  Consensus protocols play a pivotal role to balance security and efficiency in
blockchain systems. In this paper, we propose an evaluation framework for
blockchain consensus protocols termed as AlphaBlock. In this framework, we
compare the overall performance of Byzantine Fault Tolerant (BFT) consensus and
Nakamoto Consensus (NC). BFT consensus is reached by multiple rounds of quorum
votes from the supermajority, while NC is reached by accumulating credibility
with the implicit voting from appending blocks. AlphaBlock incorporates the key
concepts of Hotstu BFT (HBFT) and Proof-of-authority (PoA) as the case study of
BFT and NC. Using this framework, we compare the throughput and latency of HBFT
and PoA with practical network and blockchain configurations. Our results show
that the performance of HBFT dominates PoA in most scenarios due to the absence
of forks in HBFT. Moreover, we find out a set of optimal configurations in
AlphaBlock, which sheds a light for improving the performance of blockchain
consensus algorithms.
