MASTER IC DEVICE, BACKUP IC DEVICE FOR THE MASTER IC DEVICE, DUMMY KEY STORAGE DEVICE PROVIDING DUMMY KEY TO THE MASTER IC DEVICE, AUXILIARY DEVICE OR THE MASTER IC DEVICE AND THE BACKUP IC DEVICE, AND KEY BACKUP SYSTEM USING TWO AUXILIARY DEVICES OR OVER

摘要

PROBLEM TO BE SOLVED: To provide a master IC device by which a user itself can prevent illegal use of keys whose number is limited to a finite number while easily backing up the keys and to provide a backup IC device for the master IC device. SOLUTION: A master private key in the master IC device 1 is encrypted by an encryption/decryption processing section 40 by using a backup public key adopting the asymmetrical key encryption system copied from the backup IC device 2 and externally outputted. Since the master private key is encrypted, contents of a 1st private key cannot be leaked. The encrypted 1st private key is decrypted at an encryption/decryption processing section 130 by using a backup private key and stored in a master private key storage section 120 of the backup IC device 2. Data encrypted by the master IC device 1 are decrypted by the master private key that is backed up and made usable.