SCP: A Computationally-Scalable Byzantine Consensus Protocol For Blockchains

Abstract—In this paper, we design a new blockchain Byzantine consensus protocol SCP where the throughput scales nearly lin-early with the computation: the more computing power available, the more blocks selected per unit time. SCP is also efficient that the number of messages it requires is nearly linear in the network size. The computational scalability property offers the flexibility to tune bandwidth consumption by adjusting computational param-eters (e.g., proof-of-work difficulty). The key ideas lie in securely establishing identities for network participants, randomly placing them in several committees and running a classical consensus protocol within each committee to propose blocks in parallel. We further design a mechanism to allow reaching consensus on blocks without broadcasting actual block data, while still enabling efficient block verification. We prove that our protocol is secure, efficient and applicable to several case studies. We conduct scalability experiments on Amazon EC2 with upto 80 cores, and confirm that SCP matches its theoretical scaling properties. I.