361 research outputs found
Studying Maximum Information Leakage Using Karush-Kuhn-Tucker Conditions
When studying the information leakage in programs or protocols, a natural
question arises: "what is the worst case scenario?". This problem of
identifying the maximal leakage can be seen as a channel capacity problem in
the information theoretical sense. In this paper, by combining two powerful
theories: Information Theory and Karush-Kuhn-Tucker conditions, we demonstrate
a very general solution to the channel capacity problem. Examples are given to
show how our solution can be applied to practical contexts of programs and
anonymity protocols, and how this solution generalizes previous approaches to
this problem
Quantifying Information Leakage of Randomized Protocols
International audienceThe quantification of information leakage provides a quantitative evaluation of the security of a system. We propose the usage of Markovian processes to model and analyze the information leakage of deterministic and probabilistic systems. We show that this method generalizes the lattice of information approach and is a natural framework for modeling refined attackers capable to observe the internal behavior of the system. We also use our method to obtain an algorithm for the computation of channel capacity from our Markovian models. Finally, we show how to use the method to analyze timed and non-timed attacks on the Onion Routing protocol
Entropy and Attack Models in Information Flow
International audienceKöpf and Basin have discussed the relation between brute-force guessing attacks and entropy, in the context of information flow induced by a deterministic program. In this talk, we extend the analysis of Köpf and Basin to the probabilistic scenario, and we consider also other notions of entropy, including the family of entropies proposed by Rényi
Differential Privacy versus Quantitative Information Flow
Differential privacy is a notion of privacy that has become very popular in
the database community. Roughly, the idea is that a randomized query mechanism
provides sufficient privacy protection if the ratio between the probabilities
of two different entries to originate a certain answer is bound by e^\epsilon.
In the fields of anonymity and information flow there is a similar concern for
controlling information leakage, i.e. limiting the possibility of inferring the
secret information from the observables. In recent years, researchers have
proposed to quantify the leakage in terms of the information-theoretic notion
of mutual information. There are two main approaches that fall in this
category: One based on Shannon entropy, and one based on R\'enyi's min entropy.
The latter has connection with the so-called Bayes risk, which expresses the
probability of guessing the secret. In this paper, we show how to model the
query system in terms of an information-theoretic channel, and we compare the
notion of differential privacy with that of mutual information. We show that
the notion of differential privacy is strictly stronger, in the sense that it
implies a bound on the mutual information, but not viceversa
The internal rotation profile of the B-type star KIC10526294 from frequency inversion of its dipole gravity modes and statistical model comparison
The internal angular momentum distribution of a star is key to determine its
evolution. Fortunately, the stellar internal rotation can be probed through
studies of rotationally-split non-radial oscillation modes. In particular,
detection of non-radial gravity modes (g modes) in massive young stars has
become feasible recently thanks to the Kepler space mission. Our aim is to
derive the internal rotation profile of the Kepler B8V star KIC 10526294
through asteroseismology. We interpret the observed rotational splittings of
its dipole g modes using four different approaches based on the best seismic
models of the star and their rotational kernels. We show that these kernels can
resolve differential rotation the radiative envelope if a smooth rotational
profile is assumed and the observational errors are small. Based on Kepler
data, we find that the rotation rate near the core-envelope boundary is well
constrained to nHz. The seismic data are consistent with rigid
rotation but a profile with counter-rotation within the envelope has a
statistical advantage over constant rotation. Our study should be repeated for
other massive stars with a variety of stellar parameters in order to deduce the
physical conditions that determine the internal rotation profile of young
massive stars, with the aim to improve the input physics of their models.Comment: 52 pages, 32 figures, accepted for publication in The Astrophysical
Journa
Quantitative Information Flow as Safety and Liveness Hyperproperties
We employ Clarkson and Schneider's "hyperproperties" to classify various
verification problems of quantitative information flow. The results of this
paper unify and extend the previous results on the hardness of checking and
inferring quantitative information flow. In particular, we identify a subclass
of liveness hyperproperties, which we call "k-observable hyperproperties", that
can be checked relative to a reachability oracle via self composition.Comment: In Proceedings QAPL 2012, arXiv:1207.055
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