Recording device, recording medium, and content protection system

A content protection system for transferring a usage right of a content from a recording apparatus to an external recording medium while protecting a copyright of the content, the recording apparatus including:

• a storage unit operable to store (i) a first encrypted content generated by encrypting the content, (ii) a second encrypted content generated by performing art irreversible compression to convert the content, thereby obtaining a converted content, and by encrypting the converted content, and (iii) a content key for decryption of the first and second encrypted contents;
• a key transfer unit operable to write the content key to the external recording medium, and erase the content key stored in the storage unit;
• and
• a content transfer unit operable after the content key has been erased, to write the second encrypted content to the external recording medium, and erase the second encrypted content from the storage unit,
• wherein the recording medium includes a storage area operable to store the content key and the second encrypted context,
• wherein the key transfer unit includes:
• a writing subunit operable to write the content key to the external recording medium;
• an erasing subunit operable to erase the content key stored in the storage unit;
• a reading subunit operable to read the content key from the storage unit;
• and
• a prohibiting subunit operable, after the content key has been read, to prohibit use of the content key stored in the storage unit,
• wherein the writing subunit performs the writing after the prohibiting subunit has performed the prohibiting,
• wherein the content key is in association with usability information indicating that the content key can be used, and
• wherein the prohibiting subunit rewrites the usability information to use-prohibited information indicating that use of the content key is prohibited.

A non-transitory portable recording medium for receiving a transfer of a usage right of a content from a recording apparatus while protecting a copyright of the content, the recording apparatus including:

• a storage unit operable to store (i) a first encrypted content generated by encrypting the content, (ii) a second encrypted content generated by performing an irreversible compression to convert the content, thereby obtaining a converted content, and by encrypting the converted content, and (iii) a content key for decryption of the first and second encrypted contents;
• a key transfer unit operable to write the content key to the external recording medium, and erase the content key stored in the storage unit;
• and
• a content transfer unit operable, after the content key has been erased, to write the second encrypted content to the external recording medium and erase the second encrypted content from the storage unit,
• wherein the recording medium includes a storage area operable to store the content key and the second encrypted context,
• wherein the key transfer unit includes:
• a writing subunit operable to write the content key to the external recording medium;
• an erasing subunit operable to erase the content key stored in the storage unit;
• a reading subunit operable to read the content key from the storage unit;
• and
• a prohibiting subunit operable, after the content key has been read, to prohibit use of the content key stored in the storage unit,
• wherein the writing subunit performs the writing after the prohibiting subunit has performed the prohibiting,
• wherein the content key is in association with usability information indicating that the content key can be used, and
• wherein the prohibiting subunit rewrites the usability information to use-prohibited information indicating that use of the content key is prohibited.

A content transfer method used in a recording apparatus for transferring a usage right of a content to an external recording medium while protecting a copyright of the content,

• the recording apparatus storing in a storage unit (i) a first encrypted content generated by encrypting the content, (ii) a second encrypted content generated by performing an irreversible compression to convert the content, thereby obtaining a converted content, and by encrypting the converted content, and (iii) a content key for decryption of the first and second encrypted contents,
• the content transfer method comprising:
• a key transfer step of writing the content key to the external recording medium, and erasing the content key stored in the storage unit;
• and
• a content transfer step of, after the content key has been erased, writing the second encrypted content to the external recording medium, and erasing the second encrypted content from the storage unit,
• wherein the key transfer step includes:
• a writing step of writing the content key to the external recording medium;
• an erasing step of erasing the content key stored in the storage unit;
• a reading step of reading the content key from the storage unit;
• and
• a prohibiting step of, after the content key has been read by the reading step,
• prohibiting use of the content key stored in the storage unit,
• wherein the writing step is performed after the prohibiting step,
• wherein the content key is in association with usability information indicating that the content key can be used, and
• wherein the prohibiting step includes rewriting the usability information to use-prohibited information indicating that use of the content key is prohibited.

A non-transitory computer-readable recording medium having recorded thereon a content transfer program used in a recording apparatus for transferring a usage right of a content to an external recording medium while protecting a copyright of the content,

• the recording apparatus storing in a storage unit (i) a first encrypted content generated by encrypting the content, (ii) a second encrypted content generated by performing an irreversible compression to convert the content, thereby obtaining a converted content, and by encrypting the converted content, and (iii) a content key for decryption of the first and second encrypted contents,
• the content transfer program comprising:
• a key transfer step of writing the content key to the external recording medium, and erasing the content key stored in the storage unit;
• and
• a content transfer step of, after the content key has been erased, writing the second encrypted content to the external recording medium, and erasing the second encrypted content from the storage unit,
• wherein the key transfer step includes:
• a writing step of writing the content key to the external recording medium;
• an erasing step of erasing the content key stored in the storage unit;
• a reading step of reading the content key from the storage unit;
• and
• a prohibiting step of, after the content key has been read by the reading step,
• prohibiting use of the content key stored in the storage unit,
• wherein the writing step is performed after the prohibiting step,
• wherein the content key is in association with usability information indicating that the content key can be used, and
• wherein the prohibiting step includes rewriting the usability information to use-prohibited information indicating that use of the content key is prohibited.