IoT stands as a dynamic domain within technology and research, facilitating organizational decision-making and aiding individuals in problem-solving by linking sensors and devices to the internet for data exchange between clients and servers. Despite numerous approaches attempted by researchers, such as authentication via login IDs and encryption through attribute-based topics or the AugPake protocol, attackers can exploit vulnerabilities at various points along the communication pathway, posing a significant threat. To mitigate this risk, a novel routing strategy called STEM (Secure Transfer of Encrypted Messages) is proposed for IoT networks. STEM encrypts transmitted messages and routes them using MQTT (Message Queue Telemetry Transport) from publishers to subscribers. Encryption is accomplished using cipher techniques, with key exchange facilitated by the Diffie-Hellman algorithm. Simulation using the ECLIPSE PAHO Java Client has demonstrated promising and effective results.