Method and device for linking two techniques for managing keys in dual connectivity in mobile communication system

A method of operating a user equipment (UE) in a wireless communication system, the method comprising:

• receiving, from a master node (MN) connected to the UE, conditional PSCell change (CPC) configuration information, a first SN counter value corresponding to a first key value transferred to a first target secondary node (SN) not supporting a selective secondary cell group (SCG) function, and a plurality of second SN counters corresponding to a plurality of second key values transmitted to a second target SN supporting the selective SCG function;
• generating a first key value or a second key value based on at least one of the first SN counter value or the plurality of second SN counter values;
• and
• performing an SN change to the first target SN through the first key value or an SN change to the second target SN through the second key value.

A master node (MN) operatively connected to a user equipment (UE) in a wireless communication system, the MN comprising:

• a communication unit;
• and
• a controller,
• wherein the controller is configured to:
• select a first secondary node (SN) counter value for a first target SN not supporting a selective secondary cell group (SCG) function,
• generate a first key value for secure communication between the UE and the first target SN based on the first SN counter value,
• transmit, to the first target SN, the first key value corresponding to the first target SN,
• select a plurality of second SN counter values for a second target SN supporting the selective SCG function,
• generate a plurality of second key values for secure communication between the UE and the second target SN based on the plurality of second SN counter values,
• transmit, to the second target SN, the plurality of second key values corresponding to the second target SN, and
• transmit conditional PSCell change (CPC) configuration information, the first SN counter value, and the plurality of second SN counter values to the UE.

A user equipment (UE) operating in a wireless communication system, the UE comprising:

• a communication unit;
• and
• a controller,
• wherein the controller is configured to:
• receive, from a master node (MN) connected to the UE, conditional PSCell change (CPC) configuration information, a first SN counter value corresponding to a first key value transferred to a first target secondary node (SN) not supporting a selective secondary cell group (SCG) function, and a plurality of second SN counters corresponding to a plurality of second key values transmitted to a second target SN supporting the selective SCG function,
• generate a first key value or a second key value based on at least one of the first SN counter value or the plurality of second SN counter values, and
• perform an SN change to the first target SN through the first key value or an SN change to the second target SN through the second key value.