Unstable Throughput: When the Difficulty Algorithm Breaks
Unstable Throughput: When the Difficulty Algorithm Breaks
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吞吐量不稳定：当难度算法失效时
DOI：
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
W. Knottenbelt
中科院分区：
文献类型：
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作者：
Sam M. Werner;D. Ilie;I. Stewart;W. Knottenbelt
在工作量证明区块链中，难度算法通过动态调整区块难度来响应矿工不断变化的计算能力，从而达到维持稳定交易吞吐量的关键目的。可能经历严重哈希率波动的区块链需要快速适应挖掘难度的难度算法。然而，如果没有仔细的设计，该系统可能会被矿工使用跳币策略来操纵区块难度以获利。由于交易处理的不稳定性，这种矿工行为导致了一个不可靠的系统。我们提供了一个实证分析，说明比特币现金的难度算法设计如何导致正反馈循环导致区块求解时间的周期性。作为回应，我们数学推导出一个困难的算法，使用负指数过滤器，禁止形成正反馈，并表现出额外的理想属性，如历史不可知论。我们在模拟采矿环境中将所描述的算法与比特币现金的算法进行了比较，并验证了前者可以消除交易吞吐量的严重振荡。
In Proof-of-Work blockchains, difficulty algorithms serve the crucial purpose of maintaining a stable transaction throughput by dynamically adjusting the block difficulty in response to the miners’ constantly changing computational power. Blockchains that may experience severe hash rate fluctuations need difficulty algorithms that quickly adapt the mining difficulty. However, without careful design, the system could be gamed by miners using coin-hopping strategies to manipulate the block difficulty for profit. Such miner behavior results in an unreliable system due to the unstable processing of transactions.We provide an empirical analysis of how Bitcoin Cash’s difficulty algorithm design leads to cyclicality in block solve times as a consequence of a positive feedback loop. In response, we mathematically derive a difficulty algorithm using a negative exponential filter which prohibits the formation of positive feedback and exhibits additional desirable properties, such as history agnosticism. We compare the described algorithm to that of Bitcoin Cash in a simulated mining environment and verify that the former would eliminate the severe oscillations in transaction throughput.