A communication system for key derivation and a corresponding method and user equipment are disclosed:
communication system comprises a source base station for a User Equipment, UE, and target base station for the UE, wherein
the source base station is configured to derive multiple keys correspond to multiple cells under control of the target base station and to send the multiple keys to the target base station; and
the target base station is configured to receive the multiple keys from the source base station and to select a key from the multiple keys received by the target base station for being used in communication with the UE, the selected key correpsonding to a target cell that the UE requests to access during connection reestablishment procedure.
