Abstract: A content playback system for sharing content possessed by many users who each hold a token of encrypted content, the content playback system including a playback requesting apparatus which holds a token and which requests the playback of the encrypted content, and a temporary playback apparatus for performing the playback of the encrypted content in response to a playback request of the content. The temporary playback apparatus transmits a token sending request in a form in which an identifier of the content and a digital signature are attached. The playback requesting apparatus returns the token to the temporary playback apparatus only when an authentication procedure for the digital signature is successful.

Abstract: In order to share content possessed by each user among a plurality of users who hold a token of encrypted content, a content playback system includes a playback requesting apparatus which holds a token and which requests the playback of the encrypted content, and a temporary playback apparatus for performing the playback of the encrypted content in response to a playback request of the content. The temporary playback apparatus transmits a token sending request in a form in which an identifier of the content and a digital signature are attached. The playback requesting apparatus sends back the token to the temporary playback apparatus only when the authentication procedure for a digital signature is successful.