Digital content distribution system, right management server and user terminal

A right management server connected with a user terminal via a communication network for issuing license information to the user terminal so that the user terminal obtains the license information, said license information permitting a user to use a content, said server comprising:

• a first condition generation unit operable to generate a first condition based on a content use right owned by the user, said first condition being a condition for permitting the user to use the content;
• a second condition generation unit operable to generate a second condition that indicates a part or all of the use permitted under the first condition and indicates whether the license information is valid or invalid based on a logical product of the first condition and said second condition;
• a license generation unit operable to generate the license information including the first condition and the second condition in response to a license obtainment request from the user terminal;
• and
• a license issuance unit operable to issue the generated license information to the user terminal so that said user terminal obtains said license information.

A user terminal connected with a right management server via a communication network for obtaining license information from the right management server and using a content based on the obtained license information, said license information permitting a user to use the content, said terminal comprising:

• a license obtainment requesting unit operable to request the right management server to issue the license information so as to obtain said license information;
• an invalidity judgment unit operable to judge whether the license information is invalid or not based on a first condition and a second condition included in the obtained license information, said first condition being a condition for permitting the user to use the content based on a content use right owned by the user, said second condition indicating a part or all of the use permitted under the first condition and indicating whether the license information is valid or invalid based on a logical product of the first condition and said second condition;
• a using unit operable to provide the use of the content to the user when it is judged that the license information is not invalid;
• and
• a license information returning unit operable to return the license information to the right management server when it is judged that the license information is invalid.

A right management method in a right management server connected with a user terminal via a communication network for issuing license information to the user terminal so that the user terminal obtains the license information, said license information permitting a user to use a content, said right management method comprising:

• a first condition generation step of generating a first condition based on a content use right owned by the user, said first condition being a condition for permitting the user to use the content;
• a second condition generation step of generating a second condition that indicates a part or all of the use permitted under the first condition and indicates whether the license information is valid or invalid based on a logical product of the first condition and said second condition;
• a license generation step of generating the license information including the first condition and the second condition in response to a license obtainment request from the user terminal;
• a license issuance step of issuing the generated license information to the user terminal so that said user terminal obtains said license information;
• a return acceptance step of accepting, from the user terminal, return of the license information which is judged to be invalid;
• an invalidation cancellation step of canceling invalidation of the license information by updating the second condition included in the returned license information to a new value;
• and
• a reissuance step of reissuing, to the user terminal, the license information of which invalidation is cancelled.

A content using method in a user terminal connected with a right management server via a communication network for obtaining license information from the right management server and using a content based on the obtained license information, said license information permitting a user to use the content, said content using method comprising:

• a license obtainment requesting step of requesting the right management server to issue the license information so as to obtain said license information;
• an invalidity judgment step of judging whether the license information is invalid or not based on a first condition and a second condition included in the license information, said first condition being a condition for permitting the user to use the content based on a content use right owned by the user, said second condition indicating a part or all of the use permitted under the first condition and indicating whether the license information is valid or invalid based on a logical product of the first condition and said second condition;
• a using step of providing the use of the content to the user when it is judged that the license information is not invalid;
• and
• a license information returning step of returning the license information to the right management server when it is judged that the license information is invalid.

A program for a right management server connected with a user terminal via a communication network for issuing license information to the user terminal so that the user terminal obtains the license information, said license information permitting a user to use a content, said program causing a computer to execute:

• a first condition generation step of generating a first condition based on a content use right owned by the user, said first condition being a condition for permitting the user to use the content;
• a second condition generation step of generating a second condition that indicates a part or all of the use permitted under the first condition and indicates whether the license information is valid or invalid based on a logical product of the first condition and said second condition;
• a license generation step of generating the license information including the first condition and the second condition in response to a license obtainment request from the user terminal;
• a license issuance step of issuing the generated license information to the user terminal so that said user terminal obtains said license information;
• a return acceptance step of accepting, from the user terminal, return of the license information which is judged to be invalid;
• an invalidation cancellation step of canceling invalidation of the license information by updating the second condition included in the returned license information to a new value;
• and
• a reissuance step of reissuing, to the user terminal, the license information of which invalidation is cancelled.

A program for a user terminal connected with a right management server via a communication network for obtaining license information from the right management server and using a content based on the obtained license information, said license information permitting a user to use the content, said program causing a computer to execute:

• a license obtainment requesting step of requesting the right management server to issue the license information so as to obtain said license information;
• an invalidity judgment step of judging whether the license information is invalid or not based on a first condition and a second condition included in the license information, said first condition being a condition for permitting the user to use the content based on a content use right owned by the user, said second condition indicating a part or all of the use permitted under the first condition and indicating whether the license information is valid or invalid based on a logical product of the first condition and said second condition;
• a using step of providing the use of the content to the user when it is judged that the license information is not invalid;
• and
• a license information returning step of returning the license information to the right management server when it is judged that the license information is invalid.