Content playback apparatus, content playback method, computer program, key relay apparatus, and recording medium

A content playback method used in a content playback apparatus that decrypts encrypted content recorded on a recording medium, thereby obtaining content, and plays the content,

• the recording medium having recorded thereon a plurality of pieces of encrypted content respectively in correspondence with a plurality of pieces of management source information, each piece of management source information showing, from among a plurality of management source apparatuses, a management source apparatus that manages usage of the corresponding piece of encrypted content,
• the content playback method comprising the steps of:
• a designation acquisition step of acquiring a designation of one of the pieces of encrypted content;
• a management source acquisition step of acquiring, from among the pieces of management source information recorded on the recording medium, a piece of management source information that corresponds to the designated piece of encrypted content;
• a key information acquisition step of acquiring, from the management source apparatus shown by the acquired piece of management source information, a piece of key information that shows usage permission for the designated piece of encrypted content;
• a decryption step of generating a content key based on the acquired piece of key information, and generating a piece of content by decrypting the designated piece of encrypted content with use of the generated content key;
• and
• a playback step of playing the generated piece of content.

A computer program used in a content playback apparatus that decrypts encrypted content recorded on a recording medium, thereby obtaining content, and plays the content,

• the recording medium having recorded thereon a plurality of pieces of encrypted content respectively in correspondence with a plurality of pieces of management source information, each piece of management source information showing, from among a plurality of management source apparatuses, a management source apparatus that manages usage of the corresponding piece of encrypted content,
• the computer program comprising the steps of:
• a designation acquisition step of acquiring a designation of one of the pieces of encrypted content;
• a management source acquisition step of acquiring, from among the pieces of management source information recorded on the recording medium, a piece of management source information that corresponds to the designated piece of encrypted content;
• a key information acquisition step of acquiring, from the management source apparatus shown by the acquired piece of management source information, a piece of key information that shows usage permission for the designated piece of encrypted content;
• a decryption step of generating a content key based on the acquired piece of key information, and generating a piece of content by decrypting the designated piece of encrypted content with use of the generated content key;
• and
• a playback step of playing the generated piece of content.

A key relay apparatus that relays key information showing usage permission for encrypted content recorded on a recording medium, the key relay apparatus comprising:

• a request reception unit operable to receive, from a content playback apparatus that performs reading from the recording medium, (i) a piece of content designation information that designates a piece of the encrypted content, and (ii) a piece of key management apparatus information that shows a key management apparatus that manages key information;
• a key information acquisition unit operable to acquire, from key management apparatus shown by the piece of key management apparatus information, a piece of key information that corresponds to the received piece of content designation information;
• and
• a key information transmission unit operable to transmit the acquired piece of key information.