We need to have a secure communication between IoT device and AWS IoT. To achieve this goal, AWS IoT applies a security certificate as a part of securing communication. When we register a new IoT device, we also provide a security certificate file that is generated by AWS IoT or upload our own security certificate.
Since AWS IoT uses a security certificate, our IoT devices should support this feature. Ensure that your IoT device supports SSL certificates. Arduino Yún and Raspberry Pi 3 are examples of IoT devices with a supported SSL certificate. This certificate file should be uploaded to your IoT device.
Each IoT device has its own guidelines to upload a security certificate file. For Arduino Yún and Raspberry Pi 3, you can read how to work with AWS IoT in Chapter 2, Connecting IoT Devices to AWS IoT Platform.