The latest message driven (LMD) greedy heaviest observed sub-tree (GHOST) consensus protocol is a critical component of proof-of-stake (PoS) Ethereum. In its current form, the protocol is brittle, and intricate to reason about, as evidenced by recent attacks and patching attempts. We report on Goldfish, a considerably simplified variant of the current protocol, and a candidate under consideration for a future Ethereum protocol upgrade. We prove that Goldfish is secure in synchronous networks under dynamic participation, assuming a majority of the nodes (called validators) follows the protocol. Goldfish improves over Nakamoto's longest-chain consensus in that it is reorg resilient (i.e., honestly produced blocks are guaranteed inclusion in the ledger) and supports fast confirmation (i.e., the expected confirmation latency is independent of the desired security level). We show that subsampling validators can improve the communication efficiency of Goldfish, and that Goldfish is composable with finality gadgets and accountability gadgets, which improves state-of-the-art ebb-and-flow protocols. Akin to traditional propose-and-vote-style consensus protocols, Goldfish is organized in slots, at the beginning of which a leader proposes a block containing new transactions, and subsequently members of a committee take a vote towards block confirmation. But instead of using quorums, Goldfish is powered by a new mechanism to carefully synchronize the inclusion and exclusion of blocks and votes in honest validators' views.

翻译：最新消息驱动（LMD）贪婪最重观察子树（GHOST）共识协议是权益证明（PoS）以太坊的关键组成部分。目前该协议较为脆弱且难以推理，近期发生的攻击与修补尝试即为例证。我们提出金鱼协议（Goldfish）——当前协议的显著简化变体，也是未来以太坊协议升级的候选方案。我们证明，在动态参与下的同步网络中，若多数节点（称为验证者）遵循协议，金鱼协议可确保安全性。相较于中本聪最长链共识，金鱼协议的改进在于具有重组弹性（即诚实生成的区块可确保包含于账本中）并支持快速确认（即预期确认延迟与目标安全等级无关）。研究表明，对验证者进行子采样可提升金鱼协议的通信效率，且该协议可与终局性装置及问责装置组合使用，从而改进当前最先进的潮汐流协议。与传统提议-投票式共识协议类似，金鱼协议按槽（slot）组织：每个槽开始时由领导者提议包含新交易的新区块，随后委员会成员投票确认区块。但金鱼协议并非采用法定人数机制，而是通过新型机制精确同步诚实验证者视图中区块与投票的包含与排除过程。