The core problem of blockchain is consensus. In this paper, the current consensus mechanisms of blockchain are classified as follows: the proof-of-work (PoW) consensus, the proof-of-stake (PoS) consensus, the hybrid consensus based on single-committee and hybrid consensus based on multiple-committees. The basic procedure of every kind of consensus is listed and enumerate corresponding typical schemes are given. Then the advantages and disadvantages of different kinds of consensus are analyzed. Finally, the future research direction of consensus is given.
blockchain; consensus mechanism; PoW; PoS; byzantine fault tolerance