An amazing utilization of internet of things (IoT)-based smart technologies has been observed in recent years. Internet of things (IoT) became smarter and autonomous, leading the way by interconnecting and interacting with the environment. Existing technologies such as big data, AI, and cloud computing have been supported by IoT but with some limitations. Blockchain is the better solution to access and share data with the decentralized system. IoT spreads its applications in healthcare, industrial internet of things, supply chain management, traffic management, etc., out of which smart cities take special attention in recent days by integrating with IoT to create a sustainable ecosystem by using information and communication technology (ICT). Smart cities can offer various smart applications for boosting the life prominence of society. These characteristics of blockchain are beneficial to the creation of smart cities. In this regard, the authors have conducted a systematic review of articles. This study highlights the integration of blockchain with IoT.
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With the advancement of numerous technologies and the emergence of novel concepts such as Big Data, Cloud Computing, Cyber Physical Systems (CPS), Artificial Intelligence (AI), and so on, the future seems bright, the modern industry has been promoted to a new level (Wan et al., 2019). The expanding global population, along with the rapid growth of inhabitants in cities, has resulted in a slew of social, technical, organizational, and economic issues that threaten cities' environmental and economic viability. (Bhushan et al., 2020). Most of the sectors are introducing “smart” concepts in the environment to improvise the visible and invisible assets. Smart cities offer different applications like Smart e-commerce, smart e-voting, smart healthcare systems, smart transportation, smart governance, and so on are all examples of smart technologies. Smart cities, in this context, strive to improve inhabitants' quality of life and establish a sustainable urbanization by incorporating sophisticated information and communication technologies (ICT) into local administration and services. (Wong et al.,2020). To integrate the various technologies to enhance the infrastructure of cities. In this context, IoT combined with different new concepts like Cloud computing, big data, AI. Internet of Things (IoT) smart devices become smart and autonomous. IoT devices will be interconnected with the environment in order to collect information and mechanize certain data. Internet of Things plays a critical role in transforming contemporary cities into smart cities, electrical grids into smart grids, and homes into smart homes. According to numerous study projections, by 2020, the number of interconnected massive gadgets is expected to increase from 20 to 50 billion. (Ana et al., 2018). Traditionally, the data collection over internet of things (IoT) devices are stored on central server. It may lead to privacy challenges, lack of data loss and security. Unlike traditional methods, blockchain technology facilitates digital assets without any mediators or third-party entities. Further, threats attempting to acquire access to personal information or control over the entire system are protected by blockchain-based technologies. (Bhushan et al., 2020).
Many researchers are highlighted different directions to addressed blockchain IoT applications in smart cities. The research directions are addressed various attacks, authentication issues in various applications such as healthcare sector (Thomas et al, 2019), e-voting system. It is related to patient data leaks at some manner during cyber security attacks (Yaqoob et al., 2021) To overcome that challenges block chain can assist streamline operations in healthcare system. The authors Provides fundamental security goals based on blockchain technology in smart homes (Dorri et al.,2021). Helo & Hao (2019) discussed about supply chain management for transaction details. Taş & Tanrover (2020) discussed the challenges involved in accomplishing blockchain-based e-voting. Due to cyber-security concerns, remote voting is considered impracticable. Several examples of diverse applications are shown in Table 1.