An Efficient and Secure Node-sampling Consensus Mechanism for Blockchain Systems

The consensus mechanism plays a pivotal role in guaranteeing the security and consistency of blockchain systems and substantially affects system performance. However, an increasing number of blockchain nodes degrade the consensus performance dramatically because of the high communication complexity in traditional consensus mechanisms. In this paper, we propose NS-consensus, a secure node-sampling blockchain consensus mechanism reducing the communication complexity significantly. The key novelty lies in the sampling of blockchain nodes so that the leader only needs to interact with the sampling nodes in each consensus epoch. However, NS-consensus imposes two challenges in determining an optimal sample size and denying malicious proposals. To address the challenges, we determine the sample size under the constraints of a confidence level and a margin of error to enhance communication efficiency without compromising system security. Furthermore, we design a mechanism to enable the leader to interact with all blockchain nodes in the last consensus phase, ensuring the denial of malicious proposals. The extensive experimental results indicate that NS-consensus outperforms the state-of-the-art with up to 175.1% higher system throughput and 79.9% lower time overhead in the sampling phases.

I. Introduction

The consensus mechanism is one of the critical components of blockchain systems, guaranteeing the security and consistency [1]. The performance of a blockchain system is primarily determined by consensus [2]. Moreover, with the popularity of blockchain in a wide range of applications, the traditional consensus mechanisms are proven to be less efficient because of the large number of blockchain nodes and stringent requirements of transaction processing in real-time [3]–[5]. It remains a grand challenge to design an efficient consensus mechanism for large-scale blockchain systems [6].