Private Multi-party Matrix Multiplication and Trust Computations

This paper deals with distributed matrix multiplication. Each player owns only one row of both matrices and wishes to learn about one distinct row of the product matrix, without revealing its input to the other players. We first improve on a weighted average protocol, in order to securely compute a dot-product with a quadratic volume of communications and linear number of rounds. We also propose a protocol with five communication rounds, using a Paillier-like underlying homomorphic public key cryptosystem, which is secure in the semi-honest model or secure with high probability in the malicious adversary model. Using ProVerif, a cryptographic protocol verification tool, we are able to check the security of the protocol and provide a countermeasure for each attack found by the tool. We also give a randomization method to avoid collusion attacks. As an application, we show that this protocol enables a distributed and secure evaluation of trust relationships in a network, for a large class of trust evaluation schemes.Comment: Pierangela Samarati. SECRYPT 2016 : 13th International Conference on Security and Cryptography, Lisbonne, Portugal, 26--28 Juillet 2016. 201

Generating S-Boxes from Semi-fields Pseudo-extensions

Block ciphers, such as the AES, correspond to a very important family of secret-key cryptosystems. The security of such systems partly relies on what is called the S-box. This is a vectorial Boolean function f : F n 2 ֒→ F n 2 , where n is the size of the blocks. It is often the only non linear opera-tion in the algorithm. The most well-known attacks against block ciphers algorithms are the known-plaintext attacks called differential cryptanal-ysis [4, 10] and linear cryptanalysis [11]. To protect such cryptosystems against linear and differential attacks, S-boxes are designed to fulfill some cryptographic criteria (balancedness, high nonlinearity, high algebraic de-gree, avalanche, or transparency [2, 12]) and are usually defined on finite fields, like F2n [7, 3]. Unfortunately, it seems difficult to find good S-Boxes, at least for bijective ones: random generation does not work [8, 9] and the one used in the AES or Camellia are actually variations around a single function, the inverse function in F2n . Would the latter function have an unforeseen weakness (for instance if more practical algebraic attacks are developped), it would be desirable to have some replacement candidates. For that matter, we propose to weaken a little bit the algebraic part of the design of S-Boxes and use finite semi-fields instead of finite fields to build such S-Boxes. Finite semi-fields relax the associativity and com-mutativity of the multiplication law. While semi-fields of a given order are unique up to isomorphism, on the contrary semi-fields of a given order can be numerous: nowadays, on the one hand, it is for instance easy to generate all the 36 semi-fields of order 2 4 , but, on the other hand, it is not even known how many semi-fields are there of order 2 8 . Therefore, we propose to build S-Boxes via semi-fields pseudo extensions of the form S 2 2 4 , where S 2 4 is any semi-field of order 2 4 , and mimic in this structure the use of the inverse function in a finite field. We report here the construction of 10827 S-Boxes, 7052 non CCZ-equivalent, with maximal nonlinearity, differential invariants, degrees and bit interdependency. Among the latter 2963 had fix points, and among the ones without fix points, 3846 had the avalanche level of AES and 243 1 the better avalanche level of Camellia. Among the latter 232 have a better transparency level than the inverse function on a finite field

Meeting the demand of women affected by ongoing crisis: Increasing contraceptive prevalence in North and South Kivu, Democratic Republic of the Congo

Context Over 20 years of conflict in the DRC, North and South Kivu have experienced cycles of stability and conflict, resulting in a compromised health system and poor sexual and reproductive health outcomes. Modern contraceptive use is low (7.5%) and maternal mortality is high (846 deaths per 100,000 live births). Program partners have supported the Ministry of Health (MOH) in North and South Kivu to provide good quality contraceptive services in public health facilities since 2011. Methods Cross-sectional population-based surveys were conducted in the program areas using a two-stage cluster sampling design to ensure representation in each of six rural health zones. Using MOH population estimates for villages in the catchment areas of supported health facilities, 25 clusters in each zone were selected using probability proportional to size. Within each cluster, 22 households were systematically selected, and one woman of reproductive age (15–49 years) was randomly selected from all eligible women in each household. Results Modern contraceptive prevalence among women in union ranged from 8.4% to 26.7% in the six health zones; current use of long-acting or permanent method (LAPM) ranged from 2.5% to 19.8%. The majority of women (58.9% to 90.2%) reported receiving their current method for the first time at a health facility supported by the program partners. Over half of women in four health zones reported wanting to continue their method for five years or longer. Conclusion Current modern contraceptive use and LAPM use were high in these six health zones compared to DRC Demographic and Health Survey data nationally and provincially. These results were accomplished across all six health zones despite their varied socio-demographic characteristics and different experiences of conflict and displacement. These findings demonstrate that women in these conflict-affected areas want contraception and will choose to use it when good quality services are available to them

A system-engineering model to analyze gap-FRAP in multicellular models.

International audienceIntroduction. Developed in the 70s, the Fluorescence Recovery After Photobleaching (FRAP) technique is based on the progressive increase of fluorescence intensity in a photobleaching area obtained after an illumination with a LASER beam. This enhancement corresponds to the gradual arrival (through gap junctions) of intact fluorescent molecules towards the targeted zone. This widely used method is principally dedicated to study fluorescent constituents mobility in cellular membranes and gap junctional intercellular communication (GJIC) at microscopic scale. Purpose. The final addressed question is to assess the relevance to use GJIC characteristics to discriminate different cancer cell lines. With this aim in view, we have proposed a model-based approach in which some parameters could be potentially used as decision statistics. As proof of concept, we have tested the applicability of a compartmental model to describe differences between gap-FRAP responses of two human head and neck carcinoma cell lines (FaDu and KB). . Methods and Materials. Cx43, a protein of the connexin family responsible for GJIC, distribution and intercellular communication of FaDu and KB cells were performed in monolayer cultured cells and spheroids. Six experiments were performed for each case and data were collected through an imaging system composed of a macroscope combined to a fluorescence excitation source (Hg) and a CCD camera. The pixel intensities were measured in three concentric Regions of Interest (ROI) every 15 seconds for 15 minutes on each images. The measured values were assumed to be proportional to the mean amount of photons emitted in each ROI. After normalization with respect to the fluorescence intensity values before photobleaching, the data were plotted across the time. Modeling method. To study gap-Fluorescence Recovery After Photobleaching (gap-FRAP), the perturbation-relaxation kinetic equation is commonly used but is sometimes unable to describe some parts of the fluorescence response. A new behavioral model is proposed to study fluorescence recovery. The latter is based on a three-compartment representation (one compartment for each ROI) and the rates between each compartment represent the flow coefficients of the different gap junctions. This model provides a set of differential equations for which the associated continuous-time second-order transfer function was identified using the Simplified Refined Instrumental Variable in Continuous-time (SRIVC) algorithm. The algorithm returns three estimated parameters (a static gain and two time constants) and their standard deviations. Results. Two model parameters have allowed us to discriminate gap junctions functionalities. Indeed, parameters of KB cells, which is positive for Cx43 expression, are significantly superior to those of FaDu cells in culture 2-D and 3-D. No significant differences were observed for KB cells data independently of culture type confirming negligible contribution from underlying layers during fluorescence restitution in Z plan by confocal microscopy. Conclusions. Our study exemplifies the contributions brought by dynamic models of biological phenomena to diagnostic applications in biomedicine

Security Architecture for Point-to-Point Splitting Protocols

International audienceThe security of industrial supervisory control and data acquisition systems (SCADA) has become a major concern since the Stuxnet worm in 2010. As these systems are connected to the physical world, this makes them possibly hazardous if a malicious attacker is able to take over their control. SCADA can live up to 40 years, are particularly hard to patch, and quite often have no security feature at all. Thus, rather than securing them, network segregation is often used to prevent attackers from entering the industrial system. In this paper, we propose a generic solution: embed a point-to-point splitting protocol within a physical device, thus able to physically isolate networks, perform deep packet inspection and also provide encryption if necessary. We obtain a kind of next generation firewall, encompassing at least both diode and firewall features, for which conformity to security policies can be ensured. Then we define a set of associated security properties for such devices and the requirements for such a device's security architecture and filtering rules. Finally, we propose a secure hardware implementation

Synchronization in periodically driven and coupled stochastic systems-A discrete state approach

Wir untersuchen das Verhalten von stochastischen bistabilen und erregbaren Systemen auf der Basis einer Modellierung mit diskreten Zuständen. In Ergänzung zum bekannten Markovschen Zwei-Zustandsmodell bistabiler stochastischer Dynamik stellen wir ein nicht Markovsches Drei-Zustandsmodell für erregbare Systeme vor. Seine relative Einfachheit, verglichen mit stochastischen Modellen erregbarer Dynamik mit kontinuierlichem Phasenraum, ermöglicht eine teilweise analytische Auswertung in verschiedenen Zusammenhängen. Zunächst untersuchen wir den gemeinsamen Einfluß eines periodischen Treibens und Rauschens. Dieser wird entweder mit Hilfe spektraler Größen oder durch Synchronisation des Systems mit dem treibenden Signal charakterisiert. Wir leiten analytische Ausdrücke für die spektrale Leistungsverstärkung und das Signal-zu-Rauschen Verhältnis für periodisch getriebene Renewal-Prozesse her und wenden diese auf das diskrete Modell für erregbare Dynamik an. Stochastische Synchronization des Systems mit dem treibenden Signal wird auf der Basis der Diffusionseigenschaften der Übergangsereignisse zwischen den diskreten Zuständen untersucht. Wir leiten allgemeine Formeln her, um die mittlere Häufigkeit dieser Ereignisse sowie deren effektiven Diffusionskoeffizienten zu berechnen. Über die konkrete Anwendung auf die untersuchten diskreten Modelle hinaus stellen diese Ergebnisse ein neues Werkzeug für die Untersuchung periodischer Renewal-Prozesse dar. Schließlich betrachten wir noch das Verhalten global gekoppelter bistabiler und erregbarer Systeme. Im Gegensatz zu bistabilen System können erregbare Systeme synchronisiert werden und zeigen kohärente Oszillationen. Alle Untersuchungen des nicht Markovschen Drei-Zustandsmodells werden mit dem prototypischen Modell für erregbare Dynamik, dem FitzHugh-Nagumo System, verglichen und zeigen eine gute Übereinstimmung.We investigate the behavior of stochastic bistable and excitable dynamics based on a discrete state modeling. In addition to the well known Markovian two state model for bistable dynamics we introduce a non Markovian three state model for excitable systems. Its relative simplicity compared to stochastic models of excitable dynamics with continuous phase space allows to obtain analytical results in different contexts. First, we study the joint influence of periodic signals and noise, both based on a characterization in terms of spectral quantities and in terms of synchronization with the periodic driving. We present expressions for the spectral power amplification and signal to noise ratio for renewal processes driven by periodic signals and apply these results to the discrete model for excitable systems. Stochastic synchronization of the system to the driving signal is investigated based on diffusion properties of the transition events between the discrete states. We derive general results for the mean frequency and effective diffusion coefficient which, beyond the application to the discrete models considered in this work, provide a new tool in the study of periodically driven renewal processes. Finally the behavior of globally coupled excitable and bistable units is investigated based on the discrete state description. In contrast to the bistable systems, the excitable system exhibits synchronization and thus coherent oscillations. All investigations of the non Markovian three state model are compared with the prototypical continuous model for excitable dynamics, the FitzHugh-Nagumo system, revealing a good agreement between both models

Predictors of hospital discharge and mortality in patients with diabetes and COVID-19: updated results from the nationwide CORONADO study

AIMS/HYPOTHESIS: This is an update of the results from the previous report of the CORONADO (Coronavirus SARS-CoV-2 and Diabetes Outcomes) study, which aims to describe the outcomes and prognostic factors in patients with diabetes hospitalised for coronavirus disease-2019 (COVID-19). METHODS: The CORONADO initiative is a French nationwide multicentre study of patients with diabetes hospitalised for COVID-19 with a 28-day follow-up. The patients were screened after hospital admission from 10 March to 10 April 2020. We mainly focused on hospital discharge and death within 28 days. RESULTS: We included 2796 participants: 63.7% men, mean age 69.7 ± 13.2 years, median BMI (25th-75th percentile) 28.4 (25.0-32.4) kg/m(2). Microvascular and macrovascular diabetic complications were found in 44.2% and 38.6% of participants, respectively. Within 28 days, 1404 (50.2%; 95% CI 48.3%, 52.1%) were discharged from hospital with a median duration of hospital stay of 9 (5-14) days, while 577 participants died (20.6%; 95% CI 19.2%, 22.2%). In multivariable models, younger age, routine metformin therapy and longer symptom duration on admission were positively associated with discharge. History of microvascular complications, anticoagulant routine therapy, dyspnoea on admission, and higher aspartate aminotransferase, white cell count and C-reactive protein levels were associated with a reduced chance of discharge. Factors associated with death within 28 days mirrored those associated with discharge, and also included routine treatment by insulin and statin as deleterious factors. CONCLUSIONS/INTERPRETATION: In patients with diabetes hospitalised for COVID-19, we established prognostic factors for hospital discharge and death that could help clinicians in this pandemic period. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT04324736

De novo TBR1 variants cause a neurocognitive phenotype with ID and autistic traits:report of 25 new individuals and review of the literature

TBR1, a T-box transcription factor expressed in the cerebral cortex, regulates the expression of several candidate genes for autism spectrum disorders (ASD). Although TBR1 has been reported as a high-confidence risk gene for ASD and intellectual disability (ID) in functional and clinical reports since 2011, TBR1 has only recently been recorded as a human disease gene in the OMIM database. Currently, the neurodevelopmental disorders and structural brain anomalies associated with TBR1 variants are not well characterized. Through international data sharing, we collected data from 25 unreported individuals and compared them with data from the literature. We evaluated structural brain anomalies in seven individuals by analysis of MRI images, and compared these with anomalies observed in TBR1 mutant mice. The phenotype included ID in all individuals, associated to autistic traits in 76% of them. No recognizable facial phenotype could be identified. MRI analysis revealed a reduction of the anterior commissure and suggested new features including dysplastic hippocampus and subtle neocortical dysgenesis. This report supports the role of TBR1 in ID associated with autistic traits and suggests new structural brain malformations in humans. We hope this work will help geneticists to interpret TBR1 variants and diagnose ASD probands