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

TL;DR

This paper analyzes the impact of stubborn mining attacks on GHOST-based Bitcoin-like blockchains using an analytical model, revealing attack profitability thresholds and system vulnerabilities.

Contribution

It introduces a Markov chain-based analytical model and a new 'Hazard Index' metric to evaluate stubborn mining attack severity in imperfect GHOST blockchains.

Findings

Attacker with over 30% computing power gains high profit and reduces throughput.

Less than 25% computing power makes attack unprofitable.

Stubborn mining causes more damage than selfish mining in GHOST.

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 blockchains of Bitcoin and its variants (Bitcoin-like). This paper explores an analytical-model-based method to investigate the impact of stubborn mining attack in imperfect GHOST Bitcoin-like blockchains. We first quantify chain dynamics based on Markov chain and then derive the formulas of miner revenue and system throughput. We also propose a new metric, "Hazard Index", which can be used to compare attack severity and also assist attacker in determining whether it is profitable to conduct an attack. The experiment results show that 1) An attacker with more than 30% computing power can get huge profit and extremely downgrade system throughput by launching stubborn mining attack. 2) A rational attacker 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.