The Cipher Key Sequence Number is used in key management in a GSM system. Since the Kc (cipher key) is dynamically generated through the authentication process some mechanism to ensure key consistency is required. The CKSN is employed to achieve this. If encryption is used there is no requirement to authenticate the user for every call. It is possible to refer to previously used cipher keys already generated in the network. The CKSN is used to refer to these keys.