Evaluation of the Communication Efficiency in MQTT 5.0 End-to-End Security Architecture

MQTT is a lightweight communication protocol where messages are relayed through a Broker, which enables curious brokers potentially peer into client messages. In recent years, end-to-end security (E2E) channel, publisher-subscriber channel, has become a focal point, and several proposals have been introduced to add Client-to-Client E2E secure communication within the MQTT framework. Conventionally both the original client-broker channel and this additional E2E channel have been suggested to provide both encryption and integrity protection, which results in duplicate encryption; it not only increases the computational cost but also the communication cost. It potentially degrades the performance of MQTT system.This study focuses on two main challenges: one is to evaluate the additional cost incurred by the combination of the E2E channel and the client-broker channel; the other is to improve the communication and the computation by designing new client-broker-channel security schemes.Experimental results show that, as the number of subscribers increases, the additional overhead of the duplicate encryption become more serious, and the improvements of the proposed improved scheme become increasingly apparent. The experiments utilize Mosquitto[1] and Paho[2] libraries for implementation. The 'top' tool is used to monitor the running efficiency of virtual machines, and which facilitates the identification of the overhead issues and the performance of several proposed schemes.