Content playback system, content playback method, content playback requesting apparatus, and temporary playback apparatus

A content playback method for playing back encrypted content which can be decrypted by a token in a system comprising a playback requesting apparatus which holds a token and which requests the playback of encrypted content, and a temporary playback apparatus for performing playback of the encrypted content in response to the content playback request, said content playback method comprising:

• a step (a) in which said playback requesting apparatus transmits a content playback request with an attached content identifier;
• a step (b) in which said temporary playback apparatus transmits a token in a form in which an identifier of content for which playback has been requested and a digital signature are attached;
• a step (c) in which said playback requesting apparatus sends back the token to said temporary playback apparatus only when an authentication procedure for the digital signature is successful;
• and
• a step (d) in which said temporary playback apparatus plays back the content for which playback has been requested by using the received token.

A playback requesting apparatus for requesting the playback of encrypted content which can be decrypted by a token, said playback requesting apparatus comprising:

• token holding means for holding a token;
• content storage means for storing encrypted content;
• interfacing means for exchanging data with an external apparatus;
• and
• control means for controlling the operation of the apparatus.

A temporary playback apparatus for temporarily playing back encrypted content which can be decrypted by a token, said temporary playback apparatus comprising:

• signature holding means for holding a digital signature;
• secret key holding means for holding the secret key of the apparatus itself;
• content storage means for storing encrypted content;
• interfacing means for exchanging data with an external apparatus;
• content playback means for playing back content which is converted to plain text;
• and
• control means for controlling the operation of the apparatus.