**EXHIBIT 31.2**
**CERTIFICATIONS REQUIRED BY****RULE 13a-14(a) UNDER THE SECURITIES EXCHANGE ACT OF 1934**
I, Matthew Hale, certify that:
1.  I have reviewed this Form 10-Q of S1 Corporation; 2.  Based on my knowledge, this report does not contain any untruestatement of a material fact or omit to state a material factnecessary to make the statements made, in light of thecircumstances under which such statements were made, notmisleading with respect to the period covered by this report; 3.  Based on my knowledge, the financial statements, and otherfinancial information included in this report, fairly presentin all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, theperiods presented in this report; 4.  The registrant’s other certifying officers and I areresponsible for establishing and maintaining disclosurecontrols and procedures (as defined in Exchange Act Rules13a-15(e) and 15d-15(e)) and internal control over financialreporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f)) for the registrant and have:
 a)  designed such disclosurecontrols and procedures, orcaused such disclosure controlsand procedures to be designedunder our supervision, to ensurethat material informationrelating to the registrant,including its consolidatedsubsidiaries, is made known tous by others within thoseentities, particularly duringthe period in which this reportis being prepared;  b)  designed such internal controlover financial reporting, orcaused such internal controlover financial reporting to bedesigned under our supervisionto provide reasonable assuranceregarding the reliability offinancial reporting and thepreparation of financialstatements for external purposesin accordance with generallyaccepted accounting principles;  c)  evaluated the effectiveness ofthe registrant’s disclosurecontrols and procedures andpresented in this report ourconclusions about theeffectiveness of the disclosurecontrols and procedures, as ofthe end of the period covered bythis report based on suchevaluation; and  d)  disclosed in this report anychange in the registrant’sinternal control over financialreporting that occurred duringthe registrant’s most recentfiscal quarter (the registrant’sfourth fiscal quarter in thecase of an annual report) thathas materially affected, or isreasonably likely to materiallyaffect, the registrant’sinternal control over financialreporting,
5.  The registrant’s other certifying officers and I havedisclosed, based on our most recent evaluation of internalcontrol over financial reporting, to the registrant’s auditorsand the audit committee of the registrant’s board of directors(or persons performing the equivalent function):
 a)  all significant deficiencies andmaterial weaknesses in thedesign or operation of internalcontrol over financial reportingwhich are reasonably likely toadversely affect theregistrant’s ability to record,process, summarize and reportfinancial information; and  b)  any fraud, whether or notmaterial, that involvesmanagement or other employeeswho have a significant role inthe registrant’s internalcontrol over financialreporting.
Date: May 9, 2005   /s/ Matthew Hale  Matthew Hale  Chief Financial Officer