Document:

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                                                                    Exhibit 10.1
                                                                    ------------

                                  ENTRUST, INC.

                            Option Exchange Agreement
                                    Revised

     THIS AGREEMENT is made this 21st day of February, 2002, between Entrust,
Inc., a Maryland corporation (the "Company"), and F. William Conner (the
"Participant").

     WHEREAS the Company executed a Stock Option Agreement dated May 5, 1999
evidencing the grant by the Company to the Participant on such date of an option
to purchase 13,000 shares of common stock, $0.01 par value per share, of the
Company (the "Common Stock"), at a purchase price of $22.875 per share under the
Company's Amended and Restated 1996 Stock Incentive Plan, as amended (the
"Plan"), and a Stock Option Agreement dated April 27, 2000 evidencing the grant
by the Company to the Participant on such date of an option to purchase 8,000
shares of Common Stock at a purchase price of $45.125 per share under the Plan
(together, such agreements, the "Option Agreements, " and together, such
options, the "Options").

     For valuable consideration, receipt of which is acknowledged, the parties
hereto agree as follows:

     1. Exchange of Options for Cash. The Participant hereby surrenders to the
        -----------------------------
Company all of his right, title and interest in, to and under the Option
Agreements and the Options, in each case, effective as of the date hereof. In
consideration of the Participant's surrender of the Options in accordance with
the immediately preceding sentence, the Company hereby pays to the Participant
the sum of $1.00 in cash.

     2. Binding Effect. This Agreement shall be binding upon and inure to the
        --------------
benefit of the Company and the Participant and their respective heirs,
executors, administrators, legal representatives, successors and assigns.

     3. Entire Agreement. This Agreement and the Plan constitute the entire
        ----------------
agreement between the parties, and supersedes all prior agreements and
understandings, relating to the subject matter of this Agreement, including but
not limited to, the Option Agreements. This Agreement may be amended or modified
only by a written instrument executed by both the Company and the Participant.

     4. Governing Law. This Agreement shall be construed, interpreted and
        -------------
enforced in accordance with the internal laws of the State of Maryland without
regard to any applicable conflicts of laws.

     5. Participant's Acknowledgments. The Participant acknowledges that he or
        -----------------------------
she: (i) has read this Agreement; (ii) has been represented in the preparation,
negotiation and execution of this Agreement by legal counsel of the
Participant's own choice or has voluntarily declined to seek such counsel; (iii)
understands the terms and consequences of this Agreement; (iv) is fully aware of
the legal and binding effect of this Agreement; and (v) understands that the law
firm of Hale and Dorr LLP is acting as counsel to the Company in connection with
the transactions contemplated by the Agreement, and is not acting as counsel for
the Participant.

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

                                               ENTRUST, INC.

                                               By: /s/ David L. Thompson
                                                   -----------------------------
                                                   David L. Thompson
                                                   Senior Vice President and CFO

                                                   Address: Entrust, Inc.
                                                            One Hanover Park
                                                            16633 Dallas Parkway
                                                            Suite 800
                                                            Addison, Texas 75001

                                                   /s/ F. William Conner
                                                   -----------------------------
                                                   F. William Conner

                                                   Address: 6130 Tulip Lane
                                                            Dallas, Texas 75230<PAGE>

                                                                    Exhibit 10.2
                                                                    ------------

                                  ENTRUST, INC.

                           Restricted Stock Agreement
    Granted Under Amended and Restated 1996 Stock Incentive Plan, as amended
    ------------------------------------------------------------------------

     AGREEMENT made this 21st day of February 2002, between Entrust, Inc., a
Maryland corporation (the "Company"), and David L. Thompson (the "Participant").

     Reference is hereby made to that certain Stock Option Agreement dated
October 11, 1999 evidencing the grant by the Company to the Participant on such
date of an option to purchase 200,000 shares of common stock, $0.01 par value
per share, of the Company (the "Common Stock"), at a purchase price of $19.25
per share under the Company's Amended and Restated 1996 Stock Incentive Plan, as
amended (the "Plan"), and that certain Stock Option Agreement dated May 15, 2000
evidencing the grant by the Company to the Participant on such date of an option
to purchase 25,000 shares of Common Stock at a purchase price of $47.50 per
share under the Plan (together, such agreements, the "Option Agreements, " and
together, such options, the "Options").

     For valuable consideration, receipt of which is acknowledged, the parties
hereto agree as follows:

     1. Exchange of Options for Shares.
        ------------------------------

          (a) The Participant hereby surrenders to the Company all of his right,
title and interest in, to and under the Option Agreements and the Options, in
each case, effective as of the date hereof.

          (b) In consideration of the Participant's surrender of the Options
pursuant to subsection (a) above, the Company hereby issues and sells to the
Participant, and the Participant hereby accepts and purchases from the Company,
subject to the terms and conditions set forth in this Agreement and in the Plan,
an aggregate of 12,500 shares of Common Stock (the "Shares"). The Participant
agrees that 50% of the Shares shall be subject to the purchase option set forth
in Section 2 of this Agreement and the restrictions on transfer set forth in
Section 4 of this Agreement.

                                        1

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     2. Purchase Option.
        ---------------

          (a) In the event that the Participant ceases to be employed by the
Company for any reason or no reason, with or without cause, prior to the 90th
day following the date hereof (such 90th day, the "Vesting Date"), the Company
shall have the right and option (the "Purchase Option") to purchase from the
Participant, for a per share purchase price equal to the closing price per share
of the Common Stock as reported on The Nasdaq National Market on the date hereof
(the "Option Price"), some or all of the Unvested Shares. "Unvested Shares"
means (i) 6,250 Shares from the date hereof until the calendar day immediately
prior to the Vesting Date and (ii) no Shares on or after the Vesting Date.

          (b) For purposes of this Agreement, employment with the Company shall
include employment with a parent or subsidiary of the Company.

     3. Exercise of Purchase Option and Closing.
        ---------------------------------------

          (a) The Company may exercise the Purchase Option by delivering or
mailing to the Participant (or his estate), within 10 days after the termination
of the employment of the Participant with the Company, a written notice of
exercise of the Purchase Option. Such notice shall specify the number of Shares
to be purchased. If and to the extent the Purchase Option is not so exercised by
the giving of such a notice within such 10-day period, the Purchase Option shall
automatically expire and terminate effective upon the expiration of such 10-day
period.

          (b) Within five days after delivery to the Participant of the
Company's notice of the exercise of the Purchase Option pursuant to subsection
(a) above, the Participant (or his estate) shall, pursuant to the provisions of
the Joint Escrow Instructions referred to in Section 5 below, tender to the
Company at its principal offices the certificate or certificates representing
the Shares which the Company has elected to purchase in accordance with the
terms of this Agreement, duly endorsed in blank or with duly endorsed stock
powers attached thereto, all in form suitable for the transfer of such Shares to
the Company. Promptly following its receipt of such certificate or certificates,
the Company shall pay to the Participant the aggregate Option Price for such
Shares (provided that any delay in making such payment shall not invalidate the
Company's exercise of the Purchase Option with respect to such Shares).

          (c) After the time at which any Shares are required to be delivered to
the Company for transfer to the Company pursuant to subsection (b) above, the
Company shall not pay any dividend to the Participant on account of such Shares
or permit the Participant to exercise any of the privileges or rights of a
stockholder with respect to such Shares, but shall, in so far as permitted by
law, treat the Company as the owner of such Shares.

          (d) The Option Price may be payable, at the option of the Company, in
cancellation of all or a portion of any outstanding indebtedness of the
Participant to the Company or in cash (by check) or both.

          (e) The Company shall not purchase any fraction of a Share upon
exercise of the Purchase Option.

          (f) The Company may assign its Purchase Option to one or more persons
or entities.

     4. Restrictions on Transfer.
        ------------------------

     The Participant shall not sell, assign, transfer, pledge, hypothecate or
otherwise dispose of, by operation of law or otherwise (collectively "transfer")
any Shares, or any interest therein, that are subject to the Purchase Option.

                                        2

<PAGE>

     5. Escrow.
        ------

     The Participant shall, upon the execution of this Agreement, execute Joint
Escrow Instructions in the form attached to this Agreement as Exhibit A. The
                                                              ---------
Joint Escrow Instructions shall be delivered to the Secretary of the Company, as
escrow agent thereunder. The Participant shall deliver to such escrow agent a
stock assignment duly endorsed in blank, in the form attached to this Agreement
as Exhibit B, and hereby instructs the Company to deliver to such escrow agent,
   ---------
on behalf of the Participant, the certificate(s) evidencing the Unvested Shares
issued hereunder. Such materials shall be held by such escrow agent pursuant to
the terms of such Joint Escrow Instructions.

     6. Restrictive Legends.
        -------------------

     All certificates representing Shares shall have affixed thereto legends in
substantially the following form, in addition to any other legends that may be
required under federal or state securities laws:

          "The shares of stock represented by this certificate are subject to
          restrictions on transfer and an option to purchase set forth in a
          certain Restricted Stock Agreement between the corporation and the
          registered owner of these shares (or his predecessor in interest), and
          such Agreement is available for inspection without charge at the
          office of the Secretary of the corporation."

     7. Provisions of the Plan.
        ----------------------

     This Agreement is subject to the provisions of the Plan, a copy of which
has been furnished to the Participant.

     8. Withholding Taxes; Section 83(b) Election.
        -----------------------------------------

          (a) The Participant acknowledges and agrees that the Company has the
right to deduct from payments of any kind otherwise due to the Participant any
federal, state or local taxes of any kind required by law to be withheld with
respect to the purchase of the Shares by the Participant or the lapse of the
Purchase Option.

          (b) The Participant has reviewed with the Participant's own tax
advisors the federal, state, local and foreign tax consequences of this
investment and the transactions contemplated by this Agreement. The Participant
is relying solely on such advisors and not on any statements or representations
of the Company or any of its agents. The Participant understands that the
Participant (and not the Company) shall be responsible for the Participant's own
tax liability that may arise as a result of this investment or the transactions
contemplated by this Agreement. The Participant understands that it may be
beneficial in many circumstances to elect to be taxed at the time the Shares are
purchased rather than when and as the Company's Purchase Option expires by
filing an election under Section 83(b) of the Code with the I.R.S. within 30
days from the date of purchase.

          THE PARTICIPANT ACKNOWLEDGES THAT IT IS THE PARTICIPANT'S SOLE
RESPONSIBILITY AND NOT THE COMPANY'S TO FILE TIMELY THE ELECTION UNDER SECTION
83(b), EVEN IF THE PARTICIPANT REQUESTS THE COMPANY OR ITS REPRESENTATIVES TO
MAKE THIS FILING ON THE PARTICIPANT'S BEHALF.

     9. Miscellaneous.
        -------------

          (a) No Rights to Employment. The Participant acknowledges and agrees
              -----------------------
that the vesting of the Shares pursuant to Section 2 hereof is earned only by
continuing service as an employee at the will of the Company (not through the
act of being hired or purchasing shares hereunder). The Participant further
acknowledges and agrees that the transactions contemplated hereunder and the
vesting schedule set forth herein do not constitute an express or implied
promise of continued engagement as an employee or consultant for the vesting
period, for any period, or at all.

                                       3

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          (b) Severability. The invalidity or unenforceability of any provision
              ------------
of this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement, and each other provision of this Agreement shall be
severable and enforceable to the extent permitted by law.

          (c) Waiver. The Board of Directors of the Company may waive any
              ------
provision for the benefit of the Company contained in this Agreement, either
generally or in any particular instance.

          (d) Binding Effect. This Agreement shall be binding upon and inure to
              --------------
the benefit of the Company and the Participant and their respective heirs,
executors, administrators, legal representatives, successors and assigns,
subject to the restrictions on transfer set forth in Section 4 of this
Agreement.

          (e) Notice. All notices required or permitted hereunder shall be in
              ------
writing and deemed effectively given upon personal delivery or five days after
deposit in the United States Post Office, by registered or certified mail,
postage prepaid, addressed to the other party hereto at the address shown
beneath his or its respective signature to this Agreement, or at such other
address or addresses as either party shall designate to the other in accordance
with this Section 9(e).

          (f) Pronouns. Whenever the context may require, any pronouns used in
              --------
this Agreement shall include the corresponding masculine, feminine or neuter
forms, and the singular form of nouns and pronouns shall include the plural, and
vice versa.

          (g) Entire Agreement. This Agreement and the Plan constitute the
              ----------------
entire agreement between the parties, and supersedes all prior agreements and
understandings, relating to the subject matter of this Agreement, including but
not limited to, the Option Agreements.

          (h) Amendment. This Agreement may be amended or modified only by a
              ---------
written instrument executed by both the Company and the Participant.

          (i) Governing Law. This Agreement shall be construed, interpreted and
              -------------
enforced in accordance with the internal laws of the State of Maryland without
regard to any applicable conflicts of laws.

          (j) Participant's Acknowledgments. The Participant acknowledges that
              -----------------------------
he or she: (i) has read this Agreement; (ii) has been represented in the
preparation, negotiation and execution of this Agreement by legal counsel of the
Participant's own choice or has voluntarily declined to seek such counsel; (iii)
understands the terms and consequences of this Agreement; (iv) is fully aware of
the legal and binding effect of this Agreement; and (v) understands that the law
firm of Hale and Dorr LLP is acting as counsel to the Company in connection with
the transactions contemplated by the Agreement, and is not acting as counsel for
the Participant.

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

                                    ENTRUST, INC.

                                    By: /s/ F. William Conner
                                       -----------------------------------------
                                       F. William Conner
                                       President and Chief Executive Officer

                                       Address: Entrust, Inc.
                                                One Hanover Park
                                                16633 Dallas Parkway
                                                Suite 800
                                                Addison, Texas 75001

                                       4

<PAGE>

                                        /s/ David L. Thompson
                                       -----------------------------------------
                                       David L. Thompson

                                       Address: 5505 Kinross Drive
                                                Plano, Texas  75093

Exhibit A

                                  ENTRUST, INC.

                            Joint Escrow Instructions
                            -------------------------

                                    February 21, 2002

James D. Kendry, Esq.
Secretary
Entrust, Inc.
One Hanover Park
16633 Dallas Parkway
Suite 800
Addison, TX  75001

Dear Sir:

     As Escrow Agent for Entrust, Inc., a Maryland corporation, and its
successors in interest under the Restricted Stock Agreement (the "Agreement") of
even date herewith, to which a copy of these Joint Escrow Instructions is
attached (the "Company"), and the undersigned person ("Holder"), you are hereby
authorized and directed to hold the documents delivered to you pursuant to the
terms of the Agreement in accordance with the following instructions:

     1. Appointment. Holder irrevocably authorizes the Company to deposit with
        -----------
you any certificates evidencing 6,250 shares of the Company's common stock,
$0.01 par value per share (the "Shares"), to be held by you hereunder and any
additions and substitutions to said Shares. For purposes of these Joint Escrow
Instructions, "Shares" shall be deemed to include any additional or substitute
property. Holder does hereby irrevocably constitute and appoint you as his
attorney-in-fact and agent for the term of this escrow to execute with respect
to such Shares all documents necessary or appropriate to make such Shares
negotiable and to complete any transaction herein contemplated. Subject to the
provisions of this paragraph 1 and the terms of the Agreement, Holder shall
exercise all rights and privileges of a stockholder of the Company while the
Shares are held by you.

     2. Closing of Purchase.
        -------------------

          (a) Upon any purchase by the Company of the Shares pursuant to the
Agreement, the Company shall give to Holder and you a written notice specifying
the purchase price for the Shares, as determined pursuant to the Agreement, and
the time for a closing hereunder (the "Closing") at the principal office of the
Company. Holder and the Company hereby irrevocably authorize and direct you to
close the transaction

                                       5

<PAGE>

contemplated by such notice in accordance with the terms of said notice.

          (b) At the Closing, you are directed (a) to date the stock assignment
form or forms necessary for the transfer of the Shares, (b) to fill in on such
form or forms the number of Shares being transferred, and (c) to deliver same,
together with the certificate or certificates evidencing the Shares to be
transferred, to the Company against the simultaneous delivery to you of the
purchase price for the Shares being purchased pursuant to the Agreement.

     3. Withdrawal. The Holder shall have the right to withdraw from this escrow
        ----------
any Shares as to which the Purchase Option (as defined in the Agreement) has
terminated or expired.

     4. Duties of Escrow Agent.
        ----------------------

          (a) Your duties hereunder may be altered, amended, modified or revoked
only by a writing signed by all of the parties hereto.

          (b) You shall be obligated only for the performance of such duties as
are specifically set forth herein and may rely and shall be protected in relying
or refraining from acting on any instrument reasonably believed by you to be
genuine and to have been signed or presented by the proper party or parties. You
shall not be personally liable for any act you may do or omit to do hereunder as
Escrow Agent or as attorney-in-fact of Holder while acting in good faith and in
the exercise of your own good judgment, and any act done or omitted by you
pursuant to the advice of your own attorneys shall be conclusive evidence of
such good faith.

          (c) You are hereby expressly authorized to disregard any and all
warnings given by any of the parties hereto or by any other person or Company,
excepting only orders or process of courts of law, and are hereby expressly
authorized to comply with and obey orders, judgments or decrees of any court. In
case you obey or comply with any such order, judgment or decree of any court,
you shall not be liable to any of the parties hereto or to any other person,
firm or Company by reason of such compliance, notwithstanding any such order,
judgment or decree being subsequently reversed, modified, annulled, set aside,
vacated or found to have been entered without jurisdiction.

          (d) You shall not be liable in any respect on account of the identity,
authority or rights of the parties executing or delivering or purporting to
execute or deliver the Agreement or any documents or papers deposited or called
for hereunder.

          (e) You shall be entitled to employ such legal counsel and other
experts as you may deem necessary properly to advise you in connection with your
obligations hereunder and may rely upon the advice of such counsel.

          (f) Your rights and responsibilities as Escrow Agent hereunder shall
terminate if (i) you cease to be Secretary of the Company or (ii) you resign by
written notice to each party. In the event of a termination under clause (i),
your successor as Secretary shall become Escrow Agent hereunder; in the event of
a termination under clause (ii), the Company shall appoint a successor Escrow
Agent hereunder.

          (g) If you reasonably require other or further instruments in
connection with these Joint Escrow Instructions or obligations in respect
hereto, the necessary parties hereto shall join in furnishing such instruments.

          (h) It is understood and agreed that should any dispute arise with
respect to the delivery and/or ownership or right of possession of the
securities held by you hereunder, you are authorized and directed to retain in
your possession without liability to anyone all or any part of said securities
until such dispute shall have been settled either by mutual written agreement of
the parties concerned or by a final order, decree or judgment of a court of
competent jurisdiction after the time for appeal has expired and no appeal has
been perfected, but you shall be under no duty whatsoever to institute or defend
any such proceedings.

                                       6

<PAGE>

          (i) These Joint Escrow Instructions set forth your sole duties with
respect to any and all matters pertinent hereto and no implied duties or
obligations shall be read into these Joint Escrow Instructions against you.

          (j) The Company shall indemnify you and hold you harmless against any
and all damages, losses, liabilities, costs, and expenses, including attorneys'
fees and disbursements, for anything done or omitted to be done by you as Escrow
Agent in connection with this Agreement or the performance of your duties
hereunder, except such as shall result from your gross negligence or willful
misconduct.

     5. Notice. Any notice required or permitted hereunder shall be given in
        ------
writing and shall be deemed effectively given upon personal delivery or upon
deposit in the United States Post Office, by registered or certified mail with
postage and fees prepaid, addressed to each of the other parties thereunto
entitled at the following addresses, or at such other addresses as a party may
designate by ten days' advance written notice to each of the other parties
hereto.

          COMPANY:
                          Entrust, Inc.
                          One Hanover Park
                          16633 Dallas Parkway
                          Suite 800
                          Addison, TX 75001
                          Attn: James D. Kendry

          HOLDER:         Notices to Holder shall be sent to the address set
                          forth below Holder's signature below.

          ESCROW AGENT:   Notices to the Escrow Agent shall be sent to the
                          address set forth above for the Company.

     6. Miscellaneous.
        -------------

          (a) By signing these Joint Escrow Instructions, you become a party
hereto only for the purpose of said Joint Escrow Instructions, and you do not
become a party to the Agreement.

          (b) This instrument shall be binding upon and inure to the benefit of
the parties hereto and their respective successors and permitted assigns.

                                      Very truly yours,

                                      ENTRUST, INC.

Date: February __, 2002               By:
                                         ---------------------------------------
                                          F. William Conner
                                          President and Chief Executive Officer

                                       7

<PAGE>

                                      HOLDER:

Date: February   , 2002
               --                     ------------------------------------------
                                      David L. Thompson
                                      5505 Kinross Drive
                                      Plano, Texas 75093

ESCROW AGENT:

------------------------------------
James D. Kendry

                                    Exhibit B

                  (STOCK ASSIGNMENT SEPARATE FROM CERTIFICATE)

     FOR VALUE RECEIVED, I hereby sell, assign and transfer unto
                   (_________) shares of Common Stock, $0.01 par value per
------------------
share, of Entrust, Inc. (the "Corporation") standing in my name on the books of
said Corporation represented by Certificate(s) Number            herewith, and
                                                      ----------
do hereby irrevocably constitute and appoint                        attorney to
                                             ----------------------
transfer the said stock on the books of the within named Corporation with full
power of substitution in the premises.

                                            Dated:
                                                   --------------------

IN PRESENCE OF:

-------------------                                   --------------------------

     NOTICE: The signature(s) to this assignment must correspond with the name
as written upon the face of the certificate, in every particular, without
alteration, enlargement, or any change whatever and must be guaranteed by a
commercial bank, trust company or member firm of the Boston, New York or Midwest
Stock Exchange.

                                       8

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