Synchronous, with a Chance of Partition Tolerance

Sync HotStuff: Simple and Practical Synchronous State Machine Replication

“…Synchronous protocols proven secure under the standard synchrony assumption fail to provide safety if a single message between honest replicas is delayed. Recently, Guo et al [6] proposed a "weak synchrony" model that allows the message delay bound ∆, at any point in time, to be violated for a set of honest replicas. We call these replicas sluggish.…”

“…We use this observation atop Sync-HotStuff-under-standardsynchrony to obtain a protocol in the mobile sluggish model. The resulting protocol ensure safety as long as the number of sluggish plus Byzantine faults combined is less than one-half; in other words, at any time, a majority of replicas must be honest and prompt, which has been shown to be a necessary condition [6] in the mobile sluggish model.…”

Brief Announcement

“…This model is stronger than partial synchrony or asynchrony; however, we have a better fault tolerance. As Guo et al [7] show, we can have consensus protocols where the fraction of Byzantine and sluggish replicas together is up to one-half. The model is also a strict generalization of synchrony since synchrony requires there to be no sluggish replicas.…”

“…For all other uses, contact the owner/author(s). In a recent work from Crypto'19, Guo, Pass, and Shi [7] presented a weakly synchronous model where the synchrony assumption holds for most of the network but allows for messages from a few replicas to be arbitrarily delayed. In particular, the model states that, at any time, a fraction of the replicas are honest and prompt, i.e., they respect the synchrony assumption.…”

“…Subsequent to the work of Guo et al [7], there have been multiple works presenting consensus protocols under a synchrony assumption as well as a version that tolerates mobile sluggish faults [2,3,5]. In these works, the techniques to make a synchronous protocol tolerant to mobile sluggish faults seem specific to the protocol itself.…”