I have created a small instruction to patch the APK file and get all required info to interact with windows and unlock your home.
The app is only required once to get the all the keys.
Btw:
I was able to generate and exchange all other keys via web API except for the HashSignKey which seems to be generated when the app connects directly to the gateway. I could log that exchange with wireshark (~9 requests and responses between app + local gateway) but data seems to be encoded/encrypted.
But having all the keys allows to create own APIs (eg Node-RED).
Maybe this is useful to some people, like everything here was for me.