Results 1  10
of
17
Making random choices invisible to the scheduler
 In Proc. of CONCUR’07). To appear
, 2007
"... Abstract. When dealing with process calculi and automata which express both nondeterministic and probabilistic behavior, it is customary to introduce the notion of scheduler to resolve the nondeterminism. It has been observed that for certain applications, notably those in security, the scheduler ne ..."
Abstract

Cited by 21 (10 self)
 Add to MetaCart
(Show Context)
Abstract. When dealing with process calculi and automata which express both nondeterministic and probabilistic behavior, it is customary to introduce the notion of scheduler to resolve the nondeterminism. It has been observed that for certain applications, notably those in security, the scheduler needs to be restricted so not to reveal the outcome of the protocol’s random choices, or otherwise the model of adversary would be too strong even for “obviously correct ” protocols. We propose a processalgebraic framework in which the control on the scheduler can be specified in syntactic terms, and we show how to apply it to solve the problem mentioned above. We also consider the definition of (probabilistic) may and must preorders, and we show that they are precongruences with respect to the restricted schedulers. Furthermore, we show that all the operators of the language, except replication, distribute over probabilistic summation, which is a useful property for verification. 1
Deriving syntax and axioms for quantitative regular behaviours
, 2009
"... We present a systematic way to generate (1) languages of (generalised) regular expressions, and (2) sound and complete axiomatizations thereof, for a wide variety of quantitative systems. Our quantitative systems include weighted versions of automata and transition systems, in which transitions ar ..."
Abstract

Cited by 10 (4 self)
 Add to MetaCart
We present a systematic way to generate (1) languages of (generalised) regular expressions, and (2) sound and complete axiomatizations thereof, for a wide variety of quantitative systems. Our quantitative systems include weighted versions of automata and transition systems, in which transitions are assigned a value in a monoid that represents cost, duration, probability, etc. Such systems are represented as coalgebras and (1) and (2) above are derived in a modular fashion from the underlying (functor) type of these coalgebras. In previous work, we applied a similar approach to a class of systems (without weights) that generalizes both the results of Kleene (on rational languages and DFA’s) and Milner (on regular behaviours and finite LTS’s), and includes many other systems such as Mealy and Moore machines. In the present paper, we extend this framework to deal with quantitative systems. As a consequence, our results now include languages and axiomatizations, both existing and new ones, for many different kinds of probabilistic systems.
Compositional Methods for InformationHiding
"... Protocols for informationhiding often use randomized primitives to obfuscate the link between the observables and the information to be protected. The degree of protection provided by a protocol can be expressed in terms of the probability of error associated to the inference of the secret inform ..."
Abstract

Cited by 7 (1 self)
 Add to MetaCart
(Show Context)
Protocols for informationhiding often use randomized primitives to obfuscate the link between the observables and the information to be protected. The degree of protection provided by a protocol can be expressed in terms of the probability of error associated to the inference of the secret information. We consider a probabilistic process calculus approach to the specification of such protocols, and we study how the operators affect the probability of error. In particular, we characterize constructs that have the property of not decreasing the degree of protection, and that can therefore be considered safe in the modular construction of protocols. As a case study, we apply these techniques to the Dining Cryptographers, and we are able to derive a generalization of Chaum’s strong anonymity result.
A Probabilistic Kleene Theorem
"... We provide a Kleene Theorem for (Rabin) probabilistic automata over finite words. Probabilistic automata generalize deterministic finite automata and assign to a word an acceptance probability. We provide probabilistic expressions with probabilistic choice, guarded choice, concatenation, and a sta ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
(Show Context)
We provide a Kleene Theorem for (Rabin) probabilistic automata over finite words. Probabilistic automata generalize deterministic finite automata and assign to a word an acceptance probability. We provide probabilistic expressions with probabilistic choice, guarded choice, concatenation, and a star operator. We prove that probabilistic expressions and probabilistic automata are expressively equivalent. Our result actually extends to twoway probabilistic automata with pebbles and corresponding expressions.
Kleene Coalgebra  an overview
"... Coalgebras provide a uniform framework for the study of dynamical systems, including several types of automata. The coalgebraic view on systems has recently been proved relevant by the development of a number of expression calculi which generalize classical results by Kleene, on regular expressions, ..."
Abstract
 Add to MetaCart
(Show Context)
Coalgebras provide a uniform framework for the study of dynamical systems, including several types of automata. The coalgebraic view on systems has recently been proved relevant by the development of a number of expression calculi which generalize classical results by Kleene, on regular expressions, and by Kozen, on Kleene algebra. This note contains an overview of the motivation and results of the generic framework we developed – Kleene Coalgebra – to uniformly derive the aforementioned calculi. We present an historical overview of work on regular expressions and axiomatizations, as well a discussion of related work. We show applications of the framework to three types of probabilistic systems: simple Segala, stratified and PnueliZuck.
On Compositionality, Efficiency, and Applicability of Abstraction in Probabilistic Systems
"... Abstract. A branching bisimulation for probabilistic systems that is preserved under parallel composition has been defined recently for the alternating model. We show that besides being compositional, it is decidable in polynomial time and it preserves the properties expressible in probabilistic Com ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract. A branching bisimulation for probabilistic systems that is preserved under parallel composition has been defined recently for the alternating model. We show that besides being compositional, it is decidable in polynomial time and it preserves the properties expressible in probabilistic Computation Tree Logic (pCTL). In the groundcomplete axiomatization, only a single axiom is added to the axioms for strong bisimulation. We show that the Concurrent Alternating Bit protocol can be verified using the process algebra and a set of recursive rules. 1
Abstract QAPL 2007 Probabilistic Barbed Congruence
"... This paper defines a probabilistic barbed congruence which turns out to coincide with observational equivalence in a probabilistic extension of CCS. Based on this coincidence result, we provide a sound and complete axiomatisation for the barbed congruence in a finite fragment of probabilistic CCS. ..."
Abstract
 Add to MetaCart
(Show Context)
This paper defines a probabilistic barbed congruence which turns out to coincide with observational equivalence in a probabilistic extension of CCS. Based on this coincidence result, we provide a sound and complete axiomatisation for the barbed congruence in a finite fragment of probabilistic CCS.