A Survey on Off-chain Networks: Frameworks, Technologies, Solutions and Challenges
Xiaojie Wang, Hanxue Li, Ling Yi, Zhaolong Ning, Xiaoming Tao, Song Guo, Yan Zhang
Abstract
Off-chain networks that support transactions outside of the blockchain can handle large numbers of transactions and relieve the pressure on on-chain storage, showing great potential in mitigating scalability challenges of blockchain. However, since off-chain networks are still in the early stage of development, how to ensure off-chain data security, off-chain trust, off-chain transaction privacy and efficiency has become an important challenge. Against this background, this article provides a comprehensive review on off-chain networks. We first introduce the background, including design motivations, overview, and application scenarios. We then propose key issues related to off-chain networks. After that, we introduce off-chain technologies, including security and privacy based technologies, intelligent off-chain networking and routing technologies, off-chain edge computing technologies, and off-chain transaction scheduling technologies. Subsequently, we summarize mainstream solutions for corresponding key issues and provide learned lessons. Finally, we discuss some research challenges and open issues.