The emergence of the Internet of Things (IoT) has brought forth a revolutionary wave, characterized by a diverse array of intelligent and interconnected devices integrated into our digital landscape. These devices, permeating various sectors such as smart cities, healthcare, and societies, generate copious amounts of sensitive data. Given the inherent resource constraints of IoT systems in terms of computing power, memory, and communication capabilities, ensuring their secure access has become a complex challenge. In the context of blockchain, a decentralized network of nodes collectively validates and authenticates exchanged data before incorporating it into the system. Whether it involves financial transactions, sensor measurements, or authentication messages, this consensus-driven validation process significantly reduces the potential for unauthorized and unreliable interactions. Recognizing the limitations of conventional identification and authentication techniques in the face of the IoT's rapid proliferation, safeguarding these devices becomes paramount to ensure their efficiency and security. Addressing this need, a decentralized authentication and access control protocol for lightweight IoT systems has been proposed in this study. This novel approach leverages the principles of blockchain and fog computing to establish secure identity management and communication with IoT nodes. In contrast to existing blockchain-based verification systems, the proposed mechanism showcases superior performance, demonstrated through empirical testing. Our solution capitalizes on the inherent strengths of blockchain, combining them with enhanced authentication systems. This amalgamation yields a robust blockchain-based methodology that offers transparency, consistency, and tamper-proof record-keeping. The article delineates the comprehensive architectural design and presents a real-world prototype implementation to underscore the system's practicality and effectiveness. This method not only capitalizes on blockchain's innate advantages but also intertwines them with advanced authentication mechanisms, yielding a comprehensive solution that effectively addresses the unique challenges posed by lightweight IoT systems.