The Internet of Things (IoT) is rapidly expanding and evolving into a widely used computing service that requires substantial processing resources and storage for handling large amounts of data. Many IoT systems encounter inherent challenges such as resource constraints, limited storage capacity, and restricted connectivity, which often necessitate reliance on outsourced cloud services for storage and computation. Blockchain technology has emerged as a promising alternative due to its robust data security and privacy features. It facilitates automatic transaction processing and eliminates the need for intermediary verification, thereby significantly improving transaction speeds. Despite its advantages, blockchain faces challenges such as high computational demands and complexity, which can be incompatible with lightweight IoT devices that require scalable solutions. This paper examines how blockchain technology can be used to implement smart contracts in IoT applications. It focuses on creating a scalable and lightweight blockchain model called LightBlock. LightBlock is specifically designed to optimize the balance between security, privacy, and efficiency for IoT devices. The objective is to be reached by enhancing different components of an agile and flexible blockchain framework. The study is focused on enhancing security and privacy for users of IoT, guaranteeing complete security and usefulness. The evaluation of the discoveries was conducted using MetaMask, a web3 interface, and simulation tools. Subsequent research could include exploring different blockchain platforms and conducting real-world experiments with a wider range of IoT devices.