According to the examination by the inventors of the present invention, the following techniques are known for the memory card.
For example, as the external storage devices of the personal computer and the mobile device, a memory card such as a multimedia card (registered trademark) standardized by the MMCA (MultiMediaCard Association), the standardization body, is widely known, and the multimedia card is used for the static image recording on a digital video camera, the data recording on a mobile phone, and the sound recording on a mobile audio player.
In the multimedia card mentioned above, various operations to a flash memory in the card such as data read, write, and erase are controlled by the various commands issued from such host machines as the personal computer and the mobile device. For example, the Lock_Unlock command standardized in pp. 32 to 34 of MultiMediaCard System Specification Version 3.1 by the MMCA (official release June 2001) can execute the password set/password clear/lock_unlock/erase, and the protection of the user data stored in the flash memory can be achieved by this command.