EXHIBIT 99.1

                     CERTIFICATE OF CHIEF EXECUTIVE OFFICER
                          AND CHIEF FINANCIAL OFFICER


        This  Certificate is being  delivered  pursuant to the  requirements  of
Section  1350 of  Chapter  63 (Mail  Fraud)  of Title 18  (Crimes  and  Criminal
Procedures)  of the United  States Code and shall not be relied on by any person
for any other purpose.

        The undersigned, who are the Chief Executive Officer and Chief Financial
Officer, respectively, of S1 Corporation (the "Company"), hereby each certify as
follows:

        To the knowledge of the  undersigned,  the Annual Report on Form 10-K of
the Company (the "Report"),  which accompanies this Certificate,  fully complies
with the  requirements of Section 13(a) or 15(d) of the Securities  Exchange Act
of 1934, and all  information  contained in the Report fairly  presents,  in all
material  respects,  the  financial  condition  and results of operations of the
Company.


         Dated this 28th day of March 2003.


                                /S/ JAIME W. ELLERTSON
                                ------------------------------------------------
                                Jaime W. Ellertson, Chief Executive Officer

                                /S/ MATTHEW HALE
                                ------------------------------------------------
                                Matthew Hale, Chief Financial Officer