A Game-Theoretic Analysis of the Consistency Requirement for Permissioned Blockchains

Although BFT(Byzantine Fault Tolerance) is one of the most distinctive features of a blockchain system, many permissioned blockchains adopt RAFT as their consensus protocols, which cannot tolerate any Byzantine nodes. This paper analyzes this phenomenon base on the hypothesis of Rational Man. We propose a new consistency requirement in terms of Nash equilibrium, called NE-consistency, which requires a blockchain to guarantee consistency given that all participants are rational when choosing their strategies. We prove that both PBFT and RAFT can satisfy NE-consistency by modeling a permissioned blockchain as a repeated game. Particularly, we prove that in the sole subgame perfect equilibrium of both PBFT and RAFT, all participants tend to be good to maximize their profits.