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Resumo(s)
This paper presents two asynchronous Byzantine faulttolerant
state machine replication (BFT) algorithms that are
minimal in several senses. First, they require only 2 f +1
replicas, instead of the usual 3 f +1. Second, the trusted
service in which this reduction of replicas is based is arguably
minimal, so it is simple to verify and implement
(which is possible even using commercial trusted hardware).
Third, in nice executions the two algorithms run
in the minimum number of communication steps for nonspeculative
and speculative algorithms, respectively 4 and
3 steps. Besides the obvious benefits in terms of cost, resilience
and management complexity of having less replicas
to tolerate a certain number of faults, our algorithms
are simpler than previous ones (being closer to crash faulttolerant
replication algorithms). The performance evaluation
shows that, even with the trusted component access
overhead, they can have better throughput than Castro and
Liskov’s PBFT, and better latency in networks with nonnegligible
communication delays.
Comparing with the previous paper [49], this version
presents a slight modifications of the algorithms, the proof
of their correctness and a new performance evaluation.