I have in fact the iBTS AES keys provided by Kerlink.
Some more info on :
My concern is the following. I am not using the chirpstack-gateway-bridge.ipk module running into the iBTS, but the one premise on my server (in other words iBTS send data over UDP to the server).
Are both chirpstack-gateway-bridge software (the one for iBTS and the one on the server) identicals ?