Data management apparatus, data management method, and storage medium

A computer program stored on a non-transitory storage medium for a computer having a removable storage device and a nonvolatile memory which saves a first conversion key, and the computer program when executed by a processor, performing steps comprising:

• a first instruction of encrypting the first conversion key by a second conversion key, and converting the first conversion key into a third conversion key, the third conversion key being the encrypted first conversion key;
• a second instruction of writing the third conversion key into the storage device;
• a third instruction of encrypting the third conversion key by a fourth conversion key which is different from the second conversion key, and converting the third conversion key into a fifth conversion key, the fourth conversion key being a master key unique to the computer, the fifth conversion key being the encrypted third conversion key;
• a fourth instruction of converting a datum to be saved in the storage device into an encrypted datum by the fifth conversion key;
• a fifth instruction of writing the encrypted datum into the storage device;
• a sixth instruction of reading the encrypted datum from the storage device;
• a seventh instruction of decrypting the encrypted datum by the fifth conversion key;
• and
• an eighth instruction of deleting the fifth conversion key after encryption of the datum and after decryption of the encrypted datum.

A method for data management which is applicable to a computer having a processor and having a removable storage device and a nonvolatile memory which saves a first conversion key, the method for data management when executed by a processor, performing the steps of:

• a first step of encrypting the first conversion key by a second conversion key, and converting the first conversion key into a third conversion key, the third conversion key being the encrypted first conversion key;
• a second step of writing the third conversion key into the storage device;
• a third step of encrypting the third conversion key by a fourth conversion key which is different from the second conversion key, and converting the third conversion key into a fifth conversion key, the fourth conversion key being a master key unique to the computer, the fifth conversion key being the encrypted third conversion key;
• a fourth step of converting a datum to be saved in the storage device into an encrypted datum by the fifth conversion key;
• a fifth step of writing the encrypted datum into the storage device;
• a sixth step of reading the encrypted datum from the storage device;
• a seventh step of decrypting the encrypted datum by the fifth conversion key;
• and
• an eighth step of deleting the fifth conversion key after encryption of the datum and after decryption of the encrypted datum.