Protection of initial non-access stratum protocol message in 5g systems

An apparatus of an Access and Mobility Function (AMF) of a public land mobile network (PLMN), the apparatus comprising:

• a processor configured to:
• encode a public key of the PLMN for transmission in a system information block (SIB) or non-access stratum (NAS) message;
• decode, from a UE, an initial NAS message comprising an information element (IE) encrypted using the public key, wherein an entire NAS message payload of the initial NAS message is encrypted using the public key, wherein the initial NAS message is a first NAS message sent after the UE transitions from an idle state;
• and
• decrypt the IE of the initial NAS message using a private key associated with the public key.

A user equipment device (UE), comprising:

• a radio;
• and
• a processor operably connected to the radio and configured to cause the UE to:
• store a public key from a home public land mobile network (PLMN);
• determine whether a security context for a serving PLMN is stored;
• in response to a determination that the security context is not stored, encrypt an information element (IE) using the public key from the home PLMN to form an encrypted IE;
• and
• transmit, to the serving PLMN, an initial non-access stratum (NAS) message for initial registration with the serving PLMN, the initial NAS message comprising the encrypted IE, wherein an entire NAS message payload of the initial NAS message is encrypted using the public key, wherein the initial NAS message is a first NAS message sent after the UE transitions from an idle state.