Content data processing device, recording/reproduction device, and recording/reproduction system

A content data processing device in which a plurality of recording devices or recording media are connected, comprising:

• a unique ID reading means for reading at least two unique IDs from said plurality of recording devices or recording media;
• a mutual ID creating means for creating a mutual encryption key from said at least two unique IDs, creating a mutual ID, with said mutual encryption key and said at least two unique IDs as elements, and recording said mutual ID in any one of said plurality of recording devices or recording media;
• and
• an original data suppressing means for encrypting data recorded in said recording devices or recording media by using said mutual encryption key included in said mutual ID, and recording the encrypted data in any one of said plurality of recording devices or recording media, and deleting original data or making it unreadable.