You must set parameters and obtain return values based on the corresponding specifications when your application server calls operations of the authentication server. Otherwise, the call may fail. This topic describes the API operations related to device access credentials in ApsaraMQ for MQTT.
| API operation | Description |
| RegisterDeviceCredential | Creates an access credential for a device. |
| GetDeviceCredential | Queries the access credential of a device. |
| UnRegisterDeviceCredential | Deletes the access credential of a device. |
| RefreshDeviceCredential | Updates the access credential of a device. |