Most PoW blockchain protocols operate with a simple mechanism whereby a threshold is set for each block and miners generate block hashes until one of those values falls below the threshold. Although largely effective, this mechanism produces blocks at a highly variable rate and also leaves a blockchain susceptible to chain death, i.e. abandonment in the event that the threshold is set too high to attract any miners. A recent innovation called real-time block rate targeting, or RTT, fixes these problems by reducing the target throughout the mining interval. RTT exhibits much less variable block times and even features the ability to fully adjust the target after each block. However, as we show in this paper, RTT also suffers from a critical vulnerability whereby miners deviate form the protocol to increase their profits. We introduce the Radium protocol, which mitigates this vulnerability in RTT while retaining lower variance block times, responsive target adjustment, and lowering the risk of chain death. We also show that Radium's susceptibility to the doublespend attack and orphaned blocks remains similar to Bitcoin.

中文翻译：

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镭：改进动态 PoW 目标

大多数 PoW 区块链协议以一种简单的机制运行，即为每个块设置阈值，矿工生成块哈希，直到其中一个值低于阈值。虽然在很大程度上有效，但这种机制以高度可变的速度产生块，并且也使区块链容易受到链死亡的影响，即在阈值设置得太高而无法吸引任何矿工的情况下被放弃。最近一项名为实时区块率目标 (RTT) 的创新通过在整个挖掘间隔期间减少目标来解决这些问题。RTT 表现出更少的可变块时间，甚至具有在每个块之后完全调整目标的能力。然而，正如我们在本文中所展示的，RTT 也存在一个严重的漏洞，即矿工偏离协议以增加他们的利润。我们引入了 Radium 协议，它减轻了 RTT 中的这个漏洞，同时保持了较低的差异块时间、响应式目标调整，并降低了链死亡的风险。我们还表明，镭对双花攻击和孤立块的敏感性与比特币相似。