1,597 research outputs found
A Distinguisher-Based Attack of a Homomorphic Encryption Scheme Relying on Reed-Solomon Codes
Bogdanov and Lee suggested a homomorphic public-key encryption scheme based
on error correcting codes. The underlying public code is a modified
Reed-Solomon code obtained from inserting a zero submatrix in the Vandermonde
generating matrix defining it. The columns that define this submatrix are kept
secret and form a set . We give here a distinguisher that detects if one or
several columns belong to or not. This distinguisher is obtained by
considering the code generated by component-wise products of codewords of the
public code (the so called "square code"). This operation is applied to
punctured versions of this square code obtained by picking a subset
of the whole set of columns. It turns out that the dimension of the
punctured square code is directly related to the cardinality of the
intersection of with . This allows an attack which recovers the full set
and which can then decrypt any ciphertext.Comment: 11 page
A Distinguisher-Based Attack on a Variant of McEliece's Cryptosystem Based on Reed-Solomon Codes
Baldi et \textit{al.} proposed a variant of McEliece's cryptosystem. The main
idea is to replace its permutation matrix by adding to it a rank 1 matrix. The
motivation for this change is twofold: it would allow the use of codes that
were shown to be insecure in the original McEliece's cryptosystem, and it would
reduce the key size while keeping the same security against generic decoding
attacks. The authors suggest to use generalized Reed-Solomon codes instead of
Goppa codes. The public code built with this method is not anymore a
generalized Reed-Solomon code. On the other hand, it contains a very large
secret generalized Reed-Solomon code. In this paper we present an attack that
is built upon a distinguisher which is able to identify elements of this secret
code. The distinguisher is constructed by considering the code generated by
component-wise products of codewords of the public code (the so-called "square
code"). By using square-code dimension considerations, the initial generalized
Reed-Solomon code can be recovered which permits to decode any ciphertext. A
similar technique has already been successful for mounting an attack against a
homomorphic encryption scheme suggested by Bogdanoc et \textit{al.}. This work
can be viewed as another illustration of how a distinguisher of Reed-Solomon
codes can be used to devise an attack on cryptosystems based on them.Comment: arXiv admin note: substantial text overlap with arXiv:1203.668
Recursive regularization step for high-order lattice Boltzmann methods
A lattice Boltzmann method (LBM) with enhanced stability and accuracy is
presented for various Hermite tensor-based lattice structures. The collision
operator relies on a regularization step, which is here improved through a
recursive computation of non-equilibrium Hermite polynomial coefficients. In
addition to the reduced computational cost of this procedure with respect to
the standard one, the recursive step allows to considerably enhance the
stability and accuracy of the numerical scheme by properly filtering out second
(and higher) order non-hydrodynamic contributions in under-resolved conditions.
This is first shown in the isothermal case where the simulation of the doubly
periodic shear layer is performed with a Reynolds number ranging from to
, and where a thorough analysis of the case at is
conducted. In the latter, results obtained using both regularization steps are
compared against the BGK-LBM for standard (D2Q9) and high-order (D2V17 and
D2V37) lattice structures, confirming the tremendous increase of stability
range of the proposed approach. Further comparisons on thermal and fully
compressible flows, using the general extension of this procedure, are then
conducted through the numerical simulation of Sod shock tubes with the D2V37
lattice. They confirm the stability increase induced by the recursive approach
as compared with the standard one.Comment: Accepted for publication as a Regular Article in Physical Review
Analyse des critères d'évaluation de systèmes multi-agents adaptatifs
http://www.emse.fr/~picard/publications/kaddoum09jfsma.pdfInternational audienceLa complexité croissante des applications actuelles favorise le développement de systèmes multi-agents auto-organisateurs possédant des propriétés self-? . Ces systèmes autonomes présentent des capacités intéressantes permettant la gestion de la dynamique endogène et exogène des applications étudiées. De nouveaux critères doivent être étudiés afin de caractériser et évaluer l'apport de ces propriétés self-? et leur influence sur les performances du système. Dans cet article, différentes catégories regroupant les principaux critères d'évaluation sont décrites afin de guider l'évaluation de ce type de systèmes depuis les phases de conception jusqu'aux phases d'exécution : évaluation du système en cours de fonctionnement, caractéristiques intrinsèques et méthodologie de conception
Persistent organic pollutant burden, experimental POP exposure and tissue properties affect metabolic profiles of blubber from grey seal pups
Persistent organic pollutants (POPs) are toxic, ubiquitous, resist breakdown, bioaccumulate in living tissue and biomagnify in food webs. POPs can also alter energy balance in humans and wildlife. Marine mammals experience high POP concentrations, but consequences for their tissue metabolic characteristics are unknown. We used blubber explants from wild, grey seal (Halichoerus grypus) pups to examine impacts of intrinsic tissue POP burden and acute experimental POP exposure on adipose metabolic characteristics. Glucose use, lactate production and lipolytic rate differed between matched inner and outer blubber explants from the same individuals and between feeding and natural fasting. Glucose use decreased with blubber dioxin-like PCBs (DL-PCB) and increased with acute experimental POP exposure. Lactate production increased with DL-PCBs during feeding, but decreased with DL-PCBs during fasting. Lipolytic rate increased with blubber dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDX) in fasting animals, but declined with DDX when animals were feeding. Our data show that POP burdens are high enough in seal pups to alter adipose function early in life, when fat deposition and mobilisation are vital. Such POP-induced alterations to adipose glucose use may significantly alter energy balance regulation in marine top predators with the potential for long term impacts on fitness and survival
The AmICriM Project: A Truly Body Area Network Application
http://www.emse.fr/~picard/publications/garcia08amicrim.pdfInternational audienceThe major aim of this work is to present the AmICriM (Ambient Intelligence for Crisis Management) current activities as an upcoming research challenge in the area of body area networking by using intelligent embodied devices for supporting new crisis management services. The research outcomes of the AmICriM project will show also future directions in the area of body-area networks and communications, as well as its applications to novel approaches in which firemen would receive critical and valuable information when acting in real situations of crisis, as in case of fire in a building. This work will boost development of new technologies and solutions that will be used in the future for networking embodied intelligent devices. Moreover, the AmICriM developed technologies will be evaluated through a real service for assisting firemen in crisis situations
A linear stability analysis of compressible hybrid lattice Boltzmann methods
An original spectral study of the compressible hybrid lattice Boltzmann
method (HLBM) on standard lattice is proposed. In this framework, the mass and
momentum equations are addressed using the lattice Boltzmann method (LBM),
while finite difference (FD) schemes solve an energy equation. Both systems are
coupled with each other thanks to an ideal gas equation of state. This work
aims at answering some questions regarding the numerical stability of such
models, which strongly depends on the choice of numerical parameters. To this
extent, several one- and two-dimensional HLBM classes based on different energy
variables, formulation (primitive or conservative), collision terms and
numerical schemes are scrutinized. Once appropriate corrective terms
introduced, it is shown that all continuous HLBM classes recover the
Navier-Stokes Fourier behavior in the linear approximation. However, striking
differences arise between HLBM classes when their discrete counterparts are
analysed. Multiple instability mechanisms arising at relatively high Mach
number are pointed out and two exhaustive stabilization strategies are
introduced: (1) decreasing the time step by changing the reference temperature
and (2) introducing a controllable numerical dissipation via
the collision operator. A complete parametric study reveals that only HLBM
classes based on the primitive and conservative entropy equations are found
usable for compressible applications. Finally, an innovative study of the
macroscopic modal composition of the entropy classes is conducted. Through this
study, two original phenomena, referred to as shear-to-entropy and
entropy-to-shear transfers, are highlighted and confirmed on standard
two-dimensional test cases.Comment: 49 pages, 23 figure
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