Bitcoin's (BTC) Difficulty Adjustment Algorithm (DAA) has been a source of vulnerability for incentive attacks such as selfish mining, block withholding and coin hopping strategies. In this paper, first, we rigorously study the short-term revenue change per hashpower of the adversarial and honest miners for these incentive attacks. To study the long-term effects, we introduce a new efficiency metric defined as the revenue/cost per hashpower per time for the attacker and the honest miners. Our results indicate that the short-term benefits of intermittent mining strategies are negligible compared to the original selfish mining attack, and in the long-term, selfish mining provides better efficiency. We further demonstrate that a coin hopping strategy between BTC and Bitcoin Cash (BCH) relying on BTC DAA benefits the loyal honest miners of BTC in the same way and to the same extent per unit of computational power as it does the hopper in the short-term. For the long-term, we establish a new boundary between the selfish mining and coin hopping attack, identifying the optimal efficient strategy for each parameter. For block withholding strategies, it turns out, the honest miners outside the pool profit from the attack, usually even more than the attacker both in the short-term and the long-term. Moreover, a power adjusting withholding attacker does not necessarily observe a profit lag in the short-term. It has been long thought that the profit lag of selfish mining is among the main reasons why such an attack has not been observed in practice. We show that such a barrier does not apply to power adjusting attacks and relatively small pools are at an immediate threat.

翻译：比特币（BTC）的难度调整算法（DAA）一直是自私挖矿、区块扣留和币种跳跃等激励攻击的脆弱性来源。本文首先严格研究了这些激励攻击中敌对矿工与诚实矿工单位算力的短期收益变化。为探究长期影响，我们引入了一种新的效率度量指标，定义为攻击者与诚实矿工单位时间单位算力的收益/成本比。研究结果表明，间歇性挖矿策略的短期收益相较于原始自私挖矿攻击可忽略不计，而从长期来看，自私挖矿具有更优的效率。我们进一步证明，依赖BTC DAA在BTC与比特币现金（BCH）间实施的币种跳跃策略，在短期内使BTC忠诚诚实矿工与跳跃攻击者每单位算力获得同等程度的收益。长期分析中，我们确立了自私挖矿与币种跳跃攻击的新边界，识别出不同参数下的最优效率策略。对于区块扣留策略，研究发现矿池外的诚实矿工能从攻击中获益，且通常在短期和长期均比攻击者获利更多。此外，采用算力调整的扣留攻击者未必会在短期内出现收益滞后现象。长期以来，自私挖矿的收益滞后被认为是该攻击未在实践中观测到的主要原因之一。我们证明此类障碍不适用于算力调整攻击，相对小型的矿池正面临即时威胁。