Belhassen Zouari - Academia.edu (original) (raw)

Papers by Belhassen Zouari

2009 European Control Conference (ECC)

Wireless sensor network consists of a large number of low-power, short-lived, unreliable sensors.... more Wireless sensor network consists of a large number of low-power, short-lived, unreliable sensors. One fundamental issue in this kind of networks is the coverage problem, that reflects how well the target area is monitored by sensors. According to the coverage concept, many works have introduced nodes-scheduling methods to increase the system lifetime, as well as to maintain sufficient coverage and reliability. Node-scheduling allows to turn off redundant sensors. In this paper, we propose a node-scheduling algorithm, that reduces system overall energy consumption, therefore increasing system lifetime, by turning off redundant nodes. The proposed scheduling method is based on one-hop remaining energy neighbouring knowledge. This algorithm gives an optimal node-schedul that maintains the original sensing coverage after turning off redundant nodes.

Proceedings of the 18th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications

2017 IEEE International Symposium on Parallel and Distributed Processing with Applications and 2017 IEEE International Conference on Ubiquitous Computing and Communications (ISPA/IUCC), 2017

Model checking is a powerful technique for verifying and analyzing complex systems in many applic... more Model checking is a powerful technique for verifying and analyzing complex systems in many application fields. The analysis process of complex and concurrent systems often requires large computation resources which represents a real challenge. Even with simple configurations, the well-known state explosion problem is faced as the generated state space of such systems grows exponentially with the number of the system components. Numerous methods and techniques have been developed to overcome this problem including parallel and distributed-memory processing. In this paper, we aim at improving the performances of the so called Symbolic Observation Graph (SOG) construction by using parallelization techniques. A SOG is a hybrid structure where the transitions of a system are divided into observed and unobserved ones. The nodes of this graph are then defined as sets of states linked with unobserved transitions (and encoded symbolically with a BDD) and edges are labeled with observed transitions only (and are explicitly represented). We propose two parallel algorithms to build the SOG. The first algorithm is dedicated for shared memory architectures, and is based on the distribution of the SOG construction on several threads using a dynamic load balancing scheme. The second algorithm is proposed for distributed memory architectures, and distributes the SOG construction on processes using a static load balancing scheme. These two algorithms are implemented and their performances are studied and compared to each other and to the sequential construction of the SOG.

Lecture Notes in Computer Science, 2020

Distributed Denial of Services (DDoS) attacks are still among the top major cyber threats against... more Distributed Denial of Services (DDoS) attacks are still among the top major cyber threats against online servers. One efficient way to defend against such threats is through adaptive threshold models, which can tune defense mechanisms according to network conditions and setup. However, the main challenge of such models is threshold selection which has a direct impact on detection accuracy and hence protection insurance. In this paper, we propose a new model to compute an adaptive threshold via distributed energy wavelet decomposition. Our model leverages consensus protocol to solve the single point of failure problem. The empirical evaluation, which is based on real DDoS attack traces, demonstrate that the proposed model is indeed capable to detect accurately and in real-time, DDoS threats.

2019 19th International Conference on Application of Concurrency to System Design (ACSD), 2019

An efficient way to cope with the combinatorial explosion problem induced by the model checking p... more An efficient way to cope with the combinatorial explosion problem induced by the model checking process is to compute the Symbolic Observation Graph (SOG). Given an stuttering invariant event-based LTL formula φ, involving a subset of actions E (called observed actions), the SOG is a condensed representation of the state space graph based on a symbolic encoding of the nodes (sets of states linked with unobserved actions) and an explicit representation of the edges (labelled with observed actions only). It has the advantage to be much reduced comparing to the original state space graph while being equivalent with respect to linear time properties (i.e., the original state space graph satisfies φ if and only if the corresponding SOG satisfies φ. Aiming to go further in the process of tackling the state space explosion problem, we propose in this paper to parallelize the construction of the SOG using a hybrid approach (distributed+shared memory). Doing so, we take advantage of the recent advances in computer hardware, by distributing the construction process over a large number of multi-core processors. We studied the performances of our new approach comparing to both distributed and shared memory approaches on one side, and to the sequential construction of the SOG, on the other hand. The obtained results show that the proposed approach offers an interesting alternative allowing to completely exploit the available distributed architecture while offering significant speedup.

2018 14th International Wireless Communications & Mobile Computing Conference (IWCMC), 2018

Literature contributions have shown that information theoretic techniques can effectively detect ... more Literature contributions have shown that information theoretic techniques can effectively detect various types of Distributed Denial of Service (DDoS) attacks. However, such techniques are often centralized with a limited measurement vantage point and suffer from the issue of single point of failure. Furthermore, with the flourishing of distributed and cloudbased environments, such techniques ought to adapt to such settings for scalability and performance reasons. In this paper, we address the problem of collaborative DDoS detection using information-theoretic techniques. To this end, we propose an entropy-based detection mechanism that supports collaborative agreement to identify suitable tuning network parameters for distributed DDoS inference in real-time. Empirical evaluations with real DDoS attacks demonstrate that the proposed approach is indeed capable of cooperatively inferring DDoS attacks while achieving resiliency and scalability.

Journal of Reliable Intelligent Environments, 2021

Smart Home Systems (SHSs) represent one of the most prevailing Internet of Things (IoT) applicati... more Smart Home Systems (SHSs) represent one of the most prevailing Internet of Things (IoT) applications. While IoT-based SHSs can be user-driven or automatically operated, their unauthorized or unexpected operation brings new security and safety concerns that did not exist in legacy homes. This paper provides a review of the state-of-the-art approaches for securing the operation of SHSs. We first present security threats that may lead to unauthorized/unexpected operation of an SHS for both types of operation. Then, we review existing security approaches for each type of operation. Finally, we draw some conclusions and raise open research issues based on this review.

2018 IEEE Intl Conf on Parallel & Distributed Processing with Applications, Ubiquitous Computing & Communications, Big Data & Cloud Computing, Social Computing & Networking, Sustainable Computing & Communications (ISPA/IUCC/BDCloud/SocialCom/SustainCom), 2018

Lecture Notes in Computer Science, 1995

Journal of Real-Time Image Processing, 2021

A key issue in scientific visualization is the transfer function (TF) for direct volume rendering... more A key issue in scientific visualization is the transfer function (TF) for direct volume rendering (DVR). The TF serves as a tool for translating data values into color and opacity, to visualize the relevant structures present in the volumetric data studied. An adequate transfer function should have a non-complicated interactive strategy for new users or even experts. Furthermore, it has to achieve high-quality and not time-consuming visualization. In this paper, we propose a novel image-centric method for the real-time generation of transfer functions. The method is based on incremental classification. This incremental classification-based approach is theoretically faster than that using batch classification. The method does not require users to manipulate complex widgets. We present a simple user interface adapted to the incremental learning process. Thus, this interface made it possible for the user to interact with a series of 2D images, precise the cluster, and identify some voxels. The whole volume is incrementally classified and the rendering result is shown to the user as selected voxels are added. The TF is generated by assigning the optical properties to clusters using harmonic colors. We further introduce a novel incremental classifier, namely incremental discriminant-based support vector machine( IDSVM), that can learn through time. The IDSVM was used in the classification stage of the proposed image-centric method. To evaluate the IDSVM, an extensive comparison of the model with other state-of-the-art incremental and batch classifiers on 12 real-world datasets and four other famous large datasets, namely MNIST-full, MNIST-test, USPS, and Fashion-MNIST, has been carried out. Using the area under curve, it has been found that the IDSVM outperforms the other classifiers. Furthermore, to evaluate the proposed image-centric method, we made use of several benchmark datasets. Qualitative results and a detailed user survey demonstrate the effectiveness of the proposed method and the positive effect of the incrementality in visual and interaction time performance.

Proceedings of the 7th International Conference on Informatics in Control, Automation and Robotics, 2010

2007 IEEE Conference on Emerging Technologies & Factory Automation (EFTA 2007), 2007

Lecture Notes in Computer Science, 2015

Proceedings of the 10th International Conference on Evaluation of Novel Approaches to Software Engineering, 2015

Summer Computer Simulation Conference, 2007

Abstract This paper reviews a proposal for the modular analysis of Petri nets. It improves the mo... more Abstract This paper reviews a proposal for the modular analysis of Petri nets. It improves the modularity of the verification process using modular state spaces. By adding some computations during the construction of the modular state space, one can determine the ...

2014 UKSim-AMSS 16th International Conference on Computer Modelling and Simulation, 2014

IFIP WG10.3 Publications, 1993

This paper deals with two important aspects of communicat ion protocols namely specification and ... more This paper deals with two important aspects of communicat ion protocols namely specification and verification. We present a new variant of the Formal Description Techni que Estelle called SSL which has the semantics of a High-level Petri net model. Such a semantics enables to apply efficient proof methods in order to automatically verify communication prot ocol properties. SSL is mainly

2012 IEEE 36th Annual Computer Software and Applications Conference Workshops, 2012

Nowadays Distributed Denial of Service (DDoS) attacks related to networked enterprise systems is ... more Nowadays Distributed Denial of Service (DDoS) attacks related to networked enterprise systems is a problem that has become much known. Many papers dealt with this type of attacks. Recently DDoS attacks that target large cyberspaces like national cyberspaces have become a hot topic. We start from an existing architecture called Saher Architecture. Saher is used to detect attacks threatening Tunisian National cyberspace. We improve this architecture and propose an approach that allows using a consensus algorithm executed by the probes of the Internet Service Providers in order to detect and react to massive DDoS attacks in a coordinated fashion and under Byzantine assumptions. Different levels of alerts are proposed and the reaction mechanisms depend on the type of the attack. The final outcome of this research is a framework that affords the necessary mechanisms allowing a national cyberspace to counter massive DDoS attacks by coordinating internet Service Providers effort in order to detect and respond to the attacks.