EXHIBIT 32.1

                    CERTIFICATE OF CHIEF EXECUTIVE 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 is the Chief Executive Officer of S1 Corporation
(the "Company"), hereby certifies as follows:

         To the knowledge of the undersigned, the Quarterly Report on Form 10-Q
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 15th day of March 2004.



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