Quantum entropic security and approximate quantum encryption

We present full generalisations of entropic security and entropic indistinguishability to the quantum world where no assumption but a limit on the knowledge of the adversary is made. This limit is quantified using the quantum conditional min-entropy as introduced by Renato Renner. A proof of the equivalence between the two security definitions is presented. We also provide proofs of security for two different cyphers in this model and a proof for a lower bound on the key length required by any such cypher. These cyphers generalise existing schemes for approximate quantum encryption to the entropic security model.Comment: Corrected mistakes in the proofs of Theorems 3 and 6; results unchanged. To appear in IEEE Transactions on Information Theory

From Sea to Sea: Canada's Three Oceans of Biodiversity

Evaluating and understanding biodiversity in marine ecosystems are both necessary and challenging for conservation. This paper compiles and summarizes current knowledge of the diversity of marine taxa in Canada's three oceans while recognizing that this compilation is incomplete and will change in the future. That Canada has the longest coastline in the world and incorporates distinctly different biogeographic provinces and ecoregions (e.g., temperate through ice-covered areas) constrains this analysis. The taxonomic groups presented here include microbes, phytoplankton, macroalgae, zooplankton, benthic infauna, fishes, and marine mammals. The minimum number of species or taxa compiled here is 15,988 for the three Canadian oceans. However, this number clearly underestimates in several ways the total number of taxa present. First, there are significant gaps in the published literature. Second, the diversity of many habitats has not been compiled for all taxonomic groups (e.g., intertidal rocky shores, deep sea), and data compilations are based on short-term, directed research programs or longer-term monitoring activities with limited spatial resolution. Third, the biodiversity of large organisms is well known, but this is not true of smaller organisms. Finally, the greatest constraint on this summary is the willingness and capacity of those who collected the data to make it available to those interested in biodiversity meta-analyses. Confirmation of identities and intercomparison of studies are also constrained by the disturbing rate of decline in the number of taxonomists and systematists specializing on marine taxa in Canada. This decline is mostly the result of retirements of current specialists and to a lack of training and employment opportunities for new ones. Considering the difficulties encountered in compiling an overview of biogeographic data and the diversity of species or taxa in Canada's three oceans, this synthesis is intended to serve as a biodiversity baseline for a new program on marine biodiversity, the Canadian Healthy Ocean Network. A major effort needs to be undertaken to establish a complete baseline of Canadian marine biodiversity of all taxonomic groups, especially if we are to understand and conserve this part of Canada's natural heritage

De la cryptographie sur les corps quadratiques reéls

We describe here a key-exchange protocol over real quadratic fields. This is accompanied by all the pertinent algebraic background needed for the understanding of the protocol. We also present two quantum algorithms that solve the regulator problem over real quadratic fields and the discrete logarithm problem also known as the principal ideal problem

Quantum entropic security

We present full generalizations of entropic security and entropic indistinguishability,notions introduced by Russell and Wang and then Dodis and Smith, to the quantumworld where no assumption other than a limit on the knowledge of the adversary ismade. This limit is quantified using the quantum conditional min-entropy as introducedby Renner. In this fully generalized model, we allow any kind of entanglementor correlation between the Sender and the Eavesdropper.A proof of equivalence between the two security definitions is presented. This proofof equivalence is much simpler and more powerful than what was previously doneand is by itself a worthy contribution. We also provide proofs of security for twodifferent ciphers in this model. These ciphers generalize existing schemes for approximatequantum encryption to the entropic security model. The key length requirementof these two schemes is exactly the same as their classical counterparts for separablestates. It is also, as far as we know, the first time that one can prove securityfor encryption schemes while allowing entanglement with the adversary and yet notrequiring perfect security .Une généralisation complète des notions de sécurité entropique et d'indistinguabilitéentropique, telles que définies par Russell et Wang puis par Dodis et Smith, aumonde quantique est présentée. Aucune autre hypothèse qu'une borne inférieure surl'incertitude de l'adversaire, incertitude quantifiée par la notion de min-entropie conditionellequantique telle que définie par Renner, n'est présumée. Ce modèle permettoute forme de corrélation ou d'intrication entre l'adversaire et l'émetteur du message.Une démonstration de l'équivalence entre ces deux notions de sécurité est présentéequi est beaucoup plus simple que ce qui était connue au-paravant. Cette nouvellesimplicité est une contribution notable. Deux chiffres sont aussi généralisés à ce nouveaumodèle de sécurité et leur sécurité est démontrée. La taille de la clef requise afind'assurer la sécurité de ces deux chiffres est exactement la même que celle requise parleur équivalent classique. Ces chiffres sont sécuritaires même en présence d'intricationentre l'adversaire et l'émetteur, ce qui est, autant que nous le sachions, une premièresans requérir une sécurité parfaite

Study of myocardial cell inhomogeneity of the human heart: Simulation and validation using polarized light imaging.

International audienceThe arrangement or architecture of myocardial cells plays a fundamental role in the heart's function and its change was shown to be directly linked to heart diseases. Inhomogeneity level is an important index of myocardial cell arrangements in the human heart. The authors propose to investigate the inhomogeneity level of myocardial cells using polarized light imaging simulations and experiments. The idea is based on the fact that the myosin filaments in myocardial cells have the same properties as those of a uniaxial birefringent crystal. The method then consists in modeling the myosin filaments of myocardial cells as uniaxial birefringent crystal, simulating the behavior of the latter by means of the Mueller matrix, and measuring the final intensity of polarized light and consequently the inhomogeneity level of myocardial cells in each voxel through the use of crossed polarizers. The method was evaluated on both simulated and real tissues and under various myocardial cell configurations including parallel cells, crossed cells, and cells with random orientations. When myocardial cells run perfectly parallel to each other, all the polarized light was blocked by those parallel myocardial cells, and a high homogeneity level was observed. However, if myocardial cells were not parallel to each other, some leakage of the polarized light was observed, thus causing the decrease of the polarized light amplitude and homogeneity level. The greater the crossing angle between myocardial cells, the smaller the amplitude of the polarized light and the greater the inhomogeneity level. For two populations of myocardial cell crossing at an angle, the resulting azimuth angle of the voxel was the bisector of this angle. Moreover, the value of the inhomogeneity level began to decrease from a nonzero value when the voxel was not totally homogeneous, containing for example cell crossing. The proposed method enables the physical information of myocardial tissues to be estimated and the inhomogeneity level of a volume or voxel to be quantified, which opens new ways to study the microstructures of the human myocardium and helps understanding how heart diseases modify myocardial cells and change their mechanical properties

Modeling of the Optical Behavior of Myocardial Fibers in Polarized Light Imaging

International audienceMany cardiovascular diseases are linked to anomalies in myocardial fibers. The purpose of this paper is to model the birefringence of myocardial fibers in polarized light imaging (PLI) with future application to measurements on real myocardial tissues. The method consists in modeling the behavior of a uni-axial birefringent crystal by means of the Muller matrix, and measuring the final intensity of polarized light and consequently the orientation of myocardial fibers, by using crossed polarizers. The method was illustrated with a tissue modeled as a volume of 100×100×500μm3. This volume was divided into cubes of size 20μm close to cell diameter. The fiber orientation within the cube was defined by azimuth and elevation angles. The results showed that the proposed modeling enables us to find the optimal conditions for the PLI of 3D fiber orientations and design a model for the myocardial tissue measurement from PLI