A Study on Prevention and Automatic Recovery of Blockchain Networks Against Persistent Censorship Attacks

Abstract

Blockchain techniques have been actively used in a wide range of applications owing to their unforgeable characteristics. Currently, many blockchain platforms are applying a pBFT-based Delegate PoS(DPoS) consensus mechanism in their networks, because it ensures a quick consensus process since only a few validators participate in the consensus process. However, the pBFT-based DPoS consensus mechanism has a limitation that a malicious cartel with more than 1/3 of the total stake can launch persistent censorship attacks which disrupt the consensus process. To address this limitation, we propose a new defense method against persistent censorship attacks. First, we introduce a hierarchical consensus architecture that consists of the main-validators and sub-validators. In our consensus architecture, sub-validators can disagree with the results of the consensus process of main-validators known as existing validators. As the number of disagreeing sub-validators increases, the cost of censorship attacks increases. Second, we propose a behavior-based credit-scoring function that can operate on our consensus architecture. Our proposed function changes the role of the validators based on their behavior, thereby disrupting the formation of malicious cartels and removing the persistence of censorship attacks. We show that our proposed defense method makes a blockchain network more tolerant and resistant to censorship attacks based on experimental results using validator information collected from a real blockchain network. We also demonstrate that our defense method can automatically recover the blockchain network from persistent censorship attacks.

Keywords

• Blockchain
• consensus
• censorship
• defense
• DPoS