发表机构
University of California, Santa Barbara; Duke University（加州大学圣塔芭芭拉分校; 杜克大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
eAVID 是一种带分发后剪枝的异步可验证信息分散协议，通过解耦节点存储与发送片段，在网络健康时将单节点存储减半，同时保持与标准方案相同的分散带宽和恢复能力。
AI 中文摘要
异步可验证信息分散（AVID）允许发送方将消息分散到 $N=3F+1$ 个节点，即使存在最多 $F$ 个拜占庭故障节点，消息仍可恢复。由于分散必须在收到 $N-F$ 个节点的响应后完成，标准 AVID 协议采用固定的 $(F+1,\, N)$ 纠删码，导致存储开销为 $3\ imes$，而同步系统可达到最优的 $3/2\ imes$。该成本是永久的：节点的存储占用在分散时固定，当网络健康且所有 $N$ 个节点响应时也不会调整。我们提出 eAVID，一种将节点保留的存储与发送给它的片段解耦的 AVID 协议。eAVID 用单个 $(2F+1,\, 2N)$ 里德-所罗门码对消息编码，在一个默克尔根下提交所有 $2N$ 个片段，并向每个节点发送两个不同的片段。该方法使用与标准方案相同的分散带宽，且分散在收到 $N-F$ 个节点响应后完成，与原始 AVID 一致。我们的改进在提交后：节点继续异步收集响应，一旦节点从所有 $N$ 个节点听到关于其采用的根的“完成”信号，就可以单方面安全丢弃其两个片段中的一个。由于节点间的片段不重叠，至少有 $2F+1$ 个已验证片段留存。剪枝不需要证书、存储节点间的协调或重新编码。重建方式不变：任何 $2F+1$ 个已验证片段都可解码消息，无论片段如何分布。当网络健康时，eAVID 的稳态单节点存储相比 $(F+1,\, N)$ 基线减半；当网络不健康时，存储会平滑降级至基线占用。
英文摘要
The well-known Asynchronous Verifiable Information Dispersal (AVID) problem lets a sender disperse a message across $N=3F+1$ nodes such that it remains recoverable despite up to $F$ Byzantine failures and unbounded message delays. An optimal AVID scheme requires $3\times$ the message size in communication and storage: up to $F$ nodes may be delayed in responding, and among the remaining $2F+1$ respondents, up to $F$ may be Byzantine. This paper presents eAVID, an elastic AVID scheme that provides two key improvements. First, after dissemination, nodes can prune up to half of their stored information without requiring anyone to reconstruct or recode the message. Second, pruning is enabled by an extremely simple protocol. Nodes collect acknowledgments from one another confirming receipt of their coded pieces, after which each node locally prunes its stored information. eAVID achieves this $2\times$ reduction while making two tradeoffs: the sender generates $2N$ fragments rather than $N$, and pruning may necessitate contacting $2F+1$ nodes for message retrieval rather than $F+1$. eAVID was implemented in DispersedSimplex, a simple-to-understand BFT consensus protocol that erasure-codes its blocks. The implementation demonstrates two features. First, eAVID achieves these improvements using a flat erasure-coding scheme that requires no metadata or bookkeeping at the nodes during reconstruction. Second, it delivers the storage savings without a performance cost: with all nodes responsive, pruning fires on over $99\%$ of blocks and steady-state per-node storage falls by $42$-$46\%$ for committees of $10$ to $22$ nodes. Throughput and latency match the unmodified protocol showing that we can achieve these storage savings without any performance costs.
