DATA CIPHERING AND STORING METHOD AND SYSTEM DEVICE

摘要

PROBLEM TO BE SOLVED: To provide the data ciphering and storing method and system device which can prudentially manage ciphered data stored in an external storage device by using a computer card. SOLUTION: Under the control of a control part 33, plaintext data Xa and Xb are ciphered sequentially by using a ciphering key Ka stored in a ciphering and deciphering key storage part 35 to generate corresponding ciphered data Ya and Yb in a process of transfer of the plaintext Xa and Xb expanded in the main storage device of an information terminal device to the external storage device 12. In a process of transfer of ciphered data Ya and Yb written temporarily in the external storage device 12 to the information processor 11, the ciphered data Ya and Yb are deciphered sequentially by using a deciphering key Kb stored in the ciphering and deciphering key storage part 35 to restore the original plaintext data Xa and Xb by a ciphering process part 34, which is constituted in a small-sized, lightweight computer card 13 having an authenticating function of the user individual.