Is Stubborn Mining Severe in Imperfect GHOST Bitcoin-Like Blockchains? Quantitative Analysis

Abstract

GHOST, like the longest-chain protocol, is a chain selection protocol and its capability in resisting selfish mining attack has been validated in imperfect (delay-existing-) blockchains of Bitcoin and its variants (Bitcoin-like). This paper explores an analytical-model-based approach to investigate the impact of stubborn mining attack in imperfect GHOST Bitcoin-like blockchains. We first quantify chain dynamics based on Markov chain process and then derive the formulas of miner revenue and system throughput. We also propose a new metric, “Hazard Index”, which can be used to evaluate attack threat severity and also assist the adversary in determining whether it is profitable to conduct an attack. The experiment results show that 1) An adversary with more than 30% computing power can get huge profit and extremely downgrade system throughput by launching stubborn mining attack. 2) An adversary should not launch stubborn mining attack if it has less than 25% computing power. 3) Stubborn mining attack causes more damage than selfish mining attack under GHOST. Our work provides insight into stubborn mining attack and is helpful in designing countermeasures.