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Aubert C.,CNRS Complex and Logical Algorithm Laboratory | Cristescu I.,University Paris Diderot
Electronic Proceedings in Theoretical Computer Science, EPTCS | Year: 2015

A standard contextual equivalence for process algebras is strong barbed congruence. Configuration structures are a denotational semantics for processes in which one can define equivalences that are more discriminating, i.e. that distinguish the denotation of terms equated by barbed congruence. Hereditary history preserving bisimulation (HHPB) is such a relation. We define a strong back and forth barbed congruence using a reversible process algebra and show that the relation induced by the back and forth congruence is equivalent to HHPB, providing a contextual characterization of HHPB. © C. Aubert & I. Cristescu.

Cegielski P.,CNRS Complex and Logical Algorithm Laboratory | Grigorieff S.,CNRS Laboratory of Algorithmic Informatics: Fundamentals and Applications | Guessarian I.,CNRS Laboratory of Algorithmic Informatics: Fundamentals and Applications
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

Various problems on integers lead to the class of functions defined on a ring of numbers (or a subset of such a ring) and verifying a−b divides f(a)−f(b) for all a, b.We say that such functions are “congruence preserving”. In previous works, we characterized these classes of functions for the cases ℕ → ℤ, ℤ → ℤ and ℤ/nℤ → ℤ/mℤ in terms of sums series of rational polynomials (taking only integral values) and the function giving the least common multiple of 1, 2,..., k. In this paper we relate the finite and infinite cases via a notion of “lifting”: if π: X → Y is a surjective morphism and f is a function Y → Y a lifting of f is a function F: X → X such that π ◦ F = f ◦ π. We prove that the finite case ℤ/nℤ → ℤ/nℤ can be so lifted to the infinite cases ℕ → ℕ and ℤ → ℤ. We also use such liftings to extend the characterization to the rings of p-adic and profinite integers, using Mahler representation of continuous functions on these rings. © Springer International Publishing Switzerland 2015.

Hurst W.,Liverpool John Moores University | Shone N.,Liverpool John Moores University | Monnet Q.,CNRS Complex and Logical Algorithm Laboratory
Proceedings - 15th IEEE International Conference on Computer and Information Technology, CIT 2015, 14th IEEE International Conference on Ubiquitous Computing and Communications, IUCC 2015, 13th IEEE International Conference on Dependable, Autonomic and Secure Computing, DASC 2015 and 13th IEEE International Conference on Pervasive Intelligence and Computing, PICom 2015 | Year: 2015

Over the last decade, the level of critical infrastructure technology has been steadily transforming in order to keep pace with the growing demand for the services offered. The implementation of the smart grid, which relies on a complex and intelligent level of interconnectivity, is one example of how vital amenity provision is being refined. However, with this change, the risk of threats from the digital domain must be calculated. Superior interconnectivity between infrastructures means that the future cascading impacts of successful cyberattacks are unknown. One such threat being faced in the digital domain is the Distributed Denial of Service (DDoS) attack. A DDoS has the goal of incapacitating a server, network or service, by barraging a target with external data traffic in the form of communication requests. DDoS have the potential to cause a critical infrastructure outage, and the subsequent impact on a network of such infrastructures is yet unknown. In this paper, an approach for assessing the future impacts of a cyber-attack in a network of critical infrastructures is presented; with a focus on DDoS attacks. A simulation of a critical infrastructure network provides data to represent both normal run-time and an attack scenario. Using this dataset, a technique for assessing the future impact of disruptions on integrated critical infrastructure network, is demonstrated. © 2015 Crown.

Cervelle J.,CNRS Complex and Logical Algorithm Laboratory | Formenti E.,University of Nice Sophia Antipolis | Guillon P.,University of Chile
Leibniz International Proceedings in Informatics, LIPIcs | Year: 2010

A cellular automaton (CA) is a parallel synchronous computing model, which consists in a juxtaposition of finite automata (cells) whose state evolves according to that of their neighbors. Its trace is the set of infinite words representing the sequence of states taken by some particular cell. In this paper we study the ultimate trace of CA and partial CA (a CA restricted to a particular subshift). The ultimate trace is the trace observed after a long time run of the CA. We give sufficient conditions for a set of infinite words to be the trace of some CA and prove the undecidability of all properties over traces that are stable by ultimate coincidence. © J. Cervelle, E. Formenti, and P. Guillon.

Cegielski P.,CNRS Complex and Logical Algorithm Laboratory | Grigorieff S.,University Paris Diderot | Guessarian I.,University Paris Diderot
Information Processing Letters | Year: 2014

We consider lattices of regular sets of non negative integers, i.e. of sets definable in Presburger arithmetic. We prove that if such a lattice is closed under decrement then it is also closed under many other functions: quotients by an integer, roots, etc. We characterize the family of such functions. © 2013 Elsevier B.V.

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