Radium: Improving Dynamic PoW Targeting

TL;DR

Radium enhances real-time block rate targeting in PoW blockchains by mitigating miner deviation vulnerabilities, maintaining low variance in block times, and reducing chain death risk, while preserving resistance to doublespend and orphaned blocks.

Contribution

Radium introduces a protocol that fixes RTT's vulnerability to miner deviation, improving stability and security in dynamic PoW target adjustment.

Findings

Radium reduces miner deviation from the protocol.

Radium maintains low block time variance.

Radium's security against doublespend remains similar to Bitcoin.

Abstract

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.