Message Integrity Code (MIC) doubt

[BoRRoZ]

see

Message Integrity Code (MIC)

Hi! i have a few question about the OTAA activation: I kwon that the join request is a package or message that contains AppEUI, DevEUI and DevNonce, ¿at this point this join request are encrypted by a hash function or something similar? The MIC would be the result of pass the join request and the AppKey by a hash function (AES 128) ? how the end nodes get the AppKey? and how the Aplicattion server get it? how many bits have the AppEUI, DevEUI, DevNonce and AppKey? Thanks and Sorry for my engl…