Prefix Consensus For Censorship Resistant BFT
Zhuolun Xiang, Andrei Tonkikh, Alexander Spiegelman

TL;DR
This paper introduces Prefix Consensus, a novel abstraction for censorship-resistant Byzantine Fault Tolerance (BFT), enabling leaderless, asynchronous consensus with strong guarantees against censorship and suspension.
Contribution
The paper proposes Prefix Consensus and Strong Prefix Consensus, providing tight bounds, leaderless protocols, and applications to censorship-resistant BFT state machine replication.
Findings
Achieves asynchronous consensus with tight round complexity bounds.
Enables leaderless, censorship-resistant BFT protocols with four-round decision.
Connects Prefix Consensus to optimal-latency graded and leaderless binary consensus.
Abstract
Despite broad use of BFT consensus in blockchains, censorship resistance is weak: leaders can exclude transactions, a growing concern for trading and DeFi. We address this by introducing a new abstraction and protocol stack. First, we introduce \emph{Prefix Consensus}, where parties input vectors and output that (i) extend the maximum common prefix of honest inputs and (ii) satisfy for all honest . Unlike classical consensus, no single output is required. We show Prefix Consensus is solvable asynchronously and give tight round-complexity bounds. We then define \emph{Strong Prefix Consensus}, requiring agreement on the \emph{high} output. Our protocol is leaderless and partially synchronous: one Prefix Consensus instance decides (possibly different) lows, and additional instances yield a unique safe-to-extend…
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Taxonomy
TopicsDistributed systems and fault tolerance · Blockchain Technology Applications and Security · Cryptography and Data Security
