Blockchain technology in combination with the Internet of Things (IoT) has become a topical subject to provide solutions to various important issues as the security, privacy, and trust in a decentralized system. This paper aims at investigating how Blockchain-based frameworks can transform IoT applications from the perspective of security and performance. In this paper, four algorithms which include Blockchain consensus mechanisms, smart contracts, decentralized trust models, and IoT data encryption are used to show how they can enhance IoT data security, ensure transparency in communication, and offer reliability in decision making. The performance evaluation illustrates that the Blockchain-based IoT frameworks increase data accuracy and reliability by 98%, lessen the number of unauthorized access attempts by 75%, and enhance system efficiency by 30% in comparison with traditional centralized IoT architectures. Further, the use of the proposed methodologies is contrasted against work in the same vein showing improvements in security/privacy and trust. The analysis shows how Blockchain adds security to the communication process in IoT networks while ensuring the factors of future demand-including scalability and privacy-in sectors like health care, smart cities and auto vehicles. This paper enlightens the significance of Blockchain for IoT security and discusses the potential of the future-proof decentralized system.