If I compare authentication procedure for 5G and LTE network, many changes have been introduced. I would like to highlight few of them. In LTE, HSS was the single entity to generate authentication vectors including key i.e. Kasme based on the serving network.
In LTE, network components like MME of the visited network and HSS of the home network have communication link based on roaming aggrement. Here, both the nodes believe that they are communicating with genuine node/authorized node.
In 5G, service based architecture will be used that means the same infrastructure will be used by 'n' number of network users. Though SBA provides greater flexiblity in terms of network usage but at the same security becomes major concern. That is one of the reason to introduce a change in existing LTE- AKA procedure.
Access and Management Function (AMF) supports two sub modules SEAF and SCMF. At the initial stage of authentication procedure, SEAF interacts with AUSF node which will be in the home network in case of roaming. After receiving the request from SEAF, AUSF interacts with APRF/UDM to retrieve authentication key material specific to the authentication method. Here, APRF job is to generate authentication key material from the long term key i.e. K.
After retrieving the authentication key material, AUSF generates two keys i.e. Kausf for itself and the other one i.e. Kseaf for SEAF. SEAF acts as an intermediate node when authentication messages are get exchanged between UE and AUSF. Once authentication gets successful, AUSF sends Kseaf to SEAF.
SEAF uses Kseaf to generates further key i.e. Kamf. Now, AMF is responsible to generate futher keys such as Knasint, Knasenc, Kgnb, Kn3iwf (for non-3GPP access). It is as same as MME generates keys from Kasme.
These are the differences I found based on my study so far.