时间就是金钱：激励式因果交易排序
Time Is Money: Incentivized Causal Transaction Ordering
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中文总结 AI 辅助
研究针对区块链抢先交易问题，提出PRECEDE机制，通过幂加权随机抽签按出价超线性增长排序交易，消除抢先经济激励，形成用户与攻击者均衡，防止三明治攻击，可简单部署于抗审查区块链。
中文摘要 AI 辅助
抢先交易是区块链面临的一个微妙且持久的问题。区块链是执行称为交易的指令的有状态虚拟机，用户通过发布对系统至关重要的功能性交易来获得奖励。攻击者会抢先发布自己的交易以获取奖励，这削弱了用户发布功能性交易的积极性。防止抢先交易意味着要强制因果关系，即如果攻击者收到交易tx_A然后发布tx_B，那么tx_A必须在tx_B之前排序。但实际系统按出价金额排序交易，这只会引发竞价战并侵蚀用户奖励。虽然已有多种排序方法，但都未实现因果关系。我们提出了PRECEDE，一种通过消除抢先交易的经济激励来强制交易因果关系的机制设计方法。PRECEDE通过幂加权随机抽签对交易进行排序，其获胜概率随出价超线性增长。用户发布具有威慑力出价的交易策略形成了攻击者克制竞争的均衡。此外，PRECEDE还能防止依赖抢先交易的著名三明治攻击。PRECEDE可通过简单更改交易排序机制直接部署在任何抗审查区块链中。
英文摘要
Front-running is a subtle and persistent problem for blockchains. A blockchain is a stateful virtual machine executing instructions called transactions. Users earn rewards by publishing functional transactions essential to the system. Attackers observe these transactions and publish their own ahead of the users', seizing the reward and eroding users' incentive to publish functional transactions. Preventing front-running means enforcing causality: If an attacker receives transaction tx_A and then publishes transaction tx_B, then tx_A must be ordered before tx_B. However, this causality is only observed by the attacker. Practical systems order transactions by bid amount, so transactions willing to pay more get executed first, but this only results in a bidding war eroding users' rewards. Though numerous ordering approaches have been proposed, none achieves causality, leaving users vulnerable to front-running. We present PRECEDE, a mechanism-design approach that enforces transaction causality by removing the economic incentive to front-run. PRECEDE orders transactions by a power-weighted randomized lottery, whose winning probability grows super-linearly in the bid. The user's strategy of publishing a transaction with a deterring bid forms an equilibrium where the attacker refrains from competing. Moreover, PRECEDE prevents the prominent sandwich attack, which relies on front-running. PRECEDE can be directly deployed in any censorship-resistant blockchain with a simple change to its transaction ordering mechanism.
