Methods and arrangements for secure linking of entity authentication and ciphering key generation

The present invention relates to secure communications, and more particularly to methods and arrangements that provide a logical relationship between entity authentication processes and ciphering key generation processes during a secure communication. Methods and arrangements are provided for use in communications systems that allow for secure communication sessions to be conducted over a communications link between at least two nodes. An entity authentication process is conducted using a cryptography key. During the authentication process, a ciphering offset (COF) value is generated. Each node stores the COF value and uses the COF value to generate subsequent ciphering keys that are employed to encrypt data transmitted between the nodes. As such, there is a logical relationship between the latest entity authentication process and subsequently generated ciphering keys. This increases security and can be used to reduce overhead processing/delays associated with repeating the link or entity authentication process. The methods and arrangements can be employed to enhance security in any communications system, including a mobile telecommunications system, such as, for example, a global system for mobile (GSM) communications system.