From sgcWebSockets 4.4.3, the Amazon AWS IoT client supports Signature V4 Authentication, this means that you don't need to use a certificate to authenticate against AWS MQTT Server.
Signature V4 can be used for MQTT over WebSockets and port 443.
Configuration
First you must create a new user in your AWS console and assign privileges for IoT devices. If the process ends successfully you will get an Access and Secret Key, save this because you will need later.
In TsgcIoTAmazon_MQTT_Client there is a new property called SignatureV4, you must enable it and set the keys provided by AWS and the region.