Practical Internet of Things Security - Second Edition

Authentication to the gateway

Cloud gateways often support policy configurations that define the application of encryption and authentication controls. For example, definition of the authentication options that allow MQTT clients to connect with the gateway, and restrictions on what topics MQTT clients can publish or subscribe to. 

Per-device authentication and access control in Azure are enabled through the use of either X.509 certificates or IoT Hub security tokens that map to each device's access policy and credentials. Token-based authentication allows authentication to take place without transmitting sensitive security parameters across the wire. These tokens are also limited in scope and duration. 

Within Azure, devices transmit authentication ...