IMPROVING SECURITY IN TELECOMMUNICATIONS SYSTEMS

摘要

Security of communications between a mobile terminal 1 and a cellular network node (base station 3) is enhanced. A communication session transmitted on a first traffic channel‘0’is encrypted using a key‘KA’. The security is enhanced by causing the communication channel to change to a second communication channel‘7’after a predetermined time, preferably very quickly after establishing the key. In one embodiment the communication channel then changes to a third communication channel‘25’after a predetermined time. In another embodiment the communication session is encrypted using a second key‘KB’after causing the communication channel to change to the second communication channel‘7’.