Abstract

Recently, blockchain-based IoT solutions have been proposed that address trust limitation by maintaining data consistency, immutability, and chronology in IoT environments. However, IoT ecosystems are resource-constrained and have low bandwidth and finite computing power of sensor nodes. Thus, the inclusion of blockchain requires an effective policy design regarding consensus and smart contract environments in heterogeneous IoT applications. Recent studies have presented blockchain as a potential solution in IoT, but an effective view of consensus and smart contract design to meet the end application requirements is an open problem. Motivated by the same, the survey presents the integration of suitable low-powered consensus protocols and smart contract design to assess and validate the blockchain-IoT ecosystems. We discuss the key blockchain concepts and present the scalability and performance issues of consensus protocols to support IoT. Further, we discuss smart contract vulnerabilities and blockchain attacks. Open issues and future directions are presented, supported through a case study of low-powered consensus protocol design in the blockchain- IoT ecosystem. The survey intends to drive novel solutions for future consensus and safe, smart contract designs to support applicative IoT ecosyst