Abstract: In a first processing mode for a first communication request, a communication processing unit responds to a communication request signal from a communication terminal to acquire an authentication key Ka corresponding thereto from a storage, generates pieces of enciphered authentication information Xai and Xbi enciphered by the authentication key Ka of the communication terminal and an authentication key Kb of the communication processing unit, respectively, and random information Yi and transmits these pieces of information Xai, Xbi and Yi as an authentication request signal to the communication terminal. The communication terminal sends, as an authentication response signal, information Ka[Yi] obtained by enciphering the received random information Yi with the authentication key Ka, back to the communication processing unit, and at the same time, the communication terminal stores the received enciphered pieces of authentication information Xai and Xbi.

Abstract: A method of subscriber authentication suitable for a roaming service in a telecommunication capable of realizing an improved security for the secrecy of the authentication key. In this method, an authentication data Indicative of a tentative authentication key to be used only in the authentication at the second network is transmitted from the second network to the first network, and the first network enciphers this authentication data by using a permanent authentication key shared between the first network and the mobile subscriber, and transmits this enciphered authentication data to the mobile subscriber via the second network, such that the mobile subscriber can decipher this enciphered authentication data by using the permanent authentication key to obtain the tentative authentication key and subsequently carry out the authentication at the second network by using the obtained tentative authentication key, wlthout explicitly disclosing the permanent authentication key to the second service provider.

Abstract: This invention allows a subscriber of a telephone network to receive a call by a telephone registered under his/her personal telephone number no matter where he/she carries the telephone with him/her by maintaining a reference table of a personal telephone number assigned to each subscriber, a station number assigned to each telephone, and a subscriber loop address assigned to a telephone connection terminal of the network in a memory within the network.