The next version of Mosquitto will provide SSL support for network encryption and authentication. This work is still in development, but is sufficiently advanced to make available for testing on test.mosquitto.org. In addition to the existing unencrypted access via port 1883, connections are now possible on ports 8883 and 8884.
Port 8883 provides simple encrypted access. Your client should verify the server certificate using the CA certificate available at http://test.mosquitto.org/ssl/mosquitto.org.crt
Port 8884 uses the same server certificate, but requires that your client provide a valid certificate signed by the mosquitto.org CA key. If you wish to obtain a client certificate for testing purposes, please get in touch.
The development Python module provides client SSL support. The latest version is available at http://test.mosquitto.org/ssl/mosquitto.py with a simple example at http://test.mosquitto.org/ssl/ssub.py. You will need to place the mosquitto.org CA certificate linked above in the same directory. All versions of Python from 2.7 upwards (including Python 3) are supported.
Please get in touch if you have any problems.
All clients in the development version now support SSL.