So, in a setup where the network server is separate from the app server, the Network server shouldn’t be able to decrypt the application payload. i.e. the network server has the NwkSKey but not the AppSKey, and the app server has the AppSKey (I suppose in principal it could also could hold the NwkSKey but that’s irrelevant there.)
As both NwkSKey and AppSKey are derived from the same data (AppKey, devnonce, appnonce), I wasn’t clear how the key gets to the network server - it seems sensible that the AppKey can only reside on the AppServer and not on the network server, so it can’t generate its own key from the data.
In this case how does the Network Server get hold of the NwkSKey? Does the App Server transmit the NwkSKey to the Network server in the background? Any guides I’ve looked at gloss over the fact that the AppServer and Network Server are in principal separate machines.