Formalization and Verification of MQTT-SN Communication Using CSP

The MQTT-SN protocol is a lightweight version of the MQTT protocol and is customized for Wireless Sensor Networks (WSN). It removes the need for the underlying protocol to provide ordered and reliable connections during transmission, making it ideal for sensors in WSN with extremely limited computing power and resources. Due to the widespread use of WSN in various areas, the MQTT-SN protocol has promising application prospects. Furthermore, security is crucial for MQTT-SN, as sensor nodes applying this protocol are often deployed in uncontrolled wireless environments and are vulnerable to a variety of external security threats. To ensure the security of the MQTT-SN protocol without compromising its simplicity, we introduce the ChaCha20-Poly1305 cryptographic authentication algorithm. In this paper, we formally model the MQTT-SN communication system using Communicating Sequential Process (CSP) and then verify seven properties of this model using Process Analysis Toolkit (PAT), including deadlock freedom, divergence freedom, data reachability, client security, gateway security, broker security, and data leakage. According to the verification results in PAT, our model satisfies all the properties above. Therefore, we can conclude that the MQTT-SN protocol is secure with the introduction of ChaCha20-Poly1305.