SUPPORT AGREEMENT
                               -----------------

     MEMORANDUM OF AGREEMENT made as of the 31st day of December, 1996.

BETWEEN:

               ENTRUST TECHNOLOGIES INC.,
               a corporation existing under the laws
               of the State of Maryland,

               (hereinafter referred to as "Entrust"),

                                              OF THE FIRST PART;

                                    - and -

               ENTRUST TECHNOLOGIES LIMITED,
               a corporation existing under the laws of the
               Province of Ontario,

               (hereinafter referred to as the "Corporation"),

                                              OF THE SECOND PART.

     WHEREAS the parties hereto desire to make appropriate provision and to
establish a procedure whereby Entrust will take certain actions and make certain
payments and deliveries necessary to ensure that the Corporation will be able to
make certain payments and to deliver or cause to be delivered shares of Series A
common stock, par value U.S. $0.01 per share, of Entrust ("Entrust Common
Shares") in satisfaction of the obligations of the Corporation under the
provisions (the "Exchangeable Share Provisions") attaching to the Exchangeable
Shares with respect to the payment and satisfaction of dividends, Liquidation
Amounts, Retraction Prices and Redemption Prices all in accordance with the
Exchangeable Share Provisions;

     NOW THEREFORE in consideration of the respective covenants in this
Agreement and for other good and valuable consideration (the receipt and
sufficiency of which are hereby acknowledged), the parties hereto agree as
follows:

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<PAGE>
 
                                   ARTICLE 1

                        DEFINITIONS AND INTERPRETATIONS
                        -------------------------------

1.1  DEFINED TERMS.  In this Agreement including the recitals hereto, all
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capitalized words and expressions used herein and not otherwise defined herein
shall have the meanings ascribed to such words and expressions in the
Exchangeable Share Provisions, unless the context requires otherwise.

1.2  INTERPRETATION NOT AFFECTED BY HEADINGS, ETC.  The division of this
     --------------------------------------------                       
Agreement into articles, sections and paragraphs and the insertion of headings
are for convenience of reference only and shall not affect the construction or
interpretation of this Agreement.

1.3  NUMBER, GENDER, ETC.  In this Agreement, words importing the singular
     -------------------                                                  
number only shall include the plural and vice versa, words importing the use of
any gender shall include all genders.

1.4  DATE FOR ANY ACTION.  If any date on which any action is required to be
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taken under this Agreement is not a Business Day, such action shall be required
to be taken on the next succeeding Business Day.

                                   ARTICLE 2

                    COVENANTS OF ENTRUST AND THE CORPORATION
                    ----------------------------------------

2.1  COVENANTS OF ENTRUST REGARDING EXCHANGEABLE SHARES.  So long as any
     --------------------------------------------------                 
Exchangeable Shares are outstanding, Entrust shall:

     (a)  not declare or pay any dividend on Entrust Common Shares unless (i)
          the Corporation shall have sufficient assets, funds and other property
          (including, where applicable, Entrust Common Shares or other
          securities of Entrust) available to enable the due declaration and the
          due and punctual payment in accordance with applicable law, of an
          equivalent dividend on the Exchangeable Shares in accordance with the
          Exchangeable Share Provisions, and (ii) the Corporation shall
          simultaneously declare or pay, as the case ma be, an equivalent
          dividend on the Exchangeable Shares in accordance with the
          Exchangeable Share Provisions;

     (b)  cause the Corporation to declare simultaneously with the declaration
          of any dividend on Entrust Common Shares an equivalent dividend on the
          Exchangeable Shares and, when such dividend is paid on Entrust Common
          Shares, cause the Corporation to pay simultaneously therewith

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<PAGE>
 
          such equivalent dividend on the Exchangeable Shares, in each case in
          accordance with the Exchangeable Share Provisions;

     (c)  advise the Corporation sufficiently in advance of the declaration by
          Entrust of any dividend on Entrust Common Shares and take all such
          other actions as are necessary in cooperation with the Corporation, to
          ensure that the declaration date, record date and payment date for any
          dividend on the Exchangeable Shares shall be the same as the record
          date, declaration date and payment date for the corresponding dividend
          on Entrust Common Shares, and such dates in respect of dividends on
          the Exchangeable Shares shall be in accordance with any requirement of
          the Exchangeable Share Provisions;

     (d)  ensure that the record for any dividend declared on Entrust Common
          Shares, Entrust Common Share Reorganization, Rights Offering, Special
          Distribution or Capital Reorganization is not less than ten Business
          Days after the declaration date for such dividend, Entrust Common
          Share Reorganization, Rights Offering, Special Distribution or Capital
          Reorganization;

     (e)  take all such actions and do all such things as are necessary or
          desirable to enable and permit the Corporation, in accordance with
          applicable law, to pay and otherwise perform its obligations with
          respect to the satisfaction of the Liquidation Amount in respect of
          each issued and outstanding Exchangeable Share upon the liquidation,
          dissolution or winding-up of the Corporation, including without
          limitation all such actions and all such things as are necessary or
          desirable to enable and permit the Corporation to deliver Entrust
          Common Shares to the holders of Exchangeable Shares in satisfaction of
          the Liquidation Amount for each such Exchangeable Share, in accordance
          with the provisions of Article 4 of the Exchangeable Share Provisions;

     (f)  take all such actions and do all such things as are necessary or
          desirable to enable and permit the Corporation, in accordance with
          applicable law, to pay and otherwise perform its obligations with
          respect to the satisfaction of the Retraction Price and the Redemption
          Price, including without limitation all such actions and all such
          things as are necessary or desirable to enable and permit the
          Corporation to deliver Entrust Common Shares to the holders of
          Exchangeable Shares, upon the retraction or redemption of the
          Exchangeable Shares in accordance with the provisions of Article 5 or
          Article 6 of the Exchangeable Share Provisions, as the case may be;

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<PAGE>
 
     (g)  not exercise its vote as a shareholder of the Corporation to initiate,
          consent to or approve the voluntary liquidation, dissolution or
          winding-up of the Corporation nor take any action or omit to take any
          action that is designed to result in the liquidation, dissolution or
          winding-up of the Corporation; and

     (h)  not exercise its vote as a shareholder of the Corporation to authorize
          the continuance or other transfer of the corporate existence of the
          Corporation to any jurisdiction outside Canada.

2.2  SEGREGATION OF FUNDS.  Entrust will cause the Corporation to deposit a
     --------------------                                                  
sufficient amount of funds in a separate account and segregate a sufficient
amount of such assets and other property as if necessary to enable the
Corporation to pay or otherwise satisfy the applicable dividends, Liquidation
Amount, Retraction Price or Redemption Price, and will cause the Corporation to
use such funds, assets and other property so segregated exclusively for the
payment of dividends and the payment or other satisfaction of the Liquidation
Amount, the Retraction Price or the Redemption Price, as applicable, in each
case in accordance with the Exchangeable Share Provisions.

2.3  RESERVATION OF ENTRUST COMMON SHARES.  Entrust hereby represents and
     ------------------------------------                                
warrants that it has irrevocably reserved for issuance out of its authorized and
unissued capital stock such number of Entrust Common Shares as is equal to the
number of Exchangeable Shares outstanding immediately following the Effective
Date and covenants that at all times in the future while any Exchangeable Shares
are outstanding it will keep available, free from pre-emptive and other rights
out of its authorized and unissued capital stock such number of Entrust Common
Shares (or other shares or securities into which Entrust Common Shares may be
reclassified or changed) as is necessary to enable Entrust and the Corporation
to perform their respective obligations pursuant to this Agreement and the
Exchangeable Share Provisions.

2.4  NOTIFICATION OF CERTAIN EVENTS.  In order to assist Entrust to comply with
     ------------------------------                                            
its obligations hereunder, the Corporation will give Entrust notice of each of
the following events at the time set forth below:

     (a)  in the event of any determination by the Board of Directors of the
          Corporation to institute voluntary liquidation, dissolution or winding
          up proceedings with respect to the Corporation or to effect any other
          distribution of the assets of the Corporation among its shareholders
          for the purpose of winding up its affairs, at least 60 days prior to
          the proposed effective date of such liquidation, dissolution, winding
          up or other distribution;

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<PAGE>
 
     (b)  immediately, upon the earlier of (i) receipt by the Corporation of
          notice of, and (ii) the Corporation otherwise becoming aware of, any
          threatened or instituted claim, suit, petition or other proceedings
          with respect to the involuntary liquidation, dissolution or winding up
          of the Corporation or to effect any other distribution of the assets
          of the Corporation among its shareholders for the purpose of winding
          up its affairs;

     (c)  immediately, upon receipt by the Corporation of a Retraction Request;
          and

     (d)  as soon as practicable upon the issuance by the Corporation of any
          Exchangeable Shares or rights to acquire Exchangeable Shares.

2.5  DELIVERY OF ENTRUST COMMON SHARES.  In furtherance of its obligations under
     ---------------------------------                                          
subsections 2.1(e) and (f) hereof, upon notice of any event that requires the
Corporation to cause to be delivered Entrust Common Shares to any holder of
Exchangeable Shares, Entrust shall forthwith issue and deliver the requisite
Entrust Common Shares to the Corporation or, if the Corporation so directs, to
or to the order of the former holder of the surrendered Exchangeable Shares.
All such Entrust Common Shares shall be duly issued as fully paid and non-
assessable and shall be free and clear of any Liens.  In consideration of the
issuance of each such Entrust Common Share by Entrust, the Corporation shall
issue to Entrust, or as Entrust shall direct, such number of common shares of
the Corporation as is equal to the fair value of such Entrust Common Shares.

2.6  QUALIFICATION OF ENTRUST COMMON SHARES.  Entrust shall use all reasonable
     --------------------------------------                                   
efforts to obtain or have available exemptions from the registration and
prospectus requirements of applicable Canadian and United States securities laws
to permit the issuance of the Entrust Common Shares upon any exchange of the
Exchangeable Shares to the extent possible without registration or qualification
with, or approval of, or the filing of any document including any registration
statement or prospectus or similar document with, any Canadian or United States
securities authorities.

2.7  TENDER OFFERS, ETC.  In the event that a tender offer, share exchange
     ------------------                                                   
offer, issuer bid, take-over bid or similar transaction with respect to Entrust
Common Shares (an "Offer") is proposed by Entrust or is proposed to Entrust or
its stockholders and is recommended by the board of directors of Entrust, or is
otherwise effected or to be effected with the consent or approval of the board
of directors of Entrust, Entrust will use all commercially reasonable efforts
expeditiously and in good faith to take all such actions and do all such things
as are necessary or desirable to enable and permit holders of Exchangeable
Shares to participate in such Offer to the same extent and on an economically
equivalent basis as the holders of Entrust Common Shares, without
discrimination.  Without limiting the generality of 

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<PAGE>
 
the foregoing, Entrust will use all commercially reasonable efforts
expeditiously and in good faith to ensure that holders of Exchangeable Shares
may participate in all such Offers without being required to retract
Exchangeable Shares as against the Corporation (or, if so required, to ensure
that any such retraction shall be effective only upon, and shall be conditional
upon, the closing of the Offer and only to the extent necessary to tender or
deposit to the Offer).

2.8  OWNERSHIP OF OUTSTANDING SHARES.  Entrust covenants and agrees in favor of
     -------------------------------                                           
the Corporation that, as long as any outstanding Exchangeable Shares are owned
by any person or entity other than Entrust or any of its Affiliates, Entrust
will be and remain the direct or indirect beneficial owner of all issued and
outstanding shares in the capital of the Corporation (other than one common
share and the Exchangeable Shares) and all other outstanding securities of the
Corporation carrying or otherwise entitled to voting rights in any circumstances
(other than Exchangeable Shares), unless Entrust shall have obtained the prior
approval of the Corporation and the holders of the Exchangeable Shares given in
accordance with section 9.2 of the Exchangeable Share Provisions.

2.9  ENTRUST NOT TO VOTE EXCHANGEABLE SHARES.  Entrust covenants and agrees
     ---------------------------------------                               
that it will appoint and cause to be appointed proxyholders with respect to all
Exchangeable Shares held by Entrust and its Affiliates for the sole purpose of
attending each meeting of holders of Exchangeable Shares in order to be counted
as part of the quorum for each such meeting.  Entrust further covenants and
agrees that it will not, and will cause its Affiliates not to, exercise any
voting rights that may be exercisable by holders of Exchangeable Shares from
time to time pursuant to the Exchangeable Share Provisions or pursuant to the
provisions of the OBCA with respect to any Exchangeable Shares held by it or by
its Affiliates in respect of any matter considered at any meeting of holders of
Exchangeable Shares, including without limitation any approval to be given by
holders of Exchangeable Shares pursuant to section 9.2 of the Exchangeable Share
Provision.

2.10  ECONOMIC EQUIVALENCE.  Entrust hereby acknowledges that it will be bound
      --------------------                         
by any determination of economic equivalence made by the Board of Directors of
the Corporation pursuant to section 10.1 of the Exchangeable Share Provisions.

2.11  CAPITAL REORGANIZATION OF ENTRUST.  If at any time there is a capital
      ---------------------------------                                    
reorganization of Entrust that is not provided for in subsection 1.1(o) of the
Exchangeable Share Provisions or a consolidation, merger, arrangement or
amalgamation (statutory or otherwise) of Entrust with or into another entity
(any such event being called a "Capital Reorganization"), Entrust shall take all
such actions and do all such things as are necessary to ensure that holders of
Exchangeable Shares whose Exchangeable Shares have not been exchanged for
Entrust Common Shares in accordance with the Exchangeable Share Provisions prior
to the record date for such Capital Reorganization shall receive, upon any such
exchange occurring pursuant to 

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<PAGE>
 
the Exchangeable Share Provisions at any time after the record date for such
Capital Reorganization, in lieu of the Entrust Common Shares that such holders
would otherwise have been entitled to receive pursuant to the Exchangeable Share
Provisions, the number of shares or other securities of Entrust or of the body
corporate resulting, surviving or continuing from the Capital Reorganization, or
other property, that such holders would have been entitled to receive as a
result of such Capital Reorganization if, on the record date, such holders would
have been the registered holders of the number of Entrust Common Shares to which
such holders were then entitled upon any exchange of their Exchangeable Shares
into Entrust Common Shares in accordance with the Exchangeable Share Provisions,
subject to adjustment thereafter in the same manner, as nearly as may be
possible, as is provided for in subsection 1.1(o) of the Exchangeable Share
Provisions; provided that no such Capital Reorganization shall be carried into
effect unless all necessary steps shall have been taken so that each holder of
Exchangeable Shares shall thereafter be entitled to receive, upon any exchange
of his Exchangeable Shares pursuant to the Exchangeable Share Provisions, such
numbers of shares or other securities of Entrust or of the body corporate
resulting, surviving or continuing from the Capital Reorganization, or other
property.

2.12  OTHER CHANGE IN ENTRUST COMMON SHARES.  In the case of any
      -------------------------------------           
reclassification of, or other change in, the outstanding Entrust Common Shares
other than a Common Share Reorganization or a Capital Reorganization, Entrust
shall take all such actions and do all such things as are necessary to ensure
that holders of Exchangeable Shares shall receive, upon the occurrence at any
time after such record date of any event whereby they would receive Entrust
Common Shares pursuant to the Exchangeable Share Provisions, such shares,
securities or rights as they would have received if their Exchangeable Shares
had been exchanged for Entrust Common Shares pursuant to the Exchangeable Share
Provisions immediately prior to such record date, subject to adjustment
thereafter in the same manner, as nearly as may be possible, as is provided for
in subsection 1.1(o) of the Exchangeable Share Provisions.


                                   ARTICLE 3

                                    GENERAL
                                    -------

3.1  TERM.  This Agreement shall come into force and be effective as of the date
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hereof and shall terminate and be of no further force and effect at such time as
there are no Exchangeable Shares (or securities or rights convertible into or
exchangeable for or carrying rights to acquire Exchangeable Shares) held by any
party other than Entrust and its Affiliates.

3.2  CHANGES IN CAPITAL OF ENTRUST AND THE CORPORATION.  Notwithstanding the
     -------------------------------------------------                      
provisions of section 3.4 hereof, at all times after the occurrence of any event
effected pursuant to sections 2.7, 2.11 or 2.12 hereof as a result of which
either Entrust 

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<PAGE>
 
Common Shares or the Exchangeable Shares or both are in any way changed, this
Agreement shall forthwith be amended and modified as necessary in order that it
shall apply with full force and effect, mutatis mutandis, to all new securities
into which Entrust Common Shares or the Exchangeable Shares or both are so
changed and the parties hereto shall execute and deliver an agreement in writing
giving effect to and evidencing such necessary amendments and modifications.

3.3  SEVERABILITY.  If any provision of this Agreement is held to be invalid,
     ------------                                                            
illegal or unenforceable, the validity, legality or enforceability of the
remainder of this Agreement shall not in any way be affected or impaired thereby
and this Agreement shall be carried out as nearly as possible in accordance with
its original terms and conditions.

3.4  AMENDMENTS, MODIFICATIONS, ETC.  This Agreement may not be amended or
     ------------------------------                                       
modified except by an agreement in writing executed by the Corporation and
Entrust and approved by the holders of the Exchangeable Shares in accordance
with section 11.2 of the Exchangeable Share Provisions.

3.5  MINISTERIAL AMENDMENTS.  Notwithstanding the provisions of section 3.4, the
     ----------------------                                                     
parties to this Agreement may without approval of the holders of the
Exchangeable Shares, at any time and from time to time, amend or modify this
Agreement in writing for the purposes of:

     (a)  adding to the covenants of either or both parties for the protection
          of the interests of the holders of the Exchangeable Shares;

     (b)  making such amendments or modifications not inconsistent with this
          Agreement as may be necessary or desirable with respect to matters or
          questions which, in the opinion of the board of directors of each of
          the Corporation and Entrust, it may be expedient to make, provided
          that each such board of directors shall be of the opinion that such
          amendments or modifications will not be prejudicial to the interests
          of the holders of the Exchangeable Shares; or

     (c)  making such changes or corrections which, on the advice of counsel to
          the Corporation and Entrust, are required for the purpose of curing or
          correcting any ambiguity or defect or inconsistent provision or
          clerical omission or mistake or manifest error herein, provided that
          the boards of directors of each of the Corporation and Entrust shall
          be of the opinion that such changes or corrections will not be
          prejudicial to the interests of the holders of the Exchangeable
          Shares.

3.6  MEETING TO CONSIDER AMENDMENTS.  The Corporation, at the request of
     ------------------------------                                     
Entrust, shall call a meeting or meetings of the holders of the Exchangeable
Shares for 

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<PAGE>
 
the purpose of considering any proposed amendment or modification requiring
approval pursuant to section 3.4 hereof. Any such meeting or meetings shall be
called and held in accordance with the by-laws of the Corporation and the
Exchangeable Share Provisions. In lieu of calling a meeting of holders of
Exchangeable Shares, with the consent of Entrust, any proposed amendment or
modification requiring approval of the holders of Exchangeable Shares pursuant
to section 3.4 hereof may be given by such holders executing a written
resolution evidencing the approval of such proposed amendment or modification,
which resolution must be signed by all the holders of Exchangeable Shares
entitled to vote on such matter.

3.7  WAIVERS ONLY IN WRITING.  No waiver of any of the provisions of this
     -----------------------                                             
Agreement otherwise permitted hereunder shall be effective unless made in
writing and signed by both of the parties hereto.

3.8  ENUREMENT.  This Agreement shall be binding upon and enure to the benefit
     ---------                                                                
of the parties hereto and their respective successors and permitted assigns.

3.9  ENTRUST SUCCESSORS.  Entrust shall not enter into any transaction (whether
     ------------------                                                        
by way of reconstruction, reorganization, consolidation, merger, transfer, sale,
lease or otherwise) whereby all or substantially all its undertaking, property
and assets would become the property of any other person or, in the case of a
merger, of the continuing corporation resulting therefrom, unless:

     (a)  such other person or continuing corporation is a corporation (the
          "Entrust Successor") incorporated under the laws of any state of the
          United States or the laws of Canada or any province thereof; and

     (b)  the Entrust Successor, by operation of law, becomes, without more,
          bound by the terms and provisions of this Agreement or, if not so
          bound, executes, prior to or contemporaneously with the consummation
          of such transaction, an agreement to be bound by the provisions hereof
          as if it were an original party hereto and to observe and perform all
          of the covenants and obligations of Entrust pursuant to this
          Agreement, in form satisfactory to the Corporation, acting reasonably.

Nothing herein shall be constructed as preventing the amalgamation or merger of
any wholly-owned subsidiary of Entrust with or into Entrust.

3.10  NOTICE TO PARTIES.  All notices and other communications between the
      -----------------                                                   
parties shall be in writing and shall be deemed to have been given if delivered
personally or by confirmed telecopy to the parties at the following addresses
(or at such other addresses for either such party as shall be specified in like
notice):

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<PAGE>
 
               (i)   if to Entrust Technologies Inc.:

                     Entrust Technologies Inc.
                     2 Constellation Crescent
                     Nepean, Ontario
                     K2G 5J9

                     Attention:  President
                     ---------------------

               (ii)  if to the Corporation at:

                     Entrust Technologies Limited
                     2 Constellation Crescent
                     Nepean, Ontario
                     K2G 5J9 

                     Attention:  President
                     ---------------------

Any notice or other communication given personally shall be deemed to have been
given and received upon delivery thereof and if given by telecopy shall be
deemed to have been given and received on the date of the confirmed receipt
thereof unless such day is not a Business Day or unless such notice or
communication was not given during the normal business hours of the recipient on
such day, in which case it shall be deemed to have been given and received upon
the immediately following Business Day.

3.11  COUNTERPARTS.  This Agreement may be executed in counterparts, each of
      ------------                                                          
which shall be deemed an original, and all of which taken together shall
constitute one and the same instrument.

3.12  JURISDICTION.  This Agreement shall be construed and enforced in 
      ------------                          
accordance with the laws of the Province of Ontario and the laws of Canada
applicable therein.

3.13  ATTORNMENT.  Entrust agrees that any action or proceeding arising out of
      ----------           
or relating to this Agreement may be instituted in the courts of the Province of
Ontario, waives any objection which it may have now or hereafter to the venue of
any such action or proceeding, irrevocably submits to the jurisdiction of the
said courts in any such action or proceeding, agrees to be bound by any judgment
of the said courts and not to seek, and hereby waives, any review of the merits
of any such judgment by the courts of any other jurisdiction and hereby appoints
Northern Telecom Limited, 8200 Dixie Road, Suite 100, Brampton, Ontario L6T 5P6,
attention: Corporate Secretary as Entrust's attorney for service of process in
Ontario.

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<PAGE>
 
          IN WITNESS WHEREOF the parties have executed this Agreement as of the
date first above written.

                                ENTRUST TECHNOLOGIES INC.


                                by   /s/John A. Ryan
                                     President


                                ENTRUST TECHNOLOGIES LIMITED


                                by   /s/John A. Ryan
                                     President










       

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Source: OneCLE Business Contracts.