Systems and methods of protecting an initial NAS message are described. The NAS message is encrypted using the home PLMN public key during initial registration with the network using a registration request message. An AMF of the serving PLMN sends a serving PLMN public key which is then used to encrypt information including an S-NSSAI of later initial NAS messages after initial registration is completed. The S-NSSAI may not be sent in the later initial NAS message if the S-NSSAI is provided at an access stratum level. The RRC message may contain an indication that the S-NSSAI is encrypted using the serving PLMN public key.