Authentication method and communication terminal and communication processing unit using the method

摘要

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. The communication processing unit verifies the authentication response signal by use of the authentication key Ka. In a second processing mode, the communication terminal transmits previous enciphered authentication information Xb(i-1) as a communication request signal to the communication processing unit and deciphers previous information Xa(i-1) to generate an authentication key Kci. The communication processing unit deciphers the received enciphered authentication information Xbi to generate a deciphered authentication key Kci and transmits to the communication terminal an authentication request signal containing newly generated pieces of enciphered authentication information Xai and Xbi and the random information Yi. The communication terminal stores the received pieces of enciphered authentication information Xai and Xbi and enciphers the random information Yi by the authentication key Kci and sends it as an authentication response signal Kci[Yi] to the communication processing unit, which verifies the authentication response signal by the deciphered authentication key Kci.