EXHIBIT 31.1
 CERTIFICATIONS
REQUIRED BY
RULE 13a-14(a) UNDER THE SECURITIES EXCHANGE ACT OF 1934
  1.
    
    I have reviewed this Form 10-Q of S1 Corporation;2.
    
    Based on my knowledge, this report does not contain any
untrue statement of a material fact or omit to state a
material fact necessary to make the statements made, in
light of the circumstances under which such statements
were made, not misleading with respect to the period
covered by this report;3.
    
    Based on my knowledge, the financial statements, and
other financial information included in this report,
fairly present in all material respects the financial
condition, results of operations and cash flows of the
registrant as of, and for, the periods presented in
this report;4.
    
    The registrants other certifying officers and I are
responsible for establishing and maintaining disclosure
controls and procedures (as defined in Exchange Act
Rules 13a-15(e) and 15d-15(e)) and internal control
over financial reporting (as defined in Exchange Act
Rules 13a-15(f) and 15d-15(f)) for the registrant and
have:
 a)
    
    designed such disclosure
controls and procedures,
or caused such
disclosure controls and
procedures to be
designed under our
supervision, to ensure
that material
information relating to
the registrant,
including its
consolidated
subsidiaries, is made
known to us by others
within those entities,
particularly during the
period in which this
report is being
prepared;b)
    
    designed such internal
control over financial
reporting, or caused
such internal control
over financial reporting
to be designed under our
supervision to provide
reasonable assurance
regarding the
reliability of financial
reporting and the
preparation of financial
statements for external
purposes in accordance
with generally accepted
accounting principles;c)
    
    evaluated the
effectiveness of the
registrants disclosure
controls and procedures
and presented in this
report our conclusions
about the effectiveness
of the disclosure
controls and procedures,
as of the end of the
period covered by this
report based on such
evaluation; andd)
    
    disclosed in this report
any change in the
registrants internal
control over financial
reporting that occurred
during the registrants
most recent fiscal
quarter (the
registrants fourth
fiscal quarter in the
case of an annual
report) that has
materially affected, or
is reasonably likely to
materially affect, the
registrants internal
control over financial
reporting; and
 5.
    
    The registrants other certifying officer(s) and I have
disclosed, based on our most recent evaluation of
internal control over financial reporting, to the
registrants auditors and the audit committee of the
registrants board of directors (or persons performing
the equivalent functions):
 a)
    
    all significant
deficiencies and
material weaknesses in
the design or operation
of internal control over
financial reporting
which are reasonably
likely to adversely
affect the registrants
ability to record,
process, summarize and
report financial
information; andb)
    
    any fraud, whether or
not material, that
involves management or
other employees who have
a significant role in
the registrants
internal control over
financial reporting.
  /s/ JOHANN DREYER

Johann DreyerChief Executive Officer(Principal Executive Officer)