Propagation latency is inherent to any distributed network, including blockchains. Typically, blockchain protocols provide a timing buffer for block propagation across the network. In leader-based blockchains, the leader -- block proposer -- is known in advance for each slot. A fast (or low-latency) proposer may delay the block proposal in anticipation of more rewards from the transactions that would otherwise be included in the subsequent block. Deploying such a strategy by manipulating the timing is known as timing games. It increases the risk of missed blocks due to reduced time for other nodes to vote on the block, affecting the overall efficiency of the blockchain. Moreover, proposers who play timing games essentially appropriate MEV (additional rewards over transaction fees and the block reward) that would otherwise accrue to the next block, making it unfair to subsequent block proposers. We propose a double-block proposal mechanism, 2-Prop, to curtail timing games. 2-Prop selects two proposers per slot to propose blocks and confirms one of them. We design a reward-sharing policy for proposers based on how quickly their blocks propagate to avoid strategic deviations. In the induced game, which we call the Latency Game, we show that it is a Nash Equilibrium for the proposers to propose the block without delay under homogeneous network settings. Under heterogeneous network settings, we study many configurations, and our analysis shows that a faster proposer would prefer not to delay unless the other proposer is extremely slow. Thus, we show the efficacy of 2-Prop in mitigating the effect of timing games.

翻译：传播延迟是包括区块链在内的任何分布式网络固有的特性。通常，区块链协议会为区块在网络中的传播设置一个时序缓冲。在基于领导者的区块链中，每个时隙的领导者——即区块提议者——是预先已知的。一个快速（或低延迟）的提议者可能会延迟区块提议，以期获得更多交易奖励，这些交易原本可能被包含在后续区块中。通过操纵时序来部署这种策略被称为时序博弈。这会增加区块丢失的风险，因为其他节点投票的时间减少了，从而影响区块链的整体效率。此外，进行时序博弈的提议者实质上攫取了原本应归属于下一个区块的MEV（超过交易费用和区块奖励的额外收益），这对后续区块提议者是不公平的。我们提出了一种双区块提议机制2-Prop来遏制时序博弈。2-Prop每个时隙选择两个提议者来提议区块，并确认其中一个。我们为提议者设计了一种基于其区块传播速度的奖励共享策略，以避免策略性偏离。在我们称之为延迟博弈的诱导博弈中，我们证明在均匀网络设置下，提议者不延迟地提议区块是一个纳什均衡。在非均匀网络设置下，我们研究了多种配置，分析表明，除非另一个提议者极其缓慢，否则更快的提议者倾向于不延迟。因此，我们证明了2-Prop在减轻时序博弈影响方面的有效性。