Key Management Apparatus and Key Management Method

A key management method for a key management apparatus configured to access an information storage medium comprising a user data area for storing encrypted content and encrypted content key, the encrypted content being encrypted with a content key in a plain version and the encrypted content key being encrypted on the basis of a media unique key unique to a medium and a hidden area for storing the media unique key, the method comprising:

• decrypting for obtaining a content key in a plain version, by reading a media unique key and an encrypted content key which corresponds to a selected content from a first information storage medium and decrypting the encrypted content key with the media unique key read from the first information storage medium;
• encrypting for obtaining an encrypted content key for a second information storage medium, by reading a media unique key from the second information storage medium and encrypting the content key in the plain version with the media unique key;
• and
• writing the encrypted content key for the second information storage medium to a user data area of the second information storage medium.

A key management system comprising:

• a key management apparatus configured to access an information storage medium comprising a user data area for storing encrypted content and encrypted content key, the encrypted content being encrypted with a content key in a plain version and the encrypted content key being encrypted on the basis of a media unique key unique to the medium and a hidden area for storing the media unique key;
• and
• a server connected to the key management apparatus;
• wherein the key management apparatus comprises:
• a decrypting module configured to read a media unique key and an encrypted content key which corresponds to a selected content from a first information storage medium and to decrypt the encrypted content key with the media unique key read from the first information storage medium in order to obtain a content key in a plain version;
• an encryption module configured to read a media unique key from the second information storage medium and to encrypt the content key in the plain version with the media unique key read from the second information storage medium in order to obtain an encrypted content key for the second information storage medium;
• and
• a write module configured to write the encrypted content key for the second information storage medium to a user data area of the second information storage medium, and
• the server manages move status information on a key, and comprises:
• a determination module configured to determine whether or not the move status information indicates that a content is moving;
• and
• a reissue module configured to reissue a content key when the determining module determines that the move status information indicates that a content is moving.