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32
Approximate NonInterference
 JOURNAL OF COMPUTER SECURITY
, 2002
"... We address the problem of characterising the security of a program against unauthorised information flows. Classical approaches are based on noninterference models which depend ultimately on the notion of process equivalence. In these models confidentiality is an absolute property stating the absen ..."
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Cited by 104 (11 self)
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We address the problem of characterising the security of a program against unauthorised information flows. Classical approaches are based on noninterference models which depend ultimately on the notion of process equivalence. In these models confidentiality is an absolute property stating the absence of any illegal information flow. We present a model in which the notion of noninterference is approximated in the sense that it allows for some exactly quantified leakage of information. This is characterised via a notion of process similarity which replaces the indistinguishability of processes by a quantitative measure of their behavioural difference. Such a quantity is related to the number of statistical tests needed to distinguish two behaviours. We also present two semanticsbased analyses of approximate noninterference and we show that one is a correct abstraction of the other.
Probabilistic Constraint Handling Rules
, 2002
"... Classical Constraint Handling Rules (CHR) provide a powerful tool for specifying and implementing constraint solvers and programs. The rules of CHR rewrite constraints (nondeterministically) into simpler ones until they are solved. In this paper we introduce an extension of Constraint Handling Rule ..."
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Cited by 24 (5 self)
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Classical Constraint Handling Rules (CHR) provide a powerful tool for specifying and implementing constraint solvers and programs. The rules of CHR rewrite constraints (nondeterministically) into simpler ones until they are solved. In this paper we introduce an extension of Constraint Handling Rules (CHR), namely Probabilistic CHRs (PCHR). These allow the probabilistic “weighting ” of rules, specifying the probability of their application. In this way we are able to formalise various randomised algorithms such as for example Simulated Annealing. The implementation is based on sourcetosource transformation (STS). Using a recently developed prototype for STS for CHR, we could implement probabilistic CHR in a concise way with a few lines of code in less than one hour.
Concurrent Constraint Programming: Towards Probabilistic Abstract Interpretation
 Proc. of the 23rd International Symposium on Mathematical Foundations of Computer Science, MFCS'98, Lecture Notes in Computer Science
, 2000
"... We present a method for approximating the semantics of probabilistic programs to the purpose of constructing semanticsbased analyses of such programs. The method resembles the one based on Galois connection as developed in the Cousot framework for abstract interpretation. The main difference betwee ..."
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Cited by 22 (8 self)
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We present a method for approximating the semantics of probabilistic programs to the purpose of constructing semanticsbased analyses of such programs. The method resembles the one based on Galois connection as developed in the Cousot framework for abstract interpretation. The main difference between our approach and the standard theory of abstract interpretation is the choice of linear space structures instead of ordertheoretic ones as semantical (concrete and abstract) domains. We show that our method generates "best approximations" according to an appropriate notion of precision defined in terms of a norm. Moreover, if recasted in a ordertheoretic setting these approximations are correct in the sense of classical abstract interpretation theory. We use Concurrent ...
Prioritised fuzzy constraint satisfaction problems: axioms, instantiation and validation
, 2003
"... ..."
Quantitative Observables and Averages in Probabilistic Constraint Programming
 New Trends in Constraints, number 1865 in Lecture Notes in Computer Science
, 1999
"... We investigate notions of observable behaviour of programs which include quantitative aspects of computation along with the most commonly assumed qualitative ones. We model these notions by means of a transition system where transitions occur with a given probability and an associated `cost' ex ..."
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Cited by 11 (6 self)
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We investigate notions of observable behaviour of programs which include quantitative aspects of computation along with the most commonly assumed qualitative ones. We model these notions by means of a transition system where transitions occur with a given probability and an associated `cost' expressing some complexity measure (e.g. running time or, in general, resources consumption).
Probabilistic rewrite strategies: Applications to ELAN
 Rewriting Techniques and Applications
"... Abstract. Recently rule based languages focussed on the use of rewriting as a modeling tool which results in making specications executable. To extend the modeling capabilities of rule based languages, we explore the possibility of making the rule applications subject to probabilistic choices. We p ..."
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Cited by 11 (4 self)
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Abstract. Recently rule based languages focussed on the use of rewriting as a modeling tool which results in making specications executable. To extend the modeling capabilities of rule based languages, we explore the possibility of making the rule applications subject to probabilistic choices. We propose an extension of the ELAN strategy language to deal with randomized systems. We argue through several examples that we propose indeed a natural setting to model systems with randomized choices. This leads us to interesting new problems, and we address the generalization of the usual concepts in abstract reduction systems to randomized systems. 1
Rewriting logic and probabilities
 Rewriting Techniques and Applications (RTA), volume 2706 of L.N.C.S
, 2003
"... Abstract Rewriting Logic has shown to provide a general and elegant framework for unifying a wide variety of models, including concurrency models and deduction systems. In order to extend the modeling capabilities of rule based languages, it is natural to consider that the firing of rules can be sub ..."
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Cited by 10 (2 self)
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Abstract Rewriting Logic has shown to provide a general and elegant framework for unifying a wide variety of models, including concurrency models and deduction systems. In order to extend the modeling capabilities of rule based languages, it is natural to consider that the firing of rules can be subject to some probabilistic laws. Considering rewrite rules subject to probabilities leads to numerous questions about the underlying notions and results. In this paper, we discuss whether there exists a notion of probabilistic rewrite system with an associated notion of probabilistic rewriting logic. 1
Probabilistic Confinement in a Declarative Framework
 IN DECLARATIVE PROGRAMMING – SELECTED PAPERS FROM AGP 2000 – ENTCS
, 2001
"... We show how to formulate and investigate security notions in the context of declarative programming. We concentrate on a particular class of security properties, namely the one called in [11] confinement properties. Our reference language is concurrent constraint programming. We use a probabilistic ..."
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Cited by 6 (2 self)
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We show how to formulate and investigate security notions in the context of declarative programming. We concentrate on a particular class of security properties, namely the one called in [11] confinement properties. Our reference language is concurrent constraint programming. We use a probabilistic version of this language to highlight via simple programs examples the difference between probabilistic and nondeterministic confinement as pointed out in the work by Volpano and Smith [9, 12] in the context of imperative languages. The different role played by variables in imperative and constraint programming hinders a direct translation of the notion of confinement into our declarative setting. Therefore, we introduce the notion of &quot;identity confinement &quot; which is more appropriate for constraint languages. Finally, we present an approximating probabilistic semantics which can be used as a base for the analysis of confinement properties.
Modelbased Programming: Controlling Embedded Systems by Reasoning About Hidden State
 In Eighth Int. Conf. on Principles and Practice of Constraint Programming
, 2002
"... Abstract. Programming complex embedded systems involves reasoning through intricate system interactions along paths between sensors, actuators and control processors. This is a timeconsuming and errorprone process. Furthermore, the resulting code generally lacks modularity and robustness. Modelba ..."
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Cited by 6 (4 self)
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Abstract. Programming complex embedded systems involves reasoning through intricate system interactions along paths between sensors, actuators and control processors. This is a timeconsuming and errorprone process. Furthermore, the resulting code generally lacks modularity and robustness. Modelbased programming addresses these limitations, allowing engineers to program by specifying highlevel control strategies and by assembling commonsense models of the system hardware and software. To execute a control strategy, modelbased executives reason about the models “on the fly”, to track system state, diagnose faults and perform reconfigurations. This paper describes the Reactive Modelbased Programming Language (RMPL) and its executive, called Titan. RMPL provides the features of synchronous reactive languages within a constraintbased modeling framework, with the added ability of being able to read and write to state variables that are hidden within the physical plant. 1
Analysing Approximate Confinement under Uniform Attacks
, 2002
"... We are concerned to give certain guarantees about the security of a system. We identify two kinds of attack: the internally scheduled attack (exemplified by Trojan Horse attacks) and externally scheduled attacks (exemplified by timing attacks). In this paper we focus on the latter. We present a sema ..."
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Cited by 5 (2 self)
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We are concerned to give certain guarantees about the security of a system. We identify two kinds of attack: the internally scheduled attack (exemplified by Trojan Horse attacks) and externally scheduled attacks (exemplified by timing attacks). In this paper we focus on the latter. We present a semantic framework for studying such attacks in the context of PCCP, a simple process algebra with a constraint store. We show that a measure of the efficacy of an attacker can be determined by considering its observable behaviour over the "average" store of the system (for some number of steps). We show how to construct an analysis to determine the average store using the technique of probabilistic abstract interpretation.