LONG-TERM SIGNATURE TERMINAL, LONG-TERM SIGNATURE SERVER, LONG-TERM SIGNATURE TERMINAL PROGRAM, AND LONG-TERM SIGNATURE SERVER PROGRAM

A client terminal 3 can generate PAdES while performing communication with a long-term signature server 2 without delivering a PDF document and a secret key used in an electronic signature to the long-term signature server 2. PAdES is a long-term signature format which is specified for a PDF file. The client terminal 3 transmits CAdES with the electronic signature before time stamp issuance to the long-term signature server 2 to request to issue a time stamp to CAdES. The client terminal 3 requests the long-term signature server 2 to collect verification information, acquires the verification information, further generates information for confirming unfalsification of a signed PDF document and the verification information therefrom, and transmits the information to the long-term signature server 2 to request to generate DTS. With the above, it is possible to perform a long-term signature while retaining confidential information on a user side.