A Review on Blockchain and IoT Integration from Energy, Security and Hardware Perspectives

Blockchain is one of the promising technologies nowadays due to its unique characteristics like security, privacy, data integrity, decentralization, immutability, and traceability. Originally used to implement cryptocurrencies, recently numerous applications have employed blockchain in their architectures including applications targeted for the internet of things (IoT) environments. It is expected that by 2025 more than 21 billion IoT devices will be used especially with use of cloud, fog and edge computing architectures. Integrating blockchain in the IoT architecture provides many advantages such as enhancing security and privacy, better speed and costs, traceability and reliability, and elimination of single point of failure. On the other hand, many issues and challenges have arisen and should be addressed. Typically, IoT system consists of lightweight devices with limited hardware resources and constraints. Hence, the energy efficiency is a fundamental challenge in such devices. The main motivation of this paper is to survey designing a secure and energy efficient blockchain-based IoT implementation using a suitable hardware design. The paper classifies, presents and analyzes existing solutions to better implement IoT environment combined with blockchain technology. Our investigation demonstrations that most of lightweight solutions handle either the energy or security issue separately. Moreover, many works are theoretical-based analysis and solutions without considering the real blockchain-based IoT validation design. Energy evaluation for IoT hardware devices is not given the adequate research bandwidth. Additionally, limited works evaluated their techniques from hardware constrained device perspective. It is recommended that the performance of any proposed solution should be validated using real designs. The hardware perspective evaluation should be in mind for efficient blockchain-based IoT hardware implementation. The proposed lightweight solutions should focus more on efficient energy implementation while considering the lightweight security mechanisms.