| 摘要 |
PROBLEM TO BE SOLVED: To increase security and to obtain compatibility with memory cards now in use by providing a ciphering means which ciphers data stored in a nonvolatile semiconductor memory and a control means which controls the ciphering. SOLUTION: Serial data are converted into parallel data in a serial/parallel converter 309 through a bidirectional data communication line I/O between a memory stick which is made intelligent and an external device. To cipher and store the data, a scrambler 311a is supplied with plaintext data and a cipher key and generates ciphered data through specific ciphering algorithm and finally stores them in a flash memory 315. The data are possibly not ciphered and stored in the flash memory 315 in the form of the plaintext data when necessary. Thus, the data are ciphered and stored in the flash memory 315, so the security of the stored data is enhanced. |
