File protection system, software utilization system using the file

Abstract

A file protection system for protecting a file which is stored in a storage unit includes a storage position deciding unit for deciding a positional-information corresponding to an area in which information of the file is stored in the storage unit and an encryption unit for encrypting the information of the file in accordance with a predetermined algorithm using at least a part of the positional-information decided by the storage position deciding unit. Information obtained by the encryption unit is stored in the area identified by the positional-information in the storage unit. A file protection system is operable when information of a file which was encrypted as described above is read out from a storage unit. The file protection system includes a decryption unit for decrypting the encrypted information of the file which is read out from an area in the storage unit using information corresponding the area, an extracting unit for extracting the positional-information from information obtained by the decryption unit, and a determination unit for determining whether or not the positional-information extracted by the extracting unit is equal to corresponding positional-information which is at least a part of the information corresponding to the area from which the encrypted information of the file is read out. When the determination unit determines that two pieces of positional-information are not equal to each other, it is determined that the information obtained by the decryption unit does not include correct information of the file.