Document:

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                                                                   EXHIBIT 10.1

                            STOCK PURCHASE AGREEMENT

                                  BY AND AMONG

                                 S1 CORPORATION

                                       AND

                  THE PURCHASERS IDENTIFIED ON EXHIBIT A HERETO

                            DATED AS OF MAY 25, 2000

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                                TABLE OF CONTENTS

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     SECTION 1. PURCHASE AND SALE OF THE SHARES...........................................................1
        1.1  Sale and Issuance of the Shares..............................................................1
        1.2  Closing......................................................................................1
        1.3  Anti-dilution Provision......................................................................2

     SECTION 2. REPRESENTATIONS AND WARRANTIES OF THE CORPORATION.........................................2
        2.1  Organization and Standing....................................................................2
        2.2  Authorization; Binding Obligation............................................................2
        2.3  Capitalization...............................................................................3
        2.4  Validity of Shares; Issuance.................................................................3
        2.5  No Consents..................................................................................4
        2.6  Non-Contravention............................................................................4
        2.7  Additional Information.......................................................................4
        2.8  Financial Statements.........................................................................5
        2.9  Absence of Certain Changes or Events.........................................................5
        2.10 Legal Proceedings............................................................................5
        2.11 Compliance with Applicable Laws..............................................................6
        2.12 No Undisclosed Liabilities...................................................................6

     SECTION 3. REPRESENTATIONS AND WARRANTIES OF THE PURCHASERS..........................................6
        3.1  Organization and Standing....................................................................6
        3.2  Authorization................................................................................7
        3.3  Non-Contravention............................................................................7
        3.4  No Consents..................................................................................7
        3.5  Adequate Resources...........................................................................8
        3.6  Investment Experience........................................................................8
        3.7  Investment Intent............................................................................8
        3.8  Registration or Exemption Requirements.......................................................8
        3.9  No Legal, Tax or Investment Advice...........................................................9
        3.10 Hart-Scott-Rodino Filings....................................................................9

     SECTION 4. ADDITIONAL AGREEMENTS.....................................................................9
        4.1  Lock-up Covenant.............................................................................9
        4.2  Release From Lock-Up........................................................................10
        4.3  Commercially Reasonable Efforts.............................................................10
        4.4  Basic Financial Information.................................................................11
        4.5  Certificate of Designations.................................................................12
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        4.6  Registration Rights Agreement...............................................................12
        4.7  Use of Proceeds.............................................................................12
        4.8  Access to Information.......................................................................12

     SECTION 5. CONDITIONS TO CLOSING....................................................................13
        5.1  Conditions to Obligations of All Parties....................................................13
        5.2  Conditions to the Obligations of the Purchasers.............................................13
        5.3  Conditions to Obligations of the Corporation................................................14

     SECTION 6. CLOSING..................................................................................15
        6.1  Deliveries by the Corporation...............................................................15
        6.2  Deliveries by the Purchasers................................................................15

     SECTION 7. LEGEND...................................................................................16
        7.1  Endorsement.................................................................................16
        7.2  Removal of Legend...........................................................................16

     SECTION 8. TERMINATION..............................................................................17
        8.1  Termination.................................................................................17
        8.2  Effect of Termination.......................................................................17

     SECTION 9. MISCELLANEOUS............................................................................18
        9.1  Additional Actions and Documents............................................................18
        9.2  Expenses....................................................................................18
        9.3  Notices.....................................................................................18
        9.4  Waiver......................................................................................19
        9.5  Binding Effect..............................................................................19
        9.6  Entire Agreement; Amendment.................................................................19
        9.7  Severability................................................................................19
        9.8  Headings....................................................................................20
        9.9  Governing Law...............................................................................20
        9.10 Signature in Counterparts...................................................................20
        9.11 No Third Party Beneficiaries................................................................20
        9.12 Assignability...............................................................................20
        9.13 Parties Not Partners........................................................................21
        9.14 Survival of Representations and Warranties..................................................21
        9.15 Additional Definitions......................................................................21
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                            STOCK PURCHASE AGREEMENT

              This Stock Purchase Agreement (this "Agreement"), is entered into
as of the 25th day of May, 2000, by and among S1 Corporation, a Delaware
corporation (the "Corporation"), and each of the persons and entities, severally
and not jointly, whose names are set forth on the Schedule of Purchasers
attached hereto as Exhibit A (each, individually, a "Purchaser" and,
collectively, the "Purchasers").

              WHEREAS, the Purchasers desire to subscribe for, and acquire from
the Corporation, shares of the Corporation's Series D Convertible Preferred
Stock, par value $.01 per share ("Series D Preferred Stock"), having the rights,
preferences, privileges and restrictions set forth in the Corporation's
Certificate of Designations, a copy of which is attached hereto as Exhibit B
(the "Certificate"), on the terms and under the conditions specified herein; and

              WHEREAS, the Corporation desires to sell and issue to the
Purchasers shares of the Corporation's Series D Preferred Stock on the terms and
under the conditions specified herein and subject to the rights of the
Purchasers contained the Registration Rights Agreement, dated as of the date
hereof, among the Corporation and the Purchasers (the "Registration Rights
Agreement").

              NOW, THEREFORE, in consideration of the mutual promises,
representations, warranties, covenants and conditions set forth in this
Agreement, the sufficiency of which is hereby acknowledged, the parties mutually
agree as follows:

SECTION 1. PURCHASE AND SALE OF THE SHARES.

       1.1    SALE AND ISSUANCE OF THE SHARES.

              At the Closing (as defined below in Section 1.2) and subject to
the terms and conditions of this Agreement, the Corporation agrees to issue and
sell to each Purchaser, and each Purchaser, severally and not jointly, hereby
subscribes for, and agrees to purchase from the Corporation, the number of
shares (the "Shares") set forth opposite such Purchaser's name on Exhibit A, at
a price per share equal to $1,000.00.

       1.2    CLOSING.

              The "Closing" shall take place on May 26, 2000 or on such other
date as the parties shall mutually agree. The Closing shall take place at 9:00
a.m. Eastern time at the offices of Hogan & Hartson L.L.P., 555 13th Street,
N.W., Washington, D.C. 20004, or at such other time and place as the parties
shall mutually agree.

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       1.3    ANTI-DILUTION PROVISION.

              In the event the Corporation changes the number of shares of
common stock, par value $0.01 per share (the "Common Stock"), of the Corporation
issued and outstanding prior to the Closing as a result of a stock split, stock
dividend or similar recapitalization with respect to the Common Stock and the
record date therefor or the effective date thereof, as the case may be, shall be
prior to the Closing, then the number of Shares to be purchased and the purchase
price per Share at the Closing shall be proportionately adjusted, without any
corresponding adjustment to the aggregate purchase price for the Shares to be
purchased at the Closing.

SECTION 2.    REPRESENTATIONS AND WARRANTIES OF THE CORPORATION.

              The Corporation represents, warrants and covenants to each
Purchaser as follows:

       2.1    ORGANIZATION AND STANDING.

              Each of the Corporation and each of its subsidiaries (the
"Subsidiaries") is a corporation duly incorporated, validly existing and in good
standing under the laws of its jurisdiction of incorporation, and has the full
corporate power and authority to own and operate its properties and assets and
to carry on its business as currently conducted. The Corporation and each of its
Subsidiaries hold all licenses and permits required for the conduct of their
respective business as now conducted which, if not in the Corporation's or such
Subsidiary's possession, is likely to have a Material Adverse Effect on the
Corporation. Each of the Corporation and each of its Subsidiaries is duly
qualified as a foreign corporation and is in good standing in all jurisdictions
where the conduct of its business or its ownership or leasing of property
requires such qualification, except where the failure so to qualify would not
have a Material Adverse Effect on the Corporation.

       2.2    AUTHORIZATION; BINDING OBLIGATION.

              The Corporation has all requisite corporate power and authority to
enter into and to deliver this Agreement and the Registration Rights Agreement
and perform its obligations hereunder and thereunder. The execution, delivery
and performance of this Agreement and the Registration Rights Agreement by the
Corporation and the consummation of the transactions contemplated hereby and
thereby have been duly authorized by all necessary corporate action on the part
of the Corporation. This Agreement and the Registration Rights Agreement, when
executed and delivered by the Corporation, shall constitute valid and binding

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obligations of the Corporation enforceable in accordance with their respective
terms, except as may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or other similar laws effecting the enforcement of
creditor's rights.

       2.3    CAPITALIZATION.

              The authorized capital stock of the Corporation consists of
350,000,000 shares of Common Stock, of which 51,163,353 were issued and
outstanding as of March 31, 2000, and 25,000,000 shares of preferred stock, of
which 97,450 of the 1,637,832 shares designated Series A Convertible Preferred
Stock were issued and outstanding as of March 31, 2000, of which 749,064 of the
749,064 shares designated Series B Redeemable Convertible Preferred Stock were
issued and outstanding as of March 31, 2000, and of which 215,000 of the 215,000
shares designated Series C Redeemable Convertible Preferred Stock were issued
and outstanding as of March 31, 2000. All of the Corporation's outstanding
shares of capital stock were validly issued and are fully paid and
nonassessable. The 1,061,514 shares of preferred stock outstanding as of March
31, 2000 were convertible as of such date into an aggregate of 1,694,990 shares
of Common Stock. As of March 31, 2000, there were 19,412,466 shares of Common
Stock reserved for issuance pursuant to employee stock options, of which options
to purchase 15,954,379 shares were then outstanding, and 6,425,413 shares of
Common Stock reserved for issuance upon exercise of other options and warrants
to purchase Common Stock. Except for 4,500,000 shares of Common Stock reserved
for issuance to the former owners of FICS Group N.V. if FICS meets specified
performance targets while operating as a Subsidiary, and except as described on
Schedule 2.3, there are no shares of the Corporation's capital stock reserved
for issuance or any options, warrants, rights (including conversion or
preemptive rights) or agreements for the purchase from the Corporation of any
shares of its capital stock or securities exercisable for or convertible into
its capital stock.

       2.4    VALIDITY OF SHARES; ISSUANCE.

              The Shares, when issued upon payment of the consideration therefor
in compliance with the provisions of this Agreement, and the shares of Common
Stock issuable upon conversion thereof (the "Underlying Common Stock"), when
issued, will be validly issued, fully paid and nonassessable, and free of any
liens or encumbrances, and will be issued in compliance with all applicable
laws. The issuance of the Shares and the Underlying Common Stock is not subject
to any preemptive right, right of first refusal or similar right in favor of any
stockholder of the Corporation or any other person.

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       2.5    NO CONSENTS.

              No governmental orders, permissions, consents, approvals or
authorizations are required to be obtained by the Corporation and no filings are
required to be made by the Corporation in connection with the execution and
delivery of this Agreement and the Registration Rights Agreement and the
issuance of the Shares hereunder, except as have been so obtained or made prior
to the Closing, or, with respect to any that need to be obtained or made
subsequent to the Closing, as will be obtained or made in a timely manner after
the Closing, except where the failure to obtain such orders, permissions,
consents, approvals or authorizations or to make such filings would not affect
the Corporation's ability to issue the Shares or the rights of Purchaser
hereunder or thereunder.

       2.6    NON-CONTRAVENTION.

              The execution, delivery and performance of, and compliance with,
this Agreement and the Registration Rights Agreement will not (a) violate any
provision of the certificate of incorporation or bylaws of the Corporation; (b)
except as would not result in a Material Adverse Effect on the Corporation,
conflict with or result in a breach of, or default under, terminate, or create a
right of termination under, or result in the creation of, any lien, claim,
charge or other encumbrance upon any of the assets or properties of the
Corporation or any Subsidiary pursuant to the provisions of any material
agreement, mortgage, indenture or other document or instrument to which the
Corporation or such Subsidiary is a party or by which the Corporation or such
Subsidiary or any of their respective properties or assets is bound, or (c)
except as would not result in a Material Adverse Effect on the Corporation,
violate any existing statutes, laws, ordinances, regulations, orders and other
rules of law applicable to the Corporation or any Subsidiary or any of their
respective properties or assets, or applicable to the Corporation's power or
authority to perform its obligations under this Agreement and the Registration
Rights Agreement.

       2.7    ADDITIONAL INFORMATION.

              The information contained in the Corporation's Annual Report on
Form 10-K for the year ended December 31, 1999, and all other reports filed
subsequent thereto through the date of the Closing (collectively, the "SEC
Reports") pursuant to Section 13(a) or 15(d) of the Exchange Act, did not and
will not, as the case may be, at the respective dates of filing with the
Securities and Exchange Commission (the "SEC"), contain any untrue statement of
a material fact or omit to state a material fact necessary in order to make the
statements therein, in light of the circumstances under which they were made,
not misleading. The SEC Reports complied, or will comply, as the case may be, in
all material respects with the

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applicable requirements of the Securities Act of 1933, as amended, the
Securities Exchange Act of 1934, as amended, and the rules and regulations of
the SEC promulgated thereunder.

       2.8    FINANCIAL STATEMENTS.

              Each of the consolidated financial statements (including, in each
case any related notes thereto) contained in the SEC Reports (the "Financial
Statements"), (x) was prepared in accordance with generally acceptable
accounting principles ("GAAP") applied on a consistent basis throughout the
periods involved (except as may be indicated in the notes thereto or, in the
case of unaudited interim financial statements, as may be permitted by the SEC
on Form 10-Q under the Exchange Act) and (y) fairly presented the consolidated
financial position of the Corporation and its subsidiaries as of or at, as the
case may be, the respective dates thereof and the consolidated results of its
operations and cash flows for the periods indicated consistent with the books
and records of the Corporation, except that the unaudited interim financial
statements were or are subject to normal and recurring year-end adjustments
which were not, or are not expected to be, material in amount. The balance sheet
of the Corporation contained in the Corporation's Annual Report on Form 10-K for
the year ended December 31, 1999 is referred to in this Agreement as the
"Balance Sheet."

       2.9    ABSENCE OF CERTAIN CHANGES OR EVENTS.

              Except as disclosed in the Corporation's Annual Report on Form
10-K for the fiscal year ended December 31, 1999, or any other public press
release or report filed under Sections 13(a), 13(c), 14 or 15(d) of the Exchange
Act, since December 31, 1999 through the date of this Agreement, (i) the
Corporation has not incurred any material liability, except as contemplated by
this Agreement or in the ordinary course of its business consistent with its
past practices, and (ii) no event has occurred which has had, or is likely to
have, individually or in the aggregate, a Material Adverse Effect on the
Corporation.

       2.10   LEGAL PROCEEDINGS.

              2.10(a). Except as set forth in Schedule 2.10, neither the
Corporation nor any Subsidiary is a party to any, and there are no pending or,
to the Corporation's knowledge, threatened, legal, administrative, arbitration
or other proceedings, claims, actions or governmental or regulatory
investigations of any nature against the Corporation or any Subsidiary.

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              2.10(b). Except as set forth in Schedule 2.10, there is no
injunction, order, judgment or decree imposed upon the Corporation or any
Subsidiary or the assets of the Corporation or any Subsidiary.

       2.11   COMPLIANCE WITH APPLICABLE LAWS.

              Each of the Corporation and the Subsidiaries has complied in all
material respects with all Laws applicable to it or to the operation of its
business. As of the date of this Agreement, neither the Corporation nor any
Subsidiary has received any notice of any material alleged or threatened claim,
violation, or liability under any such Laws that has not heretofore been cured
and for which there is any remaining liability.

       2.12   NO UNDISCLOSED LIABILITIES.

              There are no liabilities (accrued, contingent or otherwise) of the
Corporation or any Subsidiary, other than liabilities (a) reflected or reserved
against on the Balance Sheet, (b) as set forth on Schedule 2.12, or (c) incurred
since the date of this Agreement in the ordinary course of business, consistent
with past practice, of the Corporation and its Subsidiaries and which do not and
are not likely to have a Material Adverse Effect on the Corporation.

SECTION 3. REPRESENTATIONS AND WARRANTIES OF THE PURCHASERS.

              Each Purchaser severally and not jointly represents, warrants and
covenants to the Corporation as follows:

       3.1    ORGANIZATION AND STANDING.

              Purchaser is a corporation duly organized, validly existing and in
good standing under the laws of its jurisdiction of organization. Purchaser has
the full corporate power and authority to own and operate its properties and
assets and to carry on its business as currently conducted. Purchaser holds all
licenses and permits required for the conduct of its business as now conducted
which, if not in Purchaser's possession, would have a Material Adverse Effect on
Purchaser. Purchaser is duly qualified as a foreign corporation and is in good
standing in all jurisdictions where the conduct of its business or its ownership
or leasing of property requires such qualification, except where the failure to
so qualify would not have a Material Adverse Effect on Purchaser.

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       3.2    AUTHORIZATION.

              Purchaser has all requisite corporate power and authority to enter
into and to deliver this Agreement and the Registration Rights Agreement. The
execution, delivery and performance of this Agreement and the Registration
Rights Agreement by Purchaser and the consummation of the transactions
contemplated hereby and thereby have been duly authorized by all necessary
corporate action on the part of Purchaser. This Agreement and the Registration
Rights Agreement, when executed and delivered by Purchaser, shall constitute
valid and binding obligations of Purchaser enforceable in accordance with their
respective terms, except as may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or other similar laws effecting the enforcement of
creditor's rights.

       3.3    NON-CONTRAVENTION.

              The execution, delivery and performance of, and compliance with,
this Agreement will not (a) violate any provision of the governing documents of
Purchaser; (b) conflict with or result in a breach of, or default under,
terminate, or create a right of termination under, or result in the creation of
any lien, claim, charge or other encumbrance upon any of the assets or
properties of Purchaser pursuant to the provisions of any material agreement,
mortgage, indenture or other document or instrument to which Purchaser is a
party or by which Purchaser or any of its properties or assets is bound; or (c)
violate any existing statutes, laws, ordinances, regulations, orders and other
rules of law applicable to Purchaser or any of its properties or assets, in each
case only to the extent any of the foregoing would materially adversely affect
Purchaser's power or authority to perform its obligations under this Agreement.

       3.4    NO CONSENTS.

              No governmental orders, permissions, consents, approvals or
authorizations are required to be obtained by Purchaser and no filings are
required to be made by Purchaser in connection with the execution and delivery
of this Agreement and the purchase of the Shares hereunder, except as have been
so obtained or made prior to the Closing or, with respect to any that need to be
obtained or made subsequent to the Closing, as will be obtained or made in a
timely manner after the Closing, except where the failure to obtain such orders,
permissions, consents, approvals or authorizations or to make such filings would
not adversely affect in any material respect Purchaser's ability to perform its
obligations under this Agreement.

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       3.5    ADEQUATE RESOURCES.

              Purchaser has sufficient cash and other resources to perform its
obligations hereunder.

       3.6    INVESTMENT EXPERIENCE.

              Purchaser is an "accredited investor" as defined in Rule 501(a)
under the Securities Act. Purchaser is aware of the Corporation's business
affairs and financial condition and has had access to and has acquired
sufficient information about the Corporation to reach an informed and
knowledgeable decision to acquire the Shares. Purchaser has such business and
financial experience as is required to give it the capacity to protect its own
interests in connection with the purchase of the Shares. Purchaser is able to
bear the economic risk of holding the Shares for an indefinite period, including
the loss of Purchaser's entire investment. The Shares were not, and will not be,
offered or sold to Purchaser by any form of general solicitation or advertising.

       3.7    INVESTMENT INTENT.

              Purchaser is purchasing the Shares for its own account as
principal, for investment purposes only, and not with a view to, or for, resale,
distribution or fractionalization thereof, in whole or in part, within the
meaning of the Securities Act. Purchaser understands that the offer and sale of
the Shares on the Closing have not been, and will not be, registered under the
Securities Act or registered or qualified under any state securities law in
reliance on specific exemptions therefrom, which exemptions may depend upon,
among other things, the bona fide nature of Purchaser's investment intent as
expressed herein.

       3.8    REGISTRATION OR EXEMPTION REQUIREMENTS.

              Without limiting the rights of Purchaser under the Registration
Rights Agreement, Purchaser acknowledges and understands that the Shares may be
required to be held indefinitely, and they may not be resold or otherwise
transferred except in a transaction registered under the Securities Act or where
an exemption from such registration is available. Purchaser understands that the
certificate(s) evidencing the Shares will be imprinted with a legend that
prohibits the transfer of the Shares unless (a) they are registered or such
registration is not required, and (b) if the transfer is pursuant to an
exemption from registration other than Rule 144 promulgated under the Securities
Act and, if the Corporation shall so request in writing, an opinion of counsel
satisfactory to the Corporation is obtained to the effect that the transaction
is so exempt and in compliance with applicable state law.

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       3.9    NO LEGAL, TAX OR INVESTMENT ADVICE.

              Without limiting the rights of Purchaser under the Registration
Rights Agreement, Purchaser understands that nothing in this Agreement or any
other materials presented to Purchaser in connection with the purchase and sale
of the Shares constitutes legal, tax or investment advice. Purchaser has
consulted such legal, tax and investment advisors as it, in its sole discretion,
has deemed necessary or appropriate in connection with its purchase of the
Shares.

       3.10   HART-SCOTT-RODINO FILINGS.

              The acquisition of the Shares by Purchaser is not subject to any
filings under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
amended (the "HSR Act") or any other similar pre-merger notification
requirements under any applicable Laws.

SECTION 4.    ADDITIONAL AGREEMENTS.

       4.1    LOCK-UP COVENANT.

              Except as otherwise provided in Section 4.2, Purchaser covenants
that it will not, without the prior written consent of the Corporation, offer,
sell, transfer, pledge, encumber or otherwise dispose of, directly or
indirectly, any Shares or Underlying Common Stock received by Purchaser pursuant
to this Agreement (the "Lock-up"). The foregoing Lock-up is expressly agreed to
preclude Purchaser from engaging in any hedging or other transaction which is
designed to or which reasonably could be expected to lead to or result in a sale
or disposition of the Shares or Underlying Common Stock prior to the applicable
periods specified in Section 4.2, even if such Shares or Underlying Common Stock
would be disposed of by someone other than Purchaser. Such prohibited hedging or
other transactions would include without limitation any short sale or any
purchase, sale or grant of any right (including without limitation any put or
call option) with respect to any of Purchaser's Shares or Underlying Common
Stock or with respect to any security that includes, relates to, or derives any
significant part of its value from such Shares or Underlying Common Stock.
Notwithstanding the foregoing, Purchaser may transfer some or all of the Shares
or Underlying Common Stock either (A) to a corporation, partnership or other
legal entity that is controlled by, controls or is under common control with,
Purchaser, if such transferee agrees in writing to hold any Shares or Underlying
Common Stock received subject to the provisions of this Agreement and to
transfer such Shares or Underlying Common Stock back to Purchaser if such
transferee ceases to be controlled by Purchaser or (B) pursuant to Section 9.12.

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       4.2    RELEASE FROM LOCK-UP.

              4.2(a). Generally. Unless earlier released pursuant to Section
4.2(b) hereof, all of the Shares or Underlying Common Stock issuable upon
conversion thereof shall be released from the Lock-up upon the earlier of (x)
the first date on which the average closing price per share of the Corporation's
Common Stock over any 20 consecutive trading day period is equal to or more than
two times the closing price for the Common Stock of the Corporation on the
trading day immediately prior to the date of this Agreement, or (y) the first
anniversary of the Closing.

              4.2(b). Upon Occurrence of Certain Events. Notwithstanding Section
4.1 or Section 4.2(a):

                     (i)    Purchaser may offer, sell, pledge, transfer,
encumber or otherwise dispose of the Shares or the Underlying Common Stock (A)
at any time following the date on which the Corporation shall have entered into
a merger agreement or similar agreement pursuant to which all or substantially
all of the business or assets of the Corporation are to be sold; provided,
however, that this clause (A) shall not apply where the applicable agreement
contemplates that the holders of voting stock of the Corporation immediately
prior to completion of the proposed merger or other transaction will possess
more than 50% of the voting stock of the surviving entity; (B) at any time
following the date on which a person or group of persons acquires 50% or more of
the outstanding voting stock of the Corporation; (C) in connection with any
repurchase transaction or tender or exchange offer generally made available to
holders of the Corporation's Common Stock which is not opposed by the
Corporation's Board of Directors; or (D) at any time following the date, if any,
on which Purchaser brings any action or presents any claim alleging that the
Corporation breached in any material respect any of its representations and
warranties made in Section 2 hereof.

                     (ii)   Purchaser may pledge or otherwise encumber all or
any portion of the Shares or the Underlying Common Stock as collateral for
borrowings or other financing transactions if the pledgee agrees in writing to
hold any Shares or Underlying Common Stock received subject to the provisions of
this Agreement, including, without limitation, the Lock-Up.

       4.3    COMMERCIALLY REASONABLE EFFORTS.

              Purchaser and the Corporation shall use commercially reasonable
efforts to take, or cause to be taken, all actions and do, or cause to be done,
all things necessary, proper or appropriate under applicable laws and
regulations to consummate and make effective the purchase and sale of the Shares
contemplated hereby, including, without limitation, (i) if applicable, promptly
filing Notification and Report Forms, if any are required, under the HSR Act
with the Federal Trade

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Commission ("FTC") and the Antitrust Division of the Department of Justice (the
"Antitrust Division"), and responding as promptly as practicable to any
inquiries received from the FTC or the Antitrust Division for additional
information or documentation, and (ii) making all other necessary filings and
obtaining all other necessary consents, approvals or waivers, required to
consummate the transactions hereunder. Notwithstanding anything to the contrary
in this Agreement, neither Purchaser, nor the Corporation, nor any of their
subsidiaries shall be required to (i) divest, hold separate or license any
material business(es), product line(s) or asset(s), (ii) take any action or
accept any limitation that could reasonably be expected to have a Material
Adverse Effect on Purchaser or the Corporation, as applicable or (iii) agree to
any of the foregoing.

       4.4    BASIC FINANCIAL INFORMATION.

              If at any time the Corporation is not subject to the reporting
requirements at Section 13 or 15(d) of the Securities Exchange Act of 1934, the
Corporation will furnish the following reports to the Purchaser:

              4.4(a). Within 90 days after the end of each fiscal year of the
Corporation, a consolidated balance sheet of the Corporation and its
subsidiaries, if any, as of the end of such fiscal year, and consolidated
statements of income and cash flows of the Corporation and its subsidiaries, if
any, for such year, prepared in accordance with GAAP consistently applied and
audited by an independent accounting firm selected by the Corporation.

              4.4(b). Within 45 days after the end of each quarterly accounting
period in each fiscal year of the Corporation, a consolidated balance sheet of
the Corporation and its Subsidiaries, if any, as of the end of each such
quarterly period, and consolidated statements of income and cash flows of the
Corporation and its Subsidiaries, if any, for such period and for the current
fiscal year to date, prepared in accordance with generally accepted accounting
principles consistently applied and setting forth in comparative form the
figures for the corresponding periods of the previous fiscal year, subject to
changes resulting from normal year-end audit adjustments, except that such
statements need not contain the notes required by generally accepted accounting
principles.

              4.4(c). Along with any financial statements required to be
delivered to Purchaser in connection with Sections 4.4(a) and (b), management's
discussion and analysis of financial condition and results of operations
relating to the period covered by such financial statements.

                                     - 11 -
<PAGE>   15

              4.4(d). As soon as practicable following their release, copies of
all material press releases issued by the Corporation or other material reports
or communications delivered by the Corporation to the financial community.

       4.5    CERTIFICATE OF DESIGNATIONS.

              The Corporation shall cause the Certificate to be duly filed with
and accepted by the Secretary of State of the State of Delaware prior to the
Closing.

       4.6    REGISTRATION RIGHTS AGREEMENT.

              Concurrent with the execution of this Agreement, the Corporation
and the Purchasers are entering into the Registration Rights Agreement in the
form attached hereto as Exhibit C.

       4.7    USE OF PROCEEDS.

              The Corporation agrees to use the net proceeds it receives from
its sale and issuance of the Shares for general corporate purposes, which may
include, but which shall not be limited to, the following:

              -  expansion of the Corporation's ongoing operations, through:

                  -  infrastructure expansion in North America, Europe, Asia
                     Pacific and South America;

                  -  continued expansion of functionality within the
                     Corporation's product suites; and

                  -  formalization of development partner support organization
                     within the Corporation's Product Development group; and

              -   acceleration of the Corporation's strategic development
                  partner program, through:

                  -  continued investment in emerging companies offering
                     complementary products and services to those offered by the
                     Corporation; and

                  -  creation of a program to foster operating synergies among
                     the Corporation, the companies in which the Corporation has
                     invested and certain strategic investors in the
                     Corporation.

       4.8    ACCESS TO INFORMATION.

              Upon reasonable notice and subject to applicable Laws relating to
the exchange of information, the Corporation shall provide to the officers,
employees, accountants, counsel and other representatives of Purchaser, access,
during normal business hours during the period prior to the Closing, to all its
and its Subsidiaries'

                                     - 12 -
<PAGE>   16

properties, books, contracts, commitments and records and, during such period,
the Corporation shall make available to Purchaser all other information
concerning its business, properties and personnel as Purchaser may reasonably
request (except as to information which is competitively sensitive or which the
Corporation may not disclose under any existing confidentiality agreement). The
parties hereto agree and acknowledge that the access contemplated by this
Section 4.8 shall not unreasonably interfere with the business operations of the
Corporation. Purchaser agrees to hold all such information in confidence.

SECTION 5.    CONDITIONS TO CLOSING.

       5.1    CONDITIONS TO OBLIGATIONS OF ALL PARTIES.

              The obligations of each party to consummate the transactions
contemplated by this Agreement are subject to the satisfaction, on or before the
date of the Closing, of each of the following conditions precedent:

              5.1(a). Termination. This Agreement shall not have been terminated
in accordance with its terms.

              5.1(b). No Governmental Action. No action or proceeding by or
before any governmental authority shall have been instituted or threatened (and
not subsequently dismissed, settled or otherwise terminated) which is reasonably
expected to restrain, prohibit or invalidate the transactions contemplated by
this Agreement, nor shall any court or other governmental authority of competent
jurisdiction have issued an order, writ, injunction or decree or taken any other
action restraining or otherwise prohibiting the purchase of the Shares
contemplated hereby.

              5.1(c). Governmental Clearances. The HSR Act waiting period, if
any, related to this Agreement shall have expired or been terminated, and any
other required authorizations, consents, orders or approvals of, or declarations
or filings with, or expirations of waiting periods imposed by, any government
entity shall have been obtained or filed.

       5.2    CONDITIONS TO THE OBLIGATIONS OF THE PURCHASERS.

              The obligations of each Purchaser to purchase the Shares as
contemplated by this Agreement are subject to the satisfaction, on or before the
date of the Closing, of each of the following conditions precedent, any one or
more of which may be waived by such Purchaser, in its sole and absolute
discretion:

                                     - 13 -
<PAGE>   17

              5.2(a). Representations and Warranties. The representations and
warranties of the Corporation contained in this Agreement shall be true, correct
and complete in all material respects when made and shall be true and correct as
of the date of the Closing, with the same force and effect as if made on the
date of the Closing.

              5.2(b). Compliance with Covenants. The Corporation shall have in
all material respects performed all obligations and agreements and complied with
all covenants contained in this Agreement to be performed and complied with by
the Corporation on or prior to the date of the Closing.

              5.2(c). Material Adverse Event. No change, event or effect that
could reasonably be expected to have a Material Adverse Effect on the
Corporation shall have occurred and be continuing.

              5.2(d). Closing Matters. Each Purchaser whose name is set forth on
the Schedule of Purchasers attached hereto as Exhibit A shall have duly executed
and delivered this Agreement and the Registration Rights Agreement, and such
Purchaser shall have had the opportunity to review counterpart signature pages
to this Agreement from the Corporation and each other Purchaser.

       5.3    CONDITIONS TO OBLIGATIONS OF THE CORPORATION.

              The obligations of the Corporation to sell the Shares as
contemplated by this Agreement are subject to the satisfaction, on or before the
date of the Closing, of each of the following conditions precedent, any one or
more of which may be waived by the Corporation, in its sole and absolute
discretion:

              5.3(a). Representations and Warranties. The representations and
warranties of each of the Purchasers contained in this Agreement shall be true,
correct and complete in all material respects when made and shall be true and
correct as of the date of the Closing, with the same force and effect as if made
on the date of the Closing.

              5.3(b). Compliance with Covenants. Each Purchaser shall have in
all material respects performed all obligations and agreements and complied with
all covenants contained in this Agreement to be performed and complied with by
each Purchaser on or prior to the date of the Closing.

                                     - 14 -
<PAGE>   18

SECTION 6.    CLOSING.

       6.1    DELIVERIES BY THE CORPORATION.

              At the Closing, the Corporation shall deliver to each Purchaser
the following:

                     (1)    A certificate or certificates registered in
Purchaser's name, representing all of the Shares purchased by such Purchaser.

                     (2)    A copy of the resolutions of the Board of Directors
of the Corporation, as certified as of the date of the Closing by the Secretary
of the Corporation, as being true, correct and complete and in full force and
effect, authorizing the execution, delivery and performance of this Agreement
and the Registration Rights Agreement by the Corporation, the authorization,
sale, issuance and delivery of the Shares, and the performance of the
Corporation's obligations hereunder.

                     (3)    A certificate of the Corporation signed by an
authorized officer of the Corporation certifying that the representations and
warranties of the Corporation made herein were true, complete and correct in all
material respects as of the date of this Agreement and are true and correct as
of the date of the Closing, and the Corporation has in all material respects
performed all obligations and agreements and complied with all covenants
required to be performed or complied with by the Corporation on or prior to the
Closing.

                     (4)    Such other certificates, instruments or documents
as Purchaser may reasonably request in order to effect and document the
transactions contemplated hereby.

       6.2    DELIVERIES BY THE PURCHASERS.

              At the Closing, each Purchaser shall deliver to the Corporation
the following:

                     (1)    The "Purchase Price" set forth opposite such
Purchaser's name on Exhibit A in cash or by wire transfer or certified or bank
cashier's check, payable to the order of the Corporation.

                     (2)    A certificate from each Purchaser signed by an
authorized officer of such Purchaser certifying that the representations and
warranties of such Purchaser made herein were true, complete and correct in all
material respects as of the date of this Agreement and are true and correct as
of the date of the Closing (if different), and such Purchaser has in all
material respects performed all

                                     - 15 -
<PAGE>   19

obligations and agreements and complied with all covenants required to be
performed or complied with by such Purchaser on or prior to the Closing.

                     (3)    Such other certificates, instruments or documents as
the Corporation may reasonably request in order to effect and document the
transaction contemplated hereby.

SECTION 7.    LEGEND.

       7.1    ENDORSEMENT.

              Each certificate representing the Shares shall bear the following
legends (in addition to any legend required by applicable state securities
laws):

              THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
       REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT") OR
       ANY OTHER FEDERAL OR STATE SECURITIES LAWS, AND MAY NOT BE SOLD,
       TRANSFERRED, ASSIGNED OR HYPOTHECATED UNLESS THERE IS AN EFFECTIVE
       REGISTRATION STATEMENT UNDER THE ACT AND ANY OTHER APPLICABLE FEDERAL
       SECURITIES LAWS COVERING SUCH SECURITIES OR THE CORPORATION RECEIVES AN
       OPINION OF COUNSEL IN FORM SATISFACTORY TO THE CORPORATION THAT AN
       EXEMPTION FROM SUCH REGISTRATION IS AVAILABLE.

              ADDITIONALLY, THE TRANSFER OF THE SHARES REPRESENTED BY THIS
       CERTIFICATE IS SUBJECT TO CERTAIN RESTRICTIONS ON TRANSFER SPECIFIED IN
       THE STOCK PURCHASE AGREEMENT DATED MAY __, 2000 (THE "AGREEMENT") BETWEEN
       THE CORPORATION AND THE ORIGINAL PURCHASER, AND NO TRANSFER OF SHARES
       SHALL BE VALID OR EFFECTIVE ABSENT COMPLIANCE WITH SUCH RESTRICTIONS.
       SUBSEQUENT HOLDERS OF THIS CERTIFICATE MAY BE BOUND BY CERTAIN OF THE
       TERMS OF THE AGREEMENT, INCLUDING SECTIONS 4.1 AND 4.2 OF THE AGREEMENT.
       COPIES OF THE AGREEMENT MAY BE OBTAINED AT NO COST BY WRITTEN REQUEST
       MADE BY THE REGISTERED HOLDER OF THIS CERTIFICATE TO THE SECRETARY OF THE
       CORPORATION.

       7.2    REMOVAL OF LEGEND.

                                     - 16 -
<PAGE>   20

              Without limiting the rights of Purchaser under the Registration
Rights Agreement, the legend endorsed on a stock certificate pursuant to Section
7.1 of this Agreement, insofar as it relates to registration under the
Securities Act, shall be removed and the Corporation shall issue a certificate
without such legend to the holder of such Shares, if such Shares are registered
under applicable federal securities laws and a prospectus meeting the
requirements of the rules and regulations of the SEC is available or if such
holder provides to the Corporation an opinion of counsel to such holder
reasonably satisfactory to the Corporation, to the effect that a public sale,
transfer or assignment of such Shares may be made without registration and
without compliance with any restrictions. The legend endorsed on a stock
certificate pursuant to Section 7.1 of this Agreement, insofar as it relates to
additional restrictions specified in this Agreement, shall be removed upon the
expiration of the applicable provisions referenced therein.

SECTION 8.    TERMINATION.

       8.1    TERMINATION.

              This Agreement may be terminated at any time upon the mutual
consent of the parties hereto. In the event that the Closing shall not have
occurred on or before 120 days from the date hereof due to the Corporation's
failure to satisfy the conditions set forth in Sections 5.1(b), (c) and 5.2
above (and any Purchaser's failure to waive such unsatisfied condition(s)), each
Purchaser not waiving such unsatisfied condition(s) shall have the option to
terminate this Agreement with respect to its obligations hereunder at the close
of business on such date without liability to the Corporation or any other
party. In addition, in the event that the Closing shall not have occurred on or
before 120 days from the date hereof due to any Purchaser's failure to satisfy
the conditions set forth in Sections 5.1(c) and 5.3 above (and the Corporation's
failure to waive such unsatisfied condition(s)), the Corporation shall have the
option to terminate this Agreement with respect to such Purchaser at the close
of business on such date without liability to such Purchaser or any other party.

       8.2    EFFECT OF TERMINATION.

              Termination of this Agreement pursuant to this Section shall not
relieve any party of any liability for a default or other breach, default or
nonperformance under this Agreement. Notwithstanding the foregoing, no party
hereto shall be liable for consequential or punitive damages in connection with
such termination.

                                     - 17 -
<PAGE>   21

SECTION 9.    MISCELLANEOUS.

       9.1    ADDITIONAL ACTIONS AND DOCUMENTS.

              Each of the parties hereto agrees that it will, at any time, prior
to, at or after the Closing, take or cause to be taken such further actions, and
execute, deliver and file or cause to be executed, delivered and filed such
further documents and instruments (including export license applications) as may
be necessary or reasonably requested in connection with the consummation of the
purchase and sale contemplated by this Agreement or in order to fully effectuate
the purposes, terms and conditions of this Agreement.

       9.2    EXPENSES.

              Each party hereto shall pay its own expenses incurred in
connection with this Agreement and in the preparation for and consummation of
the transactions contemplated hereby.

       9.3    NOTICES.

              All notices, demands, requests, or other communications which may
be or are required to be given or made by any party to any other party pursuant
to this Agreement shall be in writing and shall be hand delivered, mailed by
first-class registered or certified mail, return receipt requested, postage
prepaid, or delivered by overnight air courier, addressed as follows:

              (i) if to the Corporation:

              S1 Corporation
              3390 Peachtree Road, NE, Suite 1700
              Atlanta, GA 30326
              Attn.: Chief Financial Officer

              with a copy (which shall not constitute notice) to:

              Hogan & Hartson L.L.P.
              555 Thirteenth Street, N.W.
              Washington, D.C. 20004
              Attn.: Stuart G. Stein, Esq.

              (ii) if to Purchaser, at the addresses of such Purchaser specified
on Exhibit A hereto.

                                     - 18 -
<PAGE>   22

or such other address as the addressee may indicate by written notice to the
other parties. Each notice, demand, request, or communication which shall be
given or made in the manner described above shall be deemed sufficiently given
or made for all purposes at such time as it is delivered to the addressee (with
the return receipt, the delivery receipt, or the affidavit of messenger being
deemed conclusive but not exclusive evidence of such delivery) or at such time
as delivery is refused by the addressee upon presentation.

       9.4    WAIVER.

              No waiver by any party of any failure or refusal of any other
party to comply with its obligations under this Agreement shall be deemed a
waiver of any other or subsequent failure or refusal so to comply by such other
party. No waiver shall be valid unless in writing signed by the party to be
charged and then only to the extent therein set forth.

       9.5    BINDING EFFECT.

              This Agreement shall be binding upon and shall inure to the
benefit of the parties hereto and their respective successors and assigns.

       9.6    ENTIRE AGREEMENT; AMENDMENT.

              This Agreement, including the other instruments and documents
referred to herein or delivered pursuant hereto, contains the entire agreement
among the parties with respect to the subject matter hereof and supersedes all
prior oral or written agreements, commitments or understandings with respect to
such matters. No amendment, modification or discharge of this Agreement shall be
valid or binding unless set forth in writing and duly executed by the party
against whom enforcement of the amendment, modification or discharge is sought.

       9.7    SEVERABILITY.

              If any part of any provision of this Agreement shall be invalid or
unenforceable under applicable law, such part shall be ineffective to the extent
of such invalidity or unenforceability only, without in any way affecting the
remaining parts of such provisions or the remaining provisions of said
Agreement.

                                     - 19 -
<PAGE>   23

       9.8    HEADINGS.

              The headings of the sections and subsections contained in this
Agreement are inserted for convenience only and do not form a part or affect the
meaning, construction or scope hereof.

       9.9    GOVERNING LAW.

              This Agreement, the rights and obligations of the parties hereto,
and any claims or disputes relating thereto, shall be governed by and construed
under and in accordance with the laws of the State of Delaware, excluding the
choice of law rules thereof.

       9.10   SIGNATURE IN COUNTERPARTS.

              This Agreement may be executed in separate counterparts, none of
which need contain the signatures of all parties, each of which shall be deemed
to be an original, and all of which taken together constitute one and the same
instrument. It shall not be necessary in making proof of this Agreement to
produce or account for more than the number of counterparts containing the
respective signatures of, or on behalf of, all of the parties hereto.

       9.11   NO THIRD PARTY BENEFICIARIES.

              Except as expressly provided herein, this Agreement is made and
entered into for the sole protection and benefit of the parties hereto, and no
other person or entity shall have any right of action hereon, right to claim any
right or benefit from the terms contained herein or be deemed a third party
beneficiary hereunder.

       9.12   ASSIGNABILITY.

              All terms and provisions of this Agreement shall be binding upon
and inure to the benefit of the parties hereto, and their respective
transferees, successors and assigns; provided, however, that neither this
Agreement nor any rights, privileges, duties and obligations of the parties
hereto may be assigned or delegated by any party hereto without the prior
written consent of all the parties to this Agreement and any such purported or
attempted assignment shall be null and void ab initio and of no force or effect;
provided, further that each Purchaser may assign this Agreement, and other
rights, privileges, duties and obligations hereunder to (i) any "affiliate" (as
such term is defined in Rule 405 under the Securities Act) of such Purchaser, so
long as such assignment does not in any way materially delay or otherwise
materially adversely impact the ability of the parties

                                     - 20 -
<PAGE>   24

hereto to effect the transactions contemplated hereby, or (ii) any acquiror of
all or a substantial part of the assets or stock of such Purchaser whether by
merger, tender offer, asset sale or other transaction.

       9.13   PARTIES NOT PARTNERS.

              Nothing contained in this Agreement shall constitute any party as
a partner with, agent for or principal of any one or more of the other parties
or their successors and assigns.

       9.14   SURVIVAL OF REPRESENTATIONS AND WARRANTIES.

              The representations and warranties of the Corporation set forth in
Sections 2.2 or 2.4 hereof shall survive for the applicable statute of
limitations. The other representations and warranties of Corporation hereunder
shall survive the execution and delivery of this Agreement and the Closing
hereunder for a period of one year from the Closing, after which no Purchaser
may bring any action or present any claim for a breach of such representations
and warranties, except for actions or claims instituted or made prior to and
pending at the time of the first anniversary of the Closing. None of the
covenants and agreements in this Agreement or in any instrument delivered
pursuant to this Agreement shall survive the Closing, except for those covenants
and agreements contained herein and therein which by their terms apply in whole
or in part after the Closing.

       9.15   ADDITIONAL DEFINITIONS.

              In addition to any other definitions contained in this Agreement,
the following words, terms and phrases shall have the following meanings when
used in this Agreement.

              "knowledge" or "know" means with respect to a party hereto, with
respect to a matter in question, that the directors or any executive officer of
such party has actual knowledge of such matter.

              "Laws": any and all statutes, laws, ordinances, rules,
regulations, orders, permits, judgments, injunctions, decrees, case law and
other rules of law enacted, promulgated or issued by any Governmental Entity.

              "Material Adverse Effect": with respect to the Corporation or
Purchaser, as the case may be, means a condition, event, change or occurrence
that, individually or in the aggregate, has had or would have a material adverse
effect upon the Corporation or Purchaser, as the case may be, taking into
account (A) the business, assets, capitalization, and financial condition of the
Corporation or Purchaser, other than as a result primarily of (i) the direct
effect of the public announcement, pendency

                                     - 21 -
<PAGE>   25

or consummation of this Agreement or (ii) changes in general economic conditions
or changes affecting the industry generally in which such entity operates, or
(B) the ability of the Corporation or Purchaser to perform its obligations
under, and to consummate the transactions contemplated by, this Agreement.

                            [SIGNATURE PAGE FOLLOWS]

                                     - 22 -
<PAGE>   26

              IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to be duly executed and delivered as of the date first above written.

                                CORPORATION:

                                S1 CORPORATION

                                By: /s/ ROBERT F. STOCKWELL
                                   --------------------------------------------
                                         Name: Robert F. Stockwell
                                              ---------------------------------
                                         Title: Chief Financial Officer
                                               --------------------------------

                                PURCHASERS:

                                STATE FARM MUTUAL AUTOMOBILE INSURANCE COMPANY

                                By: /s/ JIM RUTROUGH
                                   --------------------------------------------
                                         Name: Jim Rutrough
                                              ---------------------------------
                                         Title: Executive Vice-President
                                               --------------------------------

                                By: /s/ ANN BAUGHAN
                                   --------------------------------------------
                                         Name: Ann Baughan
                                              ---------------------------------
                                         Title: Vice-President-EIS
                                               --------------------------------

                                ZG INVESTMENTS, LTD.

                                By: /s/ MICHAEL R. DEEVY
                                   --------------------------------------------
                                         Name: Michael R. Deevy
                                              ---------------------------------
                                         Title: Director
                                               --------------------------------

                                     - 23 -
<PAGE>   27

                                ALLIANZ CAPITAL PARTNERS GMBH

                                By: /s/
                                   --------------------------------------------
                                         Name:
                                              ---------------------------------
                                         Title:
                                               --------------------------------

                                By: /s/
                                   --------------------------------------------
                                         Name:
                                              ---------------------------------
                                         Title:
                                               --------------------------------

                                FLEET PRIVATE EQUITY CO., INC.

                                By: /s/ H. JAY SARLES
                                   --------------------------------------------
                                         Name: H. Jay Sarles
                                              ---------------------------------
                                         Title: Director
                                               --------------------------------

                                J.P. MORGAN VENTURES CORPORATION

                                By: /s/ GRACE VOGEL
                                   --------------------------------------------
                                         Name: Grace Vogel
                                              ---------------------------------
                                         Title: Controller
                                               --------------------------------

                                     - 24 -
<PAGE>   28

                                    EXHIBIT A

                             SCHEDULE OF PURCHASERS

<TABLE>
<S>                                     <C>                   <C>
Name and Address                        Number of Shares       Purchase Price
State Farm Mutual Automobile            100,000                $100,000,000
Insurance Company
1 State Farm Plaza
Bloomington, IL 61710
Attention: Larry Rottunda

ZG Investments, Ltd.                    75,000                 $75,000,000
The Zurich Centre
90 Pitt's Bay Road
Pembroke HM 08
Bermuda
Attention: Mike Deevy

with a copy (which shall not
constitute notice) to:

Willkie Farr & Gallagher
787 Seventh Avenue
New York, NY 10019
Attention: Thomas M. Cerabino
</TABLE>

                                     - 25 -
<PAGE>   29

<TABLE>
<S>                                     <C>                     <C>
Allianz Capital Partners GmbH           37,500                   $37,500,000
c/o Allianz AG
Theresienstrasse 1-7
D-80333 Munich
Attention: Peter Gangsted

with a copy (which shall not
constitute notice) to:

Shearman & Sterling
599 Lexington Avenue
New York, NY 10022
Attention: Howard Sutherland
</TABLE>

                                     - 2 -

<PAGE>   30

<TABLE>
<S>                                     <C>                     <C>
Fleet Private Equity Co., Inc.           25,000                   $25,000,000
c/o FleetBoston Financial
Corporation
One Federal Street, 37th Floor
Boston, MA 02110
Attention: Brian Moynihan

with a copy (which shall not
constitute notice) to:

Edwards & Angell, LLP
2800 BankBoston Plaza
Providence, RI 02903
Attention: Joseph A. Kuzneski,Jr.

J.P. Morgan Ventures Corporation          6,500                    $6,500,000
60 Wall Street
New York, NY 10260
Fax no.: 212-235-0863
Attention: Christopher Ahearn

with a copy (which shall not
constitute notice) to:

Proskauer, Rose LLP
1585 Broadway
New York, NY 10036
Fax no.: 212-969-2900
Attention: Bruce Lieb
</TABLE>

                                     - 3 -<PAGE>   1
                                                                    EXHIBIT 10.2

                          REGISTRATION RIGHTS AGREEMENT

       THIS REGISTRATION RIGHTS AGREEMENT (this "Agreement") is dated as of May
25, 2000 by and among S1 Corporation (the "Company") and each holder of "Series
D Preferred Stock" (as that term is defined below) listed on Schedule 1 attached
hereto (each a "Series D Holder"; collectively, the "Series D Holders"). The
Series D Holders, together with their respective successors and assigns, are
sometimes hereinafter referred to collectively as the "Investors" and
individually as an "Investor." The Investors and any other persons or entities
(except the Company) becoming a party hereto or being bound by the provisions
hereof are hereinafter sometimes referred to collectively as "Stockholders" or
individually as a "Stockholder."

                                    RECITALS

       A. On the date hereof, the Company and the Investors are entering into a
Stock Purchase Agreement dated of even date herewith (the "Purchase Agreement").
A condition precedent to the obligations of the Company and the Investors under
the Purchase Agreement is the execution and delivery by the parties hereto of
this Agreement;

       B. At the closing to be held under the Purchase Agreement, each Investor
has agreed to purchase that number of shares of the Company's Series D
Convertible Preferred Stock, par value $.01 per share (the "Series D Preferred
Stock"), as is set forth opposite such Investor's name in Schedule 1 attached
hereto; and

       C. The Company and the Investors wish to enter into this Agreement in
order to provide the Investors with certain registration rights with respect to
the Company's "Registrable Stock" (as that term is defined below).

       NOW, THEREFORE, in consideration of these premises and mutual agreements,
covenants and provisions herein contained, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto, intending to be legally bound, agree as follows:

                                    ARTICLE I
                                   DEFINITIONS

       Section 1.1   Definitions.

       The following definitions shall be applicable to the terms set forth
below as used in this Agreement:

              "Affiliate." The term "Affiliate" means, with respect to any
Person, any other Person which directly, or indirectly through one or more
intermediaries, controls, is controlled by or is under common control with such
Person.

              "Board." The term "Board" shall mean the Board of Directors of the
Company.

<PAGE>   2

              "Closing." The term "Closing" shall mean the closing held pursuant
to the Purchase Agreement.

              "Commission." The term "Commission" shall mean the Securities and
Exchange Commission or any other federal agency at the time administering the
federal securities laws.

              "Common Stock." The term "Common Stock" shall mean the common
stock of the Company, par value $.01 per share.

              "Conversion Shares." The term "Conversion Shares" shall mean any
shares of Common Stock issued or issuable upon conversion of shares of Series D
Preferred Stock.

              "Exchange Act." The term "Exchange Act" shall mean the Securities
Exchange Act of 1934, as amended.

              "Filing Date." The term "Filing Date" shall mean the earlier of
the date (i) 15 business days following the date the Conversion Shares are
released from the "Lock-up" (as such term is defined in Section 4.1 of the
Purchase Agreement) pursuant to Section 4.2 of the Purchase Agreement, or (ii)
eleven months after the date of the Closing, provided, however, that if as of
such earlier date the Company shall not then have available financial statements
in a form suitable for filing on, or incorporating into, a registration
statement under the rules of the Commission, then the Filing Date shall be that
date which is three business days after such financial statements become
available.

              "Permitted Transferee." The term "Permitted Transferee" shall
mean, with respect to any Investor, (i) any other Investor; (ii) any Affiliate
of any Investor; (iii) any spouse, child and grandchild of an Investor, or a
trust for the benefit of any one or more members of such person; or (iv) any
shareholder or partner of any non-natural Investor upon a pro rata distribution
by a partnership or limited liability company to its partners or members or
otherwise upon the dissolution or liquidation of the non-natural Investor.

              "Person." The term "Person" shall mean any individual, firm,
corporation, partnership, limited liability company, trust, joint venture,
governmental authority or other entity, and shall include any successor (by
merger or otherwise) of such entity.

              "Register." The terms "register," "registered" and "registration"
refer to a registration effected by preparing and filing a registration
statement in compliance with the Securities Act.

              "Registrable Stock." The term "Registrable Stock" shall mean, (i)
any Conversion Shares which have been released from the Lock-up pursuant to
Section 4.2 of the Purchase Agreement, and (ii) any shares of Common Stock
issued or issuable with respect to such Conversion Shares by reason of a stock
dividend or stock split or in connection with a combination of shares,
recapitalization, merger, consolidation or other reorganization. A Person shall
be deemed to be a holder of Registrable Stock when such Person has a right to
acquire such Registrable Stock (whether by conversion or otherwise) regardless
of whether such acquisition has actually been effected. Each share of
Registrable Stock shall continue to be Registrable

                                      - 2 -

<PAGE>   3

Stock in the hands of each subsequent holder thereof subject to the limitations
set forth in Section 2.8 hereof; provided, however, that each share of
Registrable Stock shall cease to be Registrable Stock when (x) transferred by an
Investor to any Person who is not a Permitted Transferee, or if the transfer
does not comply with the terms of Section 2.8 of this Agreement, (y) a
registration statement covering all Registrable Stock has been declared
effective under the Securities Act by the SEC and such Registrable Stock has
been disposed of pursuant to such effective registration statement, or (z) the
entire amount of Registrable Stock held by a Person and its Affiliates may be
distributed to the public in a single sale without any limitation as to volume
for such sale pursuant to Rule 144 (or any successor provision then in effect)
under the Securities Act.

              "Securities Act." The term "Securities Act" shall mean the
Securities Act of 1933, as amended.

              "Short-Form Registration Statement." The term "Short-Form
Registration Statement" shall mean a registration statement on Form S-3 or any
similar form of registration statement adopted by the Commission from and after
the date hereof.

              "Transaction Documents." The term "Transaction Documents" means,
collectively, this Agreement and the Purchase Agreement.

       Section 1.2   Additional Definitions.

       In addition to the foregoing, capitalized terms used in this
Agreement and not otherwise defined in this Article I shall have the meanings so
given to such terms herein.

                                   ARTICLE II
                               REGISTRATION RIGHTS

       Section 2.1   Filing of Short-Form Registration Statement.

       No later than the Filing Date, the Company shall file with the SEC a
Short-Form Registration Statement under the Securities Act covering the resale
of the Registrable Stock; provided, however, that if, on the Filing Date, a
Short-Form Registration Statement is unavailable to the Company for such
registration solely due to the Corporation's failure to timely comply with its
reporting obligations under the Exchange Act, such registration will be promptly
made on Form S-1 or any similar form of registration statement adopted by the
Commission from and after the date hereof. Notwithstanding the foregoing, if,
prior to the filing of such registration statement, the Company shall have
furnished to each of the Investors a certificate signed by an authorized officer
of the Company stating that, in the good faith judgment of the Board, (A) it is
in the best interests of the Company not to disclose the existence of material
facts surrounding any proposed or pending acquisition, disposition, strategic
alliance or financing transaction involving the Company, the existence of which
the Company has a bona fide business purpose for keeping confidential and the
nondisclosure of which in the registration statement

                                     - 3 -

<PAGE>   4

would reasonably be expected to cause the registration statement to fail to
comply with applicable disclosure requirements, or (B) it would be seriously
detrimental to the Company and its stockholders for such registration statement
to be filed and it is therefore essential to defer the filing of such
registration statement, then the Company shall have the right to defer such
filing for a period of not more than 60 days from the Filing Date.

       Section 2.2   Effective Period of Registration.

       The Company shall use its reasonable best efforts to cause the
registration statement filed pursuant to Section 2.1 hereof to be declared
effective by the Commission as soon as practicable after it has been filed. Once
any registration pursuant to this Article II becomes effective, the Company
shall file all reports, financial statements and other documents necessary to
keep such registration statement current and the registration in effect until
the earlier of (i) the sale of all shares of Registrable Stock offered for sale
pursuant to the registration statement, or (ii) the second anniversary of the
Closing (the "Effective Period"); provided, however that at any time during the
Effective Period, the Company may determine, in the good faith judgment of its
Board, that offers and sales under the registration statement shall be suspended
if it is in the best interests of the Company not to disclose the existence of
material facts surrounding any proposed or pending acquisition, disposition,
strategic alliance or financing transaction involving the Company, the existence
of which the Company has a bona fide business purpose for keeping confidential
and the nondisclosure of which in the registration statement would reasonably be
expected to cause the registration statement to fail to comply with applicable
disclosure requirements. Immediately upon making such a determination, the
Company shall give notice to the Investors (a "Materiality Notice"), upon
receipt of which each Investor agrees that it will immediately discontinue
offers and sales of Registrable Stock under the registration statement until
such Investor receives copies of a supplemented or amended prospectus that
corrects the misstatement(s) or omission(s) referred to above and receives
notice that any post-effective amendment has become effective; provided, that
(x) the Company may delay, suspend or withdraw the registration statement for
such reason for no more than 30 days after the abandonment or consummation of
any of the foregoing negotiations, transactions, events or offerings or, in any
event, for not more than 60 days after delivery of the Materiality Notice at any
one time during any period of 12 consecutive months (and the Company shall not
be entitled to deliver a Materiality Notice at any time within 180 days of any
prior termination of any suspension pursuant to a prior Materiality Notice), and
(y) the Company may not impose such a suspension or a postponement following the
printing and distribution of a preliminary prospectus in any public offering of
Registrable Stock (except such suspension, not to exceed ten days, which results
from an event that is not within the reasonable control of the Company). If so
directed by the Company, each Investor will deliver to the Company all copies of
the prospectus covering the Registrable Stock current at the time of receipt of
a Materiality Notice.

       Section 2.3   Registration Procedures.

       (a) When the Company is required by the provisions of this Agreement to
effect the registration of shares of Registrable Stock, the Company shall:

                                     - 4 -

<PAGE>   5

              (i)    prepare and file with the Commission a registration
statement on the form as described in Section 2.1 hereof (advance draft copies
of which shall be furnished to the holders of Registrable Stock to be included
in such registration and their respective counsel at least five business days
prior to the filing thereof with the Commission) with respect to such shares and
use its reasonable best efforts to cause such registration statement to become
and remain effective for the Effective Period as described in Section 2.2
hereof;

              (ii)   prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectuses used in
connection therewith as may be necessary to keep such registration statement
effective and current and to comply with the provisions of the Securities Act
with respect to the sale or other disposition of all shares covered by such
registration statement, including such amendments and supplements as may be
necessary to reflect the intended method of disposition from time to time of the
holder or holders of Registrable Stock who have requested that any of their
shares be sold or otherwise disposed of in connection with the registration
(collectively, the "Prospective Sellers") or to correct or update any
misstatements or omissions which, if not corrected or updated, would reasonably
be expected to cause the registration statement or the prospectuses used in
connection therewith to fail to comply with applicable disclosure requirements;

              (iii)  furnish to each Prospective Seller such number of copies of
each prospectus, including preliminary prospectuses and amendments and
supplements to any prospectus, in conformity with the requirements of the
Securities Act, and such other documents as the Prospective Seller may
reasonably request in order to facilitate the public sale or other disposition
of the shares owned by it;

              (iv)   use its reasonable best efforts to register or qualify the
shares covered by such registration statement under such other securities or
blue sky or other applicable laws of such jurisdictions as each Prospective
Seller shall reasonably request to enable such seller to consummate the public
sale or other disposition of the shares owned by such seller, provided that the
Company shall not be required in connection therewith or as an election thereto
to qualify to do business or to file a general consent to service of process in
any such jurisdiction;

              (v)    upon written request, furnish to each Prospective Seller a
signed counterpart, addressed to the Prospective Sellers of: (A) an opinion of
counsel for the Company, dated the effective date of the registration statement;
and (B) a "comfort" letter signed by the independent public accountants of the
Company who have certified the Company's financial statements included in the
registration statement, covering substantially the same matters with respect to
the registration statement (and the prospectus included therein) and (in the
case of the accountants' "comfort" letter) with respect to the events subsequent
to the date of the financial statements, as are customarily covered (at the time
of such registration) in the opinions of issuers' counsel and in accountants'
letters delivered to underwriters in connection with underwritten public
offerings of securities;

              (vi)   cause all such Registrable Stock to be listed on the Nasdaq
National Market System or such other securities exchange or other securities
trading market on

                                     - 5 -

<PAGE>   6

which similar securities issued by the Company are then listed no later than the
first day of the Effective Period;

              (vii)  provide a transfer agent and registrar for all such
Registrable Stock not later than the effective date of such registration
statement;

              (viii) enter into such customary agreements and take all such
other customary actions as the holders of a majority of the Registrable Stock
being sold reasonably request in order to expedite or facilitate the disposition
of such Registrable Stock;

              (ix)   make available for inspection by any Prospective Seller and
any attorney, accountant or other agent retained by any such Prospective Seller,
all reasonable financial and other records, pertinent corporate documents and
properties of the Company, and cause the Company's officers, directors,
employees and independent public accountants who have certified the Company's
financial statements included in the registration statement to supply all
information reasonably requested by any such seller, attorney, accountant or
agent in connection with the preparation of such registration statement;

              (x)    permit any Prospective Seller who, in the reasonable
judgment of the Company upon advice of counsel, might be deemed to be an
underwriter or controlling person of the Company, to participate in the
preparation of such registration statement;

              (xi)   provide facsimile or written notice to each Prospective
Seller as soon as the Company becomes aware of any misstatements or omissions
which, if not corrected or updated, would reasonably be expected to cause the
registration statement or the prospectuses used in connection therewith to fail
to comply with applicable disclosure requirements; and

              (xii)  in the event of the issuance of any stop order suspending
the effectiveness of the registration statement, or of any order suspending or
preventing the use of any related prospectus or suspending the registration or
qualification of any Registrable Stock included in such registration statement
for sale in any jurisdiction where such shares had previously been registered or
qualified upon the request of a Prospective Seller, use its reasonable best
efforts to promptly obtain the withdrawal of such order.

       (b)    Each Prospective Seller of Registrable Stock shall furnish to the
Company such information as the Company may reasonably require from the
Prospective Seller for inclusion in the registration statement (and the
prospectus included therein).

       (c)    The Prospective Sellers shall not effect sales of the shares
covered by the registration statement after receipt of facsimile or other
written notice from the Company to suspend sales to permit the Company to
correct or update a registration statement or prospectus until such Investor
receives copies of a supplemented or amended prospectus that corrects the
misstatement(s) or omission(s) referred to above and receives notice that any
post-effective amendment has become effective.

       (d)    The Company shall have no obligation to permit the holders of
Registrable Stock to dispose of their shares pursuant to an underwritten
offering.

                                     - 6 -
<PAGE>   7

       Section 2.4   Registration Expenses.

       The Company shall pay all registration expenses relating to the
registration statement under Section 2.1 including all registration and filing
fees, exchange listing fees, printing expenses, fees and disbursements of
counsel for the Company, state blue sky fees and expenses and the expense of any
special audits incident to or required by any such registration, but shall
exclude Selling Expenses. As used herein, the term "Selling Expenses" shall
mean, collectively, any selling commissions, brokerage fees and the fees and
expenses of counsel for each holder of Registrable Stock.

       Section 2.5   Indemnification.

       (a)    In the event any Prospective Seller sells shares of Registrable
Stock pursuant to any registration under the Securities Act pursuant to this
Agreement, the Company shall indemnify and hold harmless each Prospective
Seller, each underwriter (as defined in the Securities Act) and each controlling
person of any Prospective Seller or underwriter, if any (within the meaning of
the Securities Act), against any losses, claims, damages or liabilities, joint
or several (or actions in respect thereof), to which such Prospective Seller,
underwriter or controlling person may be subject under the Securities Act, under
any other statute or at common law, insofar as such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon (i)
any untrue statement (or alleged untrue statement) of any material fact
contained in any registration statement under which such securities were
registered under the Securities Act, any preliminary prospectus or final
prospectus contained therein, or any summary prospectus issued in connection
with any securities being registered, or any amendment or supplement thereto, or
any other document, (ii) any omission (or alleged omission) to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, or (iii) any violation by the Company of the Securities
Act or any blue sky law, or any rule or regulation promulgated under the
Securities Act or any blue sky law, or any other law, applicable to the Company
in connection with any such registration, qualification or compliance of any
shares of Registrable Stock, and shall reimburse each such Prospective Seller,
underwriter or controlling person for any legal or other expenses reasonably
incurred by such Prospective Seller, underwriter or controlling person in
connection with investigating or defending any such loss, claim, damage,
liability or action; provided, however, that the Company shall not be liable to
any Prospective Seller, underwriter or controlling person in any such case to
the extent that any such loss, claim, damage or liability arises out of or is
based upon any such untrue statement or omission made in such registration
statement, preliminary prospectus, summary prospectus, final prospectus, or
amendment or supplement thereto, or any other document, in reliance upon and in
conformity with written information furnished to the Company by such Prospective
Seller, underwriter or controlling person, respectively, specifically for use
therein. The indemnity provided for herein shall remain in full force and effect
regardless of any investigation made by or on behalf of such Prospective Seller,
underwriter or controlling person, and shall survive the transfer of such
securities by such Prospective Seller.

       (b)    The Company may require, as a condition to including any
Registrable Stock of a Prospective Seller in any registration statement filed
pursuant to Section 2.1 that the Company shall have received an undertaking
satisfactory to it from such Prospective Seller,

                                     - 7 -

<PAGE>   8

severally and not jointly, to indemnify and hold harmless (in the same manner
and to the same extent as set forth in Section 2.5(a)) the Company, each
director of the Company, each officer of the Company who shall sign such
registration statement and each other person, if any, who controls the Company
within the meaning of the Securities Act (except the indemnifying Prospective
Seller, if such indemnifying Prospective Seller so controls the Company), with
respect to (i) any untrue statement (or alleged untrue statement) of any
material fact contained in any registration statement under which such
securities were registered under the Securities Act, any preliminary prospectus
or final prospectus contained therein, or any summary prospectus issued in
connection with any securities being registered, or any amendment or supplement
thereto, or any other document, (ii) any omission (or alleged omission) to state
therein a material fact required to be stated therein or necessary to make the
statements therein not misleading, or (iii) any violation by the Prospective
Seller of the Securities Act or any blue sky law, or any rule or regulation
promulgated under the Securities Act or any blue sky law, or any other law,
applicable to the Company in connection with any such registration,
qualification or compliance of any shares of Registrable Stock, in each case if
such statement or omission was made in reliance on and in conformity with
written information furnished to the Company by such Prospective Seller
specifically for use in preparing any such registration statement, preliminary
prospectus, final prospectus, summary prospectus or amendment or supplement
thereto, or in making any such filing or representation. Each Prospective Seller
hereunder shall promptly provide such indemnification upon request. In no event
shall a Prospective Seller's obligation to indemnify any Person hereunder exceed
the net proceeds from the sale of the Prospective Seller's Registrable Stock
pursuant to the registration statement. The indemnity provided for herein shall
remain in full force and effect regardless of any investigation made by or on
behalf of the indemnified party and shall survive any transfer of the
Registrable Stock held by the indemnifying party.

       (c)    If the indemnification provided for in Section 2.5(a) or Section
2.5(b) above is unavailable to an indemnified party in respect of any losses,
claims, damages or liabilities referred to therein, then the indemnifying party,
in lieu of indemnifying such indemnified party thereunder, shall contribute to
the amount paid or payable by such indemnified party as a result of such losses,
claims, damages or liabilities, in such proportion as is appropriate to reflect
the relative fault of the indemnifying party on the one hand and of the
indemnified parties on the other in connection with the statements or omissions
or violations which resulted in such losses, claims, damages or liabilities, as
well as any other relevant equitable considerations. The relative fault of the
indemnifying party and of the indemnified parties shall be determined by
reference to, among other things, whether the untrue or alleged untrue statement
of a material fact or the omission to state a material fact relates to
information supplied by the indemnifying party or by the indemnified parties,
and the parties' relative intent, knowledge, access to information and
opportunity to correct or prevent such statement or omission.

       The Company and the Stockholders agree that it would not be just and
equitable if contribution pursuant to this Section 2.5(c) were determined by pro
rata allocation or by any other method of allocation which does not take into
account the equitable considerations referred to in the immediately preceding
paragraph. The amount paid or payable by an indemnified party as a result of
the losses, claims, damages and liabilities or actions in respect thereof
referred to in

                                     - 8 -
<PAGE>   9

the immediately preceding paragraph shall be deemed to include, subject to the
limitations set forth above, any legal or other expenses reasonably incurred by
such indemnified party in connection with investigating or defending any such
action or claim. Notwithstanding the provisions of this Section 2.5(c), no
Prospective Seller shall be required to contribute any amount in excess of the
net proceeds from the sale of the Prospective Seller's Registrable Stock in the
Offering. No person guilty of fraudulent misrepresentations (within the meaning
of Section 11(f) of the Securities Act) shall be entitled to contribution from
any person who was not guilty of such fraudulent misrepresentation. The Company
may require, as a condition to including any Registrable Stock of a Prospective
Seller in any registration statement filed pursuant to Section 2.1, that the
Company shall have received an undertaking satisfactory to it from such
Prospective Seller of such Registrable Stock, severally and not jointly, to
contribute to the amount paid or payable by an indemnified party hereunder as
and to the extent set forth in this Section 2.5(c), and each Prospective Seller
hereunder shall promptly provide such undertaking upon request.

       (d)    Promptly after receipt by an indemnified party under Section 2.5
(a) or Section 2.5(b) above of written notice of the commencement of any action,
such indemnified party promptly shall, if a claim in respect thereof is to be
made under such Section, notify the indemnifying party in writing of the
commencement thereof; but the omission so to notify the indemnifying party shall
relieve it from any liability which it may have had to any indemnified party
hereunder only to the extent that it has been prejudiced as a proximate result
of such failure. In case any such action shall be brought against any
indemnified party, and it shall notify promptly the indemnifying party of the
commencement thereof, the indemnifying party shall assume the defense thereof,
with counsel satisfactory to such indemnified party (such approval not to be
unreasonably withheld or delayed); provided, however, that, if the defendants in
any such action include both the indemnified party and the indemnifying party
and the indemnified party shall have reasonably concluded that there may be
legal defenses available to it and/or other indemnified parties which are
different from or additional to those available to the indemnifying party, the
indemnified party or parties shall have the right to select separate counsel to
assert such legal defenses (in which case the indemnifying party shall not have
the right to direct the defense of such action on behalf of the indemnified
party or parties), at the expense of the indemnifying party. Upon the assumption
by the indemnifying party of the defense of such action, and approval by the
indemnified party of counsel, the indemnifying party shall not be liable to such
indemnified party under this Section 2.5 for any legal or other expenses
subsequently incurred by such indemnified party in connection with the defense
thereof unless (i) the indemnifying party shall not have employed counsel
satisfactory to the indemnified party to represent the indemnified party within
a reasonable time, (ii) the indemnified party and its counsel do not actively
and vigorously pursue the defense of such action, or (iii) the indemnifying
party has authorized the employment of counsel for the indemnified party at the
expense of the indemnifying party.

       Section 2.6   Rule 144 Requirements.

       The Company shall undertake to make and keep publicly available, and
available to the holders of Registrable Stock, such information as is necessary
to enable the holders of Registrable Stock to make sales of Registrable Stock
pursuant to Rule 144 of the Securities Act. The Company shall furnish to any
holder of Registrable Stock, upon request, a written statement

                                     - 9 -

<PAGE>   10

executed by the Company as to the steps it has taken to comply with the current
public information requirements of Rule 144.

       Section 2.7   Rights Which May Be Granted to Other Persons.

       The Company shall not grant any Person registration rights which shall in
any way whatsoever impair the registration rights granted to the Investors in
this Agreement.

       Section 2.8   Transfer of Registration Rights.

       The registration rights of any Investor under this Agreement may be
transferred only to any Permitted Transferee or to any Person who acquires at
least fifty percent (50%) of such Investor's Registrable Stock (held as of the
date of the initial issuance of the Series D Preferred Stock).

       Section 2.9   Changes in Series D Preferred Stock or Common Stock.

       If, and as often as, there is any change in the Series D Preferred Stock
or Common Stock by way of a stock split, stock dividend, combination or
reclassification, or through a merger, consolidation, reorganization or
recapitalization, or by any other means, appropriate adjustment shall be made in
the provisions hereof so that the rights and privileges granted hereby shall
continue with respect to the Series D Preferred Stock or Common Stock as so
changed.

                                   ARTICLE III
                                  MISCELLANEOUS

       Section 3.1   Specific Performance.

       Inasmuch as the shares of the Company's Series D Preferred Stock cannot
be readily purchased or sold in the open market, irreparable damage would result
in the event that the provisions of this Agreement are not specifically
enforced. Therefore, the rights to, or obligations of, the parties hereto shall
be enforceable in a court of equity by a decree of specific performance and
appropriate injunctive relief may be applied for and granted in connection
therewith. Such remedies, and all other remedies provided for in this Agreement,
shall, however, be cumulative and not exclusive and shall be in addition to any
other remedies which any party may have under this Agreement or otherwise.

       Section 3.2   Term.

       Notwithstanding anything contained herein to the contrary, this Agreement
shall terminate, and all rights and obligations hereunder shall cease, upon the
written agreement of each of the then parties hereto.

                                     - 10 -
<PAGE>   11

       Section 3.3   Notices.

       All notices, offers, acceptances, requests and other communications
hereunder shall be in writing and shall be deemed to have been duly given if
delivered or mailed by certified or registered mail to the Stockholders at their
addresses on the Company records, and to the Company at the Company's principal
place of business. Any party hereto may change his or its address for notice by
giving notice thereof in the manner herein above provided.

       Section 3.4   Parties in Interest.

       All covenants and agreements contained in this Agreement, by or on behalf
of any of the parties executing this Agreement shall bind such parties, and
shall bind and inure to the benefit of the respective successors and permitted
assigns of the parties hereto whether so expressed or not; provided, however,
that the foregoing shall not in and of itself permit the assignment of the
rights and obligations hereunder or thereunder.

       Section 3.5   Governing Law.

       This Agreement shall be governed by and construed in accordance with the
internal laws of the State of Delaware, without giving effect to its conflicts
of laws provisions. The parties hereto agree and acknowledge that each party has
retained counsel in connection with the negotiation and preparation of this
Agreement and the other Transaction Documents, and that any rule of construction
to the effect that any ambiguities are to be resolved against the drafting party
shall not be employed in the interpretation of the foregoing agreements or any
amendment, schedule or exhibits thereto.

       Section 3.6   Entire Agreement.

       This Agreement and the other Transaction Documents, including all related
schedules and exhibits, constitute the entire understanding and agreement of the
parties hereto, and supersede all prior agreements and understandings, oral and
written, among the parties hereto with respect to the subject matter hereof and
thereof.

       Section 3.7   Counterparts.

       This Agreement may be executed in one or more counterparts, each of which
shall be deemed an original, but all of which together shall constitute one and
the same instrument.

       Section 3.8   Amendments.

       This Agreement may not be amended or modified, and no provisions hereof
may be waived, without the written consent of the Company and each of the
Investors.

       Section 3.9   Severability.

       Each provision of this Agreement shall be treated as a separate and
independent clause, and the unenforceability of any one clause shall in no way
impair the enforceability of any of the

                                     - 11 -
<PAGE>   12

other clauses herein. If one or more of the provisions contained in this
Agreement shall for any reason be held to be excessively broad as to scope,
activity, subject or otherwise so as to be unenforceable at law, such provision
or provisions shall be construed by the appropriate judicial body by limiting or
reducing it or them, so as to be enforceable to the maximum extent compatible
with the applicable law as it shall then appear.

       Section 3.10  Titles and Subtitles.

       The titles and subtitles used in this Agreement are for convenience only
and are not to be considered in construing or interpreting any term or provision
of this Agreement.

       Section 3.11  Pronouns.

       All pronouns used herein shall be deemed to refer to the masculine,
feminine or neuter gender as the context requires.

                    [Signatures Appear On The Following Page]

                                     - 12 -
<PAGE>   13

       IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the date first above written.

                                        S1 Corporation

                                        By: /s/ ROBERT F. STOCKWELL
                                           ------------------------------------
                                           Name: Robert F. Stockwell
                                                -------------------------------
                                           Title: Chief Financial Officer
                                                 ------------------------------

                   (Schedule 1 Appears on the Following Page)

                                     - 13 -
<PAGE>   14

                          SCHEDULE 1: SERIES D HOLDERS

<TABLE>
<S>                                             <C>
            100,000 Shares                      STATE FARM MUTUAL AUTOMOBILE INSURANCE COMPANY

                                                By: /s/ JIM RUTROUGH
                                                   ----------------------------
                                                   Name: Jim Rutrough
                                                        -----------------------
                                                   Title: Executive Vice-President
                                                         ----------------------

                                                By: /s/ ANN BAUGHAN
                                                   ----------------------------
                                                   Name: Ann Baughan
                                                        -----------------------
                                                   Title: Vice-President-EIS
                                                         ----------------------

             75,000 Shares                      ZG INVESTMENTS, LTD.

                                                By: /s/ MICHAEL R. DEEVY
                                                   ----------------------------
                                                   Name: Michael R. Deevy
                                                        -----------------------
                                                   Title: Director
                                                         ----------------------
</TABLE>

                            (continued on next page)

                         [Registration Rights Agreement]

                                     - 14 -
<PAGE>   15

<TABLE>
<S>                                             <C>
            37,500 Shares                       Allianz Capital Partners GmbH

                                                By: /s/
                                                   ----------------------------
                                                   Name:
                                                        -----------------------
                                                   Title:
                                                         ----------------------

                                                By: /s/
                                                   ----------------------------
                                                   Name:
                                                        -----------------------
                                                   Title:
                                                         ----------------------

            25,000 Shares                       Fleet Private Equity Co., Inc.

                                                By: /s/ H. JAY SARLES
                                                   ----------------------------
                                                   Name: H. Jay Sarles
                                                        -----------------------
                                                   Title: Director
                                                         ----------------------

            6,500 Shares                        J.P. Morgan Ventures Corporation

                                                By: /s/ GRACE B. VOGEL
                                                   ----------------------------
                                                   Name: Grace B. Vogel
                                                        -----------------------
                                                   Title: Controller
                                                         ----------------------
</TABLE>

                                     - 15 -

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