Patent ID: 8024577

Claim:
A password recovery system for re-supplying a password, said password recovery system comprising: a communication terminal device for receiving a predetermined service via a network using the password; and a portable recording medium for storing the password, the portable recording medium being coupled to said communication terminal device, wherein said communication terminal device comprises: a controller for receiving from an external communication terminal device a signed data set, based on an indication for recovering the password from a user of said communication terminal device when the user forgets the password, the external communication terminal device guaranteeing legitimacy of the user of said communication terminal device and generating the signed data set with a secret key, and for outputting to said portable recording medium the received signed data set when said portable recording medium is coupled to said communication terminal device, and wherein said portable recording medium comprises: a memory for storing a public key corresponding to the secret key; and a controller for inputting from said communication terminal device the signed data set, and for judging, using the public key and the signed data set, whether the signed data set is signed by the external communication terminal device, said judging being performed solely by said controller of said portable recording medium, wherein said controller of said portable recording medium recovers the same password as the password stored in said memory of said portable recording medium when it is judged that the signed data set is signed by the external communication terminal device, and outputs the recovered password to said communication terminal device, and wherein said controller of said portable recording medium does not recover the same password as the password stored in said memory of said portable recording medium when it is judged that the signed data set is not signed by the external communication terminal device.