The disclosure relates to a communication scheme and system for converging a 5th generation (5G) communication system for supporting a data rate higher than that of a 4th generation (4G) system with an internet of things (IoT) technology. The disclosure is applicable to intelligent services (e.g., smart home, smart building, smart city, smart car or connected car, health care, digital education, retail, and security and safety-related services) based on the 5G communication technology and the IoT-related technology. The disclosure relates to a method and apparatus for allowing a base station to identify a ciphering key (COUNT value) for security enhancement.