2,601 research outputs found
No Place to Hide that Bytes won't Reveal: Sniffing Location-Based Encrypted Traffic to Track a User's Position
News reports of the last few years indicated that several intelligence
agencies are able to monitor large networks or entire portions of the Internet
backbone. Such a powerful adversary has only recently been considered by the
academic literature. In this paper, we propose a new adversary model for
Location Based Services (LBSs). The model takes into account an unauthorized
third party, different from the LBS provider itself, that wants to infer the
location and monitor the movements of a LBS user. We show that such an
adversary can extrapolate the position of a target user by just analyzing the
size and the timing of the encrypted traffic exchanged between that user and
the LBS provider. We performed a thorough analysis of a widely deployed
location based app that comes pre-installed with many Android devices:
GoogleNow. The results are encouraging and highlight the importance of devising
more effective countermeasures against powerful adversaries to preserve the
privacy of LBS users.Comment: 14 pages, 9th International Conference on Network and System Security
(NSS 2015
Professor - pesquisador de sua prática : dificuldades e motivações
Neste trabalho analisamos três casos de professores de ciências que pesquisaram sua prática docente. Focalizamos os processos de elaboração de suas pesquisas, que resultaram na descoberta de falhas e acertos na condução docente e numa correspondente mudança subjetiva em relação à atividade de ensinar ciências. Os dados empíricos deste trabalho são constituídos pelos diários de pesquisa, memoriais de qualificação e pelas dissertações destes professores, além das entrevistas e conversas informais com os mesmos. Destacamos a insatisfação inicial em relação a sua prática docente, a elaboração do diário de bordo, ocasião de reflexão inicial sobre sua prática e também registro fundamental de pesquisa, a adoção de referenciais para elaborar e analisar os dados e o auxílio de um grupo de interlocutores na academia, formado por colegas e orientadores
The Hubbard model in the two-pole approximation
The two-dimensional Hubbard model is analyzed in the framework of the
two-pole expansion. It is demonstrated that several theoretical approaches,
when considered at their lowest level, are all equivalent and share the
property of satisfying the conservation of the first four spectral momenta. It
emerges that the various methods differ only in the way of fixing the internal
parameters and that it exists a unique way to preserve simultaneously the Pauli
principle and the particle-hole symmetry. A comprehensive comparison with
respect to some general symmetry properties and the data from quantum Monte
Carlo analysis shows the relevance of imposing the Pauli principle.Comment: 12 pages, 8 embedded Postscript figures, RevTeX, submitted to Int.
Jou. Mod. Phys.
Hacking Smart Machines with Smarter Ones: How to Extract Meaningful Data from Machine Learning Classifiers
Machine Learning (ML) algorithms are used to train computers to perform a
variety of complex tasks and improve with experience. Computers learn how to
recognize patterns, make unintended decisions, or react to a dynamic
environment. Certain trained machines may be more effective than others because
they are based on more suitable ML algorithms or because they were trained
through superior training sets. Although ML algorithms are known and publicly
released, training sets may not be reasonably ascertainable and, indeed, may be
guarded as trade secrets. While much research has been performed about the
privacy of the elements of training sets, in this paper we focus our attention
on ML classifiers and on the statistical information that can be unconsciously
or maliciously revealed from them. We show that it is possible to infer
unexpected but useful information from ML classifiers. In particular, we build
a novel meta-classifier and train it to hack other classifiers, obtaining
meaningful information about their training sets. This kind of information
leakage can be exploited, for example, by a vendor to build more effective
classifiers or to simply acquire trade secrets from a competitor's apparatus,
potentially violating its intellectual property rights
On the speed of approach to equilibrium for a collisionless gas
We investigate the speed of approach to Maxwellian equilibrium for a
collisionless gas enclosed in a vessel whose wall are kept at a uniform,
constant temperature, assuming diffuse reflection of gas molecules on the
vessel wall. We establish lower bounds for potential decay rates assuming
uniform bounds on the initial distribution function. We also obtain a
decay estimate in the spherically symmetric case. We discuss with particular
care the influence of low-speed particles on thermalization by the wall.Comment: 22 pages, 1 figure; submitted to Kinetic and Related Model
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