Data storage device and data storage method

A service supply apparatus for transmitting data to a data storage device, wherein the data storage device includes a parent layer and a child layer, the service supply apparatus comprising:

• means for determining that an area defining area exists in the parent layer stored in the data storage device, the area defining area including an area key, wherein the area defining area serves as a directory;
• means for forming a service defining area in the child layer stored in the data storage device, the service defining area including a service key and being within the directory of the area defining area, wherein the child layer of the service defining area is arranged in a lower hierarchical level than the parent layer of the area defining area;
• a processor configured to form a service area associated with the service defining area, in the child layer, the service area storing data corresponding to a service;
• means for generating an access key for the service area with the area key in the parent layer and the service key in the child layer;
• means for certificating the service area with the access key;
• means for accessing the service area based on a result of the certification;
• and
• means for forming a new area defining area in the child layer and within the directory of the area defining area, wherein the new area defining area serves as a directory that is accessible by a manager to read from the new area defining area.