Digital signature device, digital signature method, and non-transitory storage medium storing digital signature program

A digital signature method executed by a computer comprising:

• accepting key information that specifies target information of a digital signature from a user;
• extracting one or more values that correspond to the key information that is accepted, from a database that stores a plurality of pieces of key information that includes the key information in association with each of the one or more values that are extracted;
• calculating a characteristic value that is uniquely defined for each of the one or more values based on the one or more values that are extracted;
• accepting the digital signature from the user;
• generating signature data that includes the key information, the characteristic value, and information for the digital signature for each of the one or more values;
• and
• storing the signature data in a storage unit.

A non-transitory storage medium storing a digital signature program causing a computer to execute:

• accepting key information that specifies target information of digital signature from a user;
• extracting one or more values that correspond to the key information that is accepted, from a database that stores a plurality of pieces of key information that includes the key information in association with each of the one or more values that are extracted;
• calculating a characteristic value that is uniquely defined for each of the one or more values based on the one or more values that are extracted;
• accepting the digital signature from the user;
• generating signature data that includes the key information, the characteristic value, and information for the digital signature for each of the one or more values;
• and
• storing the signature data in a storage unit.