Attacking the combination generator

We present one of the most efficient attacks against the combination generator. This attack is inherent to this system as its only assumption is that the filtering function has a good autocorrelation. This is usually the case if the system is designed to be resistant to other kinds of attacks. We use only classical tools, namely vectorial correlation, weight 4 multiples and Walsh transform

Novel families of SU(N){\rm SU}(N) AKLT states with arbitrary self-conjugate edge states

Using the Matrix Product State framework, we generalize the Affleck-Kennedy-Lieb-Tasaki (AKLT) construction to one-dimensional spin liquids with global color ${\rm SU}(N)$ symmetry, finite correlation lengths, and edge states that can belong to any self-conjugate irreducible representation (irrep) of ${\rm SU}(N)$. In particular, ${\rm SU}(2)$ spin-$1$ AKLT states with edge states of arbitrary spin $s=1/2,1,3/2,\cdots$ are constructed, and a general formula for their correlation length is given. Furthermore, we show how to construct local parent Hamiltonians for which these AKLT states are unique ground states. This enables us to study the stability of the edge states by interpolating between exact AKLT Hamiltonians. As an example, in the case of spin-$1$ physical degrees of freedom, it is shown that a quantum phase transition of central charge $c = 1$ separates the Symmetry Protected Topological (SPT) phase with spin-$1/2$ edge states from a topologically trivial phase with spin-$1$ edge states. We also address some specificities of the generalization to ${\rm SU}(N)$ with $N>2$, in particular regarding the construction of parent Hamiltonians. For the AKLT state of the ${\rm SU}(3)$ model with the $3$-box symmetric representation, we prove that the edge states are in the $8$-dimensional adjoint irrep, and for the ${\rm SU}(3)$ model with adjoint irrep at each site, we are able to construct two different reflection-symmetric AKLT Hamiltonians, each with a unique ground state which is either even or odd under reflection symmetry and with edge states in the adjoint irrep. Finally, examples of two-column and adjoint physical irreps for ${\rm SU}(N)$ with $N$ even and with edge states living in the antisymmetric irrep with $N/2$ boxes are given, with a conjecture about the general formula for their correlation lengths.Comment: 37 pages, 14 figures, 4 table

Finding low-weight polynomial multiples using discrete logarithm

Finding low-weight multiples of a binary polynomial is a difficult problem arising in the context of stream ciphers cryptanalysis. The classical algorithm to solve this problem is based on a time memory trade-off. We will present an improvement to this approach using discrete logarithm rather than a direct representation of the involved polynomials. This gives an algorithm which improves the theoretical complexity, and is also very flexible in practice

Yanis (Varoufakis), the Minotaur, and the Field of Eurocracy

This paper aims to show the binding force within the social field of Eurocracy and, more specifically, the subfield of the European economic governance, through the singular case of Yanis Varoufakis's experience as Greek minister of finance. Why is it that, while many elements might have suggested that Varoufakis was not lacking resources, his passage from economics into politics ended up in a fairly brutal shock and a mutual exclusion so extremely invested in on the symbolic level? The paper's hypothesis is that a substantial part of the strategies of the epistemic agent Varoufakis - an experienced economist as well as new ruler and new politician in the EU game - were completely out of tune with the structure of the field. To show this, the paper deliberately breaks with the causal analysis of the bargain inside the Eurogroup to build on the use of two multiple correspondence analyses (MCA). The first describes a view of (and from) the silent fraction of the field, composed of insiders in the European administrations. The second reconstructs Varoufakis's own relational position and vision of the game from the book he wrote on his experience. Thanks to these two approaches, we combine a descriptive-institutional and a narrative-individual construction of the same social space to explore its deep structure and effects in an innovative way

Caractérisation spatio-temporelle des échanges nappes/rivière à l'échelle de deux grands fleuves français : application aux secteurs de Donzère-Mondragon (Rhône) et Ecozone du Forez (Loire)

International audienceL'application de la Directive Cadre Européenne sur l'eau (DCE-eau), tant au niveau global qu'au niveau local, impose de mieux connaître le fonctionnement des zones d'interface des hydrosystèmes, notamment fluviaux, et en particulier des zones d'échanges entre eaux souterraines et superficielles (DCEeau, 2006). Pour le SDAGE (Schéma Directeur d'Aménagement et de Gestion des Eaux) du bassin Rhône Méditerranée et Corse, la connaissance de l'évolution quantitative des ressources superficielles et souterraines représente aussi un enjeu majeur (SDAGErmc, 2009). Cette problématique est également formulée en termes de besoins et d'attentes du programme Plan Rhône : « Qualité des eaux, ressources et biodiversité : compréhension des échanges entre fleuve et aquifères » (PR, 2005). De plus, une telle problématique visant à caractériser spatialement les échanges nappes/rivière a aussi une dimension temporelle en lien avec « les changements globaux » et « la prospective changement climatique » à court terme (influence des régimes transitoires au pas de temps saisonniers) ou à long terme (horizon 2100). La finalité scientifique du projet présenté dans cet article vise à proposer un outil interdisciplinaire pour l'identification et l'évaluation, tant qualitative que quantitative (caractérisation), des échanges entre le fleuve Rhône et ses aquifères superficiels depuis le lac Léman jusqu'à la mer Méditerranée en tenant compte du caractère anthropisé du fleuve. Un tel outil contribuera à la préservation des nappes phréatiques, patrimoine souterrain et invisible, et plus généralement à la préservation de la ressource en eau et de la biodiversité sur le bassin du Rhône. Dans un objectif de gestion coordonnée de la ressource en eau tant superficielle que souterraine, et plus généralement de préservation de la ressource en eau et de la biodiversité sur le corridor alluvionnaire du Rhône, les premiers résultats montrent qu'il est possible : 1) d'estimer la contribution des eaux souterraines au débit du Rhône et d'identifier leur origine ; 2) d'identifier à l'échelle du corridor alluvionnaire, les portions de nappe les plus directement sous influence du fleuve et les plus vulnérables à une pollution du Rhône ; 3) d'identifier les milieux superficiels et humides sous dépendance majoritaire d'apports souterrains ; 4) de transposer la méthode à d'autres cours d'eau comme le fleuve Loire. Après une brève description des deux secteurs d'étude, suivie d'une présentation synthétique de la méthode de caractérisation des échanges nappes/rivière. Les principaux résultats associés aux deux secteurs d'étude pour deux périodes hydrologiques caractéristiques (hautes-eaux et basses-eaux de nappe) sont présentés. Les aspects novateurs du travail sont ensuite soulignés, avant de conclure

Games, Role-Playing, Tools and models as a learning process to simulate groundwater management negotiation.

International audienceTo simulate groundwater management negotiation, with a mediator and spatial argumentation, to reduce aquifer vulnerability using an example of gravel extraction in an alluvial aquifer How to make relevant decisions to preserve the quality of the hydrosystem and protect public health? Goals of this negotiation simulation are to design a cooperative solution where the participants must decide together : Where is the best new gravel pit location within a specified territory? What is the best method of rehabilitation after gravel extraction? Who is the most appropriate to manage the site after rehabilitation

The WHO in Belgium: cross-level networking

Know and Po

Utopias as a Tentative Horizon for Spatial Justice

International audienceResearchers have already very extensively explored utopias: this issue of Justice Spatiale/Spatial Justice wishes to present more than a collection of articles on the history of utopias, a field widely covered by historians, town planners, philosophers, etc. The historical aspect will not be central here, even if going back over these analyses is essential for understanding the conditions of the articulation of the contemporary form of utopia in connection with justice. If some of the articles offered here reflect on the lessons drawn from past utopias, this reflection is always related to the use of this philosophy in the present. What we are interested in is the connexion of a utopian discourse with very contemporary demands for more justice, and the spatial issues engendered by this expression, which mobilizes very diverse scales, from the world to the community, in relationships that are at times mutually exclusive or contradictory