Bitcoin-NG, a scalable blockchain protocol, divides each block into a key block and many micro blocks to effectively improve the transaction processing capacity. Bitcoin-NG has a special incentive mechanism (i.e. splitting transaction fees to the current and the next leader) to maintain its security. However, this design of the incentive mechanism ignores the joint effect of transaction fees, mint coins and mining duration lengths on the expected mining reward. In this paper, we identify the advanced mining attack that deliberately ignores micro blocks to enlarge the mining duration length to increase the likelihood of winning the mining race. We first show that an advanced mining attacker can maximize its expected reward by optimizing its mining duration length. We then formulate a game-theoretical model in which multiple mining players perform advanced mining to compete with each other. We analyze the Nash equilibrium for the mining game. Our analytical and simulation results indicate that all mining players in the mining game converge to having advanced mining at the equilibrium and have no incentives for deviating from the equilibrium; the transaction processing capability of the Bitcoin-NG network at the equilibrium is decreased by advanced mining. Therefore, we conclude that the Bitcoin-NG blockchain protocol is vulnerable to advanced mining attack. We discuss how to reduce the negative impact of advanced mining for Bitcoin-NG.

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Bitcoin-NG区块链协议挖掘策略的博弈论分析

Bitcoin-NG是一种可扩展的区块链协议，将每个区块划分为一个关键区块和多个微区块，有效提升交易处理能力。Bitcoin-NG 有一个特殊的激励机制（即将交易费用分摊给当前和下一个领导者）来维护其安全性。然而，这种激励机制的设计忽略了交易费用、铸币和挖矿持续时间长度对预期挖矿奖励的共同影响。在本文中，我们确定了故意忽略微块以扩大挖矿持续时间长度以增加赢得挖矿竞赛的可能性的高级挖矿攻击。我们首先表明，高级挖矿攻击者可以通过优化其挖矿持续时间来最大化其预期回报。然后，我们制定了一个博弈论模型，其中多个挖矿参与者执行高级挖矿以相互竞争。我们分析了挖矿游戏的纳什均衡。我们的分析和模拟结果表明，挖矿游戏中的所有挖矿参与者都收敛到均衡时进行高级挖矿，并且没有偏离均衡的动机；比特币-NG 网络在均衡时的交易处理能力因高级挖矿而降低。因此，我们得出结论，Bitcoin-NG 区块链协议容易受到高级挖矿攻击。我们讨论如何减少高级挖矿对 Bitcoin-NG 的负面影响。我们的分析和模拟结果表明，挖矿游戏中的所有挖矿参与者都收敛到均衡时进行高级挖矿，并且没有偏离均衡的动机；比特币-NG 网络在均衡时的交易处理能力因高级挖矿而降低。因此，我们得出结论，Bitcoin-NG 区块链协议容易受到高级挖矿攻击。我们讨论如何减少高级挖矿对 Bitcoin-NG 的负面影响。我们的分析和模拟结果表明，挖矿游戏中的所有挖矿参与者都收敛到均衡时进行高级挖矿，并且没有偏离均衡的动机；比特币-NG 网络在均衡时的交易处理能力因高级挖矿而降低。因此，我们得出结论，Bitcoin-NG 区块链协议容易受到高级挖矿攻击。我们讨论如何减少高级挖矿对 Bitcoin-NG 的负面影响。