In the area of blockchain, numerous methods have been proposed for suppressing intentional forks by attackers more effectively than the random rule. However, all of them, except for the random rule, require major updates, rely on a trusted third party, or assume strong synchrony. Hence, it is challenging to apply these methods to existing systems such as Bitcoin. To address these issues, we propose another countermeasure that can be easily applied to existing proof of work blockchain systems. Our method is a tie-breaking rule that uses partial proof of work, which does not function as a block, as a time standard with finer granularity. By using the characteristic of partial proof of work, the proposed method enables miners to choose the last-generated block in a chain tie, which suppresses intentional forks by attackers. Only weak synchrony, which is already met by existing systems such as Bitcoin, is required for effective functioning. We evaluated the proposed method through a detailed analysis that is lacking in existing works. In networks that adopt our method, the proportion of the attacker hashrate necessary for selfish mining was approximately 0.31479 or higher, regardless of the block propagation capability of the attacker. Furthermore, we demonstrated through extended selfish mining that the impact of Match against pre-generated block, which is a concern in all last-generated rules, can be mitigated with appropriate parameter settings.

翻译：在区块链领域，已有诸多方法被提出以比随机规则更有效地抑制攻击者的蓄意分叉。然而，除随机规则外，所有方法均需要进行重大更新、依赖可信第三方或假设强同步性。因此，将这些方法应用于比特币等现有系统具有挑战性。为解决这些问题，我们提出了一种可轻松应用于现有工作量证明区块链系统的应对措施。我们的方法是一种利用部分工作量证明作为更细粒度时间标准的裁决规则，该部分工作量证明不具备区块功能。通过利用部分工作量证明的特性，所提方法使矿工能够在链分叉时选择最后生成的区块，从而抑制攻击者的蓄意分叉。该方法仅需现有系统（如比特币）已满足的弱同步性即可有效运行。我们通过现有研究缺乏的详细分析评估了所提方法。在采用本方法的网络中，无论攻击者的区块传播能力如何，自私挖矿所需的攻击者算力占比约为0.31479或更高。此外，我们通过扩展自私挖矿证明，所有末位生成规则中存在的"预生成区块匹配"问题可通过适当参数设置得到缓解。