A Survey on the Scalability of Blockchain Systems

In the past decade, crypto-currencies such as Bitcoin and Litecoin have developed rapidly. Blockchain as the underlying technology of these digital crypto-currencies has attracted great attention from academia and industry. Blockchain has many good features, such as trust-free, transparency, anonymity, democracy, automation, decentralization and security. Despite these promising features, scalability is still a key barrier when the blockchain technology is widely used in real business environments. In this article, we focus on the scalability issue, and provide a brief survey of recent studies on scalable blockchain systems. We first discuss the scalability issue from the perspectives of throughput, storage and networking. Then, existing enabling technologies for scalable blockchain systems are presented. We also discuss some research challenges and future research directions for scalable blockchain systems.

Introduction

In recent years, blockchain, as the underlying technology of Bitcoin and other crypto-currencies, has attracted significant attention. Academia and industry are trying to apply the promising technology into many areas, such as Internet of Things and smart cities. Blockchain has many good features, such as trust-free, transparency, anonymity, democracy, automation, decentralization and security. Trust-free means that blockchain systems can run normally in a peer-to-peer manner without a reliable third party. Blockchain enables everyone to access all transaction records, which makes it transparent. The anonymity can be realized by recording transactions using public anonymous addresses and keeping nodes' real-world identities hidden. In blockchain systems, decisions are made by all nodes, which makes it democratized. Smart contracts have the ability to perform transaction generation, decision making and data storage automatically. The decentralization of blockchain systems makes it necessary to ensure consistency by running consensus algorithms among decentralized nodes. The security of blockchain systems is related to integrity, confidentiality and authorization.