Self-stabilizing Byzantine- and Intrusion-tolerant Consensus

Abstract

One of the most celebrated problems of fault-tolerant distributed computing is the consensus problem. It was shown to abstract a myriad of problems in which processes have to agree on a single value. Consensus applications include fundamental services for the environments of the Cloud or Blockchain. In such challenging environments, malicious behavior is often modeled as adversarial Byzantine faults. At OPODIS 2010, Mostéfaoui and Raynal, in short, MR, presented a Byzantine-and intrusiontolerant solution to consensus in which the decided value cannot be a value proposed only by Byzantine processes. In addition to this validity property, MR has optimal resilience since it can deal with up to t < n/3 Byzantine processes, where n is the number of processes. We note that MR provides this multivalued consensus object (which accepts proposals taken from a set with a finite number of values) assuming the availability of a single Binary consensus object (which accepts proposals taken from the set {0, 1}).This work, which focuses on multivalued consensus, aims at the design of an even more robust solution than MR. Our proposal expands MR's fault-model with selfstabilization, a vigorous notion of fault-tolerance. In addition to tolerating Byzantine and communication failures, self-stabilizing systems can automatically recover after the occurrence of arbitrary transient-faults. These faults represent any violation of the assumptions according to which the system was designed to operate (provided that the algorithm code remains intact). We propose, to the best of our knowledge, the first self-stabilizing solution for intrusion-tolerant multivalued consensus for asynchronous message-passing systems prone to Byzantine failures.

Self-stabilizing Byzantine Fault-Tolerant Repeated Reliable Broadcast

“…Our contribution also includes an SSBFT recycling mechanism for time-free systems that are enriched with muteness de- Recall that our task specifications (Definition 1.1) follow the ones by Raynal [1,Ch. 4], and thus, our SSBRB solution can serve as a building block for multivalued consensus [33].…”