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                                                                   EXHIBIT 10.6



                         SOFTWARE DEVELOPMENT AGREEMENT

This Agreement is made and entered into as of May 13, 1997 by and between
CyberCash, Inc., a corporation organized under the laws of Delaware
("CyberCash"); and CyberCash K.K., a corporation organized under the laws of
Japan ("CCKK").

In consideration of the mutual promises set forth herein, CyberCash and CCKK
hereby agree as follows:

1.       DEFINITIONS.

         a. In addition to the capitalized terms defined elsewhere in this
            Agreement, the following capitalized terms shall have the following
            meanings when used in this Agreement.

         b. "Completion" has the meaning set forth in Section 4.a.

         c. "Gateway Software" means the Gateway software developed and
            operated by CyberCash for processing credit, coin, and check
            transactions in the United States.

         d. "Original Software" means the Gateway Software, Wallet Software,
            and Merchant Software, currently being used in the operation of the
            CyberCash services in the United States.

         e. "Local Gateway" means the Gateway Software, in object code form, as
            adapted and customized by CyberCash for CCKK hereunder, to handle
            transactions denominated in Yen with financial institutions located
            in Japan.

         f. "Local Software" means the Local Gateway Software, the Local Wallet
            Software, and the Local Merchant Software, in object code form.

         g. "Merchant Software" means the client software used by merchants in
            the operation of the CyberCash services in the United States.

         h. "Project Plan" has the meaning set forth in Section 4.a hereof.

         i. "Wallet Software" means the client software used by consumers in
            the operation of the CyberCash services in the United States.

2.       PURPOSE OF AGREEMENT.

         The purposes of this Agreement shall be to enable CCKK to: (i) prepare
         specifications for the Local Software localized for the Japanese
         market; (ii) finance the development of the Local Software; (iii)
         operate the Local Software and distribute the software necessary for
         processing in the Japanese market credit transactions, CyberCoin
         transactions, and electronic check transactions denominated in Yen
         involving Japanese financial institutions; and (iv) engage in other
         business activities in connection with the foregoing.

3.       DEVELOPMENT OF LOCAL SOFTWARE.

         a. Subject to the terms and conditions hereof, CyberCash shall develop
            for CCKK: (i) the Local Software developed for use in Japan; and
            (ii) upgrades of the Local Software. 


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            CyberCash shall also provide CCKK with maintenance and support 
            service for the use of the Local Software and its upgrades.

         b. Subject to the terms and conditions hereof, CCKK shall pay to
            CyberCash:

            (i)   CyberCash's fully burdened costs for the performance of the
                  development work specified in Section 4, plus $100,000, but 
                  not to exceed a total of US$1,100,000; and

            (ii)  CyberCash's fully-burdened costs (including out-of-pocket
                  expenses) for the incremental development work necessary to
                  adapt any upgrades or modifications to its Original Software
                  and to install such upgrades or modifications in Japan;

            (iii) After CCKK has completed an initial public offering, a fair
                  share of CyberCash's development costs for modifying and
                  upgrading its technology.

         c. With respect to the sum specified in paragraph 3b(i) CCKK shall
            make an initial payment of US$600,000. CyberCash shall furnish CCKK
            with monthly statements setting forth the progress of the work and
            the cost of the time and materials incurred. After the sum of the
            statements exceeds US$600,000, CCKK shall pay the outstanding
            balance within 15 days of presentation.

4.       SPECIFICATION OF LOCAL SOFTWARE.

         a. The parties hereto shall cooperate in the preparation of a project
            plan, to be completed not later than July 15, 1997, for the
            development and completion of the Local Software (the "Project
            Plan"). The Project Plan shall, provide for a schedule for the
            development of the Local Software. The parties hereto agree to use
            their best efforts to carry out all necessary activities required
            to meet the objectives of the Project Plan.

         b. CyberCash will use its best efforts to develop by July 15, 1997,
            proposed specifications for the Local Software. The parties shall
            make their best efforts to reach a prompt agreement on final
            specifications within 30 days of the date the specifications are
            first proposed. The Local Software shall be compliant with the
            latest version of the SET Protocol available.

         c. If CCKK requests modifications to the Local Software that are not
            contemplated in the specifications, CyberCash shall use reasonable
            efforts to accommodate such request.

         d. CyberCash shall use its best efforts to complete installation and
            acceptance testing of the Local Software pursuant to the Project
            Plan; however, CyberCash shall have no obligation to commence
            development work on the Local Software until the specifications are
            finalized.

5.       OWNERSHIP OF LOCAL SOFTWARE.

         Upon completion of the Local Software, all rights in and to the Local
         Software shall vest in CCKK, and CCKK shall have the exclusive right
         to (i) operate the Local Software for processing transactions in Japan
         involving Japanese financial institutions and merchants and (ii) keep
         and maintain a back-up copy of the object code of the Local Software.
         After the Completion, CyberCash shall have the rights to copy,
         distribute, sub-license and modify the Local Software, 

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         but only to the extent necessary for the performance of its
         obligations hereunder. Except as expressly provided herein, CyberCash
         shall not assert or claim any intellectual property rights or moral
         rights in or to any part of the Local Software. This agreement conveys
         to CCKK no rights to the Original Software or any modifications or
         derivative works thereof other than the Local Software.

6.       USE OF LOCAL SOFTWARE.

         a. CyberCash shall make its reasonably best efforts to obtain any
            licenses or permits necessary to enable CCKK to use the Local
            Software, including (i) the acquisition on behalf of CCKK of
            sublicenses of any software constituting a part of either of the
            Local Software, without any cost to CCKK and (ii) the compliance
            with any process to be taken under the applicable regulations in
            the United States. If CyberCash is unable to obtain a license or
            permit necessary for CCKK to use the Local Software without
            additional cost, CCKK shall be responsible for paying any such
            cost. A list of the third party licenses necessary to the Local
            Software is attached as Exhibit A.

         b. CyberCash shall grant CCKK a license to use in Japan the CyberCash
            name and all trademarks and service marks of CyberCash associated
            with the Local Software, free of charge. CCKK will agree to comply
            with reasonable rules established by CyberCash regarding the use of
            CyberCash's trademarks and service marks.

         c. CyberCash shall authorize CCKK to access any other Gateways that
            CyberCash currently, or in the future, operates or licenses as part
            of its global Internet payments system for the purpose of
            processing transactions involving a party outside of Japan or
            involving currencies other than yen, subject to the terms and
            conditions that CyberCash reasonably establishes for connections to
            other Gateways, including compliance with its global system
            operating rules and connectivity standards and the payment of
            standard transaction processing fees.

7.       UPGRADES

         a. On and after the Completion, CyberCash shall continue to develop,
            on behalf of CCKK, upgrades to the Local Software, which
            functionally correspond to those made to the Original Software or
            which CCKK from time to time reasonably determines necessary to its
            use of the Local Software in the Japanese market. CCKK shall
            provide and maintain adequate hardware and other resources for
            software upgrades and testing. Upon completion of each upgrade to
            the Local Software, such completed upgrade shall be considered to
            be a part of the Local Software as defined in Section 1.f hereof.

         b. As soon as possible after SET Protocol version 1.0 is available,
            necessary revision shall be made to the Local Software so that it
            is made compliant therewith.

         c. CCKK shall pay CyberCash its fully-burdened incremental costs of
            developing such upgrades as provided in paragraph 3b(ii), above in
            accordance with the agreement of the parties.

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8.       MAINTENANCE

         a. On and after the Completion, CyberCash shall provide CCKK with
            services of maintenance releases, remote support and software
            defect corrections for the Local Software (the "Maintenance and
            Support Services"). CyberCash shall retain the right, in assigning
            a software correction, to a release and the priority of a reported
            software defect. Upon completion of each maintenance release or
            software defect correction for the Local Software, such completed
            maintenance release or software defect correction shall be
            considered to be a part of the Local Software as defined in Section
            1.f hereof.

         b. CCKK shall reimburse CyberCash for its fully-burdened costs of
            providing Maintenance and Support Services (which shall not exceed
            US$250,000 per year) in accordance with the agreement of the
            parties.

         c. CyberCash shall provide Maintenance and Support Services to CCKK in
            accordance with the terms of a Support Services and Maintenance
            Agreement to be executed by CyberCash and CCKK before the
            Completion, which shall be based on the principles set out in 8.a
            and 8.b above.

9.       TRAINING OF EMPLOYEES.

         CyberCash shall provide initial training for personnel employed by
         CCKK in the operation and maintenance of the Local Software in
         accordance with the training schedule established in the Project Plan.
         The training shall be provided at CyberCash's facilities and shall be
         available to personnel possessing minimum qualifications specified by
         CyberCash. CCKK shall pay the travel and living expenses of the
         trainees, and CyberCash shall be responsible for the remaining costs
         of training.

10.      REPRESENTATIONS AND WARRANTIES BY CYBERCASH.

         a. CyberCash hereby represents and warrants as follows:

            i)   CyberCash is a corporate entity duly organized and existing in
                 good standing under the laws of the State of Delaware, and has
                 the full and complete corporate power and authority to execute
                 and deliver, and perform its obligations under, this Agreement;

            ii)  the execution and delivery by CyberCash of, and the performance
                 by CyberCash of its obligations under, this Agreement have been
                 duly authorized by all necessary corporate action;

           iii)  the execution and delivery by CyberCash of, and the
                 performance by CyberCash of its obligations under, this
                 Agreement (i) do not require any approval of its shareholders
                 or the approval or consent of any holder of any indebtedness
                 or obligations of CyberCash; (ii) except for any necessary
                 export or import licenses, do not require any consent,
                 approval, order or authorization of, or registration with, or
                 the giving of prior notice to, any governmental authority with
                 respect to the execution and delivery of this Agreement or the
                 validity and enforceability thereof or the satisfaction of all
                 obligations hereunder; (iv) do not contravene any applicable
                 law or violate the articles of incorporation or by-laws 





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                 of CyberCash; and (v) do not result in any breach of, or
                 constitute a default under, any agreement to which CyberCash
                 is a party or by which it may be bound or affected;

           iv)   this Agreement shall constitute the legal, valid and binding
                 obligations of CyberCash, enforceable against it in accordance
                 with its terms.

           v)    no part of the Local Software, the Original Software, or
                 CyberCash's service marks and trademarks now infringe or,
                 during the term of this Agreement, shall infringe on any
                 intellectual rights of a third party;

           vi)   there are no outstanding claims or pending lawsuits on the
                 date of this Agreement in connection with any aspect of the
                 Original Software or CyberCash's service marks and trademarks.

         b. CyberCash shall indemnify and hold CCKK harmless from and against
            any damages, liabilities, costs and expenses incurred by CCKK in
            connection with CyberCash's breach of the representations provided
            in this Section 10.

11.      CONFIDENTIALITY.

         a. Confidential Information. The parties acknowledge that they, their
            subsidiaries and affiliated companies are the owners of valuable
            trade secrets and other confidential information and that they
            license Confidential Information (as defined below) from others.

         b. Non-Disclosure. All confidential information disclosed by one party
            to the other party in connection with this Agreement (the
            "Confidential Information") shall remain the property of and be
            deemed proprietary to the disclosing party. The receiving party
            agrees to receive Confidential Information in strict confidence, to
            hold Confidential Information in trust for the disclosing party and
            to use Confidential Information solely and exclusively in
            accordance with the terms of this Agreement in order to carry out
            the purposes. Notwithstanding the preceding no party to this
            Agreement shall be liable for disclosure or use of Confidential
            Information if the Confidential Information was properly in the
            public domain at the time it was disclosed or is publicly released
            in response to a subpoena, court order or other legal process under
            circumstances in which a protective order or confidentiality
            agreement has been requested by rejected by the appropriate
            judicial or other lawful authority.

         c. Injunctive Relief. The parties hereto acknowledge that their
            remedies under this Agreement or otherwise available at law in the
            event of a disclosure of any Confidential Information or any
            default or threatened default by either party in the performance of
            its obligations under this Section 11 will be inadequate and agree
            that the terms of this Section 11 shall be enforceable by a decree
            for the specific performance thereof by the defaulting party, or by
            an injunction against any violation of its terms, or otherwise. The
            parties hereto further acknowledge and agree that the covenants
            contained herein are necessary for the protection of legitimate
            business interests of both parties, their subsidiaries and/or
            affiliated companies and are reasonable in scope and content.

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12.      NON-COMPETITION

         The parties hereto acknowledge and recognize the highly competitive
         nature of the business of CCKK and accordingly, to the extent
         permitted under any applicable law, agree that neither party hereof
         shall, directly or indirectly, from the date hereof until one (1) year
         after termination hereof, (i) induce employees of the other party to
         terminate their employment or to engage in any business directly
         competing with the other party, or (ii) induce any customer of the
         other party to terminate its relationship with the other party. or
         (iii) engage in the business of providing Internet payment services in
         Japan in competition with CCKK.

13.      TERM/TERMINATION.

         a. This Agreement shall become effective as of the date first above
            written and shall continue in full force and effect for an
            indefinite term thereafter, unless this Agreement is sooner
            terminated pursuant to this Section 13.

         b. Either party hereto may terminate this Agreement by giving written
            notice to the other party, upon the occurrence of any of the
            following events:

            (i)   If any note or check issued by the other party is dishonored;

            (ii)  If the other party receives a petition for attachment,
                  provisional attachment, provisional disposition or other
                  execution or is subject to any disposition for failure to pay
                  taxes

            (iii) If a petition for bankruptcy, composition, company
                  reorganization, company liquidation, or special liquidation
                  is filed in respect to either party:

            (iv)  If either party causes damage to the other party due to a
                  willful act or gross negligence in connection with the
                  performance of its obligations under this Agreement;
                  provided, however, that in such event only the damaged party
                  may terminate this Agreement; and

            (v)   If the other party's actions or inactions materially breach
                  this Agreement.

         Notwithstanding the foregoing, this Agreement may be terminated by
         written agreement of the parties hereto at any time.

         c. In the event that this Agreement is terminated pursuant to this
            Section 13, this Agreement shall terminate without any liability or
            further obligation of any party to another, except for any breach
            of this Agreement prior to termination.

         d. Sections 5, 10 and 11 shall survive any expiration or termination
            of this Agreement.

14.      FURTHER ACTS

         The parties hereto shall take whatever actions or steps are necessary
         to carry out and cause the performance of the various terms of this 
         Agreement.

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15.      DISPUTE RESOLUTION.

         Disputes arising under this Agreement shall be resolved by arbitration
         pursuant to the rules of the American Arbitration Association or such
         other arbitral body as the parties shall select by mutual agreement.
         This Agreement shall be interpreted in accordance with the laws of the
         Commonwealth of Virginia, without regard to its rules governing choice
         of law.

16.      MISCELLANEOUS PROVISIONS.

         a. Notices. All notices, consents, requests and other communications
            hereunder shall be in writing and shall be deemed to have been duly
            given when (a) delivered by hand, (b) sent by telecopier (with
            receipt confirmed), provided that a copy is sent in the manner
            provided in clause (c), or (c) when received by the addressee, if
            sent by DHL, Federal Express, Airborne Express or other generally
            recognized international express delivery service (receipt
            requested), in each case to the appropriate addresses and
            telecopier numbers set forth below (or to such other addresses and
            telecopier numbers as a party may designate as to itself by notice
            to the other parties):

            (i)  If to CCKK:

                       SoftBank Corp.
                       3-42-3 Nihonbashi-Hamacho
                       Chuo-ku
                       Tokyo  103 Japan
                       Telecopier No.: 81-3-5641-3402
                       Attention:  Yoshitaka Kitao, Executive Vice President

            (ii) If to CyberCash:

                       Reston Parkway, Suite 430
                       Reston, Virginia 22091
                       Telecopier No.: (703)264-5928
                       Attention: Bruce Wilson
                       with a copy to the General Counsel

         b. Headings. The headings in this Agreement are for convenience of
            reference only and shall not be given any effect in the
            interpretation of the Agreement.

         c. Counterparts. This Agreement may be executed in two or more
            counterparts, each of which shall be considered an original, but
            all of which together shall constitute the same instrument.

         d. Assignment. All of the terms and provisions of this Agreement shall
            be binding upon and inure to the benefit of and be enforceable by
            the parties hereto and their respective successors and permitted
            assigns. This Agreement shall not be assignable or transferable by
            either party hereto without prior written consent of the other
            party hereto.

         e. Entire Agreement; Amendment. This Agreement sets forth the entire
            understanding between the parties relating to the subject matter
            contained herein and merges all prior 


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            agreements and understandings between them. No amendment to this
            Agreement shall be effective unless it is in writing and executed
            by the parties hereto.

         f. Severability. Any term or provision of this Agreement which is
            invalid or unenforceable will be ineffective to the extent of such
            invalidity or unenforceability without rendering invalid or
            unenforceable the remaining rights of the person intended to be
            benefited by such provision or any other provisions of this
            Agreement.

         g. No Waiver. The failure of a party to insist upon strict adherence
            to any term of this Agreement on any occasion shall not be
            considered a waiver or deprive that party of the right thereafter
            to insist upon strict adherence to that term or any other term of
            this Agreement. Any waiver must be in writing.

         h. Incorporation. References herein to "this Agreement" and the words
            "herein," "hereof" and words of similar import refer to this
            Agreement, and Appendix 1 hereto, as an entirety.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly
executed, as of the date first above written.



CYBERCASH, INC.



By:  /s/ Bruce G. Wilson
     -----------------------
Name:    Bruce G. Wilson

Title:  Executive Vice President



CYBERCASH K.K.



By:  /s/ Yoshitaka Kitao
     -----------------------
Name:    Yoshitaka Kitao

Title: Director



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