The Internet of Things (IoT) has significantly altered our way of life. IoT is employed due to pressure from customers, authorities, and business partners. Although IoT opens up new possibilities, security is always a top priority when offering various services. It is particularly difficult to shield the information produced by IoT devices from security threats and to secure the exchange of this data as it passes through various nodes and gateways. Hence, group key management (GKM) is the essential method for controlling the deployment of keys for network access and safe data delivery in these kinds of dynamic situations. Nevertheless, the huge volume of IoT devices and the rising subscriber base presented a scalability difficulty unaddressed by the current authentication techniques based on GKM and devoted to the IoT. Moreover, all of the GKM models that are currently in use enable the independence of participants. They only concentrate on dependent symmetrical group keys for each subgroup, which is ineffective for subscriptions with very dynamic behavior. To address these issues, a unique Decentralized Lightweight Group Key Management framework for Network Access in the IoT environment. REMI, a dependable and efficient multicast routing system for Internet of Things networks, is also introduced in this study. REMI employs a cluster-based routing protocol that causes a quicker multiplex message distribution within the system. According to the data, this protocol is more effective than cutting-edge protocols regarding the end-to-end delay, energy consumption, memory usage, and packet delivery ratio.