5,360 research outputs found
Virtual Analysis and Reduction of Side-Channel Vulnerabilities of Smartcards
This paper focuses on the usability of the PINPAS tool. The PINPAS tool is an instruction-level interpreter for smartcard assembler languages, augmented with facilities to study side-channel vulnerabilities. The tool can simulate side-channel leakage and has a suite of utilities to analyze this. The usage of the tool, for the analysis of a cryptographic algorithm is illustrated using the standard AES and RSA. Vulnerabilities of the implementations are identified and protective measures added. It is argued, that the tool can be instrumental for the design and realization of secure smartcard implementations in a systematic wa
Predictions of variable mass loss for Luminous Blue Variables
We present radiation-driven wind models for Luminous Blue Variables (LBVs)
and predict their mass-loss rates. We study the effects of lower masses and
modified abundances in comparison to the normal OB supergiants, and we find
that the main difference in mass loss is due to the lower masses of LBVs. In
addition, we find that the increase in helium abundance changes the mass-loss
properties by small amounts (up to about 0.2 dex in log Mdot), while CNO
processing is relatively unimportant for the mass-loss rate. A comparison
between our mass loss predictions and the observations is performed for four
relatively well-studied LBVs. The comparison shows that (i) the winds of LBVs
are driven by radiation pressure on spectral lines, (ii) the variable mass loss
behaviour of LBVs during their S Doradus-type variation cycles is explained by
changes in the line driving efficiency, notably due to the
recombination/ionisation of Fe IV/III and Fe III/II, and finally, (iii) the
winds of LBVs can be used to derive their masses, as exemplified by the case of
AG Car, for which we derive a present-day mass of 35 Msun.Comment: 12 pages; A&A accepte
Metric Semantics and Full Abstractness for Action Refinement and Probabilistic Choice
This paper provides a case-study in the field of metric semantics for probabilistic programming. Both an operational and a denotational semantics are presented for an abstract process language L_pr, which features action refinement and probabilistic choice. The two models are constructed in the setting of complete ultrametric spaces, here based on probability measures of compact support over sequences of actions. It is shown that the standard toolkit for metric semantics works well in the probabilistic context of L_pr, e.g. in establishing the correctness of the denotational semantics with respect to the operational one. In addition, it is shown how the method of proving full abstraction --as proposed recently by the authors for a nondeterministic language with action refinement-- can be adapted to deal with the probabilistic language L_pr as well
A Definition Scheme for Quantitative Bisimulation
FuTS, state-to-function transition systems are generalizations of labeled
transition systems and of familiar notions of quantitative semantical models as
continuous-time Markov chains, interactive Markov chains, and Markov automata.
A general scheme for the definition of a notion of strong bisimulation
associated with a FuTS is proposed. It is shown that this notion of
bisimulation for a FuTS coincides with the coalgebraic notion of behavioral
equivalence associated to the functor on Set given by the type of the FuTS. For
a series of concrete quantitative semantical models the notion of bisimulation
as reported in the literature is proven to coincide with the notion of
quantitative bisimulation obtained from the scheme. The comparison includes
models with orthogonal behaviour, like interactive Markov chains, and with
multiple levels of behavior, like Markov automata. As a consequence of the
general result relating FuTS bisimulation and behavioral equivalence we obtain,
in a systematic way, a coalgebraic underpinning of all quantitative
bisimulations discussed.Comment: In Proceedings QAPL 2015, arXiv:1509.0816
Opportunistic behaviour by private irrigators within a capacity-sharing regime
The concept of capacity-sharing (as a specific type of demand-orientated water management strategy) is a relatively newcomer on the South African water management regime and much debate is currently under way regarding the viability of the concept for the South African context. One of the main features is that it decentralises and integrates water management to a much greater degree than state-dominated management regimes. However, as the concept of capacity-sharing allows a greater degree of decision-making autonomy to the private decision-maker, the question could be asked to what extent the management of a capacity-sharing regime would be exposed to opportunistic behaviour from private irrigators. If it is heavily exposed, there are considerable scope for opportunistic decision-making behaviour under private decision-makers and therefore problems of moral hazard / adverse selection and rent seeking could present itself. Therefore, the question arises what safety features do capacity sharing present to confine possible opportunistic decision-making practices. This article discusses two areas within a capacity-sharing regime that are likely to be exposed to opportunistic decision-making behaviour. Possible safety-features from capacity sharing to account for this type of behaviour are identified and discussed briefly. This article concludes with the notion that capacity sharing does feature some properties that could minimise opportunistic behaviour from private decision-makers.Resource /Energy Economics and Policy,
Bisimulation of Labelled State-to-Function Transition Systems Coalgebraically
Labeled state-to-function transition systems, FuTS for short, are
characterized by transitions which relate states to functions of states over
general semirings, equipped with a rich set of higher-order operators. As such,
FuTS constitute a convenient modeling instrument to deal with process languages
and their quantitative extensions in particular. In this paper, the notion of
bisimulation induced by a FuTS is addressed from a coalgebraic point of view. A
correspondence result is established stating that FuTS-bisimilarity coincides
with behavioural equivalence of the associated functor. As generic examples,
the equivalences underlying substantial fragments of major examples of
quantitative process algebras are related to the bisimilarity of specific FuTS.
The examples range from a stochastic process language, PEPA, to a language for
Interactive Markov Chains, IML, a (discrete) timed process language, TPC, and a
language for Markov Automata, MAL. The equivalences underlying these languages
are related to the bisimilarity of their specific FuTS. By the correspondence
result coalgebraic justification of the equivalences of these calculi is
obtained. The specific selection of languages, besides covering a large variety
of process interaction models and modelling choices involving quantities,
allows us to show different classes of FuTS, namely so-called simple FuTS,
combined FuTS, nested FuTS, and general FuTS
Laplacian gauge and instantons
We exhibit the connection between local gauge singularities in the Laplacian
gauge and topological charge, which opens the possibility of studying instanton
excitations without cooling. We describe our version of Laplacian gauge-fixing
for SU(N).Comment: Lattice 2000 (Topology and Vacuum), 4 pages, 3 figures -- cosmetic
change
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