| 摘要 |
PROBLEM TO BE SOLVED: To protect data in a portable computer by preventing any one of selected files from being non-ciphered till a secret key is inputted in order to obtain a ciphering key by means of an audinary sentence and, then, used. SOLUTION: When the file is ciphered and, then, a user restarts the usage of a computer, the user has to correctly input the secret key 9. Unless the user inputs the correct secret key 9, a file protecting agent 12 urges the user to input the secret key 9. This rule continues up to three times, for example, till a limit being the correction impossible parameter of a program. Unless the user inputs the secret key 9 well within the range of the limit, the file protecting key 12 erases an algorithm which is used for scrambling the secret key 9 at the time of scrambling a cipher key 3. The cipher key 3 is not obtained except scrambling by the secret key 9. |
