Patent ID: 8918633

Claim:
An information processing device comprising: encryption information storage means for storing encryption information in a database form that associates a folder, in which at least one file is stored in a hierarchical file structure, with identification information of a first encryption key corresponding to the folder; external read means for reading information stored in a portable information storage medium that stores a second encryption key including at least one of a personal key, a group key, and an element of the user's encryption key; encryption key decision means for deciding, when a save request for a file into the folder has been issued from the user, if the first encryption key corresponding to the folder designated as a save destination for a target file of the save request also corresponds to the second encryption key stored in the portable information storage medium, based on the encryption information stored in the encryption information storage means and the encryption information read by the external read means; data encryption means for encrypting the target file of the save request using the first encryption key corresponding to the folder and transmitted to the information processing device when the encryption key decision means has decided “YES”; error processing means for displaying occurrence of an error when the encryption key decision means has decided “NO”; nonvolatile storage means for storing a file to save; write means for writing the target file encrypted by the data encryption means in the nonvolatile storage means; and encryption key deletion means for deleting the first encryption key corresponding to the folder and transmitted to the information processing device when the information processing device enters a log-off-state.