohomologie lorsque leur torsion est inversible dans le corps. Nous décrivons trois représentations de ces faisceaux sur les courbes lisses ou nodales, ainsi que des algorithmes permettant d'effectuer un certain nombre d'opérations (noyaux et conoyaux de morphismes, images directes et réciproques, Hom interne et produit tensoriel) sur ces faisceaux. Nous présentons un algorithme de calcul du complexe de cohomologie d'un faisceau localement constant constructible sur une courbe lisse ou nodale X, et en déduisons une description explicite du foncteur RGamma(X,-): D^b_c(X,Z/nZ) -> D^b_c(Z/nZ), fonctoriellement en le schéma X et le complexe constructible considéré. En particulier, si X et le faisceau F proviennent par changement de base d'un sous-corps parfait, nous décrivons l'action de Galois sur le complexe (X,F) calculé. Nous donnons des bornes précises sur le nombre d'opérations effectuées par l'algorithme calculant RGamma(X,F). Nous donnons également une description explicite des cup-produits dans la cohomologie des faisceaux localement constants sur les courbes projectives lisses. Enfin, nous indiquons comment employer ces algorithmes pour calculer la cohomologie d'un faisceau constant sur une surface lisse fibrée sur la droite projective

Calcul effectif de la cohomologie des faisceaux constructibles sur le site étale d'une courbe

This thesis deals with the algorithmic representation of constructible sheaves of abelian groups on the étale site of a variety over an algebraically closed field, as well as the explicit computation of their cohomology. We describe three representations of such sheaves on curves with at worst nodal singularities, as well as algorithms performing various operations (kernels and cokernels of morphisms, pullback and pushforward, internal Hom and tensor product) on these sheaves. We present an explicit expression as well as an algorithm computing the cohomology complex of a locally constant constructible sheaf on a smooth or nodal curve, which in turn allows us to give an explicit description of the functor RGamma(X,-). This description is functorial in the scheme X and the given complex of constructible sheaves. In particular, for schemes and sheaves obtained by base change from a subfield, we describe the Galois action on the cohomology complex. We give precise bounds on the number of operations performed by the algorithm computing this complex. We also give an explicit description of cup-products in the cohomology of locally constant constructible sheaves over smooth projective curves. Finally, we show how to use these algorithms in order to compute the cohomology groups of a constant sheaf on a smooth surface fibered over the projective line.Cette thèse porte sur la représentation algorithmique des faisceaux constructibles de groupes abéliens sur le site étale d'une variété sur un corps algébriquement clos, ainsi que sur le calcul effectif de leur cohomologie lorsque leur torsion est inversible dans le corps. Nous décrivons trois représentations de ces faisceaux sur les courbes lisses ou nodales, ainsi que des algorithmes permettant d'effectuer un certain nombre d'opérations (noyaux et conoyaux de morphismes, images directes et réciproques, Hom interne et produit tensoriel) sur ces faisceaux. Nous présentons une expression explicite et un algorithme de calcul du complexe de cohomologie d'un faisceau localement constant constructible sur une courbe lisse ou nodale X, et en déduisons une description explicite du foncteur RGamma(X,-), fonctorielle en le schéma X et le complexe constructible considéré. En particulier, si le schéma et le faisceau considérés proviennent par changement de base d'un sous-corps parfait, nous décrivons l'action de Galois sur le complexe de cohomologie calculé. Nous donnons des bornes explicites sur le nombre d'opérations effectuées par l'algorithme calculant ce complexe. Nous donnons également une description explicite des cup-produits dans la cohomologie des faisceaux localement constants constructibles sur les courbes projectives lisses. Enfin, nous indiquons comment déduire de ces algorithmes une façon de calculer la cohomologie d'un faisceau constant sur une surface lisse fibrée sur la droite projective

Explicit computation of the cohomology of constructible sheaves on the étale site of a curve

Cette thèse porte sur la représentation algorithmique des faisceaux constructibles de groupes abéliens sur le site étale d'une variété sur un corps algébriquement clos, ainsi que sur le calcul effectif de leur cohomologie lorsque leur torsion est inversible dans le corps. Nous décrivons trois représentations de ces faisceaux sur les courbes lisses ou nodales, ainsi que des algorithmes permettant d'effectuer un certain nombre d'opérations (noyaux et conoyaux de morphismes, images directes et réciproques, Hom interne et produit tensoriel) sur ces faisceaux. Nous présentons un algorithme de calcul du complexe de cohomologie d'un faisceau localement constant constructible sur une courbe lisse ou nodale X, et en déduisons une description explicite du foncteur RGamma(X,-): D^b_c(X,Z/nZ) -> D^b_c(Z/nZ), fonctoriellement en le schéma X et le complexe constructible considéré. En particulier, si X et le faisceau F proviennent par changement de base d'un sous-corps parfait, nous décrivons l'action de Galois sur le complexe (X,F) calculé. Nous donnons des bornes précises sur le nombre d'opérations effectuées par l'algorithme calculant RGamma(X,F). Nous donnons également une description explicite des cup-produits dans la cohomologie des faisceaux localement constants sur les courbes projectives lisses. Enfin, nous indiquons comment employer ces algorithmes pour calculer la cohomologie d'un faisceau constant sur une surface lisse fibrée sur la droite projective.This thesis deals with the algorithmic representation of constructible sheaves of abelian groups on the étale site of a variety over an algebraically closed field, as well as the explicit computation of their cohomology. We describe three representations of these sheaves on curves with at worst nodal singularities, as well as algorithms performing various operations (kernels and cokernels of morphisms, pullback and pushforward, internal Hom and tensor product) on these sheaves. We present an algorithm computing the cohomology complex of a locally constant constructible sheaf on a smooth or nodal curve, which in turn allows us to give an explicit description of the functor RGamma(X,-): D^b_c(X,Z/nZ) -> D^b_c(Z/nZ). This description is functorial in the scheme X and the given complex of constructible sheaves. In particular, if X and the sheaf F are obtained by base change from a subfield, we describe the Galois action on the complex RGamma(X,F). We give precise bounds on the number of operations performed by the algorithm computing RGamma(X,F). We also give an explicit description of cup-products in the cohomology of locally constant sheaves over smooth projective curves. Finally, we show how to use these algorithms in order to compute the cohomology groups of a constant sheaf on a smooth surface fibered over the projective line

Evaluation subjective appliquée à la notation d'étudiants

L'évaluation d'un travail dans le cadre de jurys est un processus faisant appel à l'évaluation subjective. Nous proposons une méthode de synthèse d'évaluation d'avis d'experts à partir d'une interface web appliquée à l'agrégation de notes d'un jury de lecture de projets tuteurés. Nous explicitons le contexte qui a généré cette étude et la méthodologie de développement. Enfin, nous montrons l'application finale

Definition and verification of functional safety concepts for the definition of safe logical architectures

International audienceEvolving customer expectations, particularly growing concerns for safety, and the development of autonomous vehicles imply the development of many interconnected functions. To meet the expectations of system performances and to respect safety standards like ISO 26262, systems engineering and safety analysis have to be better integrated. In this paper we propose a conceptual framework and a method to define and verify the functional view of the logical architectures from a safety point of view

Quantifying and modeling the impact of interconnection failures on the electrical performance of crystalline silicon photovoltaic modules

Failures in the metallic interconnections are among the main degradation modes for photovoltaic modules. Fatigue accumulation due to thermomechanical stresses can result in deterioration of the solder joints or in broken ribbons. In this paper, we first quantify experimentally how the module performance is affected when one or more cell interconnect ribbons are cut or disconnected. For this purpose, we manufactured a set of minimodules, composed by six monocrystalline silicon cells with three bus bars connected in series. Cells were encapsulated in a glass/backsheet construction, employing a polymeric (ETFE) backsheet that can be easily opened. We then sequentially cut one or more ribbons. We observe that the power loss strongly depends on the ribbon's position with respect to the cell (external or central ribbon). In a second step, we implemented an electrical model in LT‐SPICE where the solar cell is composed by three subcells (as the number of cell bus bars) and show that this model is able to reproduce the experimental results with a good accuracy. We then use the model to demonstrate that these results are directly transferable to the case of large‐area modules composed of 60 or 72 cells. Finally, we analyze the case when the disconnections are randomly distributed in the module. As a first approximation, a module with 10% of disconnections has a Pmax variation between −1.34% and −2.75% in average, while 20% of disconnections lead to a Pmax variation in the range of −2.83% and −5.64%