Method and system for assuring an original

An original assurance system that assures validity of original data, comprising:

• a plurality of first signature servers;
• and
• a second signature server supervising said plurality of first signature servers;
• wherein each of said plurality of first signature servers comprises:
• a signature generation unit for generating, when the first signature server in question receives digital data as original data, as an object of assurance, a digital signature for a concatenation of said digital data and a first chain signature registered in a first log list, and adds the generated digital signature to said first log list, which is stored in a storage unit, associating said first chain signature with said digital data;
• a network interface unit for sending a first receipt including said first chain signature to a sender of the digital data;
• and
• a network interface unit for sending a first chain signature in said first log list to said second signature server, receiving a second receipt to said first chain signature from said second signature server, and storing said second receipt in the storage unit;
• and
• wherein said second signature server comprises:
• a signature generation unit for generating, when the second signature server receives a first chain signature from one of said plurality of first signature servers, a digital signature for a concatenation of the first chain signature and a second chain signature registered in a second log list, and adding said digital signature as a second chain signature to said second log list, which is stored in a storage unit;
• a network interface unit for sending a second receipt including said second chain signature to said one of said plurality of first signature servers;
• and
• a network interface unit for sending second chain signature in said second log list to an external server;
• wherein each of said plurality of first signature servers further comprises:
• a signature verification unit for verifying, when the first signature server receives a first receipt with respect to original data, as an object of verification, each of first chain signatures ranging from a first chain signature included in said first receipt to a first chain signature that has been sent to said second signature server;
• and
• a network interface unit for sending to said second signature server a second receipt, which is received from said second signature server by sending the first chain signature to said second signature server;
• and
• wherein said second signature server further comprises:
• a signature verification unit for verifying, when the second signature server receives the second receipt from said first signature server, each of second chain signatures ranging from a second chain signature included in said second receipt to a second chain signature sent to said external server.

A first signature server used in an original assurance system that assures validity of original data comprising:

• a signature generation unit for generating, when the first signature server receives digital data as original data, as an object of assurance, a digital signature for a concatenation of said digital data and a first chain signature registered in a first log list, and adding the generated digital signature to said first log list, which is stored in a storage unit, associating said first chain signature with said digital data;
• a network interface unit for sending a first receipt including said first chain signature to a sender of the digital data;
• a network interface unit for sending a first chain signature in said first log list to a second signature server, receiving second receipt to said first chain signature from said second signature server, and storing said second receipt in the storage unit;
• a signature verification unit for verifying, when the first signature server receives a first receipt with respect to original data, as an object of verification, each of first chain signatures ranging from a first chain signature included in said first receipt to a first chain signature that has been sent to said second signature server;
• and
• a network interface unit for sending to said second signature server a second receipt, which is received from said second signature server by sending the first chain signature to said second signature server.

A second signature server used in an original assurance system that assures validity of original data, comprising:

• a signature generation unit for generating, when the second signature server receives a first chain signature from one of a plurality of first signature servers, a digital signature for a concatenation of the first chain signature and a second chain signature registered in a second log list, and adding the generated digital signature to said second log list, which is stored in a storage unit;
• a network interface unit for sending a second receipt including said second chain signature to said one of said plurality of first signature servers;
• a network interface unit for sending a second chain signature in said second log list to an external server;
• and
• a signature verification unit for verifying, when the second signature server receives the second receipt from said first signature server, each of second chain signatures ranging from a second chain signature included in said second receipt to a second chain signature sent to said external server.