Pump up the Volume:Practical Database Reconstruction from Volume Leakage on Range Queries

We present attacks that use only the volume of responses to range queries to reconstruct databases. Our focus is on practical attacks that work for large-scale databases with many values and records, without requiring assumptions on the data or query distributions. Our work improves on the previous state-of-the-art due to Kellaris \emph{et al.} (CCS 2016) in all of these dimensions. Our main attack targets reconstruction of database counts and involves a novel graph-theoretic approach. It generally succeeds when RR, the number of records, exceeds N2/2N2/2, where NN is the number of possible values in the database. For a uniform query distribution, we show that it requires volume leakage from only O(N2logN)O(N2log⁡N) queries (cf.\ O(N4logN)O(N4log⁡N) in prior work). We present two ancillary attacks. The first identifies the value of a new item added to a database using the volume leakage from fresh queries, in the setting where the adversary knows or has previously recovered the database counts. The second shows how to efficiently recover the ranges involved in queries in an online fashion, given an auxiliary distribution describing the database. Our attacks are all backed with mathematical analyses and extensive simulations using real data

Cryptanalysis of MORUS

Item does not contain fulltextAdvances in Cryptology - ASIACRYPT 2018 - 24th International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, QLD, Australia, December 2-

The visual and material dimensions of legitimacy:Accounting and the search for Socie-ties

We are grateful to the Fondation Audencia for the financial support provided for our archival research.The aim of this article is to contribute to the literature on legitimacy by investigating its material and visual dimensions. By drawing on studies on rhetoric as a means of composing visions of social order and on an historical analysis of accounts in three paradigmatic eras (Roman times, Renaissance and Modernity), it shows how symmetry in accounts constituted an aesthetic code which tied members of a community together in ‘socie-ties’. We investigate the rhetorical process of ratiocinatio and explore how the visual and material dimensions of accounts provided social actors with an opportunity to explore their positions and ties within a community. This process augmented social actors’ understanding of their current relations by reducing them to a series of entries into an account, thus allowing them to reflect on what it meant to be a legitimate member of a society.PostprintPeer reviewe

Learning to Reconstruct: Statistical Learning Theory and Encrypted Database Attacks

International audienceWe show that the problem of reconstructing encrypted databases from access pattern leakage is closely related to statistical learning theory. This new viewpoint enables us to develop broader attacks that are supported by streamlined performance analyses. As an introduction to this viewpoint, we first present a general reduction from reconstruction with known queries to PAC learning. Then, we directly address the problem of ϵ-approximate database reconstruction (ϵ-ADR) from range query leakage, giving attacks whose query cost scales only with the relative error ϵ, and is independent of the size of the database, or the number N of possible values of data items. This already goes significantly beyond the state of the art for such attacks, as represented by Kellaris et al. (ACM CCS 2016) and Lacharité et al. (IEEE S&P 2018). We also study the new problem of ϵ-approximate order reconstruction (ϵ-AOR), where the adversary is tasked with reconstructing the order of records, except for records whose values are approximately equal. We show that as few as O(ϵ^-1 log ϵ^-1) uniformly random range queries suffice. Our analysis relies on an application of learning theory to PQ-trees, special data structures tuned to compactly record certain ordering constraints. We then show that when an auxiliary distribution is available, ϵ-AOR can be enhanced to achieve ϵ-ADR; using real data, we show that devastatingly small numbers of queries are needed to attain very accurate database reconstruction. Finally, we generalize from ranges to consider what learning theory tells us about the impact of access pattern leakage for other classes of queries, focusing on prefix and suffix queries. We illustrate this with both concrete attacks for prefix queries and with a general lower bound for all query classes

La mesure de l'excrétion urinaire de l'uranium par spectrofluorimétrie laser à résolution temporelle

La quantification directe rapide de l'excrétion urinaire de l'uranium est souvent perturbée par des incertitudes métaboliques et par des interférences analytiques. Ces phénomènes conduisent à des limites de détection ou à des incertitudes trop élevées. La technique proposée associe à la fois un traitement rapide de l'échantillon et un système optimisé de mesure. L'association d'un laser solide de puissance utilisé comme source d'excitation et d'un fluorimètre modifié du commerce permet d'atteindre les objectifs de l'étude : rapidité de réponse et facilité de mise en oeuvre, précision et exactitude inférieures 10 %. Les stades analytiques selon deux modalités (mesure directe et après minéralisation de l'échantillon) sont décrits. Les résultats expérimentaux portant sur 120 mesures sont comparés aux résultats obtenus par chromatographie d'extraction. Les avantages et inconvénients de la technique sont commentés. Enfin les valeurs de l'excrétion urinaire naturelle de l'uranium chez 80 travailleurs non-exposés de la région de Marcoule sont présentées en fonction de la technique analytique choisie

Ru-Pyrochlores: Compositional Tuning for Electrochemical Stability as Cathode Materials for IT-SOFCs

International audienceUsing XRD, impedance spectroscopy, and XPS, it was shown that both Bi2Ru2O7 and Pb2Ru2O6.5, generally announced as attractive electrode materials for IT-SOFCs, chemically react with CGO. In addition, a never-mentioned time-instability under electrochemical measurements with YZS as electrolyte mediates the polarization tests. For Pb2Ru2O6.5, long time experiments (stabilization time > 900 h, previously to complementary electrochemical tests), yields strong increasing of the resistance polarization. Concerning Bi2Ru2O7, a partial transformation into Bi3Ru3O11 is observed after impedance measurements. The investigation of the Bi2−xMxRu2O7−δ (M = Sr, Pb) solid solutions was performed with the aim to improve the catalytic/electric properties. For low x values, it shows a time and chemical stabilization of the electrode/electrolyte cells, able to preserve high electrode performances of these materials. For higher substitution, the chemical/electrochemical instability reappears. According to our polarization measurements versus oxygen pressure and temperature in the so-called “stabilized” samples, the electrode performance appears limited by the diffusion of adsorbed oxygen on the triple point boundary. It is fully compatible with the metallic behavior checked in all the series

Electrostatic spray deposition of Ca3Co4O9 + δ layers to be used as cathode materials for IT-SOFC

International audienceIn this paper, the deposition of Ca3Co4O9 + δ layers on CGO substrates using electrostatic spray deposition (ESD) technique, starting from calcium and cobalt nitrates as precursor salts, is reported. The microstructure was investigated as a function of process parameters such as nozzle-to-substrate distance, solvent composition, substrate temperature, flow rate and deposition time, based on an upper and a lower value. Films with controlled microstructures were obtained after annealing at 880 °C for 2 h in air. The formation of Ca3Co4O9 + δ was confirmed by X-ray diffraction, which also showed evidence of Co3O4 traces. As shown by in-situ X-ray diffraction, Ca3Co4O9 + δ starts to form at 625 °C and decomposes at 950 °C, but the transformation is reversible. Interestingly, the initial morphology of the films was maintained after annealing at either 700 or 880 °C, with the appearance of faceted crystals forming a gypsum flower-like microstructure. AC impedance spectroscopy was carried out at intermediate temperatures (600–800 °C) under air on 2 batches of symmetrical cells based on ESD and screen-printed electrodes, respectively. This work confirmed the beneficial impact of the ESD technique. The area-specific resistance was improved by at least 23% at 600 °C and 40% at 800 °C for the sample prepared by ESD compared to the reference one prepared by screen printing. This improvement was explained by a better interface between the electrode and the electrolyte

«Transport properties in promising cobaltites as SOFC cathode»

International audienceno abstrac

«Growth of Ca₃Co₄O₉ on CGO dense pellet by Pulsed Laser Deposition and XRD, TEM and Ellipsometry Characterizations»

International audienceno abstrac

Information governance in Roman finance

This paper studies the role of information as a determinant of the performance of the Roman financial system. I extend the traditional transaction cost approach by using a broader concept borrowed from organisation sciences: ‘Information Governance System’ (IGS). Information governance comprises all socially or formally instituted processes that regulate the production, circulation, valuation, storage, retrieval, and processing of information. The concept of IG system denotes how these processes are structured and which rule sets define them. I argue that the institutional framework of the Roman empire offered procedures for information governance that supported the development of a market for financial services. This public order IGS, however, required considerable knowledge and skills. As in late medieval Europe it led to the emergence of financial specialists. As such it was a positive determinant for the economic growth we see documented in the material record