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 $(v^{\sf low},v^{\sf high})$ that (i) extend the maximum common prefix of honest inputs and (ii) satisfy $v_i^{\sf low}\preceq v_j^{\sf high}$ for all honest $i,j$. 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 high, even if an adversary can suspend one party per round. We lift this to a leaderless, multi-proposer, censorship-resistant BFT SMR protocol: per slot, all parties broadcast proposals, deterministically rank them, and run one Strong Prefix Consensus on proposal hashes, committing honest proposals in \emph{four rounds}. A deterministic demotion rule updates the ranking when a party's proposal is excluded, implying that after GST at most $f$ slots can miss an honest proposal while progress remains leaderless under suspension and up to $f{-}1$ Byzantine faults. Finally, we connect Prefix Consensus to graded and binary/validated consensus: we obtain an optimal-latency graded consensus (3 message delays) and leaderless Binary/Validated Consensus with worst-case message complexity $O(n^3)$ and communication $O(n^4)$.

翻译：尽管拜占庭容错共识在区块链领域得到广泛应用，但其抗审查能力较弱：领导者可排除特定交易，这对交易和去中心化金融构成日益严峻的隐患。本文通过提出新的抽象模型与协议栈解决该问题。首先，我们提出\emph{前缀共识}机制，参与方输入向量并输出$(v^{\sf low},v^{\sf high})$，满足：(i) 扩展诚实节点输入的最大公共前缀；(ii) 对所有诚实节点$i,j$满足$v_i^{\sf low}\preceq v_j^{\sf high}$。与经典共识不同，该机制不要求单一输出结果。我们证明前缀共识可在异步环境下求解，并给出严格的轮次复杂度边界。随后定义\emph{强前缀共识}，要求对\emph{高位}输出达成一致。我们的协议采用无领导者设计与部分同步模型：单个前缀共识实例决定（可能不同的）低位输出，通过附加实例产生唯一可安全扩展的高位输出，即使敌手每轮可暂停一个参与方。我们将此提升为无领导者、多提案者、抗审查的拜占庭容错状态机复制协议：每个时隙中所有参与方广播提案，通过确定性排序算法对提案哈希值执行强前缀共识，在\emph{四轮通信}内提交诚实提案。当参与方提案被排除时，确定性降级规则将更新排序，这意味着在全局稳定时间后至多$f$个时隙可能缺失诚实提案，同时在敌手暂停攻击与最多$f{-}1$个拜占庭故障下仍保持无领导者进展。最后，我们将前缀共识与分级共识、二元/验证共识关联：获得了最优延迟的分级共识（3次消息延迟）以及最坏情况消息复杂度$O(n^3)$、通信复杂度$O(n^4)$的无领导者二元/验证共识协议。