Long-term signature data is formed at a server side while a private key and the like are held at a client side. The long-term signature data is configured by arranging ES, STS, verification information, ATS (1st), and ATS (2nd) in a predetermined long-term signature format. Among these elements, those for which processing using the private key and original data are necessary are ES and ATS. Due to processing where the original data and the private key is necessary being performed by a client terminal 3 and processing where the long-term signature data is analyzed and generated being performed by a long-term signature server 2, the long-term signature data is generated in the long-term signature server 2 while the original data and the private key are held in an inner portion of the client terminal 3. In this manner, the processing where the long-term signature data is formed is separated from the processing using the private key and the original data and the processing where the analysis and generation of XML is performed, and the former is undertaken in the client terminal 3 and the latter is undertaken in the long-term signature server 2.