A network entity and the mobile station are adapted to conduct a plurality of predetermined message exchange procedures, including encryption key generation procedures. The method comprises determining whether a received message from a mobile station is encrypted. If the received message is encrypted, it is determined whether a correct encryption key for decrypting said message is available to said network entity and, if no correct key is available, a predetermined triggering message is sent to the mobile station. The mobile station then interrupts the procedure exchange procedure and initiates an encryption key generation procedure.