Sponsored Block Withholding Attack Based On Proof-of-Work Blockchain

At present,the electronic currency with the largest market value adopts the blockchain with proof-of-work as the consensus mechanism as the underlying technology.Users can realize anonymous transactions in a trustless P2 P network,which has the characteristics of decentralization,trustlessness,and inability to tamper.Blockchain has important market value,and the security of its consensus mechanism has attracted much attention.The sponsored block withholding attack is an attack on its consensus mechanism.This paper studies the optimal computing power allocation strategy of sponsored block withholding attack in various scenarios and discusses the impact of this attack on the security of blockchain based on the proof-of-work consensus mechanism.Sponsored block withholding attack means that the attacker allocates part of the computing power to the victim pool for mining,only submits part of the proof of work but does not submit the full proof of work,and uses the full proof of work to seek sponsorship from the sponsor pool.According to the number of victim pools and the number of sponsor pools,the application scenarios of sponsored block withholding attacks can be divided into the following six types: one victim pool and one sponsor pool,one victim pool and multiple sponsor pools,and multiple victim pools and one sponsor pool,multiple victim pools and multiple sponsor pools,one victim pool without sponsor pool,multiple victim pools without sponsor pool.This paper deeply studies the relative gain formula of attackers in six scenarios.On the one hand,it conducts qualitative analysis to solve the problem of how to make the relative gain larger,and proposes the big target theorem and the always attack theorem.On the other hand,quantitative analysis is carried out to solve the problem of optimal computing power distribution strategy,and the optimal attack strategy theorem is proposed.The blockchain network model in this paper,on the one hand,fills the research gap of the traditional model in the case of multiple victim pools and multiple sponsoring pools.And on the other hand,it solves the problem of the traditional model’s limitation of computing power.That is,in addition to the attacker,victim pool,and sponsor pool,there are other pools in the network.This greatly expands the usefulness of sponsored block withholding attacks.In this paper,the computational experiment method and the simulation experiment method are adopted,and the experimental results are consistent with the expectation.First,the experimental results verify the correctness of the theorem proposed in this paper.Secondly,by comparing the relative benefits of the sponsored block withholding attack,the FAW attack and the block withholding attack,it is proved that the relative benefit of the optimal computing power allocation strategy of the sponsored block withholding attack proposed in this paper is greater.Finally,the experiments show that the sponsored block interception attack has no threshold requirement for the attacker’s computing power.Even if the attacker’s computing power is small,the strategy proposed in this paper can be used to obtain considerable relative benefits.So,the blockchain network is insecure.And it is known that this consensus mechanism will waste a lot of power and is not conducive to environmental protection.Therefore,this paper advocates not using proof of work as a consensus mechanism,and using other safe and environmentally friendly consensus mechanisms.