Method and apparatus for registration

A system for registration, wherein the system comprises:

• a first access and mobility management function (AMF) configured to:
• determine, according to a local policy, whether to perform horizontal derivation on a first key during a redirection procedure of a user equipment (UE) to or from a second AMF;
• and
• send, to the second AMF, indication information indicating that the horizontal derivation has been performed on the first key when the first AMF determine to perform the horizontal derivation on the first key, or send, to the second AMF, a first security context other than the indication information when the first AMF determines not to perform the horizontal derivation on the first key;
• and
• the second AMF coupled to the first AMF and configured to:
• when determining to perform an authentication and when receiving the first security context other than the indication information, protect an authentication request message using the first security context to generate a protected authentication request message, and send, the protected authentication request message to the UE;
• and
• when receiving the indication information, perform a non-access stratum security mode command (NAS SMC).

A method for registration, wherein the method comprises:

• receiving, by a second access and mobility management function (AMF) from a first AMF, a security context other than indication information indicating that a horizontal derivation has been performed on a first key;
• determining, by a second AMF, whether to perform an authentication;
• and
• when the second AMF determines to perform authentication and when the second AMF receives the security context other than the indication information, protecting, by the second AMF, an authentication request message using the security context to generate a protected authentication request message, and sending, the protected authentication request message to a user equipment (UE).

A second access and mobility management function (AMF) comprising:

• a transceiver configured to receive, from a first AMF, a security context other than indication information indicating that a horizontal derivation has been performed on a first key;
• and
• a processor coupled to the transceiver and configured to determine to perform an authentication,
• wherein when the processor determines to perform the authentication and when the transceiver receives the security context other than the indication information, the processor is further configured to protect an authentication request message using the security context to generate a protected authentication request message, and the transceiver is further configured to send the protected authentication request message to a user equipment (UE).