International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Srinivas Devadas

Publications

Year
Venue
Title
2020
TCC
Round-Efficient Byzantine Broadcast under Strongly Adaptive and Majority Corruptions 📺
Jun Wan Hanshen Xiao Srinivas Devadas Elaine Shi
The round complexity of Byzantine Broadcast (BB) has been a central question in distributed systems and cryptography. In the honest majority setting, expected constant round protocols have been known for decades even in the presence of a strongly adaptive adversary. In the corrupt majority setting, however, no protocol with sublinear round complexity is known, even when the adversary is allowed to {\it strongly adaptively} corrupt only 51\% of the players, and even under reasonable setup or cryptographic assumptions. Recall that a strongly adaptive adversary can examine what original message an honest player would have wanted to send in some round, adaptively corrupt the player in the same round and make it send a completely different message instead. In this paper, we are the first to construct a BB protocol with sublinear round complexity in the corrupt majority setting. Specifically, assuming the existence of time-lock puzzles with suitable hardness parameters and other standard cryptographic assumptions, we show how to achieve BB in $(\frac{n}{n-f})^2 \cdot \poly\log \lambda$ rounds with $1-\negl(\lambda)$ probability, where $n$ denotes the total number of players, $f$ denotes the maximum number of corrupt players, and $\lambda$ is the security parameter. Our protocol completes in polylogarithmically many rounds even when 99\% of the players can be corrupt.
2017
TCC
2017
TCC
2016
TCC
2016
TCC
2016
TCC
2011
CHES
2011
CHES
2009
CHES
2003
ASIACRYPT