On the minimal synchronism needed for distributed consensus
Journal of the ACM (JACM)
Perfectly secure message transmission
Journal of the ACM (JACM)
Impossibility of distributed consensus with one faulty process
Journal of the ACM (JACM)
PODC '97 Proceedings of the sixteenth annual ACM symposium on Principles of distributed computing
Reaching Agreement in the Presence of Faults
Journal of the ACM (JACM)
The Byzantine Generals Problem
ACM Transactions on Programming Languages and Systems (TOPLAS)
Distributed Algorithms
Levels of Authentication in Distributed Agreement
WDAG '96 Proceedings of the 10th International Workshop on Distributed Algorithms
Efficient Byzantine Agreement Secure Against General Adversaries
DISC '98 Proceedings of the 12th International Symposium on Distributed Computing
Byzantine Agreement Secure against General Adversaries in the Dual Failure Model
Proceedings of the 13th International Symposium on Distributed Computing
On the Number of Authenticated Rounds in Byzantine Agreement
WDAG '95 Proceedings of the 9th International Workshop on Distributed Algorithms
Authenticated Byzantine generals in dual failure model
ICDCN'10 Proceedings of the 11th international conference on Distributed computing and networking
Homonyms with forgeable identifiers
SIROCCO'12 Proceedings of the 19th international conference on Structural Information and Communication Complexity
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Three decades ago, Pease et al. introduced the problem of Byzantine Agreement [PSL80] where nodes need to maintain a consistent view of the world in spite of the challenge posed by Byzantine faults. Subsequently, it is well known that Byzantine agreement over a completely connected synchronous network of n nodes tolerating up to t faults is (efficiently) possible if and only if t n/3. Pease et al. further empowered the nodes with the ability to authenticate themselves and their messages and proved that agreement in this new model (popularly known as authenticated Byzantine agreement (ABA)) is possible if and only if t n. (which is a huge improvement over the bound of t n/3 in the absence of authentication for the same functionality). To understand the utility, potential and limitations of using authentication in distributed protocols for agreement, Gupta et al. [GGBS10] studied ABA in new light. They generalize the existing models and thus, attempt to give a unified theory of agreements over the authenticated and non-authenticated domains. In this paper we extend their results to synchronous (undirected) networks and give a complete characterization of agreement protocols. As a corollary, we show that agreement can be strictly easier than all-pair point-to-point communication. It is well known that in a synchronous network over n nodes of which up to any t are corrupted by a Byzantine adversary, BA is possible only if all pair point-to-point reliable communication is possible [Dol82, DDWY93]. Thus, a folklore in the area is that maintaining global consistency (agreement) is at least as hard as the problem of all pair point-to-point communication. Equivalently, it is widely believed that protocols for BA over incomplete networks exist only if it is possible to simulate an overlay-ed complete network. Surprisingly, we show that the folklore is not always true. Thus, it seems that agreement protocols may be more fundamental to distributed computing than reliable communication.