Abstract: A mobile communication method suitable for a purchased mobile unit system, a mobile telephone switching station, a customer management system, and a mobile unit. A temporary ID, with communication restrictions, such as a limitation on the number of calls, is written into a mobile unit along with a DN, prior to shipment of the mobile unit. After purchase, the mobile unit is operated to initiate a registration procedure via a mobile communication network by using the temporary ID and to have a permanent ID written therein. By using the temporary ID, a communication connection test can be conducted on the mobile unit prior to shipment from the factory. There is no need to install a ROM writer at a mobile unit shop to write personal information.

Abstract: To prevent illegal duplication of an ID containing type mobile unit, and illegal duplication of an IC card for an IC card insertion type mobile unit, in manufacturing a COB device, a public key KE.sub.COB, corresponding to a common secret key KD.sub.COB determined through consultation among communications carriers, is stored into a ROM in an unalterable form. In manufacturing a mobile unit, KE.sub.Cj that corresponds to a secret key KD.sub.Cj uniquely assigned to each communications carrier, is signature-encrypted with KD.sub.COB. The result E(KD.sub.COB, KE.sub.Cj) is entered into a COB device to write in KE.sub.Cj ; the COB device 22 is then assembled, prior to shipment, into the mobile unit into which a mobile unit secret key KD.sub.MSNi and public key KE.sub.MSNi have been stored. In registration of the mobile unit, E(KD.sub.Cj, ID) received from the communications carrier is entered into the COB device 22, thereby writing personal information ID. For a readout, KD.sub.MSNi is input to read out the ID.

Abstract: A mobile unit having a unit for transmitting and receiving signals to and from a base station by radio telephony, an input unit for use in entering information, a display and a control unit, is provided with a first memory in which "unwritten" or "written" is stored as a state of a password for enabling the dial lock, and a second memory in which a password for enabling the dial lock is stored. When a dial lock signal is supplied from the input unit, the control unit writes a password entered at the input unit in the second memory and changes the state of a password in the first memory from "unwritten" to "written." Thereafter, except after providing the password, the mobile unit cannot be used for calling. Moreover, the password cannot be modified.