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Tolerância a Faltas Bizantinas em Servidores RMI MSc Post-Graduation Abstract:The advances in computer hardware made it possible to improve the performance and efficiency of general applications through parallel computing. Such powerful hardware allows enterprise systems to evolve and provide better guarantees to users, like reliability, availability and byzantine fault-tolerance. A component that exhibits byzantine behaviour, continues to produce incorrect values while responding to every request. This fact makes it harder for distributed systems to endure byzantine failures, since they may remain undetected for a long period. In order to overcome such failures, byzantine fault tolerant systems rely on replication with strong agreement protocols, which harm performance and throughput. Among the techniques we may use to overcome these limitations there are: introduction of concurrent execution in the servers and speculative execution. Java’s remote method invocation (RMI) allows seamless remote method invocation on objects in different virtual machines. This mechanism is supported by a client/server architecture which, even though it presents good performance, does not help distributed applications to be reliable and fault-tolerant. Hence, our goal is to create byzantine fault-tolerant applications, through an implicit replication mechanism. In order to validate our work, we performed some tests using JNFS, a distributed file system implemented over RMI. The results allow us to conclude that the use of speculative execution minimizes the overhead generated by byzantine fault-tolerant systems. Database Systems can increase their resilience against attacks and faults through Byzantine-fault-tolerant (BFT) replication – the basic idea consists in replicating the data in multiple sites, thus guaranteeing that if one site fails or is controlled by an attacker, it is still possible to get the correct data from the other sites. Making this approach work efficiently requires specially designed systems, and the Byzantium project aims towards producing such a system by developing a middleware layer as front-end for the applications. A previous work (MSc thesis) studied how to incorporate speculation into programs that access a transactional database. This work follows the previous one and aims at designing and implementing methods and techniques for introducing speculative execution in accessing Replicated Byzantine Databases. Start Date: 2010-09-20 End Date: 2012-01-20 Post-Graduation Student / Researcher / Professor:
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