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Caires L.,New University of Lisbon | De Nicola R.,University of Florence | Pugliese R.,University of Florence | Vasconcelos V.T.,LaSIGE | Zavattaro G.,University Bolona
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Core calculi have been adopted in the Sensoria project with three main aims. First of all, they have been used to clarify and formally define the basic concepts that characterize the Sensoria approach to the modeling of service-oriented applications. In second place, they are formal models on which the Sensoria analysis techniques have been developed. Finally, they have been used to drive the implementation of the prototypes of the Sensoria languages for programming actual service-based systems. This chapter reports about the Sensoria core calculi presenting their syntax and intuitive semantics, and describing their main features by means of a common running example, namely a Credit Request scenario taken from the Sensoria Finance case study. © 2011 Springer-Verlag Berlin Heidelberg.


Da Rosa Righi R.,Applied Computer Grad. Program | Rodrigues V.F.,Applied Computer Grad. Program | Da Costa C.A.,Applied Computer Grad. Program | Chiwiacowsky L.,Applied Computer Grad. Program | And 2 more authors.
Proceedings of IEEE/ACS International Conference on Computer Systems and Applications, AICCSA | Year: 2015

Electronic transactions have become the mainstream mechanism for performing commerce activities in our daily lives. Aiming at processing them, the most common approach addresses the use of a switch that dispatches transactions to processing machines using the so-called Round-Robin scheduler. Considering this electronic funds transfer (EFT) scenario, we developed a framework model denoted GetLB which comprises not only a new and efficient scheduler, but also a cooperative communication infrastructure for handling heterogeneous and dynamic environments. The GetLB scheduler uses a scheduling heuristic that combines static data from transactions and dynamic information from the processing nodes to overcome the limitations of the Round-Robin based scheduling approaches. Scheduling efficiency takes place thanks to the periodic interaction between the switching node and processing machines, enabling local decision making with up-to-date information about the environment. Besides the description of the aforementioned model in detail, this article also presents a prototype evaluation by using both traces and configurations obtained with a real EFT company. The results show improvements in transaction makespan when comparing our approach with the traditional one over homogeneous and heterogeneous clusters. © 2014 IEEE.


Kreutz D.,University of Luxembourg | Malichevskyy O.,LaSIGE | Feitosa E.,IComp | Cunha H.,IComp | And 2 more authors.
Journal of Network and Computer Applications | Year: 2016

Authentication and authorization are two of the most important services for any IT infrastructure. Taking into account the current state of affairs of cyber warfare, the security and dependability of such services is a first class priority. For instance, the correct and continuous operation of identity providers (e.g., OpenID) and authentication, authorization and accounting services (e.g., RADIUS) is essential for all sorts of systems and infrastructures. As a step towards this direction, we introduce a functional architecture and system design artifacts for prototyping fault- and intrusion-tolerant identification and authentication services. The feasibility and applicability of the proposed elements are evaluated through two distinct prototypes. Our findings indicate that building and deploying resilient and reliable critical services is an achievable goal through a set of system design artifacts based on well-established concepts in the fields of security and dependability. Additionally, we provide an extensive evaluation of both resilient RADIUS (R-RADIUS) and OpenID (R-OpenID) prototypes. We show that our solution makes services resilient against attacks without affecting their correct operation. Our results also pinpoint that the prototypes are capable of meeting the needs of small to large-scale systems (e.g., IT infrastructures with 800k to 10M users). © 2016 Elsevier Ltd. All rights reserved.


Kreutz D.,LaSIGE | Feitosa E.,IComp | Cunha H.,IComp | Niedermayer H.,Institute of Informatics | Kinkelin H.,Institute of Informatics
Proceedings - 9th International Conference on Availability, Reliability and Security, ARES 2014 | Year: 2014

We introduce a set of tools and techniques for increasing the resilience and trustworthiness of identity providers (IdPs) based on OpenID. To this purpose we propose an architecture of specialized components capable of fulfilling the essential requirements for ensuring high availability, integrity and higher confidentiality guarantees for sensitive data and operations. Additionally, we also discuss how trusted components (e.g., TPMs, smart cards) can be used to provide remote attestation on the client and server side, i.e., how to measure the trustworthiness of the system. The proposed solution outperforms related work in different aspects, such as countermeasures for solving different security issues, throughput, and by tolerating arbitrary faults without compromising the system operations. We evaluate the system behavior under different circumstances, such as continuous faults and attacks. Furthermore, the first performance evaluations show that the system is capable of supporting environments with thousands of users. © 2014 IEEE.


Alves F.,LaSIGE | Cogo V.,University of Lisbon | Wandelt S.,Humboldt University of Berlin | Leser U.,Humboldt University of Berlin | Bessani A.,University of Lisbon
PLoS ONE | Year: 2015

The decreasing costs of genome sequencing is creating a demand for scalable storage and processing tools and techniques to deal with the large amounts of generated data. Referential compression is one of these techniques, in which the similarity between the DNA of organisms of the same or an evolutionary close species is exploited to reduce the storage demands of genome sequences up to 700 times. The general idea is to store in the compressed file only the differences between the to-be-compressed and a well-known reference sequence. In this paper, we propose a method for improving the performance of referential compression by removing the most costly phase of the process, the complete reference indexing. Our approach, called On-Demand Indexing (ODI) compresses human chromosomes five to ten times faster than other state-of-the-art tools (on average), while achieving similar compression ratios. Copyright: © 2015 Alves et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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