Data management device and data management method

A data management device for centrally storing electronic data acquired from a data processing device, the data management device comprising:

• an identification write unit configured to write first identification indicating that the electronic data is saved in a storage device into the electronic data saved in the storage device, and output the electronic data having the written first identification to the data processing device;
• an identification detection unit configured to detect second identification written in electronic data inputted from the data processing device, and determine whether the first identification and the second identification match;
• and
• a selection unit configured to record, into the storage device, the electronic data inputted from the data processing device when it is determined that the first identification and the second identification do not match or when the second identification is not detected,
• wherein the electronic data includes content data, and
• the identification write unit is configured to write the first identification to the electronic data in a manner that the first identification is altered when the content data is modified, in accordance of an extent of modification of the content data.