Toward Decentralization in DPoS Systems: Election, Voting, and Leader Selection Using Virtual Stake

Delegated Proof of Stake (DPoS) is a high throughput, low power consumption consensus mechanism is which elected participants or witnesses vote to accept blocks to be included in the blockchain ledger. However, DPoS is prone to centralization of voting power which can introduce bias and degrade the usability of the blockchain. In this work, we propose the concept of virtual stake which measures the truthfulness of witness voting throughout the round. Virtual stake at the end of a round is used as incentive for the next election of witnesses, but electors have a discretionary right to cast a portion of their votes for candidate witnesses regardless of their past behavior. Virtual stake is also used to guide the process of selecting the leader(s) to propose blocks for voting in PBFT cycles within the round, which prevents mis.behaving witnesses from submitting blocks. We describe and solve the analytical model of witness behavior, assuming that witnesses can be categorized into behavioral classes with different probability of truthful voting, false voting, and abstention. Our results show the impact of class populations, and voting behavior on virtual stakes, distribution of votes, and, most importantly, on overall consensus probability. The impact of centralization and witness misbehavior in voting can be countered by an increase of voting groups and decrease of round size, although further control of voting process during a round may be necessary to maintain the desired performance level of the blockchain system.