Our wolfMQTT project includes an example for secure firmware update. This example uses the wolfSSL embedded SSL/TLS library to hash/sign the binary image and send it over MQTT. The example has two applications. One is called fwpush, which hashes, signs and publishes the firmware image over TLS to an MQTT broker. The second is called fwclient, which subscribes to the example firmware update topic, receives the firmware image and validates the signature of it. This example is located in examples/firmware.
The latest wolfMQTT releases can be downloaded at:
https://wolfssl.com/download
Documentation for wolfMQTT can be found here:
https://www.wolfssl.com/docs/wolfmqtt-manual/
The latest source code can be found on our GitHub repo at:
https://github.com/wolfSSL/wolfMQTT
For questions please contact support at support@wolfssl.com.