Probabilistic Opacity in Refinement-Based Modeling

Given a probabilistic transition system (PTS) $\cal A$ partially observed by an attacker, and an $\omega$-regular predicate $\varphi$over the traces of $\cal A$, measuring the disclosure of the secret $\varphi$ in $\cal A$ means computing the probability that an attacker who observes a run of $\cal A$ can ascertain that its trace belongs to $\varphi$. In the context of refinement, we consider specifications given as Interval-valued Discrete Time Markov Chains (IDTMCs), which are underspecified Markov chains where probabilities on edges are only required to belong to intervals. Scheduling an IDTMC $\cal S$ produces a concrete implementation as a PTS and we define the worst case disclosure of secret $\varphi$ in ${\cal S}$ as the maximal disclosure of $\varphi$ over all PTSs thus produced. We compute this value for a subclass of IDTMCs and we prove that refinement can only improve the opacity of implementations

Opacity for Linear Constraint Markov Chains

On a partially observed system, a secret ϕ is opaque if an observer cannot ascertain that its trace belongs to ϕ. We consider specifications given as Constraint Markov Chains (CMC), which are underspec-ified Markov chains where probabilities on edges are required to belong to some set. The nondeterminism is resolved by a scheduler, and opacity on this model is defined as a worst case measure over all implementations obtained by scheduling. This measures the information obtained by a passive observer when the system is controlled by the smartest sched-uler in coalition with the observer. When restricting to the subclass of Linear CMC, we compute (or approximate) this measure and prove that refinement of a specification can only improve opacity

Interrupt Timed Automata: verification and expressiveness

We introduce the class of Interrupt Timed Automata (ITA), a subclass of hybrid automata well suited to the description of timed multi-task systems with interruptions in a single processor environment. While the reachability problem is undecidable for hybrid automata we show that it is decidable for ITA. More precisely we prove that the untimed language of an ITA is regular, by building a finite automaton as a generalized class graph. We then establish that the reachability problem for ITA is in NEXPTIME and in PTIME when the number of clocks is fixed. To prove the first result, we define a subclass ITA- of ITA, and show that (1) any ITA can be reduced to a language-equivalent automaton in ITA- and (2) the reachability problem in this subclass is in NEXPTIME (without any class graph). In the next step, we investigate the verification of real time properties over ITA. We prove that model checking SCL, a fragment of a timed linear time logic, is undecidable. On the other hand, we give model checking procedures for two fragments of timed branching time logic. We also compare the expressive power of classical timed automata and ITA and prove that the corresponding families of accepted languages are incomparable. The result also holds for languages accepted by controlled real-time automata (CRTA), that extend timed automata. We finally combine ITA with CRTA, in a model which encompasses both classes and show that the reachability problem is still decidable. Additionally we show that the languages of ITA are neither closed under complementation nor under intersection

Oxide phosphors for light upconversion; Yb3+ and Tm3+ co-doped Y2BaZnO5

Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 109, 063104 (2011) and may be found at

2es Rencontres FORMIST - 2002 (Actes complets)

Actes des 2èmes Rencontres FORMIST : Le point sur la formation des usagers ; Réseaux.Doc : formation à la recherche documentaire ; Les formations à l\u27information ; Séduction et partenariat : mise en œuvre de la formation des usagers aux bibliothèques de l\u27Université Libre de Bruxelles ; Formation des étudiants à la maîtrise de l\u27information ; l\u27expérience de l\u27Université des Sciences sociales de Toulouse 1 ; Méthodologie documentaire en BU Sciences : l\u27exemple de Nice, témoignage d\u27une expérience de terrain ; Formation à la recherche documentaire au sein de la Faculté de pharmacie de Lyon (Université Claude-Bernard Lyon 1) ; Un module de méthodologie du travail universitaire original : STIM-Sciences de la Terre en images ; Pédagogie classique versus pédagogie par projets et pédagogie inverse : l\u27expérience de l\u27INSA de Lyon ; La méthodologie du travail universitaire à la bibliothèque de Droit et de Lettres de l\u27Université de La Réunion ; Tables-rondes et synthèse

Spin Gauge Fields: from Berry Phase to Topological Spin Transport and Hall Effects

The paper examines the emergence of gauge fields during the evolution of a particle with a spin that is described by a matrix Hamiltonian with n different eigenvalues. It is shown that by introducing a spin gauge field a particle with a spin can be described as a spin multiplet of scalar particles situated in a non-Abelian pure gauge (forceless) field U(n). As the result, one can create a theory of particle evolution that is gauge invariant with regards to the group U^n(1). Due to this, in the adiabatic (Abelian) approximation the spin gauge field is an analogue of n electromagnetic fields U(1) on the extended phase space of the particle. These fields are force ones, and the forces of their action enter the particle motion equations that are derived in the paper in the general form. The motion equations describe the topological spin transport, pumping and splitting. The Berry phase is represented in this theory analogously to the Dirac phase of a particle in an electromagnetic field. Due to the analogy with the electromagnetic field, the theory becomes natural in the four-dimensional form. Besides the general theory the article considers a number of important particular examples, both known and new.Comment: 28 pages, the final (journal) versio

Le temps des fessées. Microhistoire d’un fantasme mineur

La constitution d’un club de fessée entre hommes à la fin des années 1980 en France permet d’analyser la définition d’un fantasme minoritaire et les ressorts d’un processus d’érotisation. Le club définit en premier lieu un fétichisme de la fessée qui constitue celle-ci en pratique érotique autonome, qui intègre la douleur et l’humiliation à une pratique sexuelle, et qui rend indiscernable la distinction entre la contrainte et le consentement. À travers la mobilisation de scénarios, le fantasme ouvre des possibilités d’identifications et instaure un rapport au temps où la fessée est anticipée, à la fois crainte et désirée. Les récits pornographiques publiés dans le magazine de l’association permettent également de préciser les conditions historiques de ce fantasme. L’association naît au moment où se stabilisent de nouvelles problématisations des violences et de l’enfance, caractérisées par la condamnation des châtiments corporels, la dénonciation des institutions disciplinaires et de la pédophilie. Le fantasme de la fessée, qui repose sur une temporalisation spécifique, un retour à une enfance vue à travers des désirs d’adultes, est un après-coup historiquement situé qui rejoue, sur un mode mineur, des expériences masculines en cours d’illégitimation ou de disparition

Quantifying Opacity

International audienceOpacity is a general language-theoretic framework in which several security properties of a system can be expressed. Its parameters are a predicate, given as a subset of runs of the system, and an observation function, from the set of runs into a set of observables. The predicate describes secret information in the system and, in the possibilistic setting, it is opaque if its membership cannot be inferred from observation.In this paper, we propose several notions of quantitative opacity for probabilistic systems, where the predicate and the observation function are seen as random variables. Our aim is to measure (i) the probability of opacity leakage relative to these random variables and (ii) the level of uncertainty about membership of the predicate inferred from observation. We show how these measures extend possibilistic opacity, we give algorithms to compute them for regular secrets and observations, and we apply these computations on several classical examples. We finally partially investigate the non-deterministic setting