Expected Constant Round Byzantine Broadcast under Dishonest Majority
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3748254.pdf
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Author(s)
Wan, Jun
Xiao, Hanshen
Shi, Elaine
Devadas, Srinivas
Journal
Journal of the ACM
Publisher
ACM
Citation
Jun Wan, Hanshen Xiao, Elaine Shi, and Srinivas Devadas. 2025. Expected Constant Round Byzantine Broadcast under Dishonest Majority. J. ACM 72, 4, Article 30 (August 2025), 39 pages.
Version
Final published version
Abstract
Byzantine Broadcast (BB) is a central question in distributed systems, and an important challenge is to understand its round complexity. Under the honest majority setting, it is long known that there exist randomized protocols that can achieve BB in expected constant rounds, regardless of the number of nodes n. However, whether we can match the expected constant round complexity in the corrupt majority setting --- or more precisely, when f > n/2 --- remains unknown, where f denotes the number of corrupt nodes. In this paper, we are the first to resolve this long-standing question. We show how to achieve BB in expected O((n/(n-f))2) rounds. Our results hold under a weakly adaptive adversary who cannot perform ``after-the-fact removal' of messages already sent by a node before it becomes corrupt. We also assume trusted setup and the Decision Linear (DLIN) assumption in bilinear groups.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
http://dx.doi.org/10.1145/3748254
