Bitcoin is permissionless and does not rely on any central administrator, which gives it strong censorship resistance. At the same time, it is important to incentivize miners to behave in ways that align with the interests of the system as a whole. This paper asks whether miners are individually incentivized to propagate blocks, one of the most fundamental processes in Bitcoin. Miners collectively maintain the blockchain by generating blocks and disseminating them across the network. If miners have an incentive not to propagate some blocks, this would indicate a fundamental flaw in Bitcoin's incentive design. Although prior work has studied how propagation delays affect forks and mining rewards, it has not fully characterized miners' incentives to improve block propagation under different tie-breaking rules. To address this gap, we derive analytical reward expressions for each tie-breaking rule based on a blockchain network model that captures the effect of forks on mining fairness. These expressions explicitly characterize how block propagation delays, hashrate distribution, and tie-breaking rules jointly determine mining rewards. We then use them to analyze miners' incentives to improve block propagation. Our results show, for example, that miners have no mining-reward incentive to relay blocks generated by other miners. By contrast, under the first-seen rule, every non-majority miner is incentivized to receive other miners' blocks more quickly and to propagate its own blocks more quickly. Finally, we compare tie-breaking rules and identify a trade-off between propagation incentives and mining fairness. In particular, the first-seen rule provides the strongest incentives to reduce propagation delays, but it also worsens mining fairness the most.

翻译：比特币无需许可且不依赖任何中央管理员，具备强大的抗审查能力。同时，激励矿工采取符合系统整体利益的行为至关重要。本文探讨矿工是否在个体层面上存在传播区块的动力——这是比特币中最基础的过程之一。矿工通过生成区块并将其在网络中传播来共同维护区块链。若矿工存在不传播某些区块的动机，则表明比特币的激励设计存在根本性缺陷。尽管先前研究已探讨传播延迟如何影响分叉和挖矿奖励，但尚未完全刻画不同平局判定规则下矿工改善区块传播的激励。为填补这一空白，我们基于区块链网络模型推导出每种平局判定规则下的解析奖励表达式，该模型捕捉了分叉对挖矿公平性的影响。这些表达式明确刻画了区块传播延迟、算力分布和平局判定规则如何共同决定挖矿奖励，并以此分析矿工改善区块传播的激励。例如，我们的结果表明：矿工在传播其他矿工生成的区块时，不存在基于挖矿奖励的激励；相反，在"先见规则"（first-seen rule）下，所有非多数派矿工均有动力更快接收其他矿工的区块，并更快传播自身区块。最后，我们比较了不同平局判定规则，发现传播激励与挖矿公平性之间存在权衡：先见规则虽能提供最强的延迟降低激励，但同时也是对挖矿公平性损害最大的规则。