From Decentralization to Oligopoly: A Data-Driven Analysis of Decentralization Evolution and Voting Behaviors on EOSIO

As one of the most popular blockchain systems, EOSIO has been widely used in decentralized applications (DApps). Compared with traditional proof-of-work (PoW)-based blockchain systems like Bitcoin, EOSIO achieves a high transaction throughput and an alleged decentralization with the Delegated Proof-of-Stake (DPoS) consensus protocol. However, recent reports claimed the existence of voting collusion and manipulation during the DPoS consensus procedure of EOSIO, which may greatly decline the decentralization degree, fault tolerance, and reliability of the whole system. In this article, we obtain data from up to 135 000 000 blocks of EOSIO and conduct a data-driven decentralization analysis. Specifically, we characterize the decentralization evolution of the two phases in DPoS, namely block producer election and block production. Moreover, we study the voters with similar voting behaviors and propose methods to discover abnormal mutual voting behaviors in EOSIO. The analysis results show how EOSIO gradually evolves from decentralization to oligopoly and our methods can effectively capture abnormal voting phenomena in the EOSIO, which can also provide important insights for the design and maintenance of other DPoS-based blockchains.