EXHIBIT 4.02

                            STOCKHOLDERS' AGREEMENT


     This Stockholders' Agreement (this "AGREEMENT") is made and entered into
                                         ---------                      
as of April 18, 1995, by and among the entities and individuals set forth on
Schedule A hereto (hereinafter referenced individually as a "STOCKHOLDER" and
- ----------                                                   -----------     
collectively as "STOCKHOLDERS") and Digital Certificates International, Inc., a
                 ------------                                                  
Delaware corporation (the "COMPANY").
                           -------   

                                R E C I T A L S

     A.   The Company has been organized for the purpose of providing RSA
certificate services.

     B.   Customers of the Company may be competitors of one or more of the
Stockholders. As a result, the Stockholders believe that in order for the
Company to succeed, no single Stockholder should control the Company.

     C.   The Stockholders wish to agree among themselves that no single
Stockholder shall control, directly or indirectly, more than forty-five percent
(45%) of the voting rights of the outstanding capital stock of the Company.

     D.   To prevent control, beneficially or of record, directly or indirectly,
by a single Stockholder in excess of such forty-five percent (45%), the
Stockholders wish to provide that no Stockholder owning, beneficially or of
record, directly or indirectly, more than forty-five percent (45%) of the
outstanding voting capital stock of the Company will vote or cause to be voted
more than forty-five percent (45%) of the shares eligible to be voted on any
matter.


                               A G R E E M E N T

     NOW, THEREFORE, in reliance on the foregoing Recitals and in consideration
of the mutual covenants hereinafter set forth, the parties agree as follows:

1.   SHARES SUBJECT TO THIS AGREEMENT
     --------------------------------

     Each Stockholder owns the number of shares of Common or Preferred Stock of
the Company set forth on Schedule A. All of such shares and any additional
                         ----------
shares of capital stock of the Company of any type, whether Common or Preferred,
or rights to acquire Common or Preferred Stock which may be acquired, directly
or indirectly, by the Stockholders in the future shall also be subject to this
Agreement. All of the shares set forth on Schedule A together with all such
                                          ----------
future acquired shares and

 
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Stockholders/Digital Certificates International, Inc.
Page 2                                                    

rights to acquire shares are hereafter referenced respectively as each
Stockholder's "SHARES."
               ------  

2.   CERTAIN REPRESENTATIONS; INDEMNITY
     ----------------------------------

          2.1  REPRESENTATIONS. Each of the Stockholders acknowledges and
               ---------------                                            
represents that: (i) this Agreement was prepared with his, her or its knowledge
and consent by legal counsel for the Company; (ii) he, she or it was advised by
such counsel to consider seeking independent legal counsel to review this
Agreement on his, her or its behalf; (iii) he, she or it had adequate time to
seek the advice of such independent counsel and to review this Agreement; (iv)
he, she or it either obtained such advice or knowingly and intentionally chose
not to seek such advice; (v) he, she or it fully understands this Agreement and
all of its terms and provisions, including, but not limited to, those provisions
which significantly restrict his, her or its ability to sell, transfer or
otherwise dispose of his, her or its Shares; and (vi) the restrictions imposed
upon his, her or its Shares pursuant to this Agreement are reasonable.

          2.2  INDEMNITY. Each Stockholder agrees to indemnify and hold the
               ---------
Company and the other Stockholders harmless from and against any and all
liabilities, costs or expenses, including reasonable attorneys' fees, resulting
from or arising out of any sale, transfer or other disposition of his, her or
its Shares otherwise than in accordance with the terms and provisions of this
Agreement.

3.   RESTRICTIONS ON TRANSFERS.  Except as otherwise specifically provided in
     -------------------------                                               
this Section 3, no Stockholder (or any successor in interest to any Stockholder)
shall have the right or the power, directly or indirectly, to sell, assign (with
or without consideration), donate, give away, grant an option or proxy with
respect to, pledge, hypothecate or otherwise transfer or encumber, voluntarily
or involuntarily or by reason of operation of law (for example, but not limited
to, a trustee in bankruptcy or a buyer at any creditor's or court sale), or to
commit or agree to do any of the foregoing (hereinafter referenced collectively
as a "TRANSFER") any of such Stockholder's Shares, or any right or interest
      --------                                                             
therein to any Prohibited Party (as defined below), without the prior written
consent of the Board of Directors of the Company and a majority in interest of
the other Stockholders. For purposes of this Agreement, a "majority in interest"
of the other Stockholders shall refer to parties to this Agreement holding
shares of capital stock with more than 50% of the aggregate number of votes of
all of the shares of capital

 
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Stockholders/Digital Certificates International, Inc.
Page 3

stock held by all parties hereto consenting to or approving a matter. Any
purported Transfer contrary to, or in violation of, the provisions of this
Agreement, shall not entitle the purported transferee thereof to have any such
Shares transferred on the stock ledger or books of the Company, or obligate the
Company to issue certificates evidencing such purported Transfer, nor shall such
purported transferee be vested with voting rights or any other rights of a
stockholder of the Company, and in all events, such Shares shall remain subject
to the provisions of this Agreement. "PROHIBITED PARTY" shall mean Cylink
                                      ----------------
Corporation, a California corporation ("CYLINK"), Caro-Kann Corporation, a
                                        ------
California corporation ("CARO-KANN"), Pittway Corporation, a Delaware
                         ---------   
corporation ("PITTWAY"), or any entity affiliated with Cylink, Caro-Kann or
              -------    
Pittway.

 
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Stockholders/Digital Certificates International, Inc.
Page 4

4.   VOTING RIGHTS
     -------------

          4.1  RIGHT TO VOTE UPON EXCEEDING 45% THRESHOLD.
               ------------------------------------------ 

               4.1.1  EXCLUDED SHARES. The Stockholders and the Company agree
                      ---------------
that no Stockholder shall vote, directly or indirectly, Shares with voting
rights in excess of forty-five percent (45%) of the voting rights of the total
outstanding voting capital stock of the Company entitled to vote on any matter
including without limitation election of Directors. For this purpose, Shares
shall be considered entitled to vote if they are issued and outstanding and
shall not be excluded because the holder thereof is interested in the matter. In
the event that any Stockholder directly or indirectly owns, beneficially or of
record, or has the right to vote capital stock of the Company with voting rights
in excess of such percentage, such Stockholder agrees that it shall not cast
votes on any matter on which the Stockholders are entitled to act whether at a
meeting or by written consent in excess of forty-five percent (45%) of the total
number of votes eligible to be cast thereon after excluding a number of shares
held directly or indirectly by the Stockholder which would exceed such forty-
five percent (45%) threshold. For example, if a Stockholder holds Five Million
(5,000,000) shares of Common Stock representing fifty percent (50%) of the votes
of the issued and outstanding shares of capital stock entitled to vote, such
Stockholder agrees that it shall not cast more than Four Million Ninety Thousand
Nine Hundred Nine (4,090,909) votes. Any stockholder acquiring, directly or
indirectly, the right to cast more than forty-five percent (45%) of the
aggregate votes of the issued and outstanding voting capital stock of the
Company shall immediately give notice of such event to the Company together with
the particulars thereof setting forth the total number of shares of voting
capital stock held, directly or indirectly, by such Stockholder or as to which
such Stockholder is entitled to vote, directly or indirectly. Every Stockholder
agrees that the Company shall not count any votes cast by them, directly or
indirectly, in excess of forty-five percent (45%) of the total number of votes
eligible to be voted on any matter as calculated above.

               4.1.2  PRO RATA VOTING. The holder of Shares not voted pursuant
                      ---------------
to Section 4.1.1 shall vote such shares in the following fashion. If the
exclusion of such shares causes the number of shares eligible to be voted on a
matter to be less in the aggregate than the minimum number of shares required
under Delaware General Corporation Law, the Company's Certificate of
Incorporation or Bylaws, such Stockholder shall vote such shares 

 
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Stockholders/Digital Certificates International, Inc.
Page 5

pro rata based on the number of votes actually cast on the matter excluding the
Shares being voted pursuant to this Section 4.1.2. For example, if the Company
has 10,000,000 shares issued and outstanding and entitled to vote, and a single
Stockholder has 8,000,000 shares, that Stockholder would be entitled to cast
1,636,364 votes pursuant to Section 4.1.1. Assuming 2,000,000 shares were voted
for the matter and 1,636,364 votes were voted against the matter, such
Stockholder would vote 3,500,000 shares for the matter and 2,863,636 shares
against the matter pursuant to this Section 4.1.2. If there are sufficient
Shares available to vote such that the mandatory voting provisions contained
above in this Section 4.1.2 do not apply, then a Stockholder holding Shares not
voted because of Section 4.1.1 may, but is not obligated to, vote such shares
pro rata as set forth above in this Section 4.1.2.

          4.2  CERTAIN INVOLUNTARY HOLDINGS.  In the event that a Stockholder
               ----------------------------                                  
acquires or otherwise owns, beneficially or of record, directly or indirectly,
shares of the Company's voting capital stock causing such Stockholder to hold
more than forty-five percent (45%) of the issued and outstanding voting capital
stock of the Company as a result of a merger, acquisition, redemption or other
transaction on the part of the Company, the Company shall provide written notice
to such Stockholder, which shall set forth the number of shares which such
Stockholder (and any Permitted Transferees of such Stockholder) must not vote in
order to comply with this Section 4.

          4.3  OWNERSHIP OF SHARES.  For purposes of this Section 4, a
               -------------------                                    
Stockholder shall be deemed to own all shares of the voting capital stock or
rights to acquire voting capital stock of the Company held beneficially or of
record, directly or indirectly, by the Stockholder.  A Stockholder shall be
deemed to own shares of capital stock or rights to acquire capital stock
indirectly if: he, she or it (a) owns more than fifty percent (50%) of the
outstanding voting securities of the entity that directly or indirectly owns
such shares or acquisition rights, or (b) controls, is controlled by or is under
common control with the individual or entity that directly or indirectly owns
such shares or acquisition rights.

          4.4  BOARD REPRESENTATION.  So long as Bessemer Venture Partners III
               --------------------                                           
L.P. or its general partner or affiliates of such general partner ("BESSEMER")
                                                                    --------  
owns not less than fifty percent (50%) of the shares of the Preferred Stock it
holds as set forth on Schedule A as of the date Bessemer first executes this
Agreement (or an equivalent amount of Common Stock issued upon 

 
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Stockholders/Digital Certificates International, Inc.
Page 6

conversion thereof), the Company and the Stockholders shall cause and maintain
the election to the Board of Directors of a representative of Bessemer. So long
as RSA Data Security, Inc., a Delaware corporation ("RSA"), owns not less than
                                                     ---  
the lesser of (a) ten percent (10%) of the issued and outstanding voting shares
of the Company (on an as converted basis) or (b) seventy-five percent (75%) of
the shares of Common Stock held by it as set forth on Schedule A as of the date
RSA first executes this Agreement, the Company and the Stockholders shall cause
and maintain the election to the Board of Directors of a representative of RSA.
In addition, the Company and the Stockholders shall cause and maintain the
election to the Board of Directors of a representative of Visa International
Service Association for so long as it or its affiliates own not less than 50
percent (50%) of the shares of the Preferred Stock it holds as set forth on
Schedule A as of the date it first executes this Agreement (or an equivalent
amount of Common Stock issued upon conversion thereof).

          4.5  EMPLOYEES AS DIRECTORS.  The Stockholders agree that, in
               ----------------------                                  
addition to the RSA representative set forth in Section 4.4 hereof, they shall
not vote for:  (i) more than one employee of the Company nominated to serve on
the Board of Directors of the Company, and (ii) no officers or affiliates of RSA
nominated to serve on the Board of Directors of the Company, unless a majority
of all of the Shares (on an as converted basis) held by the Stockholders and a
majority of the Preferred Stock held by parties hereto, consent in writing to
the nomination of such person to the Board of Directors prior to such vote.

          4.6  LIMITATION ON EFFECTIVENESS.
               ---------------------------

               4.6.1  This Section 4 shall not be effective until the Company
shall have sold Preferred Stock with a gross purchase price received by the
Company of Three Million Dollars ($3,000,000) or more and, unless earlier
terminated pursuant to Section 6, shall continue for a period of ten (10) years
from the date of this Agreement. This Agreement may be extended for an
additional ten (10) years upon the written consent of the holders of more than
sixty percent (60%) of the Shares. Such written consent must be delivered to the
Secretary of the Company and the registered office of the Company in Delaware
not earlier than the eighth anniversary of the effectiveness of this Agreement
and not later than 30 days before the termination hereof.

               4.6.2  This Section 4 shall not apply in instances where a class
vote (Common voting as a class and 

 
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Stockholders/Digital Certificates International, Inc.
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Preferred voting as a class) is required by law, the Company's Certificate of
Incorporation or the Company's Bylaws on matters relating to the merger,
consolidation or sale of all or substantially all of the assets of the Company.

               4.6.3  This Section 4 shall not apply where only a single
Stockholder is entitled to vote on a matter.

               4.6.4  This Section 4 shall not apply in instances where its
implementation would make it impossible under law, under the Company's
Certificate of Incorporation, or the Company's Bylaws to obtain a legal, valid
and binding vote on a matter.

5.   LEGEND ON SHARE CERTIFICATES
     ----------------------------

     In addition to any legends reflecting the restrictions on transfer imposed
under federal and applicable state securities laws, each share certificate
evidencing the Shares shall have endorsed on it the following:

     THE SECURITIES EVIDENCED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
     RESTRICTIONS ON TRANSFER, VOTING AND OTHER RESTRICTIONS PURSUANT TO
     THE TERMS OF A STOCKHOLDERS' AGREEMENT, DATED APRIL 18, 1995 BETWEEN
     THE ISSUER AND THE REGISTERED HOLDER HEREOF, A COPY OF WHICH AGREEMENT
     IS ON FILE AT THE PRINCIPAL OFFICE OF THE ISSUER.

6.   MISCELLANEOUS PROVISIONS
     ------------------------

          6.1  FURTHER ASSURANCES. Each Stockholder and the Company agrees to
               ------------------
take any and all actions and to execute any and all documents reasonably
necessary to effectuate the terms and intent of this Agreement.

          6.2  TERMINATION OF AGREEMENT. This Agreement shall terminate upon:
               ------------------------                                       

               6.2.1  The written agreement of the Company and the holders of at
least sixty-six and two-thirds percent (66 2/3%) of the Shares which are at that
time subject to the terms of this Agreement;

               6.2.2  The dissolution of the Company;

 
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Stockholders/Digital Certificates International, Inc.
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               6.2.3  A merger of the Company with or into another corporation
whereby the Stockholders do not continue to hold the Shares or do not receive
shares of the surviving corporation;

               6.2.4  The closing of a sale or exchange of all outstanding
shares of capital stock of the Company; or

               6.2.5  The public sale by the Company of securities pursuant to a
registration under the Securities Act of 1933, as amended.

          The termination of this Agreement shall not affect any right, remedy
or obligation existing hereunder prior to the effective date of such
termination.

          6.3  SPECIFIC PERFORMANCE.  The parties hereto agree that because the
               --------------------                                        
Shares have a unique and special value and cannot be readily purchased or sold
in any regular market, irreparable damage would be suffered if the terms and
provisions of this Agreement were breached and were not specifically
enforceable. Accordingly, the parties hereto agree that in the event of a breach
of this Agreement by any party hereto, the other parties hereto would not have
an adequate remedy at law and shall therefore be entitled to obtain equitable
relief from a court of competent jurisdiction enjoining the breaching party from
violating any of the terms or provisions hereof, declaring any transaction in
breach hereof rescinded and requiring specific performance of the terms hereof.

          6.4  GOVERNING LAWS.  IT IS THE INTENTION OF THE PARTIES HERETO THAT
               --------------                                                 
THE INTERNAL LAWS OF THE STATE OF DELAWARE, U.S.A. (IRRESPECTIVE OF ITS CHOICE
OF LAW PRINCIPLES) SHALL GOVERN THE VALIDITY OF THIS AGREEMENT, THE CONSTRUCTION
OF ITS TERMS, AND THE INTERPRETATION AND ENFORCEMENT OF THE RIGHTS AND DUTIES OF
THE PARTIES HERETO. THE PARTIES HEREBY EXCLUDE THE UNITED NATIONS CONVENTION ON
CONTRACTS FOR THE INTERNATIONAL SALE OF GOODS FROM THIS AGREEMENT. THE PARTIES
HEREBY AGREE THAT ANY SUIT TO ENFORCE ANY PROVISION OF THIS AGREEMENT OR ARISING
OUT OF OR BASED UPON THIS AGREEMENT OR THE BUSINESS RELATIONSHIP BETWEEN ANY OF
THE PARTIES HERETO SHALL BE BROUGHT EXCLUSIVELY IN THE UNITED STATES DISTRICT
COURT FOR THE NORTHERN DISTRICT OF CALIFORNIA OR THE SUPERIOR OR MUNICIPAL COURT
IN AND FOR THE COUNTY OF SAN MATEO, CALIFORNIA, U.S.A. Each party hereby agrees
that such courts shall have exclusive in personam jurisdiction and venue with
                                      -----------                            
respect to such party, and each party hereby 

 
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Stockholders/Digital Certificates International, Inc.
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submits to the exclusive in personam jurisdiction and venue of such courts.
                         -----------                                       

          6.5  BINDING UPON SUCCESSORS AND ASSIGNS.  Subject to, and unless
               -----------------------------------                         
otherwise provided in, this Agreement, each and all of the covenants, terms,
provisions, and agreements contained herein shall be binding upon, and inure to
the benefit of, the permitted successors, executors, heirs, representatives,
administrators and assigns of the parties hereto.  Prior to any assignment
hereunder, the assignee shall agree in writing to be bound by all of the terms
and provisions of this Agreement.  Upon any such assignment, such assignee shall
be considered another party to this Agreement, shall hold the shares he, she or
it purchases subject to all of the provisions of this Agreement and shall make
no transfers other than as permitted herein.  Except as set forth herein,
nothing in this Agreement prohibits a party from selling, assigning,
transferring or pledging shares of Preferred Stock or Common Stock of the
Company to an affiliate of said party, whether foreign, domestic or otherwise.

          6.6  SEVERABILITY.  If any provision of this Agreement, or the
               ------------                                             
application thereof, shall for any reason and to any extent be invalid or
unenforceable, the remainder of this Agreement and application of such provision
to other persons or circumstances shall be interpreted so as best to reasonably
effect the intent of the parties hereto.  The parties further agree to replace
such void or unenforceable provision of this Agreement with a valid and
enforceable provision which will achieve, to the extent possible, the economic,
business and other purposes of the void or unenforceable provision.

          6.7  ENTIRE AGREEMENT.  This Agreement, the exhibits hereto, the
               ----------------                                           
documents referenced herein, and the exhibits thereto, constitute the entire
understanding and agreement of the parties hereto with respect to the subject
matter hereof and thereof and supersede all prior and contemporaneous agreements
or understandings, inducements or conditions, express or implied, written or
oral, between the parties with respect hereto and thereto.  The express terms
hereof control and supersede any course of performance or usage of the trade
inconsistent with any of the terms hereof.

          6.8  COUNTERPARTS.  This Agreement may be executed in any number of
               ------------                                                  
counterparts, each of which shall be an original as against any party whose
signature appears thereon and all of which together shall constitute one and the
same instrument. This Agreement shall become binding when one or more
counterparts 

 
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Stockholders/Digital Certificates International, Inc.
Page 10

hereof, individually or taken together, shall bear the signatures of all of the
parties reflected hereon as signatories.

          6.9  OTHER REMEDIES.  Any and all remedies herein expressly
               --------------                                        
conferred upon a party shall be deemed cumulative with and not exclusive of any
other remedy conferred hereby or by law on such party, and the exercise of any
one remedy shall not preclude the exercise of any other.

          6.10 AMENDMENT AND WAIVERS.  Any term or provision of this Agreement
               ---------------------                                
may be amended, and the observance of any term of this Agreement may be waived
(either generally or in a particular instance and either retroactively or
prospectively) only by a writing signed by the holders of at least sixty-six and
two-thirds percent (66 2/3%) of the Shares which are at that time subject to the
terms of this Agreement. The waiver of any breach hereof for default in payment
of any amount due hereunder or default in the performance hereof shall not be
deemed to constitute a waiver of any other default or succeeding breach or
default.

          6.11 SURVIVAL OF AGREEMENTS.  All covenants, agreements, 
               ----------------------                             
representations and warranties made herein shall survive the execution and
delivery of this Agreement and the consummation of the transactions contemplated
hereby.

          6.12 NO WAIVER.  The failure of any party to enforce any of the
               ---------                                                 
provisions hereof shall not be construed to be a waiver of the right of such
party thereafter to enforce such provisions.

 
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Stockholders/Digital Certificates International, Inc.
Page 11

          6.13 ATTORNEYS' FEES.
               --------------- 

               6.13.1 Should suit or arbitration be brought to enforce or
interpret any part of this Agreement, the prevailing party shall be entitled to
recover reasonable attorneys' fees to be fixed by the court or arbitrator
(including without limitation, costs, expenses and fees on any appeal). If
either party to this Agreement shall bring any action for any relief against the
other, declaratory or otherwise, arising out of this Agreement, the losing party
shall pay to the prevailing party a reasonable sum for attorneys fees incurred
in bringing such suit and enforcing any judgment granted therein, all of which
shall be deemed to have accrued upon the commencement of such action and shall
be paid whether or not such action is prosecuted to judgment. Any judgment or
order entered in such action shall contain a specific provision providing for
the recovery of attorney fees and costs incurred in enforcing such judgment. For
the purposes of this section, attorney fees shall include, without limitation,
fees incurred in the following: (i) postjudgment motions; (ii) contempt
proceedings; (iii) garnishment, levy, and debtor and third party examinations;
(iv) discovery; and (v) bankruptcy litigation.

               6.13.2 In addition to attorneys' fees recoverable pursuant to
Section 6.13.1 above, the prevailing party in any suit or arbitration shall be
entitled to recover its reasonable attorneys' fees incurred in enforcing the
final judgment or arbitration award. Such right to attorneys' fees pursuant to
this Section 6.13 is severable from the other provisions of this Agreement,
shall survive the initial judgment or award in favor of the prevailing party,
and is not to be deemed to be merged into such judgment or award.

          6.14 NOTICES.  Whenever any party hereto desires or is required to
               -------
give any notice, demand or request with respect to this Agreement, each such
communication shall be in writing and shall be given or made by, telecopy,
telegraph, cable, mail or other delivery and telecopied, telegraphed, cabled,
mailed or delivered to the intended recipient at the addresses specified below:

     If to the Company:                 c/o Mr. D. James Bidzos
                                        RSA Data Security, Inc.
                                        100 Marine Parkway, Suite 500
                                        Redwood City, CA 94065

 
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Page 12                                                     

     with a copy to:                    Timothy Tomlinson, Esq.
                                        Tomlinson Zisko Morosoli & Maser
                                        200 Page Mill Road, Second Floor
                                        Palo Alto, CA  94306

     If to a Stockholder                At the address of such person as
     or a Permitted                     set forth on the stock record books
     Transferee:                        of the Company

Except as may be otherwise provided elsewhere in this Agreement, all such
communications shall be deemed to have been duly given when transmitted by
telecopier with verified receipt by the receiving telecopier, when delivered to
the telegraph or cable office, when personally delivered, or in the case of a
mailed notice, five (5) days after being deposited in the United States
certified or registered mail, postage prepaid. Any party may change its address
for such communications by giving notice thereof to the other parties in
conformance with this section.

          6.15 CONSTRUCTION OF AGREEMENT.  This Agreement has been negotiated 
               -------------------------                                     
by the respective parties hereto and their attorneys and the language hereof
shall not be construed for or against any party.  A reference in this Agreement
to any Section shall include a reference to every Section the number of which
begins with the number of the Section which reference is specifically made
(e.g., a reference to Section ERROR! REFERENCE SOURCE NOT FOUND. shall include a
reference to Sections ERROR! REFERENCE SOURCE NOT FOUND. and ERROR! REFERENCE
SOURCE NOT FOUND.).  The titles and headings herein are for reference purposes
only and shall not in any manner limit the construction of this Agreement, which
shall be considered as a whole.

          6.16 NO JOINT VENTURE.  Nothing contained in this Agreement shall
               ----------------                                            
be deemed or construed as creating a joint venture or partnership between any of
the parties hereto.  No party is by virtue of this Agreement authorized as an
agent, employee or legal representative of any other party.  No party shall have
the power to control the activities and operations of any other.  No party shall
have any power or authority to bind or commit any other.  No party shall hold
itself out as having any authority or relationship in contravention of this
Section.

          6.17 PRONOUNS.  All pronouns and any variations thereof shall be
               --------                                                   
deemed to refer to the masculine, feminine or neuter, singular or plural, as the
identity of the person, persons, entity or entities may require.

 
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Stockholders/Digital Certificates International, Inc.
Page 13                                                     

          6.18 ABSENCE OF THIRD PARTY BENEFICIARY RIGHTS.  No provisions of this
               -----------------------------------------                        
Agreement are intended nor shall be interpreted to provide or create any third
party beneficiary rights or any other rights of any kind in any client,
customer, affiliate, stockholder, partner of any party hereto or any other
person, unless specifically provided otherwise herein, and, except as so
provided, all provisions hereof shall be personal solely between the parties to
this Agreement.

          6.19 EMPLOYMENT.  Nothing in this Agreement shall be construed as
               ----------                                                  
granting a Stockholder or any other party hereto any right to continued
employment with the Company or any subsidiary of the Company.  Except as the
Company and a Stockholder may otherwise agree in writing, a Stockholder's
employment shall be terminable by the Company or any such subsidiary at will.

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

                              COMPANY:

                              Digital Certificates International, Inc.
                              c/o RSA Data Security, Inc. 
                              Redwood City, CA 94065
                              100 Marine Parkway, Suite 500
                              Redwood City, CA 94065


                              DIGITAL CERTIFICATES INTERNATIONAL, INC.,
                              a Delaware corporation

                              By: /s/ David Cowan
                                 -----------------------------
                              Name: David Cowan               
                                   ---------------------------
                              Title: Chairman                 
                                    --------------------------


 
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Stockholders/Digital Certificates International, Inc.
Page 14                                                     

                         STOCKHOLDERS:

                         Bessemer Venture Partners DCI
                         1025 Old County Road, Suite 205
                         Westbury, NY 11590


                         By:  BESSEMER VENTURE PARTNERS DCI

                         By:  Bessemer Venture Partners III L.P.
                              Managing General Partner

                         By:  Deer III & Co.

                         By: /s/ Robert H. Buesher
                            ----------------------------------
                         Name: Robert H. Buesher
                              --------------------------------
                         Title: Partner


                         Mitsubishi Corporation
                         6-3, Marunouchi 2- Chome,
                         Chiyoda-ku, Tokyo 100-86
                         Japan

                         MITSUBISHI CORPORATION

                         By: /s/ Yukihiro Kayama
                            ----------------------------------
                         Name: Yukihiro Kayama

                         Title: Senior Assistant to Managing Director
                         Information Systems and Services Group

                         Security Dynamics Technologies, Inc.
                         One Alewife Center
                         Cambridge, MA 02140-2312

                         SECURITY DYNAMICS TECHNOLOGIES, INC.

                         By: /s/ Charles R. Stuckey Jr.
                            ----------------------------------
                         Name: Charles R. Stuckey Jr.
                              --------------------------------
                         Title: President and CEO
                               -------------------------------


 
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Stockholders/Digital Certificates International, Inc.
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                         Intel Corporation
                         2200 Mission College Blvd.
                         Santa Clara, CA 95052

                         INTEL CORPORATION

                         By: /s/ Arvind Sodhani
                             ---------------------------------

                         Name: Arvind Sodhani
                               -------------------------------

                         Title: Vice President and Treasurer
                                ------------------------------

                         Ameritech Development Corporation
                         30 South Wacker Drive, 37th Floor
                         Chicago, Ill  60606

                         AMERITECH DEVELOPMENT CORPORATION

                         By: /s/ Thomas Touton
                             ---------------------------------

                         Name: Thomas Touton

                         Title: Vice President - Venture Capital

                         GC&H Investments       
                         3000 Sand Hill Road                                   
                         Building 3, Suite 230
                         Menlo Park, CA 94025

                         GC&H INVESTMENTS
 
                         By: /s/ James C. Kitch
                             ---------------------------------

                         Name: James C. Kitch
                               -------------------------------

                         Title: Executive Partner
                                ------------------------------

 
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Stockholders/Digital Certificates International, Inc.
Page 16                                                     
                         VISA International Service Association

                         c/o Andrew Konstantaras
                         Legal Department
                         VISA
                         900 Metro Center Boulevard
                         Foster City, CA 94404
 
                         VISA INTERNATIONAL SERVICE ASSOCIATION

                         By: /s/ William L. Powar
                             ---------------------------------

                         Name: William L. Powar
                               -------------------------------

                         Title: Vice President
                                ------------------------------

                         Fischer Security Corporation
                         4073 Mercantile Avenue
                         Naples, FL  33942

                         FISCHER SECURITY CORPORATION L.L.C.

                         By: /s/ Addison M. Fischer
                             ---------------------------------

                         Name: _______________________________

                         Title: ______________________________

                         First TZMM Investment Partnership
                         c/o Tomlinson Zisko Morosoli & Maser
                         200 Page Mill Road, Second Floor
                         Palo Alto, CA  94306

                         FIRST TZMM INVESTMENT PARTNERSHIP

                         By: /s/ Timothy Tomlinson
                             ---------------------------------

                         Name: Timothy Tomlinson
                               -------------------------------

                         Title: Partner
                                ------------------------------

 
Stockholders' Agreement
Stockholders/Digital Certificates International, Inc.
Page 17                                                     

                         RSA Data Security, Inc.
                         100 Marine Parkway
                         Suite 500
                         Redwood City, CA 94065

                         RSA DATA SECURITY, INC.

                         By: /s/ D. James Bidzos
                             -----------------------------

                         Name: D. James Bidzos
                               ---------------------------

                         Title: __________________________


                         /s/ Ronald Rivest
                         ---------------------------------
                         Ronald Rivest
                         24 Candia Street
                         Arlington, MA 02174



                         /s/ D. James Bidzos
                         ---------------------------------
                         D. James Bidzos
                         c/o RSA Data Security, Inc.
                         100 Marine Parkway, Suite 500
                         Redwood City, CA 94065


                         Kairdos L.L.C.
                         c/o D. James Bidzos
                         RSA Data Security, Inc.
                         100 Marine Parkway, Suite 500
                         Redwood City, CA 94065


                         KAIRDOS L.L.C.

                         By: /s/ D. James Bidzos
                             -----------------------------

                         Name: D. James Bidzos
                               ---------------------------

                         Title: __________________________

 
Stockholders' Agreement
Stockholders/Digital Certificates International, Inc.
Page 18                                                     

                         TZM INVESTMENT FUND
                         c/o Tomlinson Zisko Morosoli & Maser
                         200 Page Mill Road, Second Floor
                         Palo Alto, CA 94306

                         TZM INVESTMENT FUND

                         By: /s/ William E. Zisko 
                            --------------------------- 
                         Name: William E. Zisko 
                              ------------------------- 
                         Title: General Partner
                               ------------------------ 


 
Stockholders' Agreement
Stockholders/Digital Certificates International, Inc.
Page 19                                                     

                                  SCHEDULE A

                                 STOCKHOLDERS
                                 ------------

 
 
                                                            NUMBER AND CLASS
NAME OF STOCKHOLDER                                         OF SHARES OWNED
- -------------------                                         ---------------

                                                               PREFERRED
                                                               ---------
                                                         
Bessemer Venture Partners DCI                                    850,000
                                                                        
Intel Corporation                                                850,000
                                                                        
Visa International Services Association                          850,000
                                                                        
Mitsubishi Corporation                                           425,000
                                                                        
Security Dynamics Technologies, Inc.                             425,000
                                                                        
Ameritech Development Corporation                                425,000
                                                                        
Fischer Security Corp.                                           425,000
                                                                        
GC&H Investments                                                  33,333
                                                                        
First TZMM Investment Partnership                                 23,550 
 
 
                                                                 COMMON
                                                                 ------  
 
Bessemer Venture Partners DCI                                    258,333
                                                                        
Ronald Rivest                                                    125,000
                                                                        
D. James Bidzos                                                  125,000
                                                                        
Kairdos L.L.C.                                                   100,000
                                                                        
TZM Investment Fund                                               80,000
                                                                        
RSA Data Security, Inc.                                        4,000,000 


 
                  AMENDMENT NO. 1 TO STOCKHOLDERS' AGREEMENT
                  ------------------------------------------


     This Amendment No. 1 ("Amendment") to the Stockholders' Agreement dated
April 18, 1995 (the "Agreement") is made as of this 20th day of February, 1996
by and among VeriSign, Inc. (formerly Digital Certificates International, Inc.),
a Delaware corporation (the "Company"), each of the individuals and entities
listed on Schedule A to the Agreement (the "Existing Stockholders"), and each of
          ----------
the individuals and entities listed as New Stockholders on the signature page to
this Amendment (the "New Stockholders"). Capitalized terms used herein which are
not defined herein shall have the definition ascribed to them in the Agreement.


                                   RECITALS
                                   --------


   The Company desires to sell and issue to the New Stockholders and the New
Stockholders desire to purchase from the Company, shares of the Company's Series
B Preferred Stock pursuant to that certain Series B Preferred Stock Purchase
Agreement of even date herewith (the "Series B Agreement").
     
     The Existing Stockholders desire for the New Stockholders to invest in the
Company and, as a condition thereof and to induce such investment, the Existing
Stockholders and the Company are willing to enter into this Amendment to permit
the New Stockholders to become a party to the Agreement.

     The New Stockholders desire to invest in the Company and, as a condition
thereof and in order to induce the Company to accept such investment, the New
Stockholders are willing to enter into this Amendment to become parties to the
Agreement.

     In consideration of the foregoing and the promises and covenants contained
herein and other good and valuable consideration the receipt of which is hereby
acknowledged, the parties hereto agree as follows:


     1.   ADDITIONAL PARTIES TO THE AGREEMENT.
          ----------------------------------- 

     The New Stockholders hereby enter into and become parties to the Agreement.
Schedule A to the Agreement is amended to include the New Stockholders and the
- ----------                                                                    
shares of the Company's capital stock purchased pursuant to the Series B
Agreement.

     2.   AMENDMENTS TO AGREEMENT.
          ----------------------- 

          2.1  The New Stockholders and the Existing Stockholders are
collectively referred to as "Stockholders" for the purposes of the Agreement.

          2.2  Section 4.4 of the Agreement is amended in its entirety to read
as follows:


               "4.4      Board Representation. So long as Bessemer 
                         --------------------
     Venture Partners III L.P. or its general partner or affiliates of
     such general partner ("Bessemer") owns not less than fifty
                            --------
     percent (50%) of the shares of the Preferred Stock it holds as
     set forth on Schedule A as of the date Bessemer first executes
     this Agreement (or an equivalent amount of the Common Stock
     issued upon conversion thereof), the Company and the Stockholders
     shall cause and maintain the election to the Board of Directors
     of a representative of Bessemer. So long as Kleiner Perkins
     Caufield & Byers VII or its general partners or affiliates or
     partners of such general partners ("Kleiner") owns not less than
                                         -------
     fifty percent (50%) of the shares the Preferred Stock it holds as
     set forth on Schedule A as of

 
     the date Kleiner first becomes a party to this Agreement (or an
     equivalent amount of the Common Stock issued upon conversion
     thereof), the Company and the Stockholders shall cause and
     maintain the election to the Board of Directors of a
     representative of Kleiner. So long as RSA Data Security, Inc., a
     Delaware corporation ("RSA"), owns not less than the lesser of
                            ---                           
     (a) ten percent (10%) of the issued and outstanding voting shares
     of the Company (on an as converted basis) or (b) seventy-five
     percent (75%) of the shares of Common Stock held by it as set
     forth on Schedule A as of the date RSA first executes this
     Agreement, the Company and the Stockholders shall cause and
     maintain the election to the Board of Directors of a
     representative of RSA. In addition, the Company and the
     Stockholders shall cause and maintain the election to the Board
     of Directors of a representative of each of the following
     Stockholders for so long as it or its affiliates owns not less
     than 50 percent (50%) of the shares of the Preferred Stock it
     holds as set forth on Schedule A as of the date it first executes
     this Agreement (or an equivalent amount of Common Stock issued
     upon conversion thereof): Intel Corporation and VISA."

          2.3  Section 6.10 of the Agreement is amended in its entirety to read
as follows:

               "6.10     Amendment and Waivers. Except as otherwise
                         ---------------------
     provided herein, any term or provision of this Agreement may be
     amended, and the observance of any term of this Agreement may be
     waived (either generally or in a particular instance and either
     retroactively or prospectively) only by a writing signed by the
     holders of at least sixty-six and two-thirds percent (66 2/3%) of
     the Shares which are at that time subject to the terms of this
     Agreement. Notwithstanding the above, with respect to Section 4.4
     hereof and the election of representatives of Kleiner, Bessemer,
     RSA, Intel Corporation and VISA to the Board of Directors, this
     Agreement shall not be amended to remove such Board seats without
     the written consent of Kleiner, Bessemer, RSA, Intel Corporation
     or VISA with respect to their respective Board seats."

     3.   CONSENT.
          ------- 

          Each Existing Stockholder, pursuant to any rights such Existing
Stockholder may have under the Agreement, hereby, on behalf of itself and the
other Stockholders under the Agreement consents to adding the New Stockholders
as parties to the Agreement.

     4.   EFFECT OF AMENDMENT.
          ------------------- 

          Except as amended and set forth above, the Agreement shall continue in
full force and effect.

     5.   COUNTERPARTS.
          ------------ 

          This Amendment may be executed in any number of counterparts, each
which will be deemed an original, and all of which together shall constitute one
instrument .

     6.   SEVERABILITY.
          ------------ 

          If one or more provisions of this Amendment are held to be
unenforceable under applicable law, such provision shall be excluded from this
Amendment and the balance of the Amendment shall be interpreted as if such
provision were so excluded and shall be enforceable in

 
accordance with its terms.

     7.   ENTIRE AGREEMENT.
          ---------------- 

          This Amendment, together with the Agreement, constitutes the full and
entire understanding and agreement between the parties with regard to the      
subjects hereof and thereof.

     8.   GOVERNING LAW.
          ------------- 

          This Amendment shall be governed by and construed under the laws of
the State of Delaware as applied to agreements among Delaware residents entered
into and to be performed entirely within Delaware.


               [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

 
     This Amendment is hereby executed as of the date first above written.

COMPANY:               VERISIGN, INC., a Delaware corporation

                                 
                              By:/s/ Stratton Sclavos
                                 ----------------------------------------
                                   Stratton Sclavos, President


                    Address:  
                              --------------------------------------------
                             
                              --------------------------------------------
                              

EXISTING STOCKHOLDERS:   BESSEMER VENTURE PARTNERS DCI


                              By:  Bessemer Venture Partners III L.P. 
                                 Managing General Partner
                                  

                                   By:  Deer III & Co.


                                 By: /s/ Robert H. Buescher
                                     ---------------------------------------
                               
                                 Name: Robert H. Buescher
                                      --------------------------------------

                                 Title: Partner
                                        ------------------------------------
                                        

                    Address:  1025 Old Country Road, Suite 205
                              Westbury, NY  11590


                              MITSUBISHI CORPORATION


                              By:  ________________________________________


                              Name:   Yukihiro Kayama
                                   

                              Title:  Senior Assistant to Managing Director
                                       Information Systems and Services Group


                    Address:  6-3, Marunouchi 2-Chome
                              Chiyoda-ku, Tokyo 100-86
                              Japan


                      [SIGNATURE PAGE TO AMENDMENT NO. 1 
                          TO STOCKHOLDERS' AGREEMENT]

 
                              SECURITY DYNAMICS TECHNOLOGIES, INC.

                              By:/s/ Charles R. Stuckey Jr.
                                 -----------------------------------------

                              Name: Charles R. Stuckey Jr.
                                    --------------------------------------

                              Title: President and CEO
                                    --------------------------------------
                       

                    Address:  One Alewife Center
                              Cambridge, MA  02140-2312


                              INTEL CORPORATION


                              By: /s/ Arvind Sodhani
                                 -----------------------------------------
                              Name: Arvind Sodhani
                                   ----------------------------------------
                              Title: Vice President and Treasurer 
                                   ----------------------------------------
                             

                    Address:  2200 Mission College Blvd.
                              Santa Clara, CA  95052


                              AMERITECH DEVELOPMENT CORPORATION

                              By:/s/ Thomas Touton
                                 -----------------------------------------
                            
                              Name:   Thomas Touton

                              Title:  Vice President - Venture Capital


                    Address:  30 South Wacker Drive, 37th Floor
                              Chicago, IL 60606


                              GC&H INVESTMENTS


                              By:/s/ James C. Kitch
                                 ----------------------------------------
                                
                              Name: James C. Kitch
                                   --------------------------------------


                              Title:  Executive Partner
                                      ------------------------------------

                    Address:  3000 Sand Hill Road
                              Building 3, Suite 230
                              Menlo Park, CA  94025


                      [SIGNATURE PAGE TO AMENDMENT NO. 1
                          TO STOCKHOLDERS' AGREEMENT]

 
                              RSA DATA SECURITY, INC.

                              By:/s/ D. James Bidzos
                                 ----------------------------------------

                              Name: D. James Bidzos
                                    -------------------------------------
                              Title: CEO
                                    -------------------------------------

                    Address:  100 Marine Parkway, Suite 500
                              Redwood City, CA  94065

                              /s/ Ronald Rivest
                              -------------------------------------------
                                  Ronald Rivest


                    Address:  24 Candia Street
                              Arlington, MA  02174

                              /s/ D. James Bidzos
                              -------------------------------------------
                                  D. James Bidzos


                    Address:  c/o RSA Data Security, Inc.
                              100 Marine Parkway, Suite 500
                              Redwood City, CA  94065


                              KAIRDOS L.L.C.

                              By:/s/ D. James Bidzos
                                 ----------------------------------------

                              Name: D. James Bidzos
                                 ----------------------------------------
                              
                              Title: Manager
                                    -------------------------------------
                                  

                    Address:  c/o D. James Bidzos
                              RSA Data Security, Inc.
                              100 Marine Parkway, Suite 500
                              Redwood City, CA  94065


                      [SIGNATURE PAGE TO AMENDMENT NO. 1
                          TO STOCKHOLDERS' AGREEMENT]


 
                              FIRST TZMM INVESTMENT PARTNERSHIP


                              By: /s/ Timothy Tomlinson
                                  ----------------------------------------
                              Title: General Partner
                                    --------------------------------------

                    Address:  c/o Tomlinson Zisko Morosoli & Maser
                              200 Page Mill Road, Second Floor
                              Palo Alto, CA 94306


                              VISA INTERNATIONAL SERVICE 
                              ASSOCIATION


                              By: /s/ Visa International Service Association
                                  ----------------------------------------
                              Title: Group EVP
                                    --------------------------------------

                    Address:  c/o Andrew Konstantaras
                              Legal Department
                              VISA
                              900 Metro Center Boulevard
                              Foster City, CA 94404


                              FISHCER SECURITY CORPORATION L.L.C.


                              By: /s/ Addison Fischer
                                  ----------------------------------------
                              Title: Managing Director
                                    --------------------------------------

                    Address:  4073 Mercantile Avenue
                              Naples, FL 33942


NEW STOCKHOLDERS:        KLEINER PERKINS CAUFIELD & BYERS VII


                              By: /s/ Kevin R. Compton
                                 -----------------------------------------
                              Name: Kevin R. Compton
                                   ---------------------------------------
                              Title: General Partner
                                    --------------------------------------

                    Address:  2750 Sand Hill Road
                              Menlo Park, CA  94025


                      [SIGNATURE PAGE TO AMENDMENT NO. 1
                          TO STOCKHOLDERS' AGREEMENT]

 
                              KPCB VII FOUNDERS FUND


                              By: /s/ Kevin R. Compton
                                 ----------------------------------------

                              Name: Kevin R. Compton
                                   --------------------------------------

                              Title: General Partner
                                    -------------------------------------

                    Address:  2750 Sand Hill Road
                              Menlo Park, CA  94025


                      [SIGNATURE PAGE TO AMENDMENT NO. 1
                          TO STOCKHOLDERS' AGREEMENT]

 
                              KPCB INFORMATION SCIENCE           
               ZAIBATSU FUND II


                              By: /s/ Kevin R. Compton
                                 -----------------------------------------

                              Name: Kevin R. Compton
                                   ---------------------------------------

                              Title: General Partner
                                    --------------------------------------

                    Address:  2750 Sand Hill Road
                              Menlo Park, CA  94025


                      [SIGNATURE PAGE TO AMENDMENT NO. 1
                          TO STOCKHOLDERS' AGREEMENT]

 
                  AMENDMENT NO. 2 TO STOCKHOLDERS' AGREEMENT
                  ------------------------------------------


     This Amendment No. 2 ("Amendment") to the Stockholders' Agreement dated
April 18, 1995, as amended February 20, 1996 (the "Agreement"), is made as of
this 15th day of November, 1996 by and among VeriSign, Inc. (formerly Digital
Certificates International, Inc.), a Delaware corporation (the "Company"), each
of the individuals and entities listed on Schedule A to the Agreement and on the
                                          ----------                            
signature pages to Amendment No. 1 thereto dated February 20, 1996 (now
collectively defined as the "Current Stockholders"), and each of the individuals
and entities listed as New Stockholders on the signature page to this Amendment
(the "New Stockholders").  Capitalized terms used herein which are not defined
herein shall have the definition ascribed to them in the Agreement.


                                   RECITALS
                                   --------

     The Company desires to sell and issue to the New Stockholders and the New
Stockholders desire to purchase from the Company, shares of the Company's Series
C Preferred Stock pursuant to that certain Series C Preferred Stock Purchase
Agreement of even date herewith (the "Series C Agreement").

     The Current Stockholders desire for the New Stockholders to invest in the
Company and, as a condition thereof and to induce such investment, the Current
Stockholders and the Company are willing to enter into this Amendment to permit
the New Stockholders to become a party to the Agreement.

     The New Stockholders desire to invest in the Company and, as a condition
thereof and in order to induce the Company to accept such investment, the New
Stockholders are willing to enter into this Amendment to become parties to the
Agreement.

     In consideration of the foregoing and the promises and covenants contained
herein and other good and valuable consideration the receipt of which is hereby
acknowledged, the parties hereto agree as follows:

     1.   ADDITIONAL PARTIES TO THE AGREEMENT.
          ----------------------------------- 

          The New Stockholders hereby enter into and become parties to the
Agreement. Schedule A to the Agreement is amended to include the New
           ----------                                               
Stockholders and the shares of the Company's capital stock purchased pursuant to
the Series C Agreement.

     2.   STOCKHOLDERS DEFINITION.
          ----------------------- 

 
     The New Stockholders and the Current Stockholders are collectively referred
to as "Stockholders" for the purposes of the Agreement.

     3.   CONSENT.
          ------- 

          Each Current Stockholder, pursuant to any rights such Current
Stockholder may have under the Agreement, hereby, on behalf of itself and the
other Current Stockholders under the Agreement consents to adding the New
Stockholders as parties to the Agreement.

     4.   EFFECT OF AMENDMENT.
          ------------------- 

          Except as amended and set forth above, the Agreement shall continue in
full force and effect.

     5.   COUNTERPARTS.
          ------------ 

          This Amendment may be executed in any number of counterparts, each of
which will be deemed an original, and all of which together shall constitute one
instrument.

     6.   SEVERABILITY.
          ------------ 

          If one or more provisions of this Amendment are held to be
unenforceable under applicable law, such provision shall be excluded from this
Amendment and the balance of the Amendment shall be interpreted as if such
provision were so excluded and shall be enforceable in accordance with its
terms.

     7.   ENTIRE AGREEMENT.
          ---------------- 

          This Amendment, together with the Agreement, constitutes the full and
entire understanding and agreement between the parties with regard to the
subjects hereof and thereof.

     8.   GOVERNING LAW.
          ------------- 

          This Amendment shall be governed by and construed under the laws of
the State of Delaware as applied to agreements among Delaware residents entered
into and to be performed entirely within Delaware.

               [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                      -2-

 
          This Amendment is hereby executed as of the date first above written.
 
COMPANY:                      VERISIGN, INC., a Delaware corporation
 
                              By: /s/ Stratton Sclavos
                                 -----------------------------------------------
                                    Stratton Sclavos, President
 
                              Address:       2593 Coast Avenue
                                             Mountain View, CA 94043
 
CURRENT STOCKHOLDERS:         AMERITECH DEVELOPMENT CORPORATION
 
                              By: /s/ Thomas Touton
                                 -----------------------------------------------
                              Name: Thomas Touton
 
                              Title:         Vice President - Venture Capital
 
                              Address:       30 South Wacker Drive, 37th Floor
                                             Chicago, IL 60606

                              BESSEMER VENTURE PARTNERS DCI
 
                              By:   Bessemer Venture Partners III, L.P.
                                    Managing General partner
 
                                    By:  Deer III & Co.           
                                                                  
                                    By: /s/ Robert H. Buescher
                                       -----------------------------------------
                                    Name: Robert H. Buescher
                                         ---------------------------------------
                                    Title: Partner
                                          --------------------------------------
                                    Address: 1025 Old Country Road
                                             Suite 205                     
                                             Westbury, NY 11590             
 
                              /s/ D. James Bidzos
                              --------------------------------------------------
                              D. James Bidzos
 

                      [SIGNATURE PAGE TO AMENDMENT NO. 2
                         TO STOCKHOLDERS' AGREEMENT]

                                      -3-

 
                             Address:   c/o RSA Data Security, Inc.             
                                        100 Marine Parkway, Suite 500  
                                        Redwood City, CA 94065 

                             FIRST TZMM INVESTMENT PARTNERSHIP                 
                                                                               
                             By: /s/ Timothy Tomlinson
                                 -----------------------------------------------
                             Name:  Timothy Tomlinson                          
                                                                               
                             Title:     General Partner                         
                                                                               
                             Address:   c/o Tomlinson Zisko Morosoli & Maser LLP
                                        200 Page Mill Road, 2nd Floor
                                        Palo Alto, CA 94306

                             FISCHER SECURITY CORPORATION L.L.C.               
                                                                               
                             By:________________________________________________
                                                                               
                             Name:______________________________________________
                                                                               
                             Title:     Managing Director                       
                                                                               
                             Address:   4073 Mercantile Avenue                  
                                        Naples, FL 33942    

                             GC&H INVESTMENTS                                  
                                                                               
                             By: /s/ James C. Kitch
                                 -----------------------------------------------
                             Name:      James C. Kitch
                                        ----------------------------------------
                             Title:     Executive Partner
                                        ----------------------------------------
                             Address:   3000 Sand Hill Road                     
                                        Building 3, Suite 230
                                        Menlo Park, CA 94025

                             INTEL CORPORATION                                 
                                                                               
                             By: /s/ Satish Rishi
                                 -----------------------------------------------
                             Name:      Satish Rishi
                                        ----------------------------------------

                      [SIGNATURE PAGE TO AMENDMENT NO. 2
                         TO STOCKHOLDERS' AGREEMENT]

                                      -4-

 
                             Title:     Assistant Treasurer
                                        ----------------------------------------
                             Address:   2200 Mission College Boulevard        
                                        Santa Clara, CA 95052   

                             KAIRDOS L.L.C.                                  
                                                                             
                             By: /s/ D. James Bidzos
                                 -----------------------------------------------
                             Name:  D. James Bidzos                          
                                                                             
                             Title:     Manager                               
                                                                             
                             Address:   c/o D. James Bidzos                   
                                        RSA Data Security, Inc. 
                                        100 Marine Parkway, Suite 500
                                        Redwood City, Ca 94065 

                             KLEINER PERKINS CAULFIELD & BYERS VII           
                                                                             
                             By: /s/ Kevin R. Compton
                                 -----------------------------------------------
                             Name:  Kevin R. Compton                         
                                                                             
                             Title:     General Partner                       
                                                                             
                             Address:   2750 Sand Hill Road                   
                                        Menlo Park, CA 94025  

                             KPCB INFORMATION SCIENCE ZAIBATSU FUND II       
                                                                             
                             By: /s/ Kevin R. Compton
                                 -----------------------------------------------
                             Name:  Kevin R. Compton                         
                                                                             
                             Title:     General Partner                       
                                                                             
                             Address:   2750 Sand Hill Road                   
                                        Menlo Park, CA 94025   

                             KPCB VII FOUNDERS FUND                          
                                                                             
                             By: /s/ Kevin R. Compton
                                 -----------------------------------------------

                       [SIGNATURE PAGE TO AMENDMENT NO.2
                          TO STOCKHOLDERS' AGREEMENT]

                                      -5-

 
                             Name:  Kevin R. Compton                         
                                                                             
                             Title:     General Partner                       
                                                                             
                             Address:   2750 Sand Hill Road                   
                                        Menlo Park, CA 94025   
                             
                             MITSUBISHI CORPORATION                          
                                                                             
                             By:________________________________________________
                                
                             Name:  Hironori Aihara                          
                                                                             
                             Title:     Managing Director                     
                                                                             
                             Address:   6-3, Marunouchi 2-Chome               
                                        Chiyoda-ku, Tokyo 100-86  
                                        Japan 
                                                                             
                             /s/ Ronald Rivest
                             ---------------------------------------------------
                             Ronald Rivest                                   
                                                                             
                             Address:   24 Candia Street                      
                                        Arlington, MA 02174

                             RSA DATA SECURITY, INC.                         
                                                                             
                             By: /s/ D. James Bidzos
                                ------------------------------------------------
                             Name:  D. James Bidzos                           
  
                             Title:     CEO                                  
                                                                            
                             Address:   100 Marine Parkway, Suite 500        
                                        Redwood City, CA 94065 

                             SECURITY DYNAMICS TECHNOLOGIES, INC.           
                                                                            
                             By: /s/ Charles R. Stuckey Jr.
                                ------------------------------------------------
                             Name:      Charles R. Stuckey Jr.
                                        ----------------------------------------
                             Title:     Chairman and CEO
                                        ----------------------------------------

                       [SIGNATURE PAGE TO AMENDMENT NO.2
                          TO STOCKHOLDERS' AGREEMENT]

                                      -6-

 
                             Address:  20 Crosby Drive                      
                                       Bedford, MA 01730     

                             TZM INVESTMENT FUND                            
                                                                            
                             By: /s/ Timothy Tomlinson
                                ------------------------------------------------
                             Name:  Timothy Tomlinson                       
                                                                            
                             Title:    General Partner                      
                                                                            
                             Address:  c/o Tomlinson Zisko Morosoli & Maser 
                                       LLP
                                       200 Page Mill Road, 2nd Floor  
                                       Palo Alto, CA 94306     

                             VISA INTERNATIONAL SERVICE ASSOCIATION         
                                                                            
                             By: /s/ William L. Chenevich
                                ------------------------------------------------
                             Name:     William L. Chenevich
                                       -----------------------------------------
                             Title:    Group Executive V.P.
                                       -----------------------------------------
                             Address:  c/o Andrew Konstantaras
                                       Legal Department
                                       VISA
                                       900 Metro Center Boulevard
                                       Foster City, CA 94404

NEW STOCKHOLDERS:            CISCO SYSTEMS, INC.
 
 
                             By: /s/ Cisco Systems, Inc.
                                ------------------------------------------------
                             Name:     _________________________________________
                                                                            
                             Title:    _________________________________________
 
                             Address:  170 West Tasman Drive
                                       Building J-4
                                       San Jose, CA 95134
                                       Attention:  Mike Volpi


                      [SIGNATURE PAGE TO AMENDMENT NO. 2
                         TO STOCKHOLDERS' AGREEMENT]

                                      -7-

 
                             MICROSOFT CORPORATION
 
 
                             By: /s/ Gregory B. Maffei
                                ------------------------------------------------
                             Name:     Gregory B. Maffei
                                       -----------------------------------------
                             Title:    VP, Corporate Development, Treasurer
                                       -----------------------------------------
                             Address:  One Microsoft Way
                                       Redmond, WA  98052-6399
                                       Attn:

                             COMCAST INVESTMENT HOLDINGS, INC.
 
 
                             By: /s/ Julian A. Brodsky
                                ------------------------------------------------
                             Name:     Julian A. Brodsky
                                       -----------------------------------------
                             Title:    Vice Chairman
                                       -----------------------------------------
                             Address:  1500 Market Street
                                       Philadelphia, PA 19102
                                       Attn:  General Counsel

                             VENTURE FUND I, LP
 
 
 
                             By: /s/ Neal Douglas
                                ------------------------------------------------
                             Name:    Neal Douglas
                                      ------------------------------------------
                             Title:   General Partner
                                      ------------------------------------------
                             Address:  c/o AT&T Ventures
                                       3000 Sand Hill Road, Bldg. 4,
                                       Suite 235
                                       Menlo Park, CA  94025
                                       Attn:  Neal Douglas

                             INTUIT INC.


                      [SIGNATURE PAGE TO AMENDMENT NO. 2
                         TO STOCKHOLDERS' AGREEMENT]

                                      -8-

 
                             By: /s/ James J. Heeger
                                ------------------------------------------------
                             Name:     James J. Heeger
                                       -----------------------------------------
                             Title:    SVP/CFO
                                       -----------------------------------------
                             Address:  2535 Garcia Avenue
                                       P. O. Box 7850
                                       Mountain View, CA  94039-7850
                                       Attn:  General Counsel

                             REUTERS NEWMEDIA INC.
 
 
                             By: /s/ Reuters Newmedia Inc.
                                ------------------------------------------------
                             Name:     _________________________________________
                                                                            
                             Title:    CFO Reuters America Holdings, Inc.
                                       -----------------------------------------
                             Address:  c/o Reuters America Holdings
                                       1700 Broadway
                                       New York, NY  10019
                                       Attn:  Devin Wenig, Legal Dept.

                             FIRST DATA CORPORATION
 
 
                             By: /s/ Scott Loftesness
                                ------------------------------------------------
                             Name:     Scott Loftesness
                                       -----------------------------------------
                             Title:    Executive Vice President - EFS
                                       -----------------------------------------
                             Address:  400 Hansen Way
                                       -----------------------------------------
                                       Palo Alto, CA 94304
                                       -----------------------------------------

                             SOFTBANK VENTURES, INC.
 
 
                             By: /s/ Yoshitaka Kitao
                                ------------------------------------------------
                             Name:  Yoshitaka Kitao


                      [SIGNATURE PAGE TO AMENDMENT NO. 2
                         TO STOCKHOLDERS' AGREEMENT]

                                      -9-

 
                             Title:    President
 
                             Address:  24-1 Nihonbashi-Hakozakicho
                                       Chuo-ku, Tokyo 103
                                       Japan

                             MERRILL LYNCH GROUP, INC.
 
 
                             By: /s/ Theresa Lang
                                ------------------------------------
                             Name:   Theresa Lang
                                  ----------------------------------
                             Title:  President
                                   ---------------------------------
                             Address:  Merrill Lynch & Co., Inc.
                                       World Financial Center                   
                                       North Tower                            
                                       280 Vesey Street                       
                                       New York, NY  10281-1334               
                                       Attn:  Andrea Lowenthal, Esq.           

                             AMERINDO TECHNOLOGY GROWTH FUND II
 
 
                             By: /s/ Alberto W. Vilar
                                 ------------------------------------
                             Name:   Alberto W. Vilar
                                  -----------------------------------
                             Title:  Director
                                   ----------------------------------
                             Address:  c/o Amerindo Investment Advisors
                                       399 Park Avenue, 18th Floor
                                       New York, NY  10022

                             ATTRACTOR L.P.
 
 
                             By: /s/ Harvey Allison
                                ------------------------------------
                             Name:   Harvey Allison
                                  ----------------------------------
                             Title:  MM of Attractor Ventures LLC
                                   ---------------------------------

                      [SIGNATURE PAGE TO AMENDMENT NO. 2
                         TO STOCKHOLDERS' AGREEMENT]

                                      -10-


 
                             Address:  2730 Sand Hill Road, Suite 280
                                       Menlo Park, CA  94025
                                       Attn:  Harvey Allison

                             CHANCELLOR LGT ASSET MANAGEMENT
 
 
                             By: /s/ Joar DeSantis 
                                 -----------------------------------------------
                             Name:     Joar DeSantis
                                       -----------------------------------------
                             Title:    Nominee Partner
                                       -----------------------------------------
                             Address:  1166 Avenue of the Americas
                                       New York, NY  10036
                                       Attn:  Alessandro Piol

                             GEMPLUS
 
 
                             By: /s/ Mark Lassus
                                 -----------------------------------------------
                             Name:     Mark Lassus
                                       -----------------------------------------
                             Title:    President and CEO
                                       -----------------------------------------
                             Address:  Parc D'Activities De Gemenos
                                       13881 Gemenos
                                       France
                                       Attn:  Marc Lassus


                      [SIGNATURE PAGE TO AMENDMENT NO. 2
                         TO STOCKHOLDERS' AGREEMENT]

                                      -11-