The LMD GHOST consensus protocol is a critical component of proof-of-stake Ethereum. In its current form, this protocol is brittle, as evidenced by recent attacks and patching attempts. We propose Goldfish, a new protocol that satisfies key properties required of a drop-in replacement for LMD GHOST: Goldfish is secure in the sleepy model, assuming a majority of the validators follows the protocol. Goldfish is reorg resilient so that honestly produced blocks are guaranteed inclusion in the ledger, and it supports fast confirmation with expected confirmation latency independent of the desired security level. Subsampling validators can improve the communication efficiency of Goldfish, and Goldfish is composable with finality/accountability gadgets. Crucially, Goldfish is structurally similar to LMD GHOST, providing a credible path to adoption in Ethereum. Attacks on LMD GHOST exploit lack of coordination among honest validators, typically provided by a locking mechanism in classical BFT protocols. However, locking requires votes from a quorum of all participants and is not compatible with fluctuating participation. Goldfish is powered by a novel coordination mechanism to synchronize the honest validators' actions. Experiments with our prototype implementation of Goldfish suggest practicality.

翻译：LMD GHOST共识协议是权益证明以太坊的关键组成部分。其当前形式存在脆弱性，近期出现的攻击与修补尝试已证实这一点。我们提出Goldfish——一种满足替代LMD GHOST所需核心属性的新型协议：Goldfish在休眠模型下是安全的，假设大多数验证者遵循协议；Goldfish具有重组抗性，可确保诚实生成的区块被纳入账本；它还支持快速确认，确认延迟与所需安全级别无关。通过子采样验证者可提升Goldfish的通信效率，且该协议能与终结性/问责机制组合。关键之处在于，Goldfish在结构上与LMD GHOST相似，为以太坊采用提供了可靠路径。对LMD GHOST的攻击利用了诚实验证者之间缺乏协调的漏洞——这种协调通常由经典BFT协议中的锁定机制提供，但锁定需要全体参与者达成法定投票，与波动的参与状态不兼容。Goldfish通过一种新型协调机制驱动，来同步诚实验证者的行动。基于Goldfish原型实现的实验表明其具有实用性。