US Patent 10470042 Secure short message service over non-access stratum

A short message service (SMS) message is encrypted using an encryption key stored at a user equipment and an access and mobility management function (AMF) and the encrypted SMS message is added to a payload of a non-access stratum (NAS) message that includes an NAS header. Integrity protection is applied to the NAS message using an integrity key stored at the user equipment and the AMF and the integrity-protected NAS message is transmitted. The NAS message is received via an NAS link between the user equipment and the AMF. An integrity check is performed on the NAS message using the integrity key. An encrypted short message service (SMS) message is extracted from a payload of the NAS message in response to the integrity check being successful and the encrypted SMS message is decrypted using the encryption key.