[VANTAS LOGO]
OFFICING SOLUTIONS WORLDWIDE

                                              LEASE AND SERVICE AGREEMENT
                                              EXTENSION RIDER


RE:       Lease and Service Agreement between VANTAS Reston L.P. and Certicom
          ("Agreement").

DATE:     May 18, 2000

CENTER:   VANTAS Reston
          Office 307


Paragraph  "3a" of the  Agreement  is  hereby  modified  so that the term of the
Agreement shall expire on 9/29/2000.

In accordance with the Lease and Service Agreement Rebate Rider, attached to the
original Lease and Service Agreement,  and in consideration of this modification
and  extension  of the term,  the  Lessee  shall pay the  Lessor as rent for the
Premises a total rent of $16,427,  payable in 3 equal  monthly  installments  of
$5475.

All other terms and  conditions of the Agreement  shall remain in full force and
effect.



ACCEPTED BY LESSOR:                          ACCEPTED BY LESSEE:

By:  /s/ J. Morris                           By:  /s/ Richard M. Depew
    ---------------------------                   -------------------------

Date:        6/12/00                         Title: EVP of Field Operations
      -------------------------                     -----------------------

                                             Date:       6/8/00
                                                    -----------------------

<PAGE>

 [ALLIANCE LOGO]
Business Centers
                                            LEASE AND SERVICE AGREEMENT
                                            EXTENSION RIDER


RE:       Lease and Service Agreement between ALLIANCE Reston L.P. and Certicom
          ("Agreement").

DATE:     June 2, 1999

CENTER:   ALLIANCE Reston



Paragraph  "3a" of the  Agreement  is  hereby  modified  so that the term of the
Agreement shall expire on December 31, 1999.

In accordance with the Lease and Service Agreement Rebate Rider, attached to the
original Lease and the revised Service  Agreement,  and in consideration of this
modification  and extension of the term, the Lessee shall pay the Lessor as rent
for  the  Premises  a  total  rent  of  $20,190,  payable  in  6  equal  monthly
installments of $3,365.

All other terms and  conditions of the Agreement  shall remain in full force and
effect.



ACCEPTED BY LESSOR:                          ACCEPTED BY LESSEE:

By:  /s/ J. Mulson                           By:  /s/ B. MacInnis
    ---------------------------                   -------------------------

Date:        6/3/99                          Title: CFO
      -------------------------                     -----------------------

                                             Date:       6/3/99
                                                    -----------------------


<PAGE>
<TABLE>
<CAPTION>

                              Exhibit B-Continued
<S>  <C>                                                                        <C>            <C>
E.   CONCIERGE SERVICES
     1)   Arrangement for Business Supplies, Catering, Meal order taking, etc.       $25.00          Per hour
                                                                                               .20 hr minimum

F.   WORD PROCESSING GRAPHICS
     1)   Standard Word Processing Rate                                         From $30.00          Per hour
          Standard Desktop Publishing/Graphics Rate                             From $40.00     .3 hr minimum
          Word Processing and Desktop Publishing Services billed in 6 minute
          increments. Normal turnaround = 24 hours

     2)   Word Processing - Rush Turnaround Time = 1-8 hours                    From $45.00          Per hour
          Desktop Publishing - Rush Turnaround Time = 1-8 hours                 From $50.00     .3 hr Minimum
          The Word Processing and Desktop Publishing services below will be
          billed at 150% of the normal Word Processing rate if requested as
          a rush.

     3)   Overtime Charges for Word Processing                                  From $60.00          Per hour
          Overtime charges for Desktop Publishing/Graphics                      From $80.00   .3 hour minimum
          The Word Processing and Desktop Publishing services below will be
          billed at 200% of the normal rate if performed before or after
          scheduled working hours, or if overtime required or requested.

     Word Processing/Graphics Services Available
     *    Ads                                               *    Logo design/Business Cards/Stationery
     *    Bank Deposits                                     *    Photo minipulation
     *    Bill Paying                                       *    Preparation of Expenses
     *    Check Reconcilliation                             *    Proposals
     *    Invoicing (Bookkeeping)                           *    Scanning (either text or photos)
     *    Light Accounting                                  *    Straight keyboarding without any additional attributes
     *    Multi-media Presentations                         *    Tables/Forms
     *    Charts & Graphs                                   *    Tape Transcription
     *    Color Laser Printing & B&W                        *    Web Page design
     *    Database Development
     *    Database Entry/Mailmerge List Entry
     *    Excel Spreadsheets/Statistical typing
     *    Flyers & Brochures
               Industry Production Standards:
               "Landlord shall bill in accordance with Industry  Production  Standards (IPS),  published by the National
               Association of Secretarial  Services and the Executive Suite Association.  IPS are used for computing the
               time charged for document  production  and  non-keyboarding  services.  IPS are based on the average time
               required to perform specific duties by a professional word processing operator. This allows the Tenant to
               know how much a project will cost regardless of how long it takes to complete it.

     4)   Resumes:
          Typing Only - Does not include edits or additional print outs
          *    1st Page                                                               $40.00   1st Page Only
          *    Each Additional Page                                                   $20.00        Per Page
          *    Cover Letter                                                           $10.00        Per Page
          Resume Writing Consultation Services                                        $45.00        Per Hour

     5)   Technical Support                                                   $75.00-$125.00        Per Hour


          All Service pricing is subject to change with 30 days written notice to clients on contract.

          Revised 05/21/99                                                                Initials  BM
                                                                                          Initials  ________


<PAGE>

                               Exhibit B-Continued

G.   CONFERENCE ROOMS
     1)   Rental
          *    Full-Time Tenants                                                   Included       Up to 4 Hours/contract
          *    Hourly (Full-time and Part-time)                                      $25.00                     Per Hour
          *    Daily (1 to 12 people) (Full-time and Part-time)                     $150.00                      Per Day

          *    Walk-in (Hourly)                                                      $35.00                     Per Hour

     2)   Seminar Room (allowance at twice the time): Seminar rooms not available
          at all facilities.
          *    Full-Time Tenants                                                   Included  Accumulated with Conference
                                                                                                             Room rental
          *    Hourly                                                                $50.00                     Per Hour
          *    Daily (up to 40 people)                                              $300.00                      Per Day
          *    Walk-in (Hourly)                                                      $70.00                     Per Hour
     3)   Cancellation, if not within 24 hours for conference room.                                      Billable at 50%
                                                                                                        Or time reserved
          4)   Set-up/clean-up after Tenant in conference room                       $25.00                     Per Hour

H.   DIRECTORY LISTING - BUILDING LOBBY
          1)   Full-time (one-line)                                                Included                   First time
          2)   ImagePlus and Additional Listings-one time charge (Center Specific) $30-$150                     Per line

I. FURNITURE
     1)   Moves/adds/changes including administrative coordination and moving of      $25.00                   Per piece
          furniture places
     2)   Standard Furniture Set (desk, executive chair, 2 side chairs and         Included                    Month/set
          credenza)
     3)   Additional Furniture Rental - Various Pieces                                                   Varies based on
                                                                                                         Piece Requested

J.   KITCHEN FACILITIES
     (Coffee, tea, etc.)
     1)   Tenants/Clients per cup service (self-serve)                             Included
     2)   Pots for Conference Room - Set-up                                           $25.00                    Per hour
                                                                                               Actual time-Clerical rate

K.   MAIL SERVICES
     *    Deliver parcel to tenants office. All parcels are called to tenant. If     $25.00                     Per hour
          not picked up by 5:00 p.m. we will deliver to office.                                           .20 hr minimum
     *    Prepare Certified, Express, or Courier
     *    Check mailbox/hold (24-hours for packages later than mailbox)/review
          mail by phone
     *    Prepare packages, such as label/wrap
     *    Trace Shipments (Fed Ex, UPS, etc.)
     *    Mass mailings (folding, stuffing, posting, etc.)

L.   OFFICE SUPPLIES
     1)   Minimum supplies are available on site through ALLIANCE or may be      Cost + 20%
          ordered (See a clerical assistant for requests)
     2)   Weekly orders may be placed directly for tenant                            $25.00                     Per hour
                                                                                                          .20 hr minimum

M.   PARKING
     1)   Surface                                                          Center Specific
     2)   Covered Parking Garage                                                Center Specific

          All Service pricing is subject to change with 30 days written notice to clients on contract.

          Revised 05/21/99                                                                          Initials  BM
                                                                                                    Initials  ________
<PAGE>

                               Exhibit B-Continued


N.   POSTAGE FEES
     (Landlord shall serve as postal agent to all tenants and clients)
     1)   U.S. Mail/UPS                                                                                       Cost + 20%
          *    Posting of mail - 25 pieces                                    Complimentary                      Per day
          *    Posting of mail - Additional (after 25 pieces)                         $2.50  Per 25 pieces + (cost + 20%)
     2)   Courier Service                                                                                     Cost + 20%
     3)   Federal Express                                                                       Published Standard Rates

O.   PRODUCTION & COPYING
     (a medium volume copy machine is available for Tenants)
     1)   Binding, copying & transparencies (clerical time only)                     $25.00                     Per hour
                                                                                               .20 hr minimum + supplies
     2)   Photocopies
          *    up to 350                                                              $0.15                         Each
          *    351-700                                                                $0.12                         Each
          *    701-1000                                                               $0.10                         Each
          *    1001-2000                                                              $0.08
          *    2001+                                                                  $0.06

     3)   Binding (includes spine, cover & backing)                                   $4.50                  Each + time

P.   TELECOMMUNICATIONS
     1)   Standard Phone Equipment                                                  $125.00           Per Set, Per Month
          (Installation fee and set up not included)
          *    Phone with built-in Speaker phone
          *    DID Phone Number with 2 roll over lines
          *    1 line Directory Listing
          *    Other basic features of telephone system.
     2)   Phone/Fax or Date Line installation                                       $150.00             Per line/Per set
     3)   Fax or Data Line (Additional recurring charge each month plus a per        $80.00          Per line, Per month
          minute charge where applicable)
     4)   Voice mail; adding another personal box                                    $25.00          Per line, Per month
                                                                                     $25.00        Per box, installation
     5)   Programming voice mail to pager - Center Specific                          $25.00             Programming fee,
                                                                                                               per pager
     6)   Paging (not intercom services)
          *    Voice Mail Paging                                                     $25.00                    Per pager
                                                                                           Per Month - call transfer fee
          *    Paging on Demand to a pager                                            $2.50                     Per Page
     7)   Call Patching set up fee-  if available                                    $25.00                   Per number
                                                                                                        (one time charge)
          *    Up to 100 patches                                                     $50.00 Per Month + call transfer fee
          *    Additional Patches (after 40)                                          $0.50   (based on distance of call)
                                                                                         Per Patch and call transfer fee
          *    On Demand                                                              $25.0                    Per Patch
     8)   Reconnect fee (after termination of service)                              $150.00       Per Phone or Data Line
     9)   T-1 Access (Not available at all locations) (Requires LAN  Connectivity)  $100.00               Per user/month
          LAN Connectivity                                                           $25.00               Per user/month
          Installation and set up                                            $150 + $125/hr            Per user-one time
     Note: All changes are not listed for this service.
           Additional services also available.
     10)  Video Conferencing (not available at all centers)              $150.00 $350.00/hr            $50.00 set up fee
     11)  Call Screening                                                             $50.00             per person/month

          All Service pricing is subject to change with 30 days written notice to clients on contract.

          Revised: 05/21/99                                                                          Initials  BM
                                                                                                    Initials  ________
<PAGE>

                              Exhibit B-Continued

Q.   TELECOPY/FAX - PLAIN PAPER FAX AVAILABLE
     (clerical charges may be incurred for faxes sent after normal business hours)
     1)   Outgoing                                                                    $1.00      Per Page + Cost of Call
     2)   Incoming                                                                    $1.00                     Per Page

R.   IMAGEPLUS PROGRAM
     1)   Telephone Answering Only (8:30a.m. thru 5:30 p.m.; Mon-Fri)               $100.00                    Per Month
     2)   Mail Service Only - One Company Name                                       $50.00                    Per Month
     3)   ImagePlus Flex Program - Basic - No Conference Room                       $150.00                    Per Month
     4)   Extra People                                                               $25.00         Per Month/per person


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

          All Service pricing is subject to change with 30 days written notice to clients on contract.

          Revised: 05/21/99                                                                         Initials  BM
                                                                                                    Initials  ________
</TABLE>


<PAGE>

[ALLIANCE LOGO]
Business Centers

                                     LEASE AND SERVICE AGREEMENT

This  Agreement is made this 7th day of December  1998, by and between  ALLIANCE
Reston,  L.P. . d/b/a ALLIANCE Business Centers  ("Lessor") having offices known
and numbered as Suites  100/300  (the  "Facility")  in the  building  located at
12020/12030  Sunrise Valley Drive,  Reston,  Virginia 20191 (the "Building") and
Certicom ("Lessee") a(n) Deleware (corporation, partnership, individual) with an
address of 200 Matheson Blvd. West, Suite 103 Mississauga,  Ontario L5R 3L7.
The parties for  themselves,  their heirs,  legal  representatives,  successors
and assigns, agree as follows:

         1. Demise and Description of Property.

         a.  Lessor  leases  to  Lessee  and  Lessee  leases  from  Lessor,  the
"Premises"  (defined  below),  being a subpart of Lessor's total leased Facility
space, for the term and subject to the conditions and covenants  hereinafter set
forth  and  to all  encumbrances,  restrictions,  zoning  laws,  regulations  or
statutes affecting the Building, Facility or Premises.

         b. The  Premises  consists of Facility  office space  number(s)  307 as
shown in the  floor  plan  annexed  hereto.  Lessor  hereby  grants  Lessee  the
privilege  to use in common  with other  lessees  and  parties  that  Lessor may
designate  certain office amenities  located in the Facility;  the use of all of
which are subject to such reasonable  rules and regulations as Lessor  currently
has in  place  and  may  adopt  from  time  to  time.  The  amenities  are  more
particularly  described in attached  Exhibit "A." "The  Operating  Standards" as
presently  in place and  governing  the use of the Premises and the Facility are
attached in Exhibit "B".

         2. Use.

         a. The  Premises  shall be used by Lessee  solely  for  selling of data
encryption  technology  and such other  normally  incident uses and for no other
purpose, in strict accordance with the Operating Standards. Additionally, Lessee
shall not offer at the  Premises  any  services  which  Lessor  provides  to its
lessees,  including, but not limited to those amenities or services described in
attached  Exhibit  "A".  In the event  Lessee  breaches  any  provision  of this
paragraph, Lessor shall be entitled to exercise any rights or remedies available
to the Lessor  pursuant to this  Agreement  together  with such other rights and
remedies as the Lessor may otherwise have and choose to exercise.

         b. Lessee  shall not make nor permit to be made any use of the Premises
which would  violate any of the terms of this  Agreement  or which,  directly or
indirectly, is forbidden by statute, ordinance or government regulations,  which
may be dangerous to life, limb or property, which may invalidate or increase the
premium of any policy of insurance  carried on the Building or on the  Facility,
which will suffer or permit the Premises to be used in any manner or anything to
be brought into or kept there which,  in the sole  judgment of Lessor,  shall in
any way  impair or tend to impair  the high  quality  character,  reputation  or
appearance  of the Building or the  Facility,  or which may or tend to impair or
interfere with any services performed by Lessor for Lessee or for others.

         3. Term.

         a.  The term of this  Agreement  shall  be for a  period  of 6  months,
commencing  9:00 a.m.  on the 1st day of January  1999,  and ending 5:00 p.m. on
30th day of June 1999, unless renewed as provided in paragraph "3(b)" herein.

         b. Upon the ending term date set forth herein or any extension thereof,
the Agreement  shall be extended for the same period of time as the initial term
and upon the same terms and conditions as herein contained except for the amount
of base  rental  charges and  additional  service  charges,  which shall each be
increased by at least ten percent (10%),  unless either party notifies the other
in writing by  certified  or  registered  mail,  return  receipt  requested,  or
delivered  by hand that the  Agreement  shall not be extended  within the period
hereinafter  specified or automatically  renewed,  If Lessee has less than three
offices,  such  notice  shall be given at least 60 days prior to the  expiration
date of this Agreement.  If Lessee has three or more offices,  such notice shall
be given at least 90 days prior to the expiration date of this Agreement.

         c. In the  event the  entire  Premises  or the  Facility  are  damaged,
destroyed or taken by eminent domain or acquired by private  purchase in lieu of
eminent domain so as to render the Premises fully  untenantable and unrestorable
in Lessor's sole Judgment,  then within 90 days  thereafter by written notice to
the other party,  either party shall be able to terminate this Agreement,  which
will terminate as of the date thereof.

         4. Rent.

         a. For and during the term of this  Agreement,  Lessee shall pay Lessor
as rent for the Premises a total rental of $21,600,  payable in 6 equal  monthly
installments of $3600 (unless otherwise indicated on attached Rebate Rider) each
payable  in  advance  of  the  first  day  of  each  calendar  month  after  the
commencement  of the term, or a daily prorated  amount for any partial  calendar
month  during the term.  If any payment of rent or other  charges due under this
Agreement is not received  within five (5) calendar days after its due date, the
Lessee will also pay, as additional  rent, a late payment  charge which shall be
an amount equal to 10% of any amount owed to Lessor or $50 whichever is greater.

b. It is  additionally  specifically  covenanted  and agreed that the  financial
terms of this  Agreement  are  strictly  confidential  and Lessee  agrees not to
knowingly  or  willfully  divulge  this  information  to or any other  Lessee or
potential  Lessee of Lessor.  Any such disclosure by the Lessee of the financial
terms of this Agreement as set forth herein above,  shall  constitute a material
breach of this Lease.

         c. The first  such  payment  of rental  as well as the  payment  of the
Deposit  as set  forth in  below  shall be paid by  Lessee  simultaneously  with
execution of this  Agreement.  Should the Lessee fail to make such payment prior
to the  commencement  of the term of this  Agreement,  then,  at  Lessor's  sole
option, the Agreement shall be null and void and of no further effect.

         d.  The  rental  payable  during  the term of this  Agreement  shall be
increased  on the first day of the month  following  notification  of any rental
increase  (however  designated) which the Lessor might receive from the Lessor's
over-landlord  ("Building").  The term  "direct  expenses"  as used herein shall
refer  to  the  same  items  and  costs  as are  used  by  the  Building  in its
determination  of  expenses  and  costs  passed  on  to  Lessor.   Lessor  shall
immediately notify Lessee in writing of any such increase, and shall bill Lessee
for its pro rata share  thereof,  which bill Lessee shall pay promptly upon such
notification for each and every month thereafter for the balance of the term.

         e.  Rent  charges  are based on the value of the  rental  Premises  and
services  to be used by three (3)  person(s)  only.  If more than said number of
person(s)  habitually  use the Premises or services,  the Fixed  Monthly  Rental
Charges  will be increased  by a factor of $100 for each  additional  person who
habitually uses the Premises.

         f. If a Lessee  check is returned  for any  reason,  Lessee will pay an
additional  charge of  $100.00  per  returned  check  and,  for the  purpose  of
considering  default  and/or  late  charges,  it  will  be  as  if  the  payment
represented by the returned check had never been made.

[ALLIANCE LOGO]                        1
Business Centers                                        BM Initials  EV Initials
<PAGE>

         5. Security Deposit.

         a. Lessee shall deposit with Lessor an additional  $3055.00,  as a non-
interest bearing  security  deposit (Lessee  currently has $1070.00 on file as a
non-interest  bearing security deposit).  Lessor may use the security deposit to
cure any default of Lessee under this Agreement,  restore the Premises including
any and all furniture,  fixtures and equipment provided by Lessor and vendors at
the Premises to their original condition and configuration,  reasonable wear and
tear excepted, to pay for repairs to any damage to the Premises, Executive Suite
or  Building,  caused  by Lessee or  Lessee's  guests,  to pay any rent or other
charges  which  Lessee  owes  Lessor  at or  prior  to the  expiration  of  this
Agreement,  and to reimburse Lessor for costs or expenses arising from any other
obligation  of Lessee  which Lessee has failed to perform.  If Lessor  transfers
control or ownership of the Premises and Lessor  transfers the security  deposit
to such  purchaser,  Lessee will look solely to the new Lessor for the return of
the security  deposit,  and the Lessor named in this Agreement shall be released
from all liability for the return of the security deposit.

         b. The  security  deposit  (less any sums used by Lessor in  accordance
with the terms and conditions of this  Agreement)  will be returned within sixty
(60) days after the  termination  of any services  rendered or expiration of the
term hereof. The security deposit shall not under any circumstance be applied in
lieu of be the final  payment(s)  of Fixed  Monthly  Rental  charges  or service
charges under this Agreement.

         c.  In the  event  that,  by  reason  of the  Lessee's  default  in its
obligations  pursuant to this Agreement or otherwise,  including but not limited
to the payment of the Fixed Monthly Rental Charge,  any amounts due by reason of
the Lessee's use of additional  services hereto and/or by reason of the Lessee's
use of telephone  services as supplied pursuant to this Agreement,  Lessor shall
be entitled to apply any of the security deposited pursuant to this Agreement to
any outstanding sums due or owing to the Lessor, and Lessor shall have the right
to  charge  the  Lessee,  as  additional  rent,  such sums as are  necessary  to
replenish any and all amounts applied so as to cause the security to be returned
to its entire  amount.  The  failure to pay such  amounts  as are  necessary  to
replenish the security  shall be considered a breach of this Agreement and shall
entitle the Lessor to exercise any of its rights  pursuant to this  Agreement or
otherwise.

         6. Delivery of Possession.

         If, for any reason whatsoever,  Lessor cannot deliver possession of the
Premises to Lessee at the  commencement of the term, this Agreement shall not be
void nor  voidable  nor shall  Lessor be liable to Lessee for any loss or damage
resulting  therefrom;  but there  shall be an  abatement  of rent for the period
between the stated  term  commencement  and the time when  Lessor  does  deliver
possession of the Premises.

         7. Services.

         a. So long as Lessee is not in  default  hereunder,  Lessor  shall make
available certain amenities to Lessee as more particularly  described in Exhibit
"A." Such services shall be offered to Lessee, in conjunction with such services
being offered by Lessor to its other lessees,  without charge for the reasonable
use of the same.

         b.  In  addition,  provided  Lessee  is not in  default  hereunder  and
provided the cost thereof  does not exceed the  Security  Deposit,  Lessor shall
make  available  to Lessee  certain  other  services  the cost of which shall be
billed to the  Lessee  as  additional  rent and the  payment  of which  shall be
subject to the same terms and  conditions as those  governing the payment of the
Fixed Monthly Rental Charge herein regardless of when such charges are billed to
the Lessee.

         8. Telephone Services.

         a.  Provided  Lessee is not in default of any of the terms,  covenants,
conditions  or  provisions  of this  Agreement,  Lessor will make  available  to
Lessee, a  telecommunications  package which will consist of some combination of
telephone equipment, numbers, lines, conference calling, voice mail, local, long
distance and international service, and directory listing. All components of the
telecommunications  package  including any telephone numbers used by Lessee will
remain at all times the  property of Lessor and Lessee will acquire no rights in
the components beyond the term specified by Lessor.

         b. Upon Lessee's written  request,  Lessee shall be entitled to appoint
Lessor as its  exclusive  agent for the sole purpose of procuring  and arranging
Lessee's  local "white pages"  listings.  Lessor shall have no  involvement  nor
responsibility for any "yellow pages" listings desired by Lessee.

         c.  Lessor  shall not be liable  for any  interruption  or error in the
performance  of its services to Lessee  under this  Section.  Lessee  waives any
recourse  as against  the  Lessor for any  claimed  liability  arising  from the
provision of telecommunication  services including, but not limited to; injuries
to  persons or  property  arising  out of  mistakes,  omissions,  interruptions,
delays, errors or defects in transmissions occurring in the course of furnishing
telecommunications  services provided same are not caused by the willful acts of
the Lessor,  as well an claim for business  interruption  and for  consequential
damages.

         d. Lessor shall use reasonable efforts to provide Telephone Services to
Lessee in a first-class, professional manner. Telephone service charges shall be
as per Lessor's then scheduled rates for the same, or as the same may be amended
by Lessor from time to time.

         e. In the event that any toll fraud is traceable to  telecommunications
services  employed  by Lessee,  such toll fraud shall be deemed to be a material
default in the Lessee's obligations  hereunder.  Lessee further hereby agrees to
indemnify, hold harmless and to reimburse Lessor for all charges associated with
any such toll fraud including,  but not limited to,  unauthorized use of calling
cards or telephone lines.

         f. It is  expressly  acknowledged  and agreed that Lessor  shall be the
sole and  exclusive  provider of  telecommunication  services to Lessee.  Lessee
hereby agrees and covenants that it will not use any other telephone  service or
telephone  carrier to provide  it  service  in the  Premises.  In the event that
Lessee uses or acquires any other  telephone  service at the Premises,  such use
and/or  installation  shall  constitute  a  material  default  in  the  Lessee's
obligations hereunder.

         9. Furniture and Fixtures.

         At  its  own  cost  and  expense,  Lessor  shall  furnish  and  install
furniture,  fixtures and equipment as are in Lessor's sole opinion  necessary to
provide  suitable  office   accommodations  for  Lessee,  upon  such  terms  and
conditions  routinely applicable to the Facility.  All such furniture,  fixtures
and equipment shall remain Lessor's property.

         10. Insurance; Waiver of Claims.

         a.  Lessor  has no  obligation  to and will  not  carry  insurance  for
Lessee's benefit. Lessor will not be liable to Lessee or to any other person for
damages  on  account  of loss,  damage or theft,  to any  business  or  personal
property of Lessee.  Lessee  hereby  waives any claims  against  Lessor from any
loss, cost, liability or expense (including  reasonable attorneys' fees) arising
from  Lessee's use of the Premises or any common areas made  available to Lessee
by Lessor or from the conduct of Lessee's business, or from any activity,  work,
or thing done in the  Premises  or common  areas by Lessee or  Lessee's  agents,
contractors,  visitors or employees. To the extent that Lessor has any liability
for any of the forgoing pursuant to any law, ordinance or statute,  Lessee shall
seek recovery for such loss(es)/or  damage(s) from its own insurance  company as
provided  for in  subparagraph  (c) herein  prior to making  any claims  against
Lessor.

         b. The Lessor shall not be liable or  responsible to the Lessee for any
injury or damage resulting from the acts or omissions of Lessor,  its employees,
persons  leasing  office space or obtaining  services from the Lessor,  or other
persons  occupying  any part of the Premises or Building,  or for any failure of
services  provided such as water, gas or electricity,  HVAC or for any injury or
damage to person or property caused by any person except for such loss or damage
arising  from the willful or grossly  negligent  misconduct  of the Lessor,  its
agents,  servants,  or employees  or from the  Lessor's  failure to make repairs
which it is obligated to make  hereunder.  Neither  Lessor or any of its agents,
employees, officers or directors shall be responsible for damages resulting from
any error,  omission or defect in any work  performed or provided as part of the
services rendered, whether uncompensated services or compensated services.

[ALLIANCE LOGO]                        2
Business Centers                                      BM Initials    EV Initials
<PAGE>

        c.  Lessee  shall  provide   Lessor  with  a  certificate  of  insurance
evidencing  General/Public  Liability coverage with liability limits of not less
than One Million  Dollars  ($1,000,000)  per occurrence for Bodily Injury and/or
Property  Damage  Liability  and One Hundred  Thousand  Dollars  ($100,000)  per
occurrence for  Fire/Legal  Liability.  Said insurance  coverage shall remain in
force  during the term of this  Agreement  and  renewals  thereof.  The  Lessor,
Alliance National, Inc, and Alliance Business Centers, Inc. shall be named as an
additional named insured on each of these policies.  Lessee's failure to provide
or  maintain  such  insurance  shall not  reduce  or  otherwise  alter  Lessee's
liability or responsibility to pay any judgment rendered against Lessee for such
Liability  and Damages  Failure to maintain  such  insurance  and/or to name the
Lessor and its designees, as set forth above, shall constitute a material breach
of this Agreement.

         d. Both parties  hereby agree to defend,  indemnify  and hold the other
harmless from and against any and all claims, damages, injury, loss and expenses
to or of any person or property  resulting  from the acts or negligence of their
agents,  employees,  invitees and/or licensees while in the Building,  Executive
Suite and/or Premises.

         e. Any fire and extended risk casualty  insurance that Lessee maintains
shall include a waiver of subrogation in favor of Lessor and Building  Landlord,
and any fire and extended risk insurance carried on the Facility by Lessor shall
likewise contain a waiver of subrogation in favor of Lessee.

         11. Waiver of Breach.

         Should  Lessor not insist  upon the strict  performance  of any term or
condition of this  Agreement or to exercise any right or remedy  available for a
breach  thereof,  and no  acceptance  of  full or  partial  payment  during  the
continuance  of any such breach shall  constitute a waiver of any such breach or
any such term or condition.  No term or condition of this Agreement  required to
be  performed  by Lessee  and no breach  thereof,  shall be  waived,  altered or
modified,  except by a written  instrument  executed by Lessor. No waiver of any
breach shall affect or alter any term or condition in this  Agreement,  and each
term or  condition  shall  continue in full force and effect with respect to any
other then existing or subsequent breach thereof.

         12. Operating Standards.

         The Operating  Standards  attached to this Agreement as Exhibit "B" are
hereby made an integral part of this Agreement.  Lessee, its employees,  agents,
guests, invitees,  visitors and/or any other persons caused to be present in and
around the  Premises  by the  Lessee  shall  perform  and abide by the rules and
regulations  and any  amendments or additions to said rules and  regulations  as
Lessor may make.  In addition,  Lessee,  its employees and agents shall abide by
all applicable governmental rules, regulations, statutes and ordinances relating
in any way to the  Premises or the  Facility or Lessee's use or occupancy of the
Premises or the Facility; failing which Lessee shall be in default hereunder and
shall pay any fines or penalties imposed for such  violation(s)  directly to the
appropriate  governmental authority or to Lessor, if Lessor has paid such amount
on behalf of Lessee.  Such remedy shall not be exclusive.  It is hereby  further
explicitly  agreed  and  understood  that  full  compliance  with the  Operating
Standards as set forth constitutes a material obligation of this Agreement,  and
that the failure to so comply shall  constitute  a violation  of this  Agreement
entitling the Lessor to exercise any of its remedies  pursuant to this Agreement
or otherwise.

         13. Employment of Lessor's Employees.

         a. Lessee  agrees that it will not,  during the term of this  Agreement
and any renewals  thereof,  or for a period of one year after the  expiration or
sooner  termination  of this  Agreement,  hire or issue an offer to  employ  any
person who is or has been an employee of Lessor or Lessor's  agent without prior
consent  from Lessor.  If Lessee  either hires an employee of Lessor or Lessor's
agent;  or hires  any  person  who has been an  employee  of Lessor or its agent
within six months prior to the time they are hired by Lessee,  Lessee  will,  at
Lessors sole option,  be liable to Lessor for  liquidated  damages  equal to six
months wages of the employee, at the rate last paid that employee by Lessor.

         b. If Lessor assists in hiring an employee for Lessee, Lessee shall pay
the Lessor a  commission  equal to 20% of that  employee's  annual  salary.  The
provisions hereof shall survive the expiration or sooner termination of the term
thereof.

         14. Alteration.

         If  Lessee  requires  any  special  wiring or  office  alterations  for
extraordinary  business  machines  or other  purposes  not  consistent  with the
current wiring  extraordinary  telephone equipment or computer  equipment.  Such
alteration  shall be done (i) only with the express  written  permission  of the
Lessor,  and if said permission is granted,  then (ii) by an agent designated by
Lessor at Lessee's  cost.  The  electrical  current  shall be used for  ordinary
lighting  purposes only,  unless written  permission to do otherwise shall first
have been  obtained  from  Lessor at an agreed  cost to Lessee.  Lessor  further
reserves the sole and exclusive  right to limit the number and type of lines and
telephone   equipment  Lessee  can  install  in  the  leased  Premises.   Lessee
understands  that  all  provisions  must be made my  Lessee  to  return  altered
property to its previous state upon termination of the lease.

         15. Re-Entry.

         Lessor and its agents shall have the right to enter the Premises at any
time for the purpose of making any repairs,  alterations,  inspections  which it
shall  deem  necessary  for the  preservation,  safety or  improvements  of said
Premises,  without in any way being deemed or held to have committed an eviction
(constructive or otherwise) of or trespass against Lessee.

        16.     Relocation.

        a. Lessee agrees that the Lessor may, in its sole  discretion,  relocate
the lessee from its present  Premises to a like or similar  office  space within
the same facility upon ten (10) days notice to the Lessee. In the event that the
Lessor  requires the Lessee to relocate,  the Lessor  hereby  agrees to bear the
reasonable cost of any such relocation,  which cost shall be limited to the cost
associated with the physical  transfer of the Lessee's property to any different
office, which the Lessor may designate.

         b. In the event that any such relocation is effected, the Lessee hereby
acknowledges that, unless otherwise agreed in writing, that all of the terms and
conditions of this Agreement shall remain in full force and effect.

         17. Assignment and Subletting.

         No assignment or subletting of the Premises, this Agreement or any part
thereof shall be made by Lessee without  Lessor's prior written  consent,  which
consent  may be  withheld  for any or no reason  in  Lessor's  sole  discretion.
Neither all nor any part of Lessee's  interest in the Premises or this Agreement
shall be encumbered, assigned or transferred, in whole or in part, either by act
of the Lessee or by operation of law.

         18. Surrender.

         a. On expiration of the term, any extended term, or sooner  termination
of this Agreement , Lessee shall promptly  surrender and deliver the Premises to
Lessor,  without demand, and in as good condition as when let, ordinary wear and
tear excepted.

         b. Upon  Lessee  serving a notice of  cancellation  as  provided  in 3b
herein Lessor shall have the right to show Lessee's  Premises  during the 60 day
period (for one or two offices) or 90 day period (for three or more  offices) as
the case may be.

         c. Without  prior written  approval of Lessor,  Lessee shall not remove
any of its property from the Premises upon  termination  of this Agreement or at
any other time,  except during  Lessor's  normal  business  hours.  In the event
Lessor  consents to Lessee's  removing  property before or after normal business
hours, any expenses incurred by Lessor as a result, including but not limited to
expenses for personnel, security, elevator, utilities and the like shall be paid
by Lessee in advance,  to the extent determinable by Lessor, by certified and/or
bank check.

[ALLIANCE LOGO]                      3
Business Centers                                      BM Initials   EV  Initials

<PAGE>

         d. If Lessee  vacates  the  Premises  and leaves  behind any  property,
whatsoever,  same will be deemed  abandoned  by Lessee and may be disposed of by
Lessor at  Lessee's  expense.  If Lessee  defaults in the payment of sums due to
Lessor, and Lessor changes the locks,  removes Lessee's  property,  or otherwise
denies access to Lessee,  Lessor shall not be liable for  conversion or partial,
actual and/or constructive eviction.

         19. Holding Over.

         a. In the event  that  Lessee,  should  not  renew  this  Agreement  in
accordance  with the terms and conditions  hereof,  and/or fail to surrender the
Premises upon the  expiration  of the term of the Agreement as provided  herein,
Lessee  agrees to pay Lessor,  as liquidated  damages,  a sum equal to twice the
monthly  rent and all  additional  charges  for  services  provided by Lessor to
Lessee,  for each month that Lessee  retains  possession  of the Premises or any
part thereof; provided,  however, that the acceptance of such sums, representing
liquidated damages shall not be deemed to be permission to Lessee to continue in
possession of the Premises.

         20. Default and Remedies.

         a.  If the  Lessee  shall  default  in  fulfilling  any  of its  terms,
conditions, covenants or provisions of this Agreement, including but not limited
to:

         1. Payment of fixed  Monthly  Rental  Charges  and/or any other charges
hereunder within ten days of the date such charges become due;

         2.  Becomes  comes  insolvent,  makes  an  assignment  for  benefit  of
creditors, or files a voluntary petition under any bankruptcy or insolvency law,
or has filed against it an involuntary petition under any such law;

         3. Defaults in fulfilling  any of the terms,  conditions,  covenants or
provisions of this  Agreement  including but not limited to the breach of any of
the terms and conditions set forth in the exhibits attached hereto;

         4. The abandonment and/or vacatur of the Premises by the Lessee;  then,
after  five days  notice of any such  default(s),  the Lessor  may,  at its sole
discretion,  terminate this  Agreement upon five days notice to the Lessee,  and
upon the expiration of such notice  period,  the Lessee shall quit and surrender
the  Premises  to the  Lessor.  In the event that the  Lessee  fails to quit and
surrender  the  Premises,  the Lessor may  re-enter and take  possession  of the
Premises and remove all persons and property  therefrom,  as well as  disconnect
any telephone lines  installed for the benefit of Lessee,  without any liability
whatsoever to Lessee. In addition,  Lessor may elect concurrently or alternately
to accelerate all of Lessee's obligations hereunder including without limitation
the rental,  direct expenses,  Schedule B Costs,  and Telephone  Services costs,
and/or the  re-letting of the Premises or any part thereof,  for all or any part
of the remainder of said term, to a party satisfactory to Lessor, at any monthly
rental rate.  Lessor,  in its sole discretion,  may accept  notwithstanding  the
foregoing,  Lessor shall have no obligation,  implied or otherwise,  to mitigate
its damage(s) under such circumstances.

         b.  Should  Lessor be unable to re-let  the  Premises,  or should  each
monthly re-rental be less than the rental, Lessee is obligated to pay under this
Agreement or any renewal thereof, at Lessor's option Lessee shall pay the amount
of such deficiency, plus the expenses of reletting,  immediately in one lump sum
(if  allowable  under  law) to Lessor  upon  demand  and/or as such  obligations
accrue.

         c. If Lessee shall default in the observance or performance of any term
or covenant on Lessee's  part to be observed or performed  under or by virtue of
any of the terms or  provisions  in any  article  of this  lease,  then,  unless
otherwise  provided  elsewhere in this lease,  Lessor may  immediately or at any
time thereafter and with notice perform the obligation of Lessee thereunder, and
if Lessor,  in connection  therewith or in connection with any default by Lessee
in the  covenant to pay rent  hereunder,  makes any  expenditures  or incurs any
obligations  for the payment of money,  including  but not limited to attorney's
fees, in instituting,  prosecuting or defending any actions or proceeding,  such
sums so paid or obligations  incurred with interest and costs shall be deemed to
be additional rent hereunder and shall be paid by Lessee to Lessor  rendition of
any bill or statement to Lessee therefor,  and if Lessee's lease term shall have
expired  at the  time  of  making  of such  expenditures  or  incurring  of such
obligations, such sums shall be recoverable by Lessor as damages.

         21. Mail & Telephone Forwarding.

         a.  After  termination  or  expiration  of the term of this  Agreement,
Lessee  hereby  agrees  that it will take all  reasonable  steps to  notify  all
parties  of  Lessee's  new  address  and phone  numbers.  Lessor  shall  have no
obligation,  to notify any person or entity of Lessee's new address and/or phone
numbers, except as expressly provided herein.

         b.  Lessor  will,  unless  otherwise  instructed  by Lessee in writing,
forward mail to Lessee at its new address and give out new telephone  number via
a voice mail message for a period of three (3) months at the rate of $150.00 per
month,  which sums shall be deducted from any amounts  deposited with the Lessor
as security hereunder and paid to the Lessor in advance. In the event that there
is not sufficient security remaining on deposit to pay for the charges set forth
herein,  unless the Lessee  shall pay the charges set forth herein to the Lessor
in advance,  Lessor shall have no  obligation  to provide the services set forth
herein.

         22. Notices.

         Any notice under this Agreement shall be in writing and shall be either
delivered  by hand or by first  class mail to the party at the address set forth
below. Lessor hereby designates its address as:

          ALLIANCE Business Centers
          12030 Sunrise Valley Drive
          Suite 300
          Reston, Virginia 20191
          Attn:   Sales Management

          with a copy by regular first class mail to:
          ALLIANCE National, Inc.
          122 East 42nd Street, Suite 2707
          New York, NY 10168
          Attn:   Legal Department

Lessee hereby  designates  its address  (which address must be an address within
the United States), as

          Mr. Bruce MacInnis
          300 Matheson Blvd West
          Suite 103
          Mississauga, Ontario L5R 3L7
          Phone; 905-507-4220
          Fax: 905-507-4230

If such mail is  properly  addressed  and mailed,  as above,  it shall be deemed
notice for all  purposes,  given when sent or  delivered,  even if  returned  as
undelivered.

         23. Landlord's Election Under This Agreement.

         Upon early termination of the main Building lease, this Agreement shall
terminate unless the Building  Landlord under the main lease elects to have this
Agreement assigned to the Building Landlord or another entity as provided in the
main lease.  Upon notice to Lessor of the termination of the main lease and such
election,  (i) the Agreement  shall be deemed to have been assigned by Lessor to
the Building Landlord or to such other entity as is designated in such notice by
the  Building  Landlord,  (ii) the Building  Landlord  shall be deemed to be the
Lessor under this Agreement and shall assume all rights and  responsibilities of
Lessor under this  Agreement,  and (iii) Lessee shall be deemed to have attorned
to the Building Landlord as Lessor under this Agreement.

[ALLIANCE LOGO]                      4
Business Centers                                      BM Initials   EV  Initials
<PAGE>

         24. Time of Essence.

         Time  is of  the  essence  as to  the  performance  by  Lessee  of  all
covenants, terms and provisions of this Agreement.

         25. Severability.

         The  invalidity  of any  one or  more  of  the  sections,  subsections,
sentences,  clauses or words  contained  in this  Agreement  or the  application
thereof to any particular set of circumstances, shall not affect the validity of
the remaining  portions of this  Agreement or of their valid  application to any
other  set of  circumstances.  All of  said  sections,  subsections,  sentences,
clauses and words are inserted  conditionally  on being valid in law; and in the
event that one or more of the sections, subsections, sentences, clauses or words
contained  herein shall be deemed invalid,  this Agreement shall be construed as
if such invalid sections, subsections,  sentences, clauses or words had not been
inserted.  In the  event  that  any part of this  Agreement  shall be held to be
unenforceable   or  invalid,   the  remaining  parts  of  this  Agreement  shall
nevertheless continue to be valid and enforceable as though the invalid portions
had not been a part hereof. In addition,  the parties  acknowledge (i) that this
Agreement has been fully negotiated by and between the parties in good faith and
is the result of the joint efforts of both parties,  (ii) that both parties have
been provided with the  opportunity to consult with legal counsel  regarding its
terms,  conditions and  provisions  and (iii) that  regardless of whether or not
either party has elected to consult with legal counsel,  it is the intent of the
parties  that in no event  shall the terms,  conditions  or  provisions  of this
Agreement be construed against either party as the drafter of this Agreement.

         26. Execution by Lessee.

         The party or parties  executing  this Agreement on behalf of the Lessee
warrant(s) and represent(s):  (i) that such executing party (or parties) has (or
have) complete and full authority to execute this Agreement on behalf of Lessee;
(ii) that Lessee shall fully perform its obligations hereunder.

         27. Assumption Agreements and Covenants.

         This  Agreement is subject and  subordinate  to the main Building lease
governing  the  Facility,  under  which  Lessor  is  bound  as  tenant;  and the
provisions  of the main  lease,  other  than as to the  payment of rent or other
monies,  are incorporated into this Agreement as if completely herein rewritten.
Lessee shall comply with and be bound by all provisions of the main lease except
that the payment of rent shall be governed by the provisions of this  Agreement,
and Lessee shall  indemnify and hold Lessor  harmless from and against any claim
or liability  under the main lease of Lessor arising from Lessee's breach of the
Main Lease or this Agreement.  Lessor covenants and warrants that the use of the
Premises as a business  office is consistent with and does not violate the terms
of the main lease.

         28. Covenant and Conditions.

         Each term,  provision and  obligation of this Agreement to be performed
by Lessee shall be construed as both a covenant and condition.

         29. Entire Agreement.

         This Agreement embodies the entire  understandings  between the parties
relative to its subject matter, and shall not be modified, changed or altered in
any respect except in writing signed by all parties.

         30. Counterparts.

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

         IN WITNESS  WHEREOF,  Lessor and Lessee have executed this Agreement as
of the date first above written.

ALLIANCE Business Centers

ALLIANCE RESTON, L.P.

By: /s/ Elizabeth Vrooman
    -----------------------------------
    Elizabeth Vrooman - General Manager

Date:   12/18/98
      ---------------------------------

LESSEE: Certicom
(if a corporation)

By: /s/ Bruce MacInnis
    -----------------------------------

Name Printed:   Bruce MacInnis
               ------------------------

Title: VP/CFO
       --------------------------------

          [Corporate Seal]

Date:   12/18/98
        -------------------------------


LESSEE:
(if an individual or partnership)

By:
     ----------------------------------

By:
     ----------------------------------

EXHIBIT "A"

o    Furnished Private Office
o    Furnished, Decorated Reception Room with Professional Receptionist
o    Personalized Telephone Answering During Office Hours
o    24 hour Voicemail
o    12 hours of Conference Room or private furnished offices, subject to prior
     scheduling and use by other lessees
o    Corporate Identity on Lobby Directory where Available
o    Complete Mail Room Facility
o    Receipt of Mail and Packages
o    Complete Kitchen Facilities with Coffee Machine
o    Utilities and Maintenance
o    HVAC During Normal Business Hours
o    Janitorial Services
o    8  hours  per  month  courtesy  use  of  other  ALLIANCE  BUSINESS  Centers
     affiliated  facilities.   Locations  subject  to  current  affiliation  and
     availabilty.
o    24 hour access to Suite 307 and to Building 12030


[ALLIANCE LOGO]                      5
Business Centers                                      BM Initials   EV  Initials

<PAGE>

EXHIBIT "B"     OPERATING STANDARDS

1.   Lessees and their guests will conduct themselves in a businesslike  manner;
     proper  attire will be worn at all times;  and the noise level will be kept
     to a level so as not to interfere with or annoy other Lessees.

2.   Lessee  shall not  provide or offer to provide  any  services  to  Lessor's
     customers if such services are available from Lessor.

3.   Lessee  will not affix  anything to the walls of the  Premises  without the
     prior written consent of the Lessor.

4.   Lessee  will  not  prop  open  any  corridor  doors,  exit  doors  or doors
     connecting corridors during or after business hours.

5.   Lessees  using  public areas may only do so with the consent of the Lessor,
     and those areas must be kept neat and attractive at all times.

6.   Lessee will not conduct any activity  within the Premises,  Executive Suite
     or  Building,  which in the  sole  judgment  of the  Landlord  will  create
     excessive  traffic  or is  inappropriate  to  the  executive  office  suite
     environment.

7.   Lessee may not conduct  business in the corridors or any other areas except
     in its designated  offices or conference  rooms without the written consent
     of Lessor.

8.   All corridors,  halls,  elevators and stairways  shall not be obstructed by
     Lessee or used for any purpose other than normal egress and ingress.

9.   No  advertisement,  identifying  signs or other notices shall be inscribed,
     painted or affixed on any part of the corridors, doors, or public areas.

10.  Without Lessor's specific prior written permission, Lessee is not permitted
     to  place  "mass  market",  direct  mail or  advertising  (i.e.  newspaper,
     classified   advertisements,   yellow  pages,  billboards)  using  Lessor's
     assigned  telephone  number or take any such action  that would  generate a
     excessive of incoming calls.

11.  Lessee  shall not solicit  clients of Lessor or and their  employees in the
     Building without first obtaining Lessor's prior written approval.

12.  Immediately   following  Lessee's  use  of  conference  room  space  and/or
     audio/visual  equipment,  Lessee  shall  clean up and  return the space and
     equipment to the state and  condition  it was in prior to Lessee's  use. If
     not,  Lessor may charge Lessee for any other  expenses  required to restore
     the conference space and/or equipment to its original condition.

13.  Lessor  must be  notified  in  writing if Lessee  desires  to  utilize  the
     conference room or other common areas of the Executive Suite during evening
     or weekend hours. Lessor may deny the Lessee access if the desired usage is
     inappropriate and may disrupt normal operations.

14.  Lessee shall not, without  Lessor's  written consent,  store or operate any
     computer  (except a  desktop/laptop  computer or fax  machine) or any other
     large business machines,  reproduction equipment, heating equipment, stove,
     speaker phones, radios, stereo equipment or other mechanical  amplification
     equipment,  refrigerator  or coffee  equipment,  or  conduct  a  mechanical
     business,  do any cooking,  or use or allow to be used on the Premises oil,
     burning fluids,  gasoline,  kerosene for heating,  warming or lighting.  No
     article deemed extra  hazardous on account of fire or any explosives  shall
     be brought into said  Premises or Facility.  No offensive  gases,  odors on
     liquids shall be permitted.

15.  Lessee will bring no animals into the Premises or Facility except for those
     assisting disabled individuals.

16.  Lessee shall not remove  furniture  fixtures or  decorative  material  from
     offices or common areas without the written consent of Lessor.

17.  Lessee shall not make any additional  copies of any Lessor issued keys. All
     keys and  security  cards are the  property  of Lessor and must be returned
     upon  request or by the close of the business on the  expiration  or sooner
     termination  of the Agreement  term.  Any lost or unreturned  keys or cards
     shall incur a $25.00 per item charge and the cost to re-key the office.

18.  Lessee  shall  not smoke nor  allow  smoking  in any area of the  Facility,
     including the Premises, and shall comply with all governmental  regulations
     and ordinances concerning smoking.

19.  Lessee shall not allow more than three  visitors in the reception  lobby of
     the Premises at any one time.

20.  Lessee's parking rights (if any) are defined by Lessor's Agreement with the
     owner of the  Building.  Landlord  reserves  the  right to  modify  parking
     arrangements if required to do so by Building management.

21.  Lessee shall  cooperate  and be courteous  with all other  occupants of the
     Facility and Lessor's staff and personnel.

22.  Lessor  reserves  the  right  to  make  such  other  reasonable  rules  and
     regulations  as in its  judgment  may from time to time be  needed  for the
     safety, care, appropriate operation and cleanliness of the Facility.


[ALLIANCE LOGO]
Business Centers                                                      BM

<PAGE>

Tenant:                            Certicom

Landlord:                          ALLIANCE Reston

Term:                              6 months

Move in date                       January 1, 1999

Move out date:                     June 30, 1999

Office/Suite No.(s):               307
<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------------------
                                   Terms                      Quantity     Amount        Total
==================================================================================================
<S>                                <C>                        <C>        <C>             <C>
Fixed Monthly Fees:
Conference Room Usage Allowance:   12 hours per month                                    Included
Fixed Monthly Office Rental:       Suite 307                                       $        $3300
                                                                                   $            $
Fixed Monthly Furniture Rental:                               3 sets             $50     Included
Additional Furniture                                           pieces         varies            $
Fixed Monthly Phone Charge:        per set $95                   3               $95         $285
                                   $40 per data/fax/modem        1               $40          $40
                                   $125/month/T1 access          2              $125         $250
Fixed Monthly Add'l People Charge:                                               $100
Fixed Monthly Parking:             $25 per month/ per person                     $25          $50
Other Fixed Monthly Charges:       Business Support Services   offices   $100/office         $200

===================================================================================================
                                TOTAL FIXED MONTHLY CHARGES $4125.00
---------------------------------------------------------------------------------------------------
Payment Due at Signing:
Pro Rated Rent                     Pro-Rated Suite                                              $
1st Months Rent                    Suites                                                       $
1st Months Furniture                                            Set             $75      Included
1st Months Parking                 $25 per month/per person                       $             $
1st Months Telephone Charges:      $95 per set with speakerphone                $95             $
1st Months                         $40 per data/fax/modem                       $40             $
         Data/Modem/Fax Charges:   $125 T1 access/month                        $125             $
Line Installation Charges)         $150 per T1 line              2             $150          $300
                                   $50 per line transferred
                                   from 318                      3              $50          $150
1st Months Add'l Person                                                        $100             $
Start-up Fee                       $100 per office                             $100             $
Refundable Service Deposit         One months fixed costs      $1070 on file      $         $3055
Other Fixed Monthly Charges:                                                      $

===================================================================================================
                         TOTAL 1st MONTH'S RENT CHARGES & DEPOSIT $3505.00
---------------------------------------------------------------------------------------------------
<FN>

State Tax will be calculated for the following services as provided: Production, Furniture, Copies,
Catering,  Additional Furniture,  Equipment Rental, Incoming Facsimile, Line Charges, Moves, Adds &
Changes, Office Supplies and Telephone Equipment Rental.
</FN>
</TABLE>

[ALLIANCE LOGO]
Business Centers                                                           BM EV
<PAGE>

<TABLE>
<CAPTION>
                                   Exhibit C

                              SCHEDULE OF SERVICES

<S>  <C>                                                                          <C>     <C>
A.   ACCOUNTING

     1) Establishing a second account for Tenant's convenience                    $25.00                  each time

     2) Clerical fee for processing payment using MC/VISA/American Express        $10.00                  each time

     3) Fax or send duplicate statement or records (plus postage and
        faxing costs)                                                              $5.00                  each copy

     4) Research, collection calls or processing (plus postage, faxing
        and telephone incurred charges) Actual time billed as Clerical service    $24.00  Actual time-Clerical Rate

B.   ADMINISTRATIVE

     1) Credit authorization and set up fee
        o      New Full-Time Tenants                                             $150.00                 Per Office
        o      Flextime                                                          $100.00               Per Contract

     2) Moving a Tenant from one suite to another, keys, and cards                $50.00                 per person
     3) Additional employee initial set up                                       $100.00            One-time charge
        Recurring Monthly Charge - Extra People Fee                              $100.00                    Monthly

     4) Painting and cleaning fee for a lease of less than six (6)
        months including administrative coordination                             $200.00                 Per office

     5) Lost security card, lost key                                              $25.00                   Per item

     6) Tenant Storage: boxes, other items (if available)                         $40.00              Month/closest

D.   CLERICAL SERVICE

     1) Standard Clerical Rate                                                    $24.00                   Per Hour
        Clerical  Service billed in 6 minute increments
        (i.e. .10 = 6 minutes)  Normal Turnaround time = 24 hours                                   .10 hr. minimum

          Clerical Services Available
     o   Bank Deposits                             o   Ordering Office Supplies
     o   Bill Paying                               o   Photocopying for Tenants or
     o   Check Reconciliation                          Visitors
     o   Computer Maintenance                      o   Outgoing Calls for Tenants
     o   Arrange Conference Calls and Meetings     o   Payroll
     o   Extensive Fax Transmission                o   Preparation of Expense
     o   Travel Arrangements                           Reports
     o   Filing                                    o   Project Coordination
     o   Invoicing (Bookkeeping)                   o   Proofreading/editing
     o   Light Accounting                          o   Research
     o   Hand written messages                     o   Typing Forms
     o   Message taking for visitors               o   Recording messages
                                                   o   Read messages over phone


     2) Rush  Turnaround Time = 1-8 hours or Overtime Hours                       $48.00                   Per hour
        Clerical services will be billed at 200% of                                                  .10 hr minimum
        the normal Clerical rate if performed before or after
        scheduled working hours, or requested as a
        rush job or if overtime must be worked

     3) Notary                                                                     $2.00                   Per seal
                                                                                                     .10 hr minimum
     4) Patching a call through to a seven-digit number not                        $2.40            Per call + call
        set up with a patch service

E.   CONCIERGE SERVICES

     1) Arrangement for Business Supplies, Catering, Meal                         $24.00                   Per hour
        order taking, etc.                                                                           .10 hr minimum

</TABLE>
All Service  pricing is subject to Change with 30 days advance written notice to
clients on contract.

Revised: 09/24/98                                               Initials   BM
                                                                Initials   EV
<PAGE>

<TABLE>
<CAPTION>
          Exhibit C- Continued
<S>                                                                             <C>       <C>
F.   CONFERENCE ROOMS

     1) Rental
        o  Full-Time Tenants                                                    Included             up to 12 Hours
        o  Hourly                                                                 $25.00                   Per Hour
        o  Daily (1 to 12 people)                                                $150.00                    Per Day

     2) Seminar Room (allowance at twice the time): Seminar rooms not
        available at all facilties.
        o  Full-Time Tenants                                                    Included           Accumulated with
                                                                                               Conference Room rent
        o  Hourly                                                                 $50.00                   Per Hour
        o  Daily (up to 40 people)                                               $300.00                    Per Day

     3) Cancellation, if not within 24 hours for conference room.                                   Billable at 50%
                                                                                                    of time reserve
     4) Set-up/clean-up after Tenant in conference room                           $24.00                   Per hour
                                                                                                     .10 hr minimum
G.   DIRECTORY LISTING - BUILDING LOBBY

     1) Full-time                                                               Included
     2) Flex time and Additional Listings-one time charge                Center Specific                   Per line

H.   FURNITURE
     1)  Moves/adds/changes including administrative coordination and
         moving of furniture places                                               $25.00                  Per piece
     2)  Standard Furniture Set                                                 Included                  Month/set
     3)  Additional Furniture Rental - Various Pieces                                               Varies based on
                                                                                                    Piece Requested
I.   KITCHEN FACILITIES
     (Coffee, tea, etc)
     1)  Tenants/Clients per cup service                                 Center Specific
     2)  Pots for Conference Room - Set-up                                        $24.00                   Per hour
                                                                                          Actual time-Clerical rate
J.   MAIL SERVICES
     >   Deliver parcel to Tenants office. All parcels are called to              $24.00                   Per hour
         tenant. If not picked up by 5:00pm, we will deliver to office.                              .10 hr minimum
     >   Prepare Certified, Express, or Courier
     >   Check mailbox/review mail by phone
     >   Prepare  packages,  such as label/wrap
     >   Trace  Shipments (Fed Ex, UPS, etc.)
     >   Mass mailings (folding, stuffing, posting, etc.)

K.   OFFICE SUPPLIES
     1)  Minimum supplies are available on site through ALLIANCE or may       Cost + 20%
         be ordered (See a clerical assistant for requests)
     2)  Weekly orders may be placed directly for tenant                          $24.00                   Per hour
                                                                                                     .10 hr minimum
L.   PARKING
     1)  Surface                                                         Center Specific
     2)  Covered Parking Garage                                          Center Specific

All Service  pricing is subject to change with 30 days advance written notice to
clients on contract.

Revised: 09/24/98                                                 Initials  BM
                                                                  Initials  EV
<PAGE>

                             Exhibit C - Continued

M.   POSTAGE FEES
     (Landlord shall serve as postal agent to all tenants and clients.)
     1)  U.S. Mail/UPS                                                                                   Cost + 20%
         o   Posting of mail - 25 pieces                                   Complimentary                    Per day
         o   Posting of mail - Additional (after 25 pieces)                        $2.40            Per 25 pieces +
                                                                                                       (cost + 20%)
     2)  Courier Service                                                                                 Cost + 20%
     3)  Federal Express                                                                              Standard Rate

N.   PRODUCTION & COPYING
     (a medium volume copy machine is avallable for Tenants)
     1)  Binding, copying & transparencies (clerical time only)                   $24.00                   Per hour
     2)  Photocopies
         o    up to 200                                                            $0.15                       Each
         o    200-750                                                              $0.13                       Each
         o    750+                                                                 $0.10                       Each
     3)  Binding (includes spine, cover & backing)                                 $3.50                       Each

0.   TELECOMMUNICATIONS
     1)  Standard Phone Equipment                                                 $95.00         Per Set, Per Month
         (Installation fee and set up not included)
         o    Phone with built in Speaker phone,
         o    DID Phone Number with 2 roll over lines
         o    1 line Directory Listing
         o    Other basic features of telephone system.
     2)  Phone/ Fax or Data Line installation                                    $150.00           Per line/per set
     3)  Fax or Data Line (Additional recurring charge each month plus a          $40.00        Per line, Per Month
         per minute charge where applicable)
     4)  Voice mail; adding another personal box                                  $10.00         Per box, Per month
                                                                                  $25.00      Per box, installation
     5)  Programming voice mail to pager                                          $25.00           Programming fee,
                                                                                                          per pager
     6)  Paging (not intercom services)
         o    Voice Mail Paging                                                   $10.00                  Per pager
                                                                                      Per Month + call transfer fee
         o    Paging on Demand to a pager                                          $2.40                  Per pager

     7)  Call Patching set up fee- if available                                   $25.00                 Per number
                                                                                                  (one time charge)
         o    Up to 40 Patches                                                    $25.00
                                                                                      Per Month + call transfer fee
         o    Additional Patches (after 40)                                        $0.50
                                                                                    Per Patch and call transfer fee
         o    On Demand                                                            $2.40                  Per Patch

     8)  Reconnect fee (after termination of service)                            $150.00     Per Phone or Data Line

     9)  T-1 Access (Not available at all locations)                             $100.00             Per user/month
         LAN Connectivity                                                         $25.00             Per user/month
         Security for T-1 Access                                                  $90.00                   Per user
         Installation  and set up                                       $150.00 + $75/hr          Per user-one time
     Note:  All  charges  are not  listed  for this service.
     Additional services also available.

Q.   TELECOPY/FAX - PLAIN PAPER FAX AVAILABLE
     (clerical charges may be incurred for faxes sent after normal
     business hours)
     1)  Outgoing                                                                  $2.00            Per Page + Call
     2)  Incoming                                                                  $1.00                   Per Page

All Service  pricing is subject to change with 30 days advance written notice to
clients on contract.

Revised: 09/24/98                                                Initials  BM
                                                                 Initials  EV
<PAGE>


       Exhibit C - Continued

R.   WORD PROCESSING / GRAPHICS*
     1)  Standard Word Processing Rate                                      From $30.00                    Per Hour
         Standard Desk top Publishing/Graphics Rate                         From $40.00               .1 hr minimum
         Word Processing and Desktop Publishing Services billed in
         6 minute increments. Normal turnaround = 24 hours
     2)  Word  Processing - Rush Tumaround Time = 1-8 hours                 From $45.00                    Per Hour
         Desktop Publishing - Rush Turnaround Time = 1-8 hours              From $60.00               .1 hr minimum
         The Word Processing and Desktop Publishing services
         below will be billed at 150% of the normal Word
         Processing rate if requested as a rush.
     3)  Overtime charges for Word Processing                               From $60.00                    Per Hour
         Overtime charges for Desktop Publishing/Graphics                   From $80.00               .1 hr minimum
         The Word Processing and Desktop Publishing services below
         will be billed at 200% of the normal rate if performed
         before or after scheduled  working hours, or if
         overtime required or requested.
     Word Processing/Graphics Services Available
     >   Ads                                      >   Logo design/Business Cards/Stationery
     >   Multi-media Presentations                >   Photo manipulation
     >   Charts & Graphs                          >   Proposals
     >   Color Laser Printing & B&W               >   Scanning [either text or photos]
     >   Database Development                     >   Straight keyboarding without any additional attributes
     >   Database Entry/Mailmerge List Entry      >   Tables/Forms
     >   Excel Spreadsheets/Statistical typing    >   Tape Transcription
     >   Flyers & Brochures                       >   Web Page design

        Industry Production Standards-
         *Landlord shall bill in accordance with Industry  Production  Standards
         (IPS),  published by the National  Association of Secretarial  Services
         and the  Executive  Suite  Association.  IPS are used for computing the
         time charged for document production and non-keyboarding  services. IPS
         are based on the average time required to perform  specific duties by a
         professional word processing  operator.  This allows the Tenant to know
         how  much a  project  will  cost  regardless  of how  long it  takes to
         complete it.

     4)  Resumes:
         Typing Only - Does not include edits or additional print outs
         o   1st Page                                                             $40.00              1st Page Only
         o   Each Additional Page                                                 $20.00                   Per Page
         o   Cover Letter                                                         $10.00                   Per Page
         Resume Writing Consultation Services                                     $45.00                   Per Hour
     5)  Technical Support                                                        $75.00                   Per Hour

S.   FLEX TIME PROGRAM
     1)  Telephone Answering Only(8:3Oam thru 5:30 pm; Mon. -Fri)                $100.00                  Per Month
     2)  Mail Service Only                                                        $75.00                  Per Month
     3)  Flex Program - Basic - No Conference Room                               $150.00                  Per Month
     4)  Flex Program - Plus - 6 Hrs. Conf. Room                                 $195.00                  Per Month
     5)  Flex Program - Premier - 12 Hrs. Conf. Room                             $250.00                  Per Month
     6)  Flex Program - Executive - 20 Hrs. Conf. Room                           $375.00                  Per Month

-----------------------------
</TABLE>

All Service  pricing is subject to change with 30 days advance written notice to
clients on contract.

Revised: 09/24/98                                                   Initials BM
                                                                    Initials EV
<PAGE>


[ALLIANCE LOGO]
Business Centers                        LEASE AND SERVICE AGREEMENT
                                        REBATE RIDER


RE:        Lease and Service Agreement between ALLIANCE Reston, L.P. and
           Certicom  ("Agreement")

DATE:      December 4, 1998

CENTER:    ALLIANCE Reston




WHEREAS The  agreement in Paragraph  "4a" provides that the lessor shall pay, as
rent for the  premises,  a total  rent of  $21,600  payable  in 6 equal  monthly
installments of $3600, and

WHEREAS the parties agree and  understand  that the said sum reflects the market
rent for the Premises, and

WHEREAS the parties  have agreed,  that in  consideration  of entering  into the
Agreement,  that  the  Lessor  shall  accept  instead  and in  place of the rent
described  in  paragraph  "4a" the total  sum of  $19,800  payable  in 6 monthly
installments of $3300 which reflects a monthly  abatement in the amount of $300,
for a total abatement in the amount of $1800 for the term.

It is hereby agreed as follows:

1.   Paragraph "4a" is hereby  modified so that,  upon expiration of the term of
     the  Agreement  and  upon the  first  lease  renewal  thereof,  whether  by
     operation of the Agreement or otherwise, the Lessee agrees to pay and shall
     pay rent as set forth in Paragraph "4a" of the Agreement.

2.   Upon further  expiration of any such renewal term, Lessee hereby agrees and
     understands  that Paragraph  "3b" of the Agreement  shall apply to any such
     renewals.

All other terms and  conditions of the Agreement  shall remain in full force and
effect.

ACCEPTED BY LESSOR:                     ACCEPTED BY LESSEE:

By:   /s/ Elizabeth Vroomen             By:  /s/ B. MacInnis
      ---------------------------            ----------------------------

Date:     12/18/98                      Title:  VP/CFO
      ---------------------------              --------------------------

                                        Date:     12/8/98
                                               --------------------------



<PAGE>


RESTON, VA
12030 SUNRISE VALLEY DRIVE o SUITE 300 o RESTON, VA 20191 o PHONE: 703.476.2200




                              [FLOOR PLAN OMITTED]





notes


                                                                 [ALLIANCE LOGO]

                                                                 Business Center