Research On Block Withholding Attack And Defense In Blockchain

As one of the most influential digital cryptocurrencies,Bitcoin is widely recognized for its Proof-of-Work(Po W)consensus mechanism.Po W means that when verifying transactions and packaging blocks,miners need to solve certain difficult mathematical problems to prove their contribution and computing power to the network.This mechanism ensures the security and decentralization of the Bitcoin network.However,Po W-based algorithms also face many attacks and threats.Most current research has focused on analyzing the benefits and effects of a single attack,such as selfish mining attacks.However,in actual situations,attackers may use multiple attack methods,such as hybrid attacks and bribery attacks.These attack methods may pose a greater threat to the blockchain system,so more comprehensive research is needed.In view of the above problems,this paper studies the block withholding attack and defense in the blockchain attack:(1)A multi-attack Bribery Selfish mining and Block Withholding attack model(BSBWH)is proposed.BSBWH attack combines bribery attack,selfish mining attack and block withholding attack.In view of the single attack situation in the past,three typical attacks are integrated,and the selfish mining attack model is expanded,and the Markov chain is used to model the attack,and the block withholding attack is introduced to realize the block withholding and discarding attack,and conduct bribery attacks in case of block forks.The BSBWH attack is analyzed theoretically and experimentally,and it is found that there may be conflicts between different attacks.Theoretical analysis shows that BSBWH attack is superior to selfish mining block withholding attack.In the BSBWH attack,the selfish mining attack,block withholding attack and bribery attack under different attack proportions are calculated.The experimental results show that when the attack power is low,the block withholding attack is very dominant,but when the bribery attack exceeds a certain proportion,the income of the BSBWH attack will decrease.The behavior of the attacker is not only affected by its own computing power,but also by other attack methods.(2)A block withholding attack defense model that hides the target value is proposed.In this model,the mining pool administrator will hide the blockchain target difficulty value and expand the target value to the miners.Doing so can prevent the attacker from accurately knowing the difficulty of the next block,making it difficult to predict which blocks can stay and gain more benefits.Theoretical analysis of the benefit size under the hidden target value defense model is carried out,and the influence of different block withholding attack proportions in the defense model and the influence of the expansion multiple are calculated.The experimental results indicate that block withholding attacks can be limited by a small expansion factor,and excessive expansion factors have little impact on defense effectiveness.