A method for a secure detach procedure in a radio telecommunication network

The present invention concerns a network controlling device configured to perform a detach of a terminal (MS) registered to a telecommunication network (NW) by associating an identification (TMSI) for said terminal (MS), deriving a signature (TMSI_SIG) for said identification (TMSI), and allocating a pair consisting of said identification (TMSI) and said signature (TMSI_SIG) to said terminal (MS), said network controlling device comprising: receiving means adapted to receive a detach request (DET_REQ) including said identification (TMSI) and said identification signature (TMSI_SIG) from said registered terminal (MS); comparison means adapted to compare said received detach request (DET_REQ) with a record of registration data of said terminal (MS) kept at the network side; and detaching means adapted to detach said terminal (MS) from said network (NW), if said received detach request (DET_REQ) coincides with said record of registration data. Also, the present invention concerns a correspondingly adapted terminal.