<PAGE>

                                                                    Exhibit 10.4


                      ELECTRONIC DATA SYSTEMS CORPORATION
                          STANDARD SUBLEASE AGREEMENT


     THIS SUBLEASE AGREEMENT (the "Sublease") is entered into as of 1st day of
August, 2000, by and between the Sublandlord and Subtenant hereinafter named.
Upon the terms and conditions hereinafter set forth, the Sublandlord and
Subtenant agree as follows:

1.   DEFINITIONS AND BASIC PROVISIONS. The following definitions and basic
     ----------------------------------
     provisions shall be used in conjunction with and limited by the reference
     thereto in the provisions of this Sublease:

     A.   "Sublandlord":                ELECTRONIC DATA SYSTEMS CORPORATION, a
                                        Delaware corporation

     B.   Address of Sublandlord:       5400 Legacy Drive, H3-2F-53
                                        Plano, TX 75024-3105

                                        Attn: Real Estate Leasing

     C.   "Subtenant":                  ASHTON TECHNOLOGY GROUP, INC.
                                        a Delaware corporation

     D.   Address of Subtenant
             After Commencement Date
             additional notice to:      280 Trumball Street
                                        Hartford, CT 06103

     E.   Subtenant Federal Tax ID:     ________________________

     F.   "Master Landlord":            Cambridge One Commercial Plaza, LLC, a
                                        limited liability company

     G.   Address of Master Landlord:   c/o Cambridge Realty Partners, LLC
                                        280 Trumball Street
                                        Hartford, CT 06103

     H.   "Sublease Premises": All space to be occupied by Subtenant as shown on
          Exhibit "A", attached hereto and made a part of this Sublease,
          containing approximately 9,202 square feet of net rentable area in
          that certain building (containing approximately 620,000 rentable
          square feet of space on the 22/nd/ floor of the building located at
          280 Trumbull Street, Hartford, Connecticut 06103 (the "Building").

     I.   "Sublease Term": A period of approximately three (3) years and five
          (5) months, commencing on the earlier of (a) September 1' 2000, or (b)
          the date upon which Sublandlord receives Master Landlord's written
          consent to the Sublease and Subtenant's occupancy and use of the
          Sublease Premises (the "Commencement Date") and expiring on December
          30, 2003 (the "Expiration Date").

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     J.   "Base Rent": Base Rent shall be $165,636.00 per annum, payable in the
          amount of $13,803.00 per month.

     K.   "Base Year": The Base Year shall be the calendar year 2000. L.
          "Security Deposit': One month's Base Rent, or $13,803.00

     M.   "Property": That certain real property more particularly described in
          the Master Lease.

     N.   "Rent Abatement": Notwithstanding anything to the contrary in this
          Sublease, Subtenant shall receive an abatement of Base Rent hereunder
          for a period of sixty (60) days following the Commencement Date.

2.   GRANTING CLAUSE. Sublandlord, in consideration of the covenants and
     ----------------
     agreements to be performed by Subtenant and upon the terms and conditions
     hereinafter stated, does hereby lease, demise and let unto Subtenant, and
     Subtenant in consideration of the covenants and agreements to be performed
     by Sublandlord and upon the terms and conditions in this Sublease, does
     hereby take and lease from Sublandlord, the Sublease Premises, subject to
     all federal, state and local laws, statutes, codes, rules, regulations and
     zoning ordinances promulgated by any governmental authority having
     jurisdiction now in affect or adopted in the future (collectively, the
     "Law"), to have and to hold for the Sublease Term (except as the
     Commencement Date and the Expiration Date may be adjusted as herein
     provided, or unless sooner terminated as provided in this Sublease or the
     Master Lease).

3.   MASTER LEASE. This Sublease is subject to (i) that certain Lease Agreement
     --------------
     (the "Master Lease"), dated August 17, 1998, by and between Master
     Landlord, as landlord, and Sublandlord, as tenant, attached hereto as
     Exhibit "B", incorporated herein by reference), covering certain premises
     (the "Premises") more particularly described in the Master Lease; and (ii)
     that certain underlying ground lease (the "Ground Lease") between the City
     of Hartford and Master Landlord's predecessors in interest, Chase Family
     Limited Partnership No.3 and Olympia & York Hartford, Inc., dated October
     1, 1981, a copy of which lease is at the Hartford City Hall, Hartford,
     Connecticut, as the same has been and may be amended from time to time.
     This Sublease is made subject to all applicable covenants, restrictions,
     agreements, terms and conditions of the Master Lease and Ground Lease,
     which are incorporated into and made a part of this Sublease, as if
     Sublandlord were Master Landlord or Sublandlord, as appropriate, insofar as
     Sublandlord has the rights or right by law to act as so, and Subtenant were
     tenant or Subtenant, as appropriate, except as otherwise provided to the
     contrary herein, excluding Section 1.3, Article 2, Article 3, Article 4,
     Section 6.1, Article 23, Section 27.3, Article 34, Article 35, Article 41,
     and Exhibit B-1. Subtenant shall in no case have any rights with respect to
     the Sublease Premises greater than Sublandlord's rights as tenant under the
     Master Lease or Ground Lease, and Sublandlord shall have no liability to
     Subtenant for any matter or thing for which Sublandlord does not have co-
     extensive rights as tenant under the Master Lease or Ground Lease. In the
     event the specific terms of this Sublease are in conflict with the terms of
     the Master Lease or Ground Lease, then the specific terms of this Sublease
     shall prevail.

4.   MASTER LANDLORD'S CONSENT. Pursuant to the Master Lease, this Sublease is
     ---------------------------
     subject to Master Landlord's written consent (and the consent of Master
     Landlord's mortgagees, if required) and shall not be valid until Master
     Landlord's (and the applicable mortgagee's) written consent is obtained and
     delivered to each party, with such written consent of Master Landlord as to
     the Sublease and Subtenant's use and occupancy of the Sublease Premises
     being given by Master Landlord's execution of Master Landlord's Consent
     (the "Consent"), attached hereto and made a part hereof.

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<PAGE>

5.   WARRANTY BY SUBLANDLORD. Sublandlord warrants and represents to Subtenant,
     -----------------------
     to the knowledge of Sublandlord, that the Master Lease has not been amended
            ----------------------------------
     or modified, except as provided above, that Sublandlord is not now, and as
     of the Commencement Date of the Sublease Term hereof, will not be in
     default or breach of any of the provisions of the Master Lease, and that
     Sublandlord has no knowledge of any claim by Master Landlord that
     Sublandlord is in default or breach of any of the provisions of the Master
     Lease.

6.   CONDITION OF THE SUBLEASE PREMISES. Subtenant shall accept possession of
     ----------------------------------
     the Sublease Premises on an "AS IS, WHERE IS" basis, in whatever physical
                  ------------------------------------------
     condition the same may be, and Sublandlord makes no representations or
     warranties of any kind or nature, express, implied, or otherwise, or any
     covenants of any kind or nature, with regard to the condition of the
     Sublease Premises or with respect to the fitness thereof for Subtenant's
     intended uses or the quality of or manner of any services provided or to be
     provided by Master Landlord, and any such representations, warranties or
     covenants are hereby expressly disclaimed. Without limitation of the
     foregoing, Sublandlord shall have no obligation to construct or pay for any
     tenant improvements to the Sublease Premises or make any repairs or
     modifications thereto for the benefit of Subtenant.

7.   USE. Subtenant shall use the Sublease Premises for the uses set forth in
     ---
     the Master Lease, unless specifically approved by Sublandlord and Master
     Landlord. Subtenant shall additionally comply with the rules and
     regulations of the Building as set forth on Exhibit "C", attached to the
     Master Lease, which Master Landlord may reasonably amend from time to time
     during the term of this Sublease.

8.   RENT.
     ----

     A.   Base Rent. Subtenant agrees to pay equal monthly installments of Base
          Rent at the address indicated in Paragraph 1 above, or such other
          address as Sublandlord may from time to time notify Subtenant. Such
          monthly installments shall be payable on or before the first (1st) day
          of each calendar month (without demand, set-off or deduction)
          commencing as of the sixty-first (615\) day following the Commencement
          Date (i.e., upon the expiration of Subtenant's Rent Abatement period).
          Base Rent for any fractional month at the beginning or end of the
          Sublease Term shall be prorated on actual days. Base Rent shall be
          "gross" rent and include all charges Subtenant is obligated to pay,
          except for electric utility charges, Which Subtenant shall be
          obligated to pay in addition to the Base Rent.

     B.   Late Charge. In the event that any monthly installment of the Base
          Rent or any other payment required to made by Subtenant under this
          Sublease (collectively, the "Rent), is not received, Subtenant shall
          reimburse Sublandlord any and all costs Sublandlord incurs related to
          Subtenant's failure to pay the Rent When it is due and payable.

     C.   Non-Waiver of Rights. If Sublandlord, at any time or times, shall
          accept Rent or any other sum due to it hereunder after the same shall
          become due and payable, such acceptance shall not excuse delay upon
          subsequent occasions, or constitute, or be construed as, a waiver of
          any of Sublandlord's rights hereunder.

9.   SECURITY DEPOSIT AND FINANCIAL STATEMENTS. As security for the faithful
     -------------------------------------------
     performance by Subtenant of all of its obligations under this Sublease and
     for the payment of any damages to Which Sublandlord may be entitled in the
     event of a default by Subtenant hereunder, Subtenant will deposit with
     Sublandlord the Security Deposit. The Security Deposit shall be returned to
     Subtenant by Sublandlord without interest, within 30 days after the
     expiration of the Sublease Term, or renewal thereof, if applicable,
     provided that Subtenant has fully and faithfully carried out all of the
     terms, covenants and conditions under

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     this Sublease and the Master Lease. If Subtenant defaults with respect to
     any provision of this Sublease, including, but not limited to, the
     provisions relating to the payment of the Rent, Sublandlord shall have the
     right, but shall not be required to, at any time during the Sublease Term
     to use, apply or retain all or any part of the Security Deposit: a) for the
     payment of any of the Rent or any other sum in default; and/or b) for the
     payment of any other amount which Sublandlord may spend or become obligated
     to spend by reason of Subtenant's default, and/or c) to cure any default of
     Subtenant, and if Sublandlord does so, Subtenant shall, upon demand,
     immediately deposit with Sublandlord an additional sum to make the sum
     equal to the original Security Deposit amount, so that Sublandlord shall
     have the full Security Deposit available throughout the Sublease Term.
     Subtenant will provide to Sublandlord financial statements of Subtenant
     certified by a certified public accountant, reasonably approved by
     Sublandlord and Master Landlord. Such financial statements will be provided
     upon request from Sublandlord or Master Landlord.

10.  PARKING. There is are no parking facilities provided to Subtenant by
     --------
     Sublandlord pursuant to this Sublease. However, Subtenant may negotiate
     directly with the local parking garage management for fulfillment of its
     parking requirements and shall make any required payments for such parking
     as designated by such management.

11.  FURNITURE. Subtenant shall have the right to utilize the existing furniture
     ----------
     located in the Sublease Premises (the "Furniture") at no additional charge.
     Subtenant shall be obligated to maintain and repair the Furniture in good
     condition and repair, ordinary wear and tear excepted. Upon Subtenant
     surrendering the Sublease Premises at the Expiration Date, or earlier
     termination, Subtenant shall have the option to purchase the furniture from
     Sublandlord at a cost to be mutually agreed upon by the parties.

12.  ASSIGNMENT AND SUBLETTING. Subtenant shall not assign this Sublease or
     --------------------------
     further sublet all or any part of the Sublease Premises without the prior
     written consent of Sublandlord and the consent of Master Landlord, which
     may be withheld without reasonable cause. Subtenant may assign, sublease or
     transfer this Sublease or any interest therein, to a parent or affiliated
     entity of Subtenant, subject to the prior written consent of Sublandlord,
     not to be withheld, provided Master Landlord has given its written consent
     to such further transfer pursuant to the Consent herein contained. An
     "affiliate" shall mean any corporation which, directly or indirectly,
     controls or is controlled by, or is under common control with, Subtenant.
     For this purpose, "control" shall mean the possession, directly or
     indirectly, of the power to direct or cause the direction of the management
     and policies of such corporation, whether through the ownership of voting
     securities, or by contract or otherwise. Subtenant shall not be in default
     under the terms and conditions of this Sublease or the Master Lease at the
     time of any request for consent or through the period of time prior to the
     consent is granted by Sublandlord and/or Master Landlord. Any request by
     Subtenant for Sublandlord's consent to a specific assignment or sublease
     (except to an Affiliate) shall include a) the name of the proposed
     assignee, sublessee, or occupant, b) the nature of the proposed assignee's,
     sublessee's or occupant's business to be carried on in the Sublease
     Premises, c) a copy of the proposed assignment or sublease, and d) such
     financial information and such other information as Sublandlord may
     reasonably request concerning the proposed assignee, sublessee or occupant
     or its business. Any assignment or sublease approved by Sublandlord and
     Master Landlord shall be subject to the Master Lease and this Sublease.
     Subtenant shall pay to Sublandlord all reasonable costs incurred in
     connection with the review of such request and in obtaining Master
     Landlord's consent. Additionally, for purposes of this Sublease, the
     following transactions relating to Subtenant shall be deemed an assignment
     of this Sublease and shall give rise to the requirement of approval or
     consent by Sublandlord, and may result in the right to terminate or alter
     this Sublease based upon the above: any merger (including, without
     limitation, a reincorporation merger), consolidation, reorganization, stock
     exchange, sale of stock or substantially all of the assets or other similar
     or related transaction in which Subtenant is the surviving entity or, if
     Subtenant is not the surviving entity, the

                                       4
<PAGE>

     surviving entity continues to conduct the business conducted by Subtenant
     prior to consummation of the transaction.

13.  SUBTENANT'S INSURANCE. Subtenant shall, at its sole cost and expense,
     obtain and maintain the insurance under Article 9 of the Master Lease. The
                             --------------------------------
     insurance policy shall be written by good and solvent insurance companies
     able to do business in Connecticut, and reasonably satisfactory to
     Sublandlord and Master Landlord, if required by the Master Lease. On or
     before the Commencement Date of the Sublease Term, and within 30 days prior
     to the expiration of any such policy, Subtenant shall deliver to
     Sublandlord a certificate of insurance evidencing such coverages. Such
     insurance policies shall provide for no cancellation or material alteration
     without 30 days' prior written notice to Sublandlord and shall name
     Sublandlord and Master Landlord as additional insureds as their interests
     may appear.

14.  SUBLANDLORD'S OBLIGATIONS. Sublandlord shall have no obligation to perform
     any of Master Landlord's obligations under the Master Lease, including,
                   ---------------------------------------
     without limitation, (i) providing any of the services that Master Landlord
     has agreed to provide pursuant to the Master Lease (or required by law), or
     (ii) furnishing the electricity to the Sublease Premises that Master
     Landlord has agreed to furnish pursuant to the Master Lease (or required by
     law), or (iii) making any of the repairs or restorations that Master
     Landlord has agreed to make pursuant to the Master Lease (or required by
     law), or iv) complying with any laws or requirements of any governmental
     authorities, or v) take any other action that Master Landlord has agreed to
     provide, furnish, make, comply with, or take, or cause to be provided,
     furnished, made, complied with or taken under the Master Lease. Subtenant
     shall have no rights against Sublandlord arising out of the Master
     Landlord's failure to perform any of its obligations under the Master
     Lease. Subtenant shall have the right to institute an action under the
     provisions of the Master Lease to the extent such action relates to the
     Sublease Premises, provided Subtenant gives Sublandlord at least 30 days'
     prior written notice and Sublandlord has failed to take action within that
     time. Notwithstanding the foregoing, if an action or cure cannot be
     completed within 30 days after receipt, but such action or cure is
     commenced within 30 days after receipt of notice, and is diligently being
     pursued, Subtenant shall have no right to pursue Master Landlord or
     Sublandlord. If Subtenant subsequently pursues such action, Subtenant
     agrees to reimburse Sublandlord for any costs incurred by Sublandlord in
     connection with Subtenant instituting any such action. Sublandlord shall
     give reasonable assistance to Subtenant in enforcing the terms of the
     Master Lease, and will execute all documents reasonably necessary to enable
     Subtenant to pursue Master Landlord in its failure to perform any of its
     obligations under the Master Lease. Sublandlord agrees that it shall
     perform its obligations under the Master Lease when due- in accordance with
     the terms of the Master Lease.

15.  CONSENTS. Wherever consent by Master Landlord is required under the Master
     ---------
     Lease, Sublandlord's consent shall also be required. Except as specifically
     set forth herein, Sublandlord agrees that whenever its consent or approval
     is required hereunder, or where something must be done to Sublandlord's
     satisfaction, it shall not unreasonably withhold or delay such consent or
     approval, except under Paragraph 12 above; provided, however, that whenever
     the consent or approval of Master Landlord, the landlord under a superior
     lease, or the mortgagee under a mortgage shall withhold its consent or
     approval for any reason whatsoever, Sublandlord shall not be deemed to be
     acting unreasonably if it shall also withhold its consent or approval.

16.  LIMITATION OF LIABILITY OF SUBLANDLORD. In the event Sublandlord shall be
     --------------------------------------
     liable to Subtenant for any matter relating to or arising in connection
     with this Sublease, whether based upon an action or claim in contract,
     equity, negligence, intended conduct, tort or otherwise, the amount of
     damages recoverable against Sublandlord for all events, acts or omissions
     will not exceed, in the aggregate, the total amount actually to be paid by
     Subtenant to Sublandlord under this Sublease during the initial term of
     this Sublease. In no event will the measure of damages include, nor will
     Sublandlord be liable for, any

                                       5
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     amounts for loss of profits, income or savings or indirect, consequential,
     speculative or punitive damages of any party, including third parties.
     Further, no cause of action may be asserted against Sublandlord later than
     the earlier of a) the applicable statute of limitations for notice of such
     cause of action, or b) two years following the date after the date on which
     the cause of action shall have accrued. Sublandlord and Subtenant expressly
     acknowledge that the limitations contained in this Paragraph 16 have been
     the subject of active and complete negotiation between the parties and
     represent the parties' agreement.

17.  FORCE MAJEURE. Neither Sublandlord nor Subtenant shall be deemed to be in
     --------------
     breach of this Sublease by reason of failure to perform any of its
     obligations hereunder (except Subtenant's obligation to be any and all rent
     or any other amount due and payable under this Sublease) if, while and to
     the extent that such failure is due to acts of God, acts of the public
     enemy, acts of governmental authority, or any other circumstances for which
     it is not responsible and which are not within its control or any other act
     under the Master Lease; provided that this provision shall not apply to
     failures by Subtenant to pay rental fees or other charges or to make any
     other money payments required by this Sublease or to Sublandlord in making
     reimbursements to Subtenant or refunding or paying any other money payments
     to Subtenant as required by this Sublease.

18.  ATTORNEYS' FEES. In case it should be necessary for Sublandlord or
     ----------------
     Subtenant to bring any action under this Sublease, the non-prevailing party
     agrees to pay reasonable attorney's fees, including, without limitation,
     legal assistant or paralegal fees, special mailing and courier services,
     telecopies/faxes, filing fees.

19.  NOTICES. All notices and demands which mayor are to be required or
     --------
     permitted to be given by either party to the other hereunder shall be in
     writing and shall be deemed given when actually received, or if refused,
     when delivery was attempted. All notices and demands by Sublandlord to
     Subtenant shall be sent by c) Federal Express or some other bonded,
     national, professional overnight courier; d) United States Mail, certified
     or registered mail, return receipt requested, postpaid; or (c) sent by
     telecommunication ("Fax") during normal business hours in which case it
     shall be deemed delivered on the day sent, provided an original is received
     by the addressee after being sent by a nationally recognized overnight
     courier within 1 business day of the Fax, addressed to Subtenant at the
     address indicated in Paragraph 1 E above or to such other person or place
     as Subtenant may from time to time designate in a notice to Sublandlord.
     All notices and demands by Subtenant to Sublandlord shall be sent in the
     same manner as set forth above to the address set forth in Paragraph 1 B
     above or to such other person or place as Sublandlord may from time to time
     designate in a notice to Subtenant.

20.  AMENDMENTS. No agreement hereafter made shall be effective to change or
     -----------
     modify this Sublease in whole or in part unless such agreement is in
     writing and signed by both parties hereto, nor shall any custom, practice
     or course of dealing between the parties in the administration of the terms
     hereof be construed to waive or lessen the right of any party to insist
     upon the performance by the other party in strict accordance with the terms
     of this Sublease.

21.  ENTIRE AGREEMENT. It is expressly agreed by Sublandlord and Subtenant, as a
     -----------------
     material consideration for the execution of this Sublease, that there are
     and were no representations, understandings, stipulations, agreements or
     promises pertaining thereto not incorporated in writing herein.

22.  PARTIES BOUND. The preparation and submission of a draft of this Sublease
     --------------
     by either party to the other party shall not constitute an offer, nor shall
     either party be bound to any terms of this Sublease or the entirety of this
     Sublease, until both parties have fully executed a final document and an
     original

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     signature document has been received by both parties. Until such time as
     described in the previous sentence, either party is free to terminate
     negotiations without any obligation to the other party.

23.  OPTIONS PERSONAL. Any option or rights of refusal (collectively, the
     -----------------
     "Option") set forth in the Master Lease shall be personal to Sublandlord,
     and may not be exercised or assigned, voluntarily or involuntarily, by, or
     to, any person or entity other than Sublandlord. The Option is not
     assignable separate and apart from the Master Lease.

24.  SUBLEASE TERMINATION. If Subtenant and Master Landlord enter into a new
     ---------------------
     lease agreement (the "New Lease") for the Sublease Premises to be effective
     prior to the expiration of the Master Lease and this Sublease, and Master
     Landlord releases Sublandlord of all obligations and liabilities under the
     Master Lease accruing subsequent to such effective date of the New Lease,
     Sublandlord shall release Subtenant of all obligations and liabilities
     accruing subsequent to such effective date of the New Lease.

25.  JOINT AND SEVERAL LIABILITY. If more than one person or entity is defined
     ---------------------------
     as Subtenant in this Sublease, all of the duties, obligations, promises,
     covenants and agreements contained in this Sublease to be paid and
     performed by Subtenant shall be the joint and several obligation of all
     persons or entities defined as Subtenant. Each person or entity defined as
     Subtenant agrees that Sublandlord in Sublandlord's sole discretion may (i)
     institute or bring suit against them, jointly and severally, or against
     anyone or more of them, (ii) compromise or settle with anyone or more of
     them for such consideration as Sublandlord may deem proper and (iii)
     release one or more of them from liability hereunder, and that no such
     action by Sublandlord shall impair or affect Sublandlord's rights to
     collect costs, expenses, losses or damages incurred or suffered by
     Sublandlord from the other persons or entities defined as Subtenant, or any
     of them, not so sued, compromised, settled with or released.

26.  BROKERS. Subtenant and Sublandlord acknowledge that Jones Lang LaSalle
     -------
     Americas, Inc. ("JLL") and/or CB Richard Ellis ("CB"), and Colliers Dow &
     Condon Inc. ("Subtenant's Broker") are the sole real estate brokers
     responsible for bringing about or negotiating this Sublease and are the
     only brokers with whom either has dealt with regard to this Sublease.
     Sublandlord shall pay a commission to JLL in accordance with a separate
     agreement. Subtenant and Sublandlord agree to defend, indemnify and hold
     harmless each other from any expense or liability arising out of a claim
     for commission or other compensation by any other person, entity or broker
     claiming by or through the indemnifying party.

                                       7
<PAGE>

IN WITNESS WHEREOF, this Sublease is executed as of the date first written
above.

SUBLANDLORD:                            SUBTENANT:
-----------                             ---------

ELECTRONIC DATA SYSTEMS                 ASHTON TECHNOLOGY GROUP, INC.
CORPORATION

By:     /s/ Daniel F. Busch             By:    /s/ Mathew Saltzman
   --------------------------------        -------------------------------------
        Daniel F. Busch                 Printed Name: Matthew Saltzman
                                                      --------------------------

Title:  Director of Real Estate         Title: President eMC & Authorized Agent
Dated:_____________________________     Dated:__________________________________


___________________________________     ________________________________________
Witness                                 Witness
Printed Name:______________________     Printed Name:___________________________



___________________________________     ________________________________________
Witness                                 Witness
Printed Name:______________________     Printed Name:___________________________

                                       8
<PAGE>

                        CONSENT OF LANDLORD TO SUBLEASE

     Reference is hereby made to the following: (i) that certain Lease Agreement
(the "Lease"), dated August 17, 1998, by and between CAMBRIDGE ONE COMMERCIAL
PLAZA, LLC, a Connecticut limited liability company, ("Landlord"), and
ELECTRONIC DATA SYSTEMS CORPORATION, a Delaware corporation ("Tenant") which
lease covers approximately 9,202 rentable square feet (the "Premises") on the
22nd floor of the building located at 280 Trumbull Street, Hartford,
Connecticut 06103 (the "Building"); and (ii) that certain underlying ground
lease (the "Ground Lease") between the City of Hartford and Landlord's
predecessors in interest, Chase Family Limited Partnership No.3 and Olympia &
York Hartford, Inc., dated October 1' 1981, and (ii) that certain proposed
Sublease (the "Sublease"), dated August 1, 2000, by and between Tenant, and
ASHTON TECHNOLOGY GROUP, INC. a Delaware corporation ("Subtenant"), relating to
the Premises. A copy of the Sublease is attached hereto.

     Tenant hereby requests Landlord to consent to the Sublease and to
Subtenant's possible further transfer of the Sublease to an affiliate.

     Landlord hereby grants its consent to Tenant's subletting of the Premises
to Subtenant and to the occupancy of the Sublease Premises by
Subtenant, all subject to the terms and conditions of the Lease and Ground
Lease. Except as herein expressly provided, such consent shall not effect any
one or more of the following:

(a)  This consent does not constitute a modification of or amendment to any
provision of the Lease or Ground Lease.

(b)  This consent does not approve (or disapprove) the form or provisions of the
Sublease.

(c)  This consent does not constitute a release of Tenant from any of Tenant's
obligations under the Lease. Landlord shall look solely to Tenant for
performance of all obligations of the tenant arising under the Lease, including
payment of any charges attributable to Subtenant.

(d)  This consent does not create a direct relationship between Landlord and
Subtenant with respect to the Premises covered by the Lease and does not permit
any right of direct action by Subtenant against Landlord with respect to the
Lease or the Sublease.

(e)  This consent is not a waiver of Landlord's right to approve any assignment
or subletting not expressly described herein.

     Landlord also consents to Tenant's permitting Subtenant to further transfer
its interest under the Sublease, in whole but not in part, by assignment to a
Related Party. A "Related Party" is any entity controlled by, in control of, or
under common control with Subtenant. Tenant shall give Landlord not less than
thirty (30) days prior written notice of such a proposed assignment and shall
provide to Landlord the name and address of the proposed assignee, reasonable
evidence of the basis for the assignee's qualification under the prior sentence,
and such other information concerning the proposed assignment as Landlord
reasonably requests.

     Landlord covenants and agrees to deliver to Subtenant copies of all notices
of default delivered to Tenant under the Lease and to recognize and accept from
Subtenant the cure of any default of Tenant under the Lease, within the time
periods provided in the Lease, in the event Tenant does not cure any such
default within such time periods. The acceptance by Landlord of any cure by
Tenant or of direct payments from Tenant shall not operate to make Landlord a
party to the Sublease.

     Tenant covenants and agrees to deliver to Landlord copies of all notices of
default delivered to Subtenant under the Sublease. Further, Tenant agrees to
provide, as part of the written certificate required under Section 25.1 of the
Lease (relating to estoppels certificates), either a statement that Subtenant is
not in default of the Sublease or a statement specifying the nature of any
default by Subtenant thereunder.

     The Sublease is attached hereto for purposes of identification but is not
intended to be incorporated herein. The Sublease is not binding on Landlord. In
the event of any conflict between the Sublease and this letter of consent, this
letter shall control.

     If Subtenant and Landlord enter into a new lease agreement (the "New
Lease") for the Sublease Premises to be effective prior to the expiration of the
Lease, Landlord shall thereafter release Tenant of all obligations and
liabilities under the Lease accruing subsequent to such effective date of the
New Lease. If, for any reason, the Lease is terminated, the Sublease shall
automatically terminate.

IN WITNESS WHEREOF, Landlord and Tenant have executed and delivered these
presents to each other and to Subtenant as of August 14, 2000.


                              LANDLORD:

                              CAMBRIDGE ONE COMMERCIAL PLAZA, LLC

                              By: One Commercial Management, LLC
                                  Its Managing Member

                                  By: Levstone Commercial Management Corp.
                                        Its Manager

                                      By:  /s/ Mark R. Stone
                                          --------------------------------------
                                             Mark R. Stone
                                             Its Vice President

                              TENANT:

                              ELECTRONIC DATA SYSTEMS CORPORATION


                                      By:  /s/ Daniel F. Busch
                                          --------------------------------------
                                             Daniel F. Busch
                                             Title: Director of Real Estate

<PAGE>

                                  EXHIBIT "A"
                                  -----------
                               SUBLEASE PREMISES
                               -----------------

                                       10
<PAGE>

                            CONFIRMATORY AGREEMENT
                            ----------------------


     THIS CONFIRMATORY AGREEMENT (this "Agreement") is made as of the 1st day of
                                        ---------
August, 2000, by and among, the undersigned.

     WHEREAS, Ashton Technology Group, Inc. ("Ashton") is named as subtenant
                                              ------
under a certain Sublease Agreement dated as of August l' 2000 (the "Sublease")
                                                                    --------
with Electronic Data Systems Corporation, as sublandlord (the "Sublandlord"),
                                                               -----------
pertaining to certain space on the 22nd floor of the building located at 280
Trumbull Street, Hartford, Connecticut and owned by Cambridge One Commercial
Plaza, LLC (the "Master Landlord");
                 ---------------

     WHEREAS, Ashton and Electronic Market Center, Inc. ("EMC") are affiliated
companies and it was intended by such parties that EMC would be the subtenant
under the Sublease;

     WHEREAS, with the consent of the Sublandlord and the Master Landlord, the
parties hereto desire to confirm that EMC is and shall be the subtenant under
the Sublease;

     WHEREAS, the Sublandlord, Ashton and EMC desire to confirm other matters
under the Sublease as hereinafter set forth;

     NOW, THEREFORE, the parties agree to the following:

     1.   Identity of Subtenant.  The subtenant under the Sublease is and shall
          ---------------------
be EMC (in such capacity, "Subtenant"). In furtherance thereof, EMC hereby
                           ---------
ratifies and reaffirms, and agrees to be bound in all respects by, each of the
terms, conditions, covenants and obligations of subtenant under the Sublease.
Ashton hereby assigns and transfers to EMC any rights, interests, powers, and
privileges of Ashton under the Sublease and Ashton shall not be bound as the
subtenant thereunder.

     2.   Operating Expenses.  The parties to the Sublease hereby acknowledge
          -------------------
and agree that the Subtenant's Base Rent under the Sublease was intended to be
net of electric charges with a Base Year of calendar year 2000 with respect to
Operating Expenses. Therefore, Paragraph 3 of the Sublease is revised to delete
the exclusion of Article 4 of the Master Lease, and Subtenant shall pay any
increase in Operating Expenses over the Base Year amount of Operating Expenses.

     3.   Reaffirmation.  Except as set forth above, the Sublease shall remain
          -------------
and continue in full force and effect.

                                       11
<PAGE>

     4.   Consent of Master Landlord. Master Landlord consents to the foregoing
          --------------------------
subject to all of the terms and limitations of a certain "Consent of Landlord to
Sublease" dated as of August 14, 2000, between Master Landlord and Sublandlord.


     Witnesses:                              ASHTON TECHNOLOGY GROUP, INC.


                                             /s/ Mark I. Salvacion
     _______________________________         -------------------------------
     Name:                                   Name: Mark I. Salvacion
                                             Its Secretary


     Name:
     _______________________________



                                             ELECTRONIC MARKET CENTER, INC.


                                             /s/ Matthew Saltzman
     _______________________________         -------------------------------
     Name:                                   Matthew Saltzman
                                             Its President


     Name:
     _______________________________


                                       12
<PAGE>

     CONSENTED AND AGREED TO:


                                             ELECTRONIC DATA SYSTEMS
                                               CORPORATION


                                             /s/ Daniel F. Busch
     _______________________________         ----------------------------------
     Name:                                   Name: Daniel F. Busch
                                             Director of Real Estate


     _______________________________
     Name:


                                             CAMBRIDGE ONE COMMERCIAL PLAZA, LLC

                                             By: One Commercial Management, LLC
                                                 Its Managing Member

                                             By: Levstone Commercial Management
                                                 Corp.
                                                 Its Manager

                                             By:  /s/ Mark R. Stone
     _______________________________            -------------------------------
     Name:                                   Name: Mark R. Stone
                                             Its Vice President


     _______________________________
     Name:

                                       13