## 1 Introduction  
The Internet and technology have advanced so quickly that the entire world is experiencing the fourth industrial revolution (Industry 4.0) [1] in all aspects of humanity,with the Internet of Things (IoT) playing a significant role in its widespread adoption. The Internet of Things is a network of interconnected physical objects (e.g., devices, machines, and appliances) equipped with sensors, software, and electronics and assigned unique identifiers. IoT sensors can also exchange data over the Internet without the need for human intervention. The IoT can generate information about the associated objects, examine them, and make decisions. It has enormous potential to provide various elating services across a wide range of industries, including industry, healthcare, smart homes, smart cities, social media, and supply chains [2]. The IoT has made it possible for small, low-power devices to connect to the Internet and exchange massive amounts of data, enabling a new generation of services. Due to security concerns stemming from the sensitive nature of the data handled by such applications, the potential for IoT-based applications has not been fully realized to date. However, blockchains impose a significant computational demand, which is difficult to meet in a resource-constrained IoT scenario. Although IoT devices are currently unable to participate in a blockchain consensus protocol, it is anticipated that they will be required to do so in the future [3]. Hardware acceleration of the protocol's most computationally intensive part, which typically consists of massive computation of the SHA-256 hash function, is one way to achieve this. Because SHA-256 is used in many security schemes, such as hash-based message authentication code [4] and the digital signature algorithm [5], the hardware acceleration of SHA-256 can benefit the capabilities of IoT applications in other ways. Indeed, SHA-256 is one of the most widely used cryptographic hash functions today, with applications in security-critical areas such as finance and cloud computing, in addition to the IoT. Blockchain is a decentralized platform in which all parties keep a copy of each transaction [6]. The transactions are transparent, and any changes can be quickly identified. Consider a smart city where parking spaces are displayed in real-time to users. Sensors update the centralized database when they detect a free parking space. The database system administrator can reserve a parking space for himself without disclosing it to others. In this case, the data from the sensor integrity are compromised. The goal of a blockchain network of interconnected devices is to eliminate the need for a third party and, as a result, ensure that the sensor real-time data reach every node in the network without being tampered with. Furthermore, the blockchain enables IoT devices to communicate with one another and make decisions on their own. Ethereum Blockchain is a platform for developing decentralized applications, in addition to digital currencies, by executing scripting language code known as smart contracts. Such code is run on a virtual machine known as the Ethereum Virtual Machine (EVM), which acts as an abstraction layer between the code and the machine itself [7]. While Bitcoin is considered a currency, Ethereum's currency is Ether, which can be used by businesses to create decentralized applications (DApps), and changing the state of a smart contract in the blockchain requires transaction fees priced in Ether. IoT implementations are currently largely centralized, which raises security concerns such as a single point of failure, trust, and privacy. Furthermore, it limits their scalability, highlighting the need for a decentralized trust mechanism in the IoT. Without the need for a central authority, the blockchain can provide trust through cryptographic techniques. Several blockchain-based IoT applications have recently gained traction due to their potential to improve security and privacy.