<PAGE>   1
                                                                    EXHIBIT 10.2

                            STOCK PURCHASE AGREEMENT*

                                 BY AND BETWEEN


                     SECURITY FIRST TECHNOLOGIES CORPORATION

                                       AND

                             HEWLETT-PACKARD COMPANY









                          DATED AS OF FEBRUARY 19, 1999




* AS AMENDED ON APRIL 30, 1999


<PAGE>   2



                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                    Page
                                                                                                    ----

<S>                                                                                                  <C>
SECTION 1. PURCHASE AND SALE OF THE SHARES.......................................................     1
           -------------------------------
      1.1  Sale and Issuance of the Shares.......................................................     1
           -------------------------------
      1.2  Closing...............................................................................     2
           -------
SECTION 2.  REGISTRATION RIGHTS..................................................................     2
            -------------------
      2.1  Demand Registration Rights............................................................     2
           --------------------------
      2.2  Registration Procedures...............................................................     3
           -----------------------
      2.3  Registration Expenses.................................................................     4
           ---------------------
      2.4  Indemnity and Contribution............................................................     4
           --------------------------
SECTION 3.  REPRESENTATIONS AND WARRANTIES OF THE CORPORATION....................................     6
            -------------------------------------------------
      3.1  Organization and Standing.............................................................     6
           -------------------------
      3.2  Authorization; Binding Obligation.....................................................     6
           ---------------------------------
      3.3  Capitalization........................................................................     7
           --------------
      3.4  Validity of Shares; Issuance..........................................................     7
           ----------------------------
      3.5  No Consents...........................................................................     7
           -----------
      3.6  Non-Contravention.....................................................................     7
           -----------------
      3.7  Additional Information................................................................     8
           ----------------------
SECTION 4.  REPRESENTATIONS AND WARRANTIES OF
            ---------------------------------
      PURCHASER..................................................................................     8
      ---------
      4.1  Organization and Standing.............................................................     8
           -------------------------
      4.2  Authorization.........................................................................     8
           -------------
      4.3  Non-Contravention.....................................................................     8
           -----------------
      4.4  No Consents...........................................................................     9
           -----------
      4.5  Adequate Resources....................................................................     9
           ------------------
      4.6  Investment Experience.................................................................     9
           ---------------------
      4.7  Investment Intent.....................................................................     9
           -----------------
      4.8  Registration or Exemption Requirements................................................    10
           --------------------------------------
      4.9  No Legal, Tax or Investment Advice....................................................    10
           ----------------------------------
SECTION 5.  ADDITIONAL AGREEMENTS................................................................    10
            ---------------------
      5.1  Nonsolicitation.......................................................................    10
           ---------------
      5.2  Lock-up Covenant......................................................................    10
           ----------------
SECTION 6.  CONDITIONS TO CLOSING................................................................    11
            ---------------------
      6.1  Conditions to Obligations of All Parties..............................................    11
           ----------------------------------------
      6.2  Conditions to Obligations of Purchaser................................................    11
           --------------------------------------
      6.3  Conditions to Obligations of the Corporation..........................................    12
           --------------------------------------------
SECTION 7.  CLOSING..............................................................................    12
            -------
      7.1  Deliveries by the Corporation.........................................................    12
           -----------------------------
      7.2  Deliveries by the Purchaser...........................................................    13
           ---------------------------
SECTION 8.  LEGEND...............................................................................    13
            ------
      8.1  Endorsement...........................................................................    13
           -----------
      8.2  Removal of Legend.....................................................................    14
           -----------------
</TABLE>


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<TABLE>
<S>                                                                                                  <C>
SECTION 9.  TERMINATION..........................................................................    14
            -----------
      9.1  Mutual Consent........................................................................    14
           --------------
      9.2  Other Termination.....................................................................    14
           -----------------
      9.3  Effect of Termination.................................................................    15
           ---------------------
SECTION 10.  MISCELLANEOUS.......................................................................    15
             -------------
      10.1  Additional Actions and Documents.....................................................    15
            --------------------------------
      10.2  Expenses.............................................................................    15
            --------
      10.3  Notices..............................................................................    15
            -------
      10.4  Waiver...............................................................................    16
            ------
      10.5  Binding Effect.......................................................................    17
            --------------
      10.6  Entire Agreement; Amendment..........................................................    17
            ---------------------------
      10.7  Severability.........................................................................    17
            ------------
      10.8  Headings.............................................................................    17
            --------
      10.9  Governing Law........................................................................    17
            -------------
      10.10  Signature in Counterparts...........................................................    17
             -------------------------
      10.11  No Third Party Beneficiaries........................................................    17
             ----------------------------
      10.12  Assignability.......................................................................    18
             -------------
      10.13  Parties Not Partners................................................................    18
             --------------------
</TABLE>
<PAGE>   4


                            STOCK PURCHASE AGREEMENT

     This Stock Purchase Agreement ("Agreement"), dated as of the 19th day of
February, 1999, is entered into by and among Security First Technologies
Corporation, a Delaware corporation (the "Corporation") and Hewlett-Packard
Company, a Delaware corporation ("Purchaser").

     WHEREAS, concurrent with, and as an inducement to the parties entering into
this Agreement, the Corporation and Purchaser are entering into a Memorandum of
Understanding (the "MOU") pursuant to which the Corporation and Purchaser intend
to develop a strategic relationship;

     WHEREAS, as part of the aforementioned strategic relationship, Purchaser 
also desires to subscribe for, and acquire from the Corporation, such number of
shares (the "Shares") of the Corporation's common stock, par value $.01 per
share ("Common Stock"), as determined by dividing the Purchase Price (as defined
below in Section 1.1(a)) by the applicable per share price of the Shares (as
described below in Section 1.1), on the terms and under the conditions specified
herein;

     WHEREAS, the Corporation desires to sell and issue to Purchaser the Shares 
on the terms and under the conditions specified herein; and

     *

     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.

          1.1.    At the Closing (as defined below in Section 1.2(a)) and 
subject to the terms and conditions of this Agreement, Purchaser hereby
subscribes for, and agrees to purchase, the Shares, and the Corporation agrees
to sell and issue to Purchaser at the Closing for the Purchase Price, the
Shares. The aggregate purchase price to be paid by Purchaser shall be
$10,000,000 (such aggregate amount, the "Purchase Price"), and the number of
Shares shall be determined by dividing the Purchase Price by the average closing
asking price per share of the Common Stock, as quoted on the Nasdaq Stock Market
National Market Tier, for each of the 10 trading days preceding the business day
immediately before the Closing Date (as defined in Section 1.2(a) below), and
rounding down to the nearest whole share, if the quotient would otherwise
produce fractional shares. The number of Shares shall then be doubled so as to
give effect to the Split as if the Split had been paid immediately prior to the
Closing.

*  Recital deleted.
<PAGE>   5

     1.2  Closing.

               1.2(a).  The closing (the "Closing") of the transaction shall 
take place on April 30, 1999, or such other date not later than May 15, 1999 as
the parties hereto shall mutually agree (the "Closing Date").

               1.2(b).  The Closing shall take place on the Closing Date at
10:00 a.m., Washington, D.C. 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.

SECTION 2.  REGISTRATION RIGHTS.

     2.1  Demand Registration Rights.

               2.1(a).  At any time between the respective dates 18 months after
the Closing Date (or such earlier date upon which the covenant at Section 5.2 
below terminates) and two years after the Closing Date, Purchaser may request
registration for sale under the Securities Act of any Common Stock owned by
Purchaser (a "Demand Registration"), provided, however, that (i) the Corporation
shall only be obligated to effect one Demand Registration for Purchaser, and
(ii) the Corporation shall not be obligated to effect a Demand Registration
unless Purchaser requests registration for sale of Common Stock that represents
at least 50% of the aggregate amount of Common Stock then owned by Purchaser. A
Demand Registration shall specify the approximate number of shares of Common
Stock that Purchaser requests be registered and the anticipated per share price
range for such offering.

               2.1(b).  A Demand Registration shall be deemed to occur when such
registration becomes effective under the Securities Act, except that if, after
it becomes effective, such Demand Registration is interfered with by any stop
order, injunction or other order or requirement of the SEC (or any successor
regulator thereto as to federal securities laws) or any other governmental
authority, such registration shall not be deemed to have been effected unless
such stop order, injunction or other order shall have been subsequently vacated
or removed.

     2.2  Registration Procedures.

               2.2(a).  The Corporation shall have no obligation to include 
Common Stock owned by Purchaser in a registration statement unless and until 
Purchaser has furnished the Corporation with all information and statements 
about or pertaining to Purchaser in such reasonable detail and on such timely 
basis as is reasonably deemed by the Corporation to be necessary or appropriate 
for the preparation of the registration statement.
<PAGE>   6
          2.2(b).  Whenever Purchaser has requested that its Common Stock be
registered pursuant to Section 2.1 hereof, the Corporation shall, subject to the
provisions of Section 2.1 and Section 2.2:

                    (1)  prepare and file with the SEC a registration statement 
with respect to such Common Stock covered by the Demand Registration and use its
reasonable efforts to cause such registration statement to become effective as
soon as practicable after the filing thereof (provided that before filing a
registration statement or prospectus or any amendments or supplements thereto,
the Corporation shall furnish counsel for Purchaser with copies of all such
documents proposed to be filed);

                    (2)  prepare and file with the SEC such amendments and
supplements to such registration statement and prospectus contained therein as
may be necessary to keep such registration statement effective for a period of
not less than three months or until Purchaser has completed the distribution
described in such registration statement, whichever occurs first;

                    (3)  furnish to Purchaser the number of copies of such
registration statement, each amendment and supplement thereto, the prospectus
contained in such registration statement (including each preliminary
prospectus), and such other documents as Purchaser may reasonably request;

                    (4)  if required by applicable law, use reasonable efforts 
to register or qualify such shares under the state blue sky or securities laws
("Blue Sky Laws") of such jurisdictions as Purchaser reasonably requests (and to
keep such registrations and qualifications effective for a period of three
months, or until Purchaser has completed the distribution of such shares,
whichever occurs first), and to do any and all other acts and things that may be
reasonably necessary or advisable to enable Purchaser to consummate the
disposition of such shares in such jurisdictions; provided, however, that the
Corporation will not be required to do any of the following: (i) qualify
generally to do business in any jurisdiction where it would not be required but
for this Section 2.2(b), (ii) subject itself to taxation in any such
jurisdiction, or (iii) file any general consent to service of process in any
such jurisdiction;

                    (5)  promptly notify Purchaser at any time when a prospectus
relating thereto is required to be delivered under applicable federal securities
laws during the period that the Corporation is required to keep the registration
statement effective, of the occurrence of any event as a result of which the
prospectus included in such registration statement contains an untrue statement
of a material fact or omits any fact necessary to make the statements therein,
in the light of the circumstances under which they were made, not misleading,
and prepare a supplement or amendment to the prospectus so that, as thereafter
delivered to the purchasers of such shares, the prospectus will not contain an
untrue statement of a material fact or omit to state any fact necessary to make
the statements therein, in the light of the circumstances under which they were
made, not misleading; and

                    (6)  use reasonable efforts to cause all such shares of 
Common Stock to be listed on the Nasdaq Stock Market National Market Tier (or 
such other securities exchange on which the Common Stock is then listed).

     2.3  Registration Expenses.

          2.3(a).  If, pursuant to Section 2.1 hereof, Common Stock owned by
Purchaser is included in a registration statement, then Purchaser shall pay all
transfer taxes, if any, relating to the sale of its Common Stock, the fees and
expenses of its own counsel, and its pro rata portion of any underwriting
discounts or commissions or the equivalent thereof.

<PAGE>   7

          2.3(b).  Except for the fees and expenses specified in Section 2.3(a) 
hereof and except as provided below in this Section 2.3(b), the Corporation 
shall pay all expenses incident to the registration and to the Corporation's 
performance of or compliance with this Agreement, including, without limitation,
all registration and filing fees, fees and expenses of compliance, with Blue Sky
Laws, printing expenses, messenger and delivery expenses, and fees and expenses
of counsel for the Corporation and all independent certified public accountants
and other persons retained by the Corporation. With respect to any registration
pursuant to Section 2.3 hereof, the Corporation shall pay its internal expenses
(including, without limitation, all salaries and expenses of its officers and
employees performing legal or accounting duties) and the expenses and fees for
listing the securities to be registered on the Nasdaq Stock Market National
Market Tier, if applicable.

     2.4  Indemnity and Contribution.

          2.4(a).  In the event that any Common Stock owned by Purchaser is sold
by means of a registration statement pursuant to Section 2.1 hereof, Purchaser 
(for the purposes of this paragraph 2.4(a), the "Indemnifying Person") agrees to
indemnify and hold harmless the Corporation, each of the Corporation's officers
and directors, and each person, if any, who controls or may control the
Corporation within the meaning of the Securities Act (for the purposes of this
paragraph 2.4(a), the Corporation, its officers and directors, and any such
other persons being hereinafter referred to individually as an "Indemnified
Person" and collectively as "Indemnified Persons") from and against all demands,
claims, actions or causes of action, assessments, losses, damages, liabilities,
costs, and expenses, including, without limitation, interest, penalties, and
reasonable attorneys' fees and disbursements, asserted against, resulting to,
imposed upon, or incurred by such Indemnified Person, directly or indirectly
(collectively, hereinafter referred to in the singular as a "Claim" and in the
plural as "Claims"), based upon, arising out of, or resulting from (i) any
untrue statement of a material fact contained in the registration statement or
any omission to state therein a material fact necessary in order to make the
statements made therein not misleading, or (ii) any untrue statement of a
material fact contained in the prospectus, or any supplement or amendment
thereto, or any omission to state therein a material fact necessary in order to
make the statements made therein, in the light of the circumstances under which
they were made, not misleading, to the extent that such Claim is based upon,
arises out of or results from information furnished to the Corporation by
Purchaser for use in connection with the registration statement.

          2.4(b).  The Corporation (for the purposes of this paragraph 2.4(b), 
the "Indemnifying Person") agrees to indemnify and hold harmless Purchaser, its
officers and directors, each person, if any, who controls or may control
Purchaser within the meaning of the Securities Act (for the purposes of this
paragraph 2.4(b), Purchaser, its officers and directors, and any such other
persons also being hereinafter referred to individually as an "Indemnified
Person" and collectively as "Indemnified Persons") from and against all Claims
based upon, arising out of, or resulting from (i) any untrue statement of a
material fact contained in the registration statement or any omission to state
therein a material fact necessary in order to make the statement made therein
not misleading, or (ii) any untrue statement of a material fact contained in the
prospectus, or any supplement or amendment thereto, or any omission to state
therein a material fact necessary in order to make the statements made therein,
in the light of the circumstances under which they were made, not misleading, to
the extent that such Claim is based upon, arises out of or results from
information furnished by the Corporation in the registration statement.

          2.4(c).  The indemnification set forth herein shall be in addition to 
any liability the Corporation or Purchaser may otherwise have in connection with
any registration of such Common Stock. Within a reasonable time after receiving
definitive notice of any Claim in respect of which an Indemnified Person may
seek indemnification under this Section 2.4, such Indemnified Person shall
submit written notice thereof to Indemnifying Person. The failure of the
Indemnified Person so to notify the Indemnifying Person of any such Claim shall
not relieve the Indemnifying Person from 

<PAGE>   8

any liability it may have hereunder except to the extent that (a) such liability
was caused or increased by such failure, or (b) the ability of the Indemnifying
Person to reduce such liability was materially adversely affected by such
failure. In addition, the failure of the Indemnified Person to so notify the
Indemnifying Person of any such Claim shall not relieve the Indemnifying Person
from any liability it may have otherwise than hereunder. The Indemnifying Person
shall have the right to undertake, by counsel or representatives of its own
choosing, the defense, compromise, or settlement (without admitting liability of
the Indemnifying Person or the Indemnified Person) of any such Claim asserted,
such defense, compromise, or settlement to be undertaken at the expense and risk
of the Indemnifying Person, and the Indemnified Person shall have the right to
engage separate counsel, at its own expense, which counsel for the Indemnifying
Person shall keep informed and consult with in a reasonable manner. In the event
the Indemnifying Person shall fail to undertake such defense by its own
representatives, the Indemnifying Person shall give prompt written notice of
such election to the Indemnified Person, and the Indemnified Person shall
undertake the defense, compromise, or settlement (without admitting liability of
the Indemnified Person or the Indemnifying Person) thereof on behalf of and for
the account and risk of the Indemnifying Person by counsel or other
representatives designated by the Indemnified Person. In the event that any
Claim shall arise out of a transaction or cover any period or periods wherein
the Corporation and Purchaser shall each be liable hereunder for part of the
liability or obligation arising therefrom, then the parties shall, each choosing
its own counsel and bearing its own expenses, defend such Claim, and no
settlement or compromise of such Claim may be made without the joint consent or
approval of the Corporation and Purchaser. Notwithstanding the foregoing, no
Indemnifying Person shall be obligated hereunder with respect to amounts paid in
settlement of any Claim if such settlement is effected without the consent of
such Indemnifying Person (which consent shall not be unreasonably withheld).

SECTION 3.  REPRESENTATIONS AND WARRANTIES OF THE CORPORATION.

          The Corporation represents and warrants to Purchaser as follows:

     3.1  Organization and Standing.

          The Corporation is a corporation duly incorporated, validly existing 
and in good standing under the laws of the State of Delaware, 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 holds all
licenses and permits required for the conduct of its business as now conducted
which, if not in the Corporation's possession, could have a material adverse
effect on the Corporation's financial condition or results of operations, taken
as a whole. The Corporation 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 the
Corporation's financial condition or results of operations, taken as a whole.

     3.2  Authorization; Binding Obligation.

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

<PAGE>   9
     3.3  Capitalization.

          The authorized capital stock of the Corporation consists of 60,000,000
shares of Common Stock, of which 12,263,502 are issued and outstanding as of
December 31, 1998, and 5,000,000 shares of preferred stock, of which 636,464 of
the 1,637,832 shares designated Series A Preferred Stock are issued and
outstanding as December 31, 1998 and of which all of the 749,064 Shares
designated Series B Redeemable Convertible Preferred Stock are issued and
outstanding as of December 31, 1998. All of the Corporation's outstanding shares
of capital stock were validly issued and are fully paid and nonassessable. As of
December 31, 1998, except for (i) 4,399,635 shares subject to issuance upon
exercise of options and an additional 806,918 reserved for issuance pursuant to
options not yet granted, and (ii) shares reserved for issuance upon conversion
of the Series A Preferred Stock and the Series B Preferred Stock, 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.

     3.4  Validity of Shares; Issuance.

          The Shares, when issued in compliance with the provisions of this
Agreement will be validly issued, fully paid and nonassessable, and free of any
liens or encumbrances, and will be issued in compliance with all applicable
federal banking laws.

     3.5  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 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 have a material adverse effect on the Corporation's financial
condition or results of operations or business prospects, taken as a whole.

     3.6  Non-Contravention.

          The execution, delivery and performance of, and compliance with, this
Agreement will not (a) violate any provision of the articles of incorporation or
bylaws of the Corporation; (b) conflict with or result in a breach of, or
default under, or result in the creation of any lien, claim, charge or other
encumbrance upon any of the assets or properties of the Corporation pursuant to
the provisions of any material agreement, mortgage, indenture or other document
or instrument to which the Corporation is a party or by which the Corporation 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 the
Corporation or any of its properties or assets, or applicable to the
Corporation's power or authority to perform its obligations under this
Agreement.

     3.7  Additional Information.

          The information contained in the Corporation's registration statement
on Form 8-A, as filed with the SEC on September 30, 1998, and all other reports
filed subsequent thereto through the Closing Date pursuant to Section 13(a) or
15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"),
did not and will not, as the case may be, at the respective dates of filing with
the SEC, contain any untrue statement of a material fact or omit to state a
material fact 

<PAGE>   10
necessary in order to make the statements therein, in light of the circumstances
under which they were made, not misleading.

SECTION 4.  REPRESENTATIONS AND WARRANTIES OF PURCHASER.

               Purchaser represents and warrants to the Corporation as follows:

          4.1  Organization and Standing.

               Purchaser is a corporation duly organized, validly existing and
in good standing under the laws of the State of Delaware. 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, could have a material adverse effect on
Purchaser's financial condition or results of operations, taken as a whole.
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's financial condition or
results of operations, taken as a whole.

          4.2  Authorization.

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

          4.3  Non-Contravention.

               The execution, delivery and performance of, and compliance with,
this Agreement will not (a) violate any provision of the articles of
incorporation or bylaws of Purchaser; (b) conflict with or result in a breach
of, or default 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, or applicable to Purchaser's power or
authority to perform its obligations under this Agreement.

          4.4  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,

<PAGE>   11

approvals or authorizations or to make such filings would not have a material 
adverse effect on Purchaser's financial condition or results of operations 
or business prospects, taken as a whole.  

     4.5  Adequate Resources.

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

     4.6  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 offered or sold to
Purchaser by any form of general solicitation or advertising.

     4.7  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 its acquisition of the
Shares has not been 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.

     4.8  Registration or Exemption Requirements.

          Purchaser further 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.

     4.9  No Legal, Tax or Investment Advice.

          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.

<PAGE>   12

SECTION 5.  ADDITIONAL AGREEMENTS.

     5.1  Nonsolicitation.

          From the date hereof through and including until 18 months after the
Closing Date (or such earlier date upon which the covenant at Section 5.2 below
terminates), each party hereto agrees that such party's employees who are
involved in the transactions described in the MOU will not, without the other
party's prior written consent solicit for employment any person who is involved
in the transactions described in the MOU as an employee of the other party (it
being understood that this Section 5.1 shall not prohibit the placing of general
employment advertisements or solicitations not specifically targeted to any
employee or employees of the other party);

     5.2  Lock-up Covenant.

          During the period beginning on the date hereof and ending on the date
18 months after the Closing Date (or such earlier date described below),
Purchaser covenants that it will not, without the prior written consent of the
Corporation, offer, sell or otherwise dispose of, directly or indirectly, any
capital stock of the Corporation which Purchaser may own directly, indirectly or
beneficially; provided, however, that Purchaser may transfer some or all of the
Shares to a corporation, partnership or other legal entity controlled by
Purchaser, if such transferee agrees in writing to hold any Shares received
subject to the provisions of this Agreement and to transfer such Shares back to
Purchaser if such transferee ceases to be controlled by Purchaser. The
restrictions on transfer described in this Section 5.2 will terminate in the
event (i) the Corporation breaches either of Sections I(A) or (B) in the MOU or
any successor provisions thereto specifically identified as such in any other
agreement between the Corporation and the Purchaser entered into subsequent to
this Agreement, and (ii) such breach is not cured in accordance with the terms
of the MOU or such subsequent agreement.

SECTION 6.  CONDITIONS TO CLOSING.

     6.1  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:

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

          6.1(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 or to affect adversely the financial condition and business
prospects of the Corporation.

     6.2  Conditions to the Obligations of Purchaser.

          The obligations of 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 Purchaser, in its sole and absolute discretion:

<PAGE>   13

          6.2(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 on
the date of the Closing, with the same force and effect as if made on the date 
of the Closing.

          6.2(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.

          6.2(c).  Legal Opinion. The Corporation shall have delivered to the 
Purchaser an opinion of counsel to the Corporation regarding due authorization 
of the Shares by the Corporation and valid issuance of the Shares.

     6.3  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:

          6.3(a).  Representations and Warranties. The representations and 
warranties of Purchaser 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.

          6.3(b).  Compliance with Covenants. 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 it on
or prior to the date of the Closing.

SECTION 7.  CLOSING.

     7.1  Deliveries by the Corporation.

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

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

               (2)  A copy of the resolutions of the Board of Directors of the
Corporation, as certified as of the Closing Date by the Secretary of the 
Corporation, as being true, correct and complete and then in full force and 
effect, authorizing the execution, delivery and performance of this 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 are 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.

<PAGE>   14

               (4)  An opinion of counsel as described in Section 6.2(c) above.

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

     7.2  Deliveries by Purchaser.

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

               (1)  The Purchase Price, in cash or by wire transfer or certified
or bank cashier's check, payable to the order of the Corporation.

               (2)  A certificate of Purchaser signed by an authorized officer
of Purchaser certifying that the representations and warranties of Purchaser
made herein are 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 Purchaser has in all material respects performed all obligations and
agreements and complied with all covenants required to be performed or complied
with by 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 8.  LEGEND.

     8.1  Endorsement.

          Each certificate representing the Shares shall bear the following
legend (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 SPECIFIED IN THE STOCK
     PURCHASE AGREEMENT DATED FEBRUARY _, 1999 (THE "AGREEMENT") BETWEEN THE
     CORPORATION AND THE ORIGINAL PURCHASER, AND NO TRANSFER OF SHARES SHALL BE
     VALID OR EFFECTIVE ABSENT COMPLIANCE WITH SUCH RESTRICTIONS. ALL SUBSEQUENT
     HOLDERS OF THIS CERTIFICATE WILL HAVE AGREED TO BE BOUND BY CERTAIN OF THE
     TERMS OF THE AGREEMENT, INCLUDING SECTION 5.2 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.

<PAGE>   15
     8.2  Removal of Legend.

          The legend endorsed on a stock certificate pursuant to Section 8.1 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 8.1
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 9.  TERMINATION.

     9.1  Mutual Consent.

          The parties may terminate this Agreement at any time by mutual written
agreement.

     9.2  Other Termination.

          The Corporation or the Purchaser may terminate this Agreement by
giving notice (a "Termination Notice") to the other parties at the time
designated in this Section or, in the absence of such designation, at any time
up to and including the date of the Closing, if any one or more of the following
shall have occurred and be continuing:

          9.2(a).  Termination By Any Party. Any party may terminate this
Agreement under any one or more of the following circumstances:

                   (1)  at any time after May 16, 1999, or, if the Corporation
shall have extended the Closing Date pursuant to Section 1.2(a) of this
Agreement, after July 16, 1999, if the Closing shall not have occurred for any
reason other than a default or non-performance of its obligations hereunder by
the party giving such notice;

                   (2)  a court or other governmental authority of competent
jurisdiction shall have issued an order, writ, injunction or decree or shall
have taken any other action permanently restraining or otherwise prohibiting the
purchase of the Shares contemplated hereby and such order, writ, injunction,
decree or other action shall have become final and nonappealable.

          9.2(b).  Termination By Purchaser. Purchaser may terminate this
Agreement on the Closing Date, if any condition precedent set forth in Sections
6.1 or 6.2 shall not have been satisfied.

          9.2(c).  Termination By the Corporation. The Corporation may terminate
this Agreement on the Closing Date, if any condition precedent set forth in
Sections 6.1 or 6.3 shall not have been satisfied.

     9.3  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.

<PAGE>   16
Notwithstanding the foregoing, no party hereto shall be liable for consequential
or punitive damages in connection with such termination.

SECTION 10.  MISCELLANEOUS.

     10.1 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.

     10.2 Expenses.

          Except as specified in Section 2, 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.

     10.3 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:

          Security First Technologies Corporation
          3390 Peachtree Road, NE, Suite 1700
          Atlanta, Georgia  30326
          Attn.:  President

          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.

          (iii)  if to Purchaser:

          Hewlett-Packard Company
          Enterprise Computing Solutions Organization
          19447 Pruneridge Avenue
          Mail Stop 44UH
          Cupertino, California 95014-0683
          Attn.:  Controller

<PAGE>   17
               with a copy (which shall not constitute notice) to:

               Hewlett-Packard Company
               3000 Hanover Street, MS 20BQ
               Palo Alto, California 94304
               Attn.: General Counsel

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.

     10.4 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 to so comply by such other party. No
waiver shall be valid unless in writing signed by the party to be charged and
only to the extent therein set forth.

     10.5 Binding Effect.

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

     10.6 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.

     10.7 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.

     10.8 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 thereof.

     10.9 Governing Law.

<PAGE>   18
               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.

     10.10     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.

     10.11     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.

     10.12     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 Purchaser may assign this Agreement, including rights, 
privileges, duties and obligations hereunder to any affiliate of Purchaser which
is wholly or substantially owned directly or indirectly by Purchaser so long as 
such assignment does not in any way materially delay or otherwise materially
adversely impact the ability of the parties hereto to effect the transactions
contemplated hereby.

     10.13     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


                            [SIGNATURE PAGE FOLLOWS]

<PAGE>   19
               IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to be duly executed and delivered as of the date first above written.

                               SECURITY FIRST TECHNOLOGIES CORPORATION


                               By:       /s/ Robert F. Stockwell
                                  ----------------------------------------------
                                   Name:     Robert F. Stockwell
                                        ----------------------------------------
                                   Title:    Treasurer
                                         ---------------------------------------

                               HEWLETT-PACKARD COMPANY



                               By:         /s/ Jon E. Flaxman
                                  ---------------------------------------
                                   Name:       Jon E. Flaxman
                                        ---------------------------------
                                   Title:      ECSO Controller
                                         --------------------------------