Percorrer por autor "Araujo, Filipe"
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- Defeating Colluding Nodes in Desktop Grid Computing PlatformsPublication . Silaghi, Gheorghe Cosmin; Araujo, Filipe; Silva, Luis Moura; Domingues, Patrício; Arenas, Alvaro E.Desktop Grid systems reached a preeminent place among the most powerful computing platforms in the planet. Unfortunately, they are extremely vulnerable to mischief, because computing projects exert no administrative or technical control on volunteers. These can very easily output bad results, due to software or hardware glitches (resulting from over-clocking for instance), to get unfair computational credit, or simply to ruin the project. To mitigate this problem, Desktop Grid servers replicate work units and apply majority voting, typically on 2 or 3 results. In this paper, we observe that simple majority voting is powerless against malicious volunteers that collude to attack the project. We argue that to identify this type of attack and to spot colluding nodes, each work unit needs at least 3 voters. In addition, we propose to post-process the voting pools in two steps. i) In the first step, we use a statistical approach to identify nodes that were not colluding, but submitted bad results; ii) then, we use a rather simple principle to go after malicious nodes which acted together: they might have won conflicting voting pools against nodes that were not identified in step i. We use simulation to show that our heuristic can be quite effective against colluding nodes, in scenarios where honest nodes form a majority.
- A Hybrid Application for Real-Time Air Quality MonitoringPublication . Silva, Jorge; Salgueiro, Pedro; Rato, Luis; Saias, José; Nogueira, Vitor; Lucas, Pedro; Araujo, Filipe; Silva, Catarina; Gil, Paulo; Cardoso, Alberto; Arrais, Joel; Ribeiro, Bernardete; Coutinho, DanielWith the raising concerns for the environment, interest in monitoring air quality is likely to increase in the near future. However, most data comes from a limited number of government-owned sensors, which can only capture a small fraction of reality. Improving data coverage thus involves reducing the cost of sensors and make data widely available. For this, we will use a very high number of low-cost sensors as the basis for an air quality monitoring platform, capable of collecting, aggregating, storing and displaying data. This platform will use stream-based technologies capable of scaling for large numbers of sensors and users. The resulting NanoSen-AQM platform will provide vast amounts of air quality data to the public, with the aim of improving public health.
- libboincexec: A Generic Virtualization Approach for the BOINC MiddlewarePublication . Ferreira, Diogo; Araujo, Filipe; Domingues, PatricioBOINC is a client-server desktop grid middleware that has grown to power very large computational projects. BOINC clients request computing jobs to a central server and run them alongside other regular applications. Unfortunately, this kind of execution causes two kinds of problems. Firstly, developers must port their application to every single operating system target, which usually means maintaining several different versions of the same application. Secondly, any application running natively on desktop grid hardware is a potential security threat to the volunteer client. During the course of this research we sought an efficient and generic method for alternative execution of jobs in BOINC clients. Our approach is strongly guided by the principles of non-intrusiveness and contains two main components. The first is a library, libboincexec, which is able to control several virtual machines monitors. The second is a modified BOINC wrapper that provides the glue between libboincexec and the middleware. Through the use of this solution we are able to effectively use virtual machines to perform computation on desktop grids. This computation is inherently safe because virtual machines provide sand boxing. Additionally, by targeting the same virtual operating system, the problem of maintaining different versions of an application does not exist, thereby solving the heterogeneity problem of desktop grid nodes.
- A maximum independent set approach for collusion detection in voting poolsPublication . Araujo, Filipe; Farinha, Jorge; Domingues, Patrício; Silaghi, Gheorghe Cosmin; Kondo, DerrickFrom agreement problems to replicated software execution, we frequently find scenarios with voting pools. Unfortunately, Byzantine adversaries can join and collude to distort the results of an election. We address the problem of detecting these colluders, in scenarios where they repeatedly participate in voting decisions. We investigate different malicious strategies, such as naïve or colluding attacks, with fixed identifiers or in whitewashing attacks. Using a graph-theoretic approach, we frame collusion detection as a problem of identifying maximum independent sets. We then propose several new graph-based methods and show, via analysis and simulations, their effectiveness and practical applicability for collusion detection.
- Monitoring the EDGeS project infrastructurePublication . Araujo, Filipe; Santiago, David; Ferreira, Diogo; Farinha, Jorge; Domingues, Patrício; Silva, Luis Moura; Urbah, Etienne; Lodygensky, Oleg; He, Haiwu; Marosi, Attila Csaba; Gombas, Gabor; Balaton, Zoltan; Farkas, Zoltan; Kacsuk, PeterEDGeS is an European funded Framework Program 7 project that aims to connect desktop and service grids together. While in a desktop grid, personal computers pull jobs when they are idle, in service grids there is a scheduler that pushes jobs to available resources. The work in EDGeS goes well beyond conceptual solutions to bridge these grids together: it reaches as far as actual implementation, standardization, deployment, application porting and training. One of the work packages of this project concerns monitoring the overall EDGeS infrastructure. Currently, this infrastructure includes two types of desktop grids, BOINC and XtremWeb, the EGEE service grid, and a couple of bridges to connect them. In this paper, we describe the monitoring effort in EDGeS: our technical approaches, the goals we achieved, and the plans for future work.
- An Online Platform For Real-Time Air Quality MonitoringPublication . Silva, Jorge; Salgueiro, Pedro; Rato, Luis; Saias, Jose; Nogueira, Vitor; Lucas, Pedro; Araujo, Filipe; Silva, Catarina; Gil, Paulo; Cardoso, Alberto; Arrais, Joel; Ribeiro, Bernardete; Coutinho, DanielThe interest in the quality of air is likely to increase, as the public concern for health and environmental issues is on the rise. So far, most data available comes from a small numbers of government-owned sensors, lacking a wide coverage of the entire reality. Improving the amount of data available thus involves reducing the cost of sensors and make their readings accessible to the public. The NanoSen-AQM project aims to do precisely that. Create and use vast numbers of low-cost nano-sensors, to make their data accessible for the public. To achieve such an ambitious goal, the project will use state-of-the-art techniques from Machine Learning and mobile and web development frameworks. As a result, the NanoSen-AQM platform should provide free access to the public and low-cost of entry for sensor owners willing to share their data.