Blockchain search engine: Its current research status and future prospect in Internet of Things network

Blockchain has recently triggered extensive attention and concern due to the flourish of cryptocurrencies and decentralized applications. It can be considered as a database, and is utilized to store a large collection of time ordered data records in data intensive application scenarios. In such cases, search engines are put forward to access the data in a blockchain storage in order to perform analysis for different purposes. However, the research on blockchain search engine is still in its initial phase and there is no systematic study about this research area. This paper tries to analyze blockchain search engines from two aspects: its current research status and future prospect in Internet of Things (IoT) domain. In the research status aspect, the paper mainly focuses on the technique division and performance comparison of blockchain search engines from different angles. To elaborate the future prospect of blockchain search engine in IoT domain, the present search works related to IoT domains are also introduced. In the remaining parts of the paper, we outline the blockchain background. Then, the search fundamentals are introduced, including the classification principles and search requirements. After that, we present a detailed review on the state-of-the-art works for blockchain search and give some problem analysis on blockchain search in IoT domains. Finally, we outline the challenges of blockchain search and give the prospect of possible research directions in future in IoT domains.