Return to Dilemma: A Novel Block Withholding Attack on PoW-Based Blockchains

Blockchain permeates nearly every facet of daily life, providing a crucial role in securely interweaving networked elements such as smart appliances and IoT devices. Proof-of-work (PoW) retains an undiminished status as one of the most adopted technologies in the blockchain industry for its trustworthiness and proportional fairness. Transactions will be safely committed and confirmed in a PoW-based blockchain scheme as long as a malevolent party does not control the majority of miners. However, since the discovery of a block withholding (BWH) attack where a malicious mining pool participant intentionally equivocates when finding a correct answer to the cryptographic puzzle, the proportional fairness between PoW miners has been compromised and cannot be guaranteed anymore. In this article, based on existing BWH attacks such as the BWH attack and the fork-after-withholding (FAW) attack, we introduce a novel attack scheme, a return-after-withholding (RAW) attack, which can be even more injurious to the proportional fairness of PoW mining. Analytic and experimental studies prove that our attack scheme is advantageous over the existing BWH attacks and distinguished by unique characteristics from the other BWH attacks.