I have done a bit of work on the use_paho_linux_version branch of the MqttClient app. I have enabled TLS support for for server side certificates. What this means is that if you specify your URI as
ssl://eu.airvantage.net:8883 instead of
tcp://eu.airvantage.net:1883 your messages will be encrypted. I have only tested this with the AirVantage MQTT broker, but I would expect it to work for others as well.
Unfortunately, the ArduinoBridge app used on mangOH Green depends on the DataRouter app which depends on the API exposed by the master branch of MqttClient. This makes it difficult to promote the use_paho_linux_version branch to become master until the DataRouter can be updated. I think the DataRouter update requires quite a bit of work, so I don’t know when that will happen.
If you’re interested in contributing to the mangOH project and you want something small to start out on, take a look at trying to add support for “will” messages to the use_paho_linux_version branch of MqttClient.