ECDH support needed

[macman]

I want to implement ECDH and the documentation is to me a bit unclear. Using an ESP32-S3 I want to exchange a key with ECDH and a server that is running a python script that is communicating over MQTT. I have difficulties how to send the key to the python server and at the python server calculate the correct shared key. At the ESP32-S3 I often get a shared key containing 0x00, which is not good at all. Does anyone has experience with this and could give me an example? At this moment I use the ESP-IDF version 5.0.