Catfish Effect Between Internal and External Attackers:Being Semi-honest is Helpful

TL;DR

This paper introduces a novel two-attacker model in proof-of-work systems, analyzing how internal and external attackers influence each other's revenue and proposing a semi-honest mining strategy called PIR that can be advantageous in multi-attacker scenarios.

Contribution

It is the first to theoretically and quantitatively analyze multi-attacker mining attacks, revealing dynamics and proposing the PIR semi-honest strategy.

Findings

Internal attacker's RR drops by up to 31.9% in multi-attacker systems.

External attacker overestimates RR by up to 44.6%.

PIR strategy can increase rewards in specific multi-attacker situations.

Abstract

The consensus protocol named proof of work (PoW) is widely applied by cryptocurrencies like Bitcoin. Although security of a PoW cryptocurrency is always the top priority, it is threatened by mining attacks like selfish mining. Researchers have proposed many mining attack models with one attacker, and optimized the attacker's strategy. During these mining attacks, an attacker pursues a higher relative revenue (RR) by wasting a large amount of computational power of the honest miners at the cost of a small amount of computational power of himself. In this paper, we propose a mining attack model with two phases: the original system and the multi-attacker system. It is the first model to provide both theoretical and quantitative analysis of mining attacks with two attackers. We explain how the original system turns into the multi-attacker system by introducing two attackers: the internal attacker and the external attacker. If both attackers take the attacking strategy selfish mining, the RR of the internal attacker in multi-attacker system will drop by up to 31.9% compared with his RR in original system. The external attacker will overestimate his RR by up to 44.6% in multiattacker system. Unexpected competitions, auctions between attackers and overestimation of attackers' influence factor are three main causes of both attackers' dropping RR. We propose a mining strategy named Partial Initiative Release (PIR) which is a semi-honest mining strategy in multi-attacker system. In some specific situations, PIR allows the attacker to get more block reward by launching an attack in multi-attacker system.