Document:

<PAGE>
                                                                   EXHIBIT 10.23

                          STRATEGIC ALLIANCE AGREEMENT

                                     BETWEEN

                 AUTHENTIDATE HOLDING CORP., AUTHENTIDATE, INC.

                                       AND

                        THE UNITED STATES POSTAL SERVICE

                                    REGARDING

                     THE USPS ELECTRONIC POSTMARK(R) SERVICE
<PAGE>
                                                                   EXHIBIT 10.23

                                TABLE OF CONTENTS

<TABLE>
<S>                        <C>                                              <C>                           <C>
ARTICLE I.                 PURPOSE AND SCOPE
     Section 1.01          Purpose..............................................................3

ARTICLE I.                 SECTION 1.02.....................................................SCOPE         3

ARTICLE II.                DEFINITIONS
     Section 2.01          AD Core Technology...................................................3
     Section 2.02          AD Derivatives.......................................................3
     Section 2.03          AD Marks.............................................................3
     Section 2.04          Channel Partner......................................................3
     Section 2.05          Customer.............................................................4
     Section 2.06          Derivatives..........................................................4
     Section 2.07          Digital Signature....................................................4
     Section 2.08          Effective Date.......................................................4
     Section 2.09          Electronic File......................................................4
     Section 2.10          EPM..................................................................4
     Section 2.11          EPM Practice Statement...............................................4
     Section 2.12          EPM Software.........................................................4
     Section 2.13          EPM System...........................................................4
     Section 2.14          Exhibit..............................................................5
     Section 2.15          Gross Revenues.......................................................5
     Section 2.16          Hardware.............................................................6
     Section 2.17          Hash Function........................................................6

ARTICLE II.                SECTION 2.18.....................................INTELLECTUAL PROPERTY         6
     Section 2.19          Joint Products and Services..........................................6
     Section 2.20          Licensed Rights......................................................6
     Section 2.21          Sales and Marketing Plan.............................................6
     Section 2.22          SDK..................................................................6
     Section 2.23          Server...............................................................6
     Section 2.24          Service Launch Date..................................................7
     Section 2.25          Transaction..........................................................7
     Section 2.26          USPS Marks...........................................................7

ARTICLE III.               GRANT OF CERTAIN RIGHTS AND PRODUCT
                           DESCRIPTION
     Section 3.01          The USPS - Branded EPM...............................................7
     Section 3.02          USPS Grant to AD.....................................................7

ARTICLE III.               SECTION 3.03..........................................AD GRANT TO USPS         8
     Section 3.04          AD Products..........................................................8

ARTICLE IV.                EXHIBITS
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                                                                   EXHIBIT 10.23

<TABLE>
<S>                        <C>                                                             <C>
     Section 4.01          Exhibit List.....................................................9, 10
     Section 4.02          Final Exhibits......................................................10

ARTICLE V.                 DUTIES AND OBLIGATIONS OF AD
     Section 5.01          Operation...........................................................11
     Section 5.02          Technical Innovations...........................................11, 12
     Section 5.03          Privacy Act.........................................................12
     Section 5.04          Sales and Marketing.............................................12, 13
     Section 5.05          Pricing.............................................................13
     Section 5.06          USPS Use of the EPM System..........................................13
     Section 5.07          Insurance.......................................................13, 14
     Section 5.08          Monthly Reports.....................................................14
     Section 5.09          Annual Projection Reports.......................................14, 15
     Section 5.10          USPS Brand..........................................................15
     Section 5.11          Compliance with Metrics.............................................15
     Section 5.12          Financial Responsibility............................................15

ARTICLE VI.                USPS RESPONSIBILITIES
     Section 6.01          Start Up Costs......................................................15
     Section 6.02          Existing USPS Electronic Postmark(R)
                           Customers.......................................................15, 16
     Section 6.03          Sales Contracts.....................................................16
     Section 6.04          General Responsibilities of USPS....................................16
     Section 6.05          Sales and Marketing.............................................16, 17

ARTICLE VII.               ADDITIONAL AREAS OF OPPORTUNITY; SUCCESS
                           RIGHTS
     Section 7.01          Additional Areas of Opportunity.................................17, 18
     Section 7.02          Success Rights..................................................18, 19

ARTICLE VIII.              ADVISORY COMMITTEE
     Section 8.01          Establishment.......................................................19
     Section 8.02          Composition.........................................................19
     Section 8.03          Guidelines..........................................................19

ARTICLE IX.                SECURITY AND CERTIFICATION PROVISIONS
     Section 9.01          USPS ISA Process....................................................19
     Section 9.02          Service Launch Date.............................................19, 20
     Section 9.03          Remedial Measures...................................................20
     Section 9.04          Suspension of Services..............................................20
     Section 9.05          AD Compliance with USPS Security Regulations........................20

ARTICLE X.                 PRIVACY PROTECTION
     Section 10.01         Privacy Act.....................................................20, 21
     Section 10.02         Customer or Visitor Data............................................21
     Section 10.03         Online Assistance...............................................21, 22
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                                                                   EXHIBIT 10.23

<TABLE>
<S>                        <C>                                                      <C>                   <C>
ARTICLE XI.                FINANCIAL TERMS
     Section 11.01         Costs...............................................................22

ARTICLE IV.                SECTION 11.02............................................GROSS REVENUE         22, 23
     Section 11.03         Collection and Tracking of Customer Funds...........................23
     Section 11.04         Distribution of Customer Funds..................................23, 24
     Section 11.05         Return of Customer Funds............................................24
     Section 11.06         International Sales.................................................24

ARTICLE XII.               DISPUTE RESOLUTION
     Section 12.01         Mediation...........................................................24
     Section 12.02         Arbitration.....................................................24, 25
     Section 12.03         Choice of Law.......................................................25
     Section 12.04         Jurisdication and Venue.............................................25

ARTICLE XIII.              SERVICE COMMITMENTS
     Section 13.01         Service Level Agreements............................................25
     Section 13.02         SLA Reports.........................................................25
     Section 13.03         Notice of Failure to Meet SLAs......................................25
     Section 13.04         Failure to Meet SLA Requirements....................................26

ARTICLE XIV.               INTELLECTUAL PROPERTY RIGHTS
     Section 14.01         General Intellectual Property Rights............................26, 27
     Section 14.02         AD and AD Holding Corp. Retention of Rights.........................27
     Section 14.03         [****]..........................................................27, 28
     Section 14.04         Notice of Development of Improvements...............................28
     Section 14.05         Assignment of Rights by Third Parties and
                           Employees...........................................................28

ARTICLE XV.                LICENSE GRANTS - MARKS
     Section 15.01         Branding and Trademarks.............................................28
     Section 15.02         Ownership of USPS Marks.............................................29
     Section 15.03         Untitled............................................................29
     Section 15.04         AD and AD Holding Corp. Materials and Marks
                           License.............................................................29
     Section 15.05         Ownership of Authenthidate Marks....................................29
     Section 15.06         Untitled........................................................29, 30
     Section 15.07         Notification of Claims..............................................30

ARTICLE XVI.               CHANGES TO SERVICES AND SPECIFICATIONS

ARTICLE XVII.              PUBLIC ANNOUNCEMENTS

                           [ * Certain information on this page has been omitted
                           and filed separately with the Commission.
                           Confidential treatment has been requested with
                           respect to the omitted portions.]
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                                                                   EXHIBIT 10.23

<TABLE>
<S>                        <C>                                                            <C>
     Section 17.01         Public Announcements................................................30

ARTICLE XVIII.             CONFIDENTIALITY
     Section 18.01         Untitled............................................................31
     Section 18.02         Untitled............................................................31
     Section 18.03         Disclosure of Confidential Information..............................31
     Section 18.04         Untitled........................................................31, 32

ARTICLE XIX.               SOURCE CODE ESCROW
     Section 19.01         Untitled............................................................32

ARTICLE XX.                AUDIT AND INSPECTION
     Section 20.01         Audit by a Party....................................................33
     Section 20.02         Audit by a Third Party..............................................33

ARTICLE XXI.               TERM AND TERMINATION
     Section 21.01         Term................................................................33
     Section 21.02         Events of Termination...........................................33, 34
     Section 21.03         AD Change of Control ...........................................34, 35

ARTICLE XXII.              EFFECT OF TERMINATION
     Section 22.01         Wind Down Strategy..................................................35
     Section 22.02         AD's Obligations Upon Termination...................................35
     Section 22.03         USPS's Obligation Upon Termination .............................35, 36

ARTICLE XXIII.             BANKRUPTCY
     Section 23.01         Untitled............................................................36

ARTICLE XXIV.              REPRESENTATIONS, WARRANTIES, AND
                           UNDERTAKINGS
     Section 24.01         Representations and Warranties..................................36, 37
     Section 24.01         Representations and Warranties by AD to USPS........................37

ARTICLE XXV.               AMENDMENTS OR MODIFICATIONS
     Section 25.01         Untitled............................................................37

ARTICLE XXVI.              ASSIGNMENT
     Section 26.01         Assignment..........................................................38

ARTICLE XXVII.             SUBCONTRACTING
     Section 27.01         Subcontracting......................................................38

ARTICLE XXVIII.            GUARANTEE
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                                                                   EXHIBIT 10.23

<TABLE>
<S>                        <C>                                                  <C>                       <C>
     Section 28.01         Untitled............................................................38
ARTICLE XXIX.              NOTICES
     Section 29.01         Notices.........................................................38, 39

ARTICLE XXX.               SEVERABILITY
     Section 30.01         Construction....................................................39, 40
     Section 30.02         Untitled............................................................40

ARTICLE XXXI.              EQUAL OPPORTUNITY
     Section 31.01         No Discrimination...................................................40
     Section 31.02         Solicitations.......................................................40
     Section 31.03         Executive Order 11246...............................................40
     Section 31.04         Audit Requirements..................................................40
     Section 31.05         Cancellation for Failure to Comply .................................40
     Section 31.06         Inclusion in Subcontracts.......................................40, 41

ARTICLE XXXII.             AFFIRMATIVE ACTION FOR HANDICAPPED
                           WORKERS
     Section 32.01         Discrimination Against Handicapped Workers..........................41
     Section 32.02         Compliance with Regulations.........................................41
     Section 32.03         Failure to Comply with Regulations..................................41
     Section 32.04         Posting Notices.....................................................41
     Section 32.05         Inclusion of Clause in Subcontracts.................................41

ARTICLE XXXIII.            AFFIRMATIVE ACTION FOR DISABLED VETERANS
                           AND VETERANS OF THE VIETNAM ERA
ARTICLE V.                 SECTION 33.01........................................NO DISCRIMINATION         41, 42
     Section 33.02         Recruitment.........................................................42
     Section 33.03         Listings............................................................42
     Section 33.04         Vietnam Era Veterans................................................42

ARTICLE XXXIV.             THIRD - PART AGREEMENTS
     Section 34.01         Right of Termination................................................42
     Section 34.02         Limitation on Indemnification.......................................42

ARTICLE XXXV.              EFFECT OF VARIOUS LAWS
     Section 35.01         Procurement Laws................................................42, 43
     Section 35.02         Untitled............................................................43
     Section 35.03         Untitled............................................................43
     Section 35.04         Untitled............................................................43
     Section 35.05         Sovereign Acts......................................................43
     Section 35.06         Force Majeure...................................................43, 44
     Section 35.07         Compliance and Cooperation..........................................44
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                                                                   EXHIBIT 10.23

<TABLE>
<S>                        <C>                                                             <C>
ARTICLE XXXVI.             LEGAL RESPONSIBILITIES
     Section 36.01         Indemnification of USPS.........................................44, 45
     Section 36.02         Indemnification of AD...............................................45
     Section 36.03         Indemnification Procedure.......................................45, 46
     Section 36.04         Limitations on Liability............................................46

ARTICLE XXXVII.            NO JOINT VENTURE
     Section 37.01         Untitled............................................................46

ARTICLE XXXVIII.           COUNTERPARTS
     Section 38.01         Untitled............................................................46

ARTICLE XXXIX.             SEVERABILITY
     Section 39.01         Untitled............................................................47

ARTICLE XL.                ENTIRE AGREEMENT
     Section 40.01         Untitled............................................................47

ARTICLE XLI.               EFFECTIVE DATE
     Section 41.01         Untitled............................................................47

ARTICLE XLII.              SURVIVAL
     Section 42.01         Untitled............................................................47

ARTICLE XLIII.             HEADINGS
     Section 43.01         Untitled............................................................47

ARTICLE XLIV.              SIGNATURE BLOCK
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<PAGE>
                                                                   EXHIBIT 10.23

                          STRATEGIC ALLIANCE AGREEMENT

                                     BETWEEN

                 AUTHENTIDATE HOLDING CORP., AUTHENTIDATE, INC.

                                       AND

                        THE UNITED STATES POSTAL SERVICE

                                    REGARDING

                     THE USPS ELECTRONIC POSTMARK(R) SERVICE

         This Agreement is entered into by and between

         The United States Postal Service, an independent establishment of the
executive branch of the Government of the United States, having its principle
place of business at 475 L'Enfant Plaza, S.W., Washington, D.C. 20260 ("USPS" or
"Postal Service"); and

         AuthentiDate Holding Corp. ("AD Holding Corp."), a corporation existing
under the laws of the State of Delaware and registered to do business in the
State of New York, whose principal place of business is 2165 Technology Drive,
Riverside Technology Park, Schenectady, New York 12308, and AuthentiDate, Inc.
("AD") a corporation existing under the laws of the State of Delaware and
registered to do business in the State of New York, whose principal place of
business is 2 World Financial Center, 225 Liberty Street, 43rd Floor, New York,
NY 10281.

         (USPS, AD Holding Corp. and AD are sometimes hereinafter referred to
together as "Parties").

         WHEREAS, USPS has previously determined that verifying and providing
electronic time and date security services to the public under its brand is
consistent with its mission;

         WHEREAS, USPS published a Request for Information seeking information
from third parties as to their ability to provide electronic time and date
security services;

         WHEREAS, USPS reviewed the information submitted by AD and others
concerning their electronic time and date security services in response to the
Request for Information and determined that AD is the party capable of providing
such electronic services under the USPS brand;

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                                                                   EXHIBIT 10.23

         WHEREAS, AD Holding Corp and AD desire to provide patent-pending AD
Core Technology, together with AD Derivatives and AD's supporting hardware,
technical support, marketing and sales expertise under the USPS marks and brand
(defined below) and USPS is willing to license its brand and USPS marks to AD
for purposes of providing USPS-branded electronic time and date security
services to the public;

         WHEREAS, USPS also determined that entering into an Alliance Agreement
with AD whereby AD serves as the preferred provider of the EPM for USPS furthers
USPS's best interests;

         WHEREAS, in the event USPS develops new requirements for electronic
time and date security services based on market demand, USPS may elect to seek
proposals from third parties to satisfy the new requirements, and USPS will
provide AD the opportunity to provide such services in accordance with the new
requirements on terms USPS considers to be the same or better than the terms
offered by other third parties

         NOW THEREFORE, in consideration of the premises and the mutual
agreements and covenants contained herein, the Parties hereby agree as follows:

Page 9 of 163
<PAGE>
                                                                   EXHIBIT 10.23

ARTICLE I. PURPOSE AND SCOPE

         Section 1.01 Purpose. The purpose of this Agreement is to provide,
         electronic time and date security services ("EPM" as defined below) of
         a quality and in a manner approved by USPS

                  (a) using technology furnished by AD Holding Corp. and AD;

                  (b) using expertise from AD, AD Holding Corp. and USPS; and

                  (c) marketed and supplied under and branded with USPS Marks
                  (defined below),

         to consumers, businesses, government entities, and the public. The
         provision of EPM system services will include product development,
         operation of the EPM System under the USPS Marks in accordance with
         industry and USPS standards, marketing and sales, integration and
         interoperation of the EPM System into other systems, and allocation of
         gross revenues between the USPS and AD.

         Section 1.02 Scope. Beginning on the Effective Date, the Parties will
         work together to establish an EPM System (defined below) branded with
         the USPS Marks to provide the EPM System to the public.

ARTICLE II. DEFINITIONS

         All capitalized terms in this Agreement shall have the meaning as set
         forth in this article:

         Section 2.01 AD Core Technology. Intellectual Property (defined below),
         including all AD Derivatives, owned and/or licensed now or during the
         term of this Agreement by AD Holding Corp. and/or AD that provides EPM
         systems, (including that which is in whole or in part claimed in
         pending patent applications), wherever and whenever developed.

         Section 2.02 AD Derivatives. All Derivatives of or relating to or
         concerning the same or similar functions as AD Core Technology made by
         or on behalf of, AD or AD Holding Corp.

         Section 2.03 AD Marks. The mark "AuthentiDate" and the logo or icon
         adopted and used by AD or AD Holding Corp.

         Section 2.04 Channel Partner. Any third party that provides access to a
         distribution network into a market place.

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                                                                   EXHIBIT 10.23

         Section 2.05 Customer. An individual, business or governmental entity
         that uses the EPM System, including parties that enter into Sales
         Contracts as may be appropriate for use of the EPM System, the standard
         form(s) of which is contained in Exhibit F.

         Section 2.06 Derivatives. Works of authorship that are a modification,
         translation, abridgment, condensation, compilation, expansion,
         recasting, transformation, or adaptations, improvements, discoveries
         and/or inventions, whether patentable or not, whether copyrightable or
         not.

         Section 2.07 Digital Signature shall mean a transformation of an
         Electronic File using an asymmetric cryptosystem and a Hash Function
         such that a person having the initial Electronic File and the public
         key can accurately determine (a) whether the transformation was created
         using the private key that corresponds to the public key, and (b)
         whether the initial Electronic File has been altered since the
         transformation was made.

         Section 2.08 Effective Date. The date of signature of the last party to
         sign this Agreement.

         Section 2.09 Electronic File. Computer-generated textual and/or
         graphical communication or document capable of being transmitted
         electronically.

         Section 2.10 EPM. Electronic time and date security services that
         verify the authenticity of Electronic Files, as described in the
         Technical Description attached hereto as Exhibit E, that complies with
         industry standards and USPS policies and procedures.

         Section 2.11 EPM Practice Statement. A statement of the practices and
         procedures that AD follows in providing services based upon AD Core
         Technology in accordance with Exhibit C.

         Section 2.12 EPM Software. Software module based upon AD Core
         Technology, together with any updates provided by AD or AD Holding
         Corp. and potentially customized under this Agreement to permit
         recipients to verify EPM-Processed Electronic Files received from a
         sender.

         Section 2.13 EPM System. The combination of the Hardware, software,
         billing systems, Transactions, management reports, archiving, updates,
         upgrades, and all activities supporting the use of an EPM. The EPM
         System will provide trusted third-party validation of the time and date
         that an Electronic File is received by the Server, and validation that
         an Electronic File is not changed after its processing by the Server.
         The EPM System will hash the Electronic File, and attach a time/date
         token to it, in accordance with the Technical Description set forth in
         Exhibit E.

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                                                                   EXHIBIT 10.23

         Section 2.14 Exhibit. Each document referenced herein as an Exhibit,
         attached hereto and incorporated herein, including any later amendments
         or additions agreed upon by AD and USPS.

         Section 2.15 Gross Revenues. The aggregate cash, licensing fees,
         transaction fees, or other compensation received from Customers or
         users for the right to use, or the use of, the EPM System, including
         any such compensation arising from the EPM component of the AD Products
         defined in Section 3.04, below.

         Gross Revenues do not include the following:

                  (a) The aggregate cash, licensing fees, transaction fees or
                  other compensation received from Customers or users for the
                  right to use, or the use of the [ * * * * ] as follows if such
                  use satisfies all of the following conditions: (1) use does
                  not [ * * * * ], (2) time and date is not provided by
                  independent source, and (3) such use is not compliant [ * * *
                  * ] and its future revisions; and

                  (b) Fees that AD may charge Customers for integrating [ * * *
                  * ].

         Section 2.16 Hardware. The Server, the cryptographic module and the
         time/date device currently owned or licensed, and maintained by AD
         located at [ * * * * ].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

         Section 2.17 Hash Function. An algorithm mapping or translating one
         sequence of bits into another, generally a smaller set (the "Hash
         Result") such that an Electronic File yields the same Hash Result every
         time the same version of the algorithm is executed using the same
         Electronic File.

         Section 2.18 Intellectual Property. Wherever existing in the world, (i)
         patents, whether in the form of utility patents or design patents,
         and/or all pending patent applications therefor, (ii) trademarks, trade
         names, service marks, domain names, designs, logos, trade dress and
         trade styles, whether or not registered, and all pending applications
         for registration thereof, (iii) copyrights, whether or not registered,
         and all pending applications for registration thereof, (iv) know-how,
         inventions, research records, trade secrets, confidential information,
         production designs, engineering specifications and drawings, technical
         information, formulas, customer lists, supplier lists and market
         analyses, (v) computer software and programs and related flow charts,
         programmer notes, documentation, updates, and date, whether in object
         or

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                                                                   EXHIBIT 10.23

         source code form, and (vi) all other similar intellectual property
         rights, whether or not registered.

         Section 2.19 Joint Products and Services. All Intellectual Property,
         including all derivative works, modifications, improvements,
         discoveries, and/or inventions, whether patentable or not and whether
         or not subject to copyrights, made by AD or AD Holding Corp. and USPS,
         as a joint effort, in connection with this Agreement concerning EPM
         systems.

         Section 2.20 Licensed Rights. Rights in Intellectual Property owned by
         AuthentiDate Holding Corp. or AD that are necessary for USPS to provide
         the EPM System.

         Section 2.21 Sales and Marketing Plan. The Sales and Marketing Plan for
         the EPM system developed by AD upon consultation with, and subject to
         the approval of the USPS, a proposal for which is attached hereto as
         Exhibit A. Within thirty (30) days of the Effective Date, the Sales and
         Marketing Plan shall replace the sales and marketing Proposal currently
         attached as Exhibit A.

         Section 2.22 SDK. Software Development Kit. A toolkit that a software
         developer uses to allow its software application to gain access to the
         EPM System.

         Section 2.23 Server. The computer server(s) supporting the EPM , owned
         and/or operated by AD currently located at [ * * * * ] as referred to
         in Exhibit E, and sometimes referred to as "Central Server."

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

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                                                                   EXHIBIT 10.23

         Section 2.24 Service Launch Date. The date on which the EPM System is
         made available to the public pursuant to this Agreement.

         Section 2.25 Transaction. Each application of a Digital Signature, Hash
         Function, and Time and Date to an Electronic File.

         Section 2.26 USPS Marks. The trademarks "United States Postal Service",
         "USPS", United States Postal Service logo and typeface design, "USPS
         Electronic Postmark", "Electronic Postmark", "United States Postal
         Service Electronic Postmark" (in English or in a literal translation)
         and the logo or icon approved by USPS to designate the EPM System.

ARTICLE III. GRANT OF CERTAIN RIGHTS AND PRODUCT DESCRIPTION

         Section 3.01 The USPS-Branded EPM . The Parties agree to offer the EPM
         System to Customers under USPS Marks in accordance with this Agreement
         and the Exhibits attached hereto and incorporated by reference, as well
         as other policies and service descriptions referenced herein. The EPM
         System offered or provided to any Customer shall be solely a
         USPS-branded service; however, marketing or promotional materials (such
         as, but not limited to, collateral, advertisements, etc.) shall
         acknowledge AD's role in the provision of this service by displaying
         language such as "By Authentidate" or "Operated by Authentidate"
         subject to USPS's reasonable approval.

         Section 3.02 USPS Grant to AD

             (a) USPS licenses AD the USPS Marks for use as the brand for EPM
             services provided by the Parties under this Agreement for the Term,
             subject to AD's compliance with the terms of this Agreement and
             subject to its maintenance of a standard of quality of EPM System
             approved by USPS in accordance with Exhibit D, Service Level
             Agreement ("SLA").

             (b) AD's use of USPS Marks shall always be subject to USPS's
             approval.

             (c) Until USPS has approved a use of a USPS Mark which approval
             shall not be unreasonably withheld, AD has no right to use the mark
             in any manner before the public or customers or other businesses.

             (d) USPS licenses AD the right use such other Intellectual Property
             that USPS uses in providing the EPM system under this Agreement in
             accordance with USPS's directions and restrictions and subject to
             USPS's reasonable approval. This Intellectual Property includes
             advice, know-how, and ideas provided under and in accordance with
             this Agreement.

             (e) USPS licenses to AD the use of a USPS Private Digital Signature
             provided by USPS for the purpose of this Agreement.

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                                                                   EXHIBIT 10.23

         Section 3.03 AD Grant to USPS. AD licenses USPS during the Term of this
         Agreement the Licensed Rights for the purposes of this Agreement.

         Section 3.04 AD Products. In the event AD, AD Holding Corp., or their
         affiliates incorporate the AD Core Technology or AD Derivatives into
         their products or services, ("AD Products"), the EPM component of the
         AD products shall be offered in accordance with the Pricing Policy
         Guidelines and Provisional Pricing Schedule attached hereto as Exhibit
         B.

         AD entered into Transaction License Agreements with customers listed on
         Exhibit G prior to the Effective Date of this Agreement that contain
         prices which vary from the Pricing Policy Guidelines and Provisional
         Price Schedule. [ * * * * ]. The price for the [ * * * * ] with the
         Pricing Policy Guidelines and Provisional Price Schedule.

         Gross Revenue from such EPM components of AD Products shall be
         allocated between USPS and AD pursuant to this Agreement.

         AD will brand the EPM component of AD products with USPS Marks. In the
         event an AD product [ * * * * ] unless USPS has elected in writing not
         to associate its brand with that product. USPS may terminate this
         Agreement for cause pursuant to the termination provisions set forth
         below if AD fails to cease such actions within 30 days after USPS
         furnishes AD with written notice.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

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                                                                   EXHIBIT 10.23

ARTICLE IV. EXHIBITS

         Section 4.01 Exhibit List. Except as set forth in Section 4.02 below,
         completion of these Exhibits is a condition precedent to execution of
         the Agreement, and this Agreement shall fail if the following Exhibits
         are not completed as of the Effective Date, unless extended by mutual
         agreement of the Parties:

                  (a) Exhibit A. Sales and Marketing Proposal

                  (b) Exhibit B. Pricing Policy Guidelines and Provisional Price
                  Schedule

                  (c) Exhibit C. Draft EPM Practice Statement

                  (d) Exhibit D. Service Level Agreement ("SLA") between USPS
                  and AD

                  (e) Exhibit E. Technical Description

                  (f) Exhibit F. Sales Contract (to be completed)

                  (g) Exhibit G. Existing Customers

                  (h) Exhibit H. Advisory Committee Guidelines

                  (i) Exhibit I. Trademark Usage Guidelines

                  (j) Exhibit J. Alliance Metrics

                  (k) Exhibit K. Concept of Operations

                  (l) Exhibit L. Nondisclosure Agreement

                  (m) Exhibit M. Information Security Requirements

                  (n) Exhibit N. WIND DOWN/CONTINUITY OF SERVICE PLAN

                  (o) Exhibit O. Success Rights Agreement

                  (p) Exhibit P. Return of Customer Funds

                  (q) Exhibit Q. Source Escrow Agreement

         Section 4.02 Final Exhibits. The Parties understand that the following
         Exhibits have not been created and/or finalized as of the Effective
         Date and the Parties agree to cooperate, and use their best efforts, to
         promptly revise and/or create the following Exhibits which shall be
         approved by each Party within thirty (30)

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<PAGE>
                                                                   EXHIBIT 10.23

         days of the Effective Date. This Agreement shall fail and be void ab
         initio and as if not executed if the following Exhibits are not
         completed and approved by each Party prior to Service Launch Date:

                           Exhibit A, Sales and Marketing Plan;

                           Exhibit C, EPM Practice Statement

                           Exhibit F, Sales Contract

                           Exhibit N, Wind Down/Continuity of Service Plan

                           Exhibit O, Success Rights Agreement

                           Exhibit P, Return of Customer Funds

                           Exhibit Q, Source Code Escrow Agreement

ARTICLE V. DUTIES AND OBLIGATIONS OF AD

         Section 5.01 Operation. Pursuant to the terms of this Agreement, AD
         will develop, operate, and promote the USPS-branded EPM System as
         follows:

                  (a) Cooperate with USPS in the testing and acceptance
                  processes with respect to the EPM System in order to meet the
                  projected Service Launch Date to be agreed to by AD and USPS.
                  Complete, to the satisfaction of USPS, the items identified in
                  Exhibit M, Information Security Requirements within the time
                  frames set forth therein.

                  (b) Develop, integrate, operate, host and maintain all
                  elements of the EPM System in accordance with this Agreement,
                  including the Exhibits attached hereto;

                  (c) Provide the staff and resources as necessary to support
                  the EPM development, operation and promotion efforts in
                  accordance with this Agreement;

                  (d) Enable EPM to interoperate with products or systems used
                  by Customers;

                  (e) Implement billing and accounting systems to ensure prompt
                  and efficient aggregation of Gross Revenue from Customers, and
                  to support prompt payment of Gross Revenue shares to AD and
                  USPS.

                  (f) Provide customer support in accordance with the Service
                  Level Agreement set forth in Exhibit D.

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                                                                   EXHIBIT 10.23

                  (g) Comply with all the terms and conditions of third party
                  license agreements necessary for the EPM System.

                  (h) Develop, implement and maintain the necessary systems,
                  when at such time the EPM System is made available to retail
                  customers so that retail customers can register for and obtain
                  EPM services through the EPM System.

         Section 5.02 Technical Innovations.

                  (a) Implement, as approved by the Advisory Committee
                  throughout the term of this Agreement, technical innovations
                  or other enhancements in order to meet market demands at the
                  sole cost of AD, provided, however, that AD shall not be
                  required to incur unreasonable costs. Such implementation
                  shall include any adaptive maintenance to ensure compatibility
                  with the most current and widely used computing standards and
                  in accordance with Exhibit D, SLA as it may be amended from
                  time to time.

                  (b) Implement, as reasonably required by USPS, USPS policies
                  or other applicable law, regulations, and standards, at the
                  sole cost of AD, including but not limited to remedial
                  maintenance necessary to guarantee the integrity of the
                  services and products contemplated under this Agreement.

         Section 5.03 Privacy Act. Develop processes and systems that conform
         with Postal Service privacy and security policies pursuant to this
         Agreement.

         Section 5.04 Sales and Marketing. AD is responsible for the sale and
         marketing of USPS-branded EPM System, subject to consultation and
         approval by the Advisory Committee, in accordance with the Sales and
         Marketing Proposal to be attached hereto as Exhibit A, as amended from
         time to time. AD's responsibilities include, but are not limited to the
         following:

                  (a) Developing the Sales and Marketing Plan to be attached
                  hereto as Exhibit A, within 30 days of the Effective Date of
                  this Agreement. The USPS has right to approve the initial
                  Sales and Marketing Plan, which may be subsequently modified
                  as necessary by the Advisory Committee. The Advisory Committee
                  shall review the Sales and Marketing Plan, no less frequently
                  than quarterly.

                  (b) Executing the EPM Sales and Marketing Plan, including, but
                  not limited to, attending appropriate trade shows to promote
                  the EPM System, and otherwise promoting the EPM System to
                  third parties.

Page 18 of 163
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                                                                   EXHIBIT 10.23

                  (c) Conducting market research, mutually agreed upon by the
                  Parties, to identify prospective customers, market demand for
                  EPM as well as enhancements to the EPM, and competitive
                  offerings.

                  (d) Establishing, training, and managing a sufficient EPM
                  sales force and work with Channel Partners and through its own
                  sales resources to generate sales and achieve revenue targets,
                  in accordance with the Sales and Marketing Plan, and the
                  Alliance Metrics, attached hereto as Exhibits A and J,
                  respectively.

                  (e) Distributing the EPM to new and existing Customers (e.g.,
                  billing systems, customer set-up and support, software release
                  and management), in accordance with this Agreement.

                  (f) AD shall submit to USPS, for execution by USPS within 2
                  business days of receipt, proposed Sales Contracts for EPM in
                  the format(s), to be developed and attached hereto as Exhibit
                  F, unless otherwise agreed in writing. AD shall cooperate with
                  the Postal Service to facilitate other marketing and/or
                  distribution arrangements with third parties with respect to
                  sales of EPM, or interoperation of other systems with the EPM
                  System.

                  (g) In the event a third party requires the payment of fees or
                  other compensation as a condition to using the EPM or
                  incorporating the EPM into its product line, such as referral
                  fees or credit card fees, then AD shall be solely responsible
                  for paying such fees or compensation, and no portion of such
                  fees or compensation shall be deducted from Gross Revenue
                  under this Agreement, unless otherwise agreed in writing by
                  USPS.

                  (h) In the event USPS elects to undertake studies, or retain
                  third parties to conduct studies of the market demand, market
                  impact, cost or economics relating to electronic time and date
                  security services, including the EPM System, or related
                  topics, AD will provide information, as requested, in
                  connection with any such studies.

         Section 5.05 Pricing. The initial Pricing Policy Guidelines and
         Provisional Pricing Schedule are attached hereto as Exhibit B.
         Procedures for amending the Pricing Policy Guidelines and Provisional
         Pricing Schedule are set forth in Exhibit B, incorporated herein by
         reference. Prices set through the Pricing Policy Guidelines and
         Provisional Pricing Schedule shall be subject to, and modified to
         comply with all applicable laws and regulations governing the USPS. The
         pricing of all EPM incorporated into AD Products shall comply with the
         Pricing Policy Guidelines and Provisional Pricing Schedule, and Gross
         Revenue derived from such AD Products shall be allocated between AD and
         USPS. Notwithstanding the foregoing, any agreements for EPM System
         executed prior to the effective

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                                                                   EXHIBIT 10.23

         date of this agreement are exempt from the Pricing Guidelines and
         Provisional Price Schedule only for the term of that agreement.

         Section 5.06 USPS Use of the EPM System. In the event USPS elects to
         use the EPM System in the conduct of its business, or replaces any
         existing EPM products it offers to third parties with the EPM System,
         the price paid for the EPM System will be a price that is no more than
         the current best available pricing of the EPM System. Any existing
         pricing agreements entered into prior to the Effective Date of this
         agreement shall not be considered in determining best available price.
         USPS shall, at its cost and expense, integrate the EPM System into its
         operations or existing products it offers to third parties.

         Section 5.07 Insurance. AD and AD Holding Corp., shall at their
         expense, during the entire term of this Agreement, keep in full force
         and effect, policies of insurance meeting or exceeding the following
         specifications which shall cover all of the EPM Service:

                  (a) Crime insurance, including Employee Dishonesty and
                  Computer Fraud coverage for theft of money or securities that
                  AD holds, or for which AD is legally liable, arising out of
                  the dishonest acts committed by the employees of AD or its
                  subcontractors, acting alone or in collusion with others, or
                  through the use of AD's computer system to fraudulently cause
                  a transfer, with coverage in a minimum amount of [ * * * * ].

                  (b) General Liability insurance in a minimum amount of [ * * *
                  * ] and an Excess Liability policy (umbrella form) with a [ *
                  * * * ].

                  (c) Errors or Omissions Liability insurance in a [ * * * * ]
                  and an Excess Liability policy form with a [ * * * * ].
                  Cyberliability insurance in an amount of [ * * * * ] per year
                  with a [ * * * * ].

                  (d) USPS shall be listed as an additional insured on each
                  policy, and AD and AD Holding Corp. will provide USPS a
                  Certificate of Insurance within thirty (30) days of the
                  Effective Date of this Agreement. All certificates shall
                  provide for thirty (30) day cancellation notice from the
                  insurance carrier. AD and AD Holding Corp. shall immediately
                  notify USPS of any cancellation notice by the insurance
                  carrier.

                  (e) The Advisory Committee will annually review the adequacy
                  of the insurance and recommend changes as deemed appropriate.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 20 of 163
<PAGE>
                                                                   EXHIBIT 10.23

         Section 5.08 Monthly Reports. Commencing on the Service Launch Date, AD
         will submit to USPS and the Advisory Committee Monthly reports
         containing the following information concerning the EPM System: names
         of potential Customers contacted; status of negotiations with any
         potential Customers; list of Sales Contracts signed; number of EPM
         transactions; Gross Revenue collected from Customers or Channel
         partners; amount of Gross Revenue paid to the Parties; deviation from
         SLA requirements; security breaches; EPM System problems; results of
         satisfaction surveys; claims received or suits filed relating to the
         EPM System; accounts receivable with aging schedule; status of
         compliance with Alliance Metrics set forth in Exhibit J, management and
         other reports as required by the SLA set forth in Exhibit D. AD will
         also submit with each monthly report, a short management summary that
         analyzes the report data.

         Section 5.09 Annual Projection Reports. Commencing on the Service
         Launch Date, by April 30 of each year, AD will submit to USPS and the
         Advisory Committee a projection report, containing the following
         projections for the two-year period commencing on October 1 of that
         year: Gross Revenue; projected EPM transactions; number of customers to
         be contacted; sales and marketing budget. In addition, each calendar
         quarter AD shall furnish a report indicating deviations (if any) from
         the projections.

         Section 5.10 USPS Brand. Obtain prior approval from USPS Manager of
         Corporate Identity, or successor, for any and all uses of the USPS
         Marks in accordance with this Agreement; and,

         Section 5.11 Compliance with Metrics: AD shall comply with the Alliance
         Metrics attached hereto as Exhibit J.

         Section 5.12 Financial Responsibility. AD will be solely responsible
         for financing and maintaining its business operations in fulfillment of
         its obligations under this agreement. In no case shall the Postal
         Service be liable for any costs for fulfillment of AD obligations under
         this Agreement.

ARTICLE VI. USPS RESPONSIBILITIES

         Section 6.01 Start Up Costs. USPS will pay a total of $250,000 to AD
         provided that neither AD nor AD Holding Corp. are in default under this
         Agreement. USPS shall make [ * * * * ] of [ * * * * ] each in
         accordance with the following schedule:

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

Page 21 of 163

<PAGE>
                                                                   EXHIBIT 10.23

            (a) [ * * * * ] Sales and Marketing Plan. Upon [ * * * * ] the Sales
            and Marketing Plan, not unreasonably withheld, to [ * * * * ] the
            Sales and Marketing Proposal attached hereto as Exhibit A. AD shall
            apply the [ * * * * ] as [ * * * * ] or in connection with USPS
            products. The price for the EPM Service component of such USPS
            products shall not exceed the best available price at the time the
            EPM is used by customers.

            (b) [ * * * * ] Back-Up Recovery Plan, and [ * * * * ] Customer
            Sales Contracts: Upon the last of the following to occur:

                  (i) AD submitting to USPS, [ * * * * ], Customer Sales
            Contracts for [ * * * * ] Customers in the format to be developed
            for Exhibit F. These [ * * * * ] do not include current Customers
            listed in Exhibit G.

                  (ii) [ * * * * ] the "hot back-up recovery" plan for the EPM
            System including plans for a full redundant system at a remote
            location within the 48 contiguous United States.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

      Section 6.02 Existing USPS Electronic Postmark(R) Customers: USPS will use
      its best efforts to encourage its existing USPS Electronic Postmark (R)
      customers to use the EPM System. USPS will work with AD to integrate USPS
      existing customers into the EPM System, at the cost and expense of USPS.
      USPS will not renew any existing licenses, or sell any new licenses for
      the existing USPS Electronic Postmark (R) after Service Launch Date;
      provided, however, that any contract signed or renewed after the Effective
      Date shall contain a provision to automatically convert such Customer to
      the USPS EPM Service on the Service Launch Date, or as soon as practicable
      thereafter.

      Section 6.03 Sales Contracts. Within two (2) business days, execute
      standard Sales Contracts submitted by AD in the form to be attached hereto
      as Exhibit F, provided that pricing conforms to the Pricing Policy
      Guidelines and Provisional Pricing Schedule on Exhibit B. In the event
      that AD does not submit a standard form Sales Contract, or the pricing
      does not conform to the Pricing Policy Guidelines and Provisional Pricing
      Schedule shown at Exhibit B, USPS shall have the opportunity to review and
      approve or disapprove the Sales Contract, provided that USPS shall not
      unreasonably withhold its approval.

      Section 6.04 General Responsibilities of USPS. The USPS will be
      responsible for the following pursuant to the terms of this Agreement:

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                                                                   EXHIBIT 10.23

            (a) Provide necessary access to USPS technical personnel and
            information to assist AD in development efforts for program
            management, on-site security inspection, and USPS certification and
            accreditation.

            (b) Exercise management oversight to ensure adherence to relevant
            USPS policies and regulations.

            (c) The U.S. Postal Inspection Service, may, at its sole discretion,
            review allegations of fraud arising from the use of the EPM System.

            (d) Review the Pricing Schedule for EPM that is proposed by the
            Advisory Committee.

      Section 6.05 Sales and Marketing. USPS will support the marketing and sale
      of EPM by:

            (a) Promoting the EPM System on USPS.com; provide hyperlinks in
            accordance with standard USPS practice, where AD will provide flash
            demos for the system to be inserted;

            (b) Working with AD through the Advisory Committee to review the
            Marketing and Sales Plan for the EPM;

            (c) Using best efforts to identify potential corporate and
            government customers and participating in strategic sales efforts to
            acquire Customers including, but not limited to attendance at trade
            shows, seminars, and conferences, as identified by the Advisory
            Committee in accordance with the Sales and Marketing Plan;

            (d) Issuing public announcements and press releases as mutually
            agreed upon pursuant to this Agreement. At the Postal Service's sole
            discretion, send appropriate USPS representatives for events, press
            tours, interviews, and speaking engagements;

            (e) providing introductions to USPS contract public relations and
            advertising agency firms;

            (f) identify a single point of contact for all marketing issues that
            will serve as the liaison to the various USPS organizations

            (g) agree to acknowledge AD's role in providing the EPM System (i.e.
            "by Authentidate") for any and all promotional and marketing
            purposes.

ARTICLE VII. ADDITIONAL AREAS OF OPPORTUNITY; SUCCESS RIGHTS

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                                                                   EXHIBIT 10.23

      Section 7.01 Additional Areas of Opportunity. In the event AD, AD Holding
      Corp., or their affiliates proposes to enter into an agreement (excluding
      a standard form Sales Contract) with a third party that relates to the
      operation, sales, marketing, development, or enhancement of the EPM
      System, and such proposed agreement references the role of USPS, then AD
      or AD Holding Corp. shall:

            (a) as soon as practicable, verbally advise USPS of the proposed
            agreement;

            (b) provide USPS with an opportunity to negotiate any provisions
            related to its business; and

            (c) furnish USPS with a copy of the proposed agreement at least
            fifteen (15) business days prior to the proposed execution of that
            agreement, as well as a copy of the final fully-executed agreement
            and all amendments thereto.

      In the event USPS proposes to enter into an agreement (excluding a
      standard form Sales Contract) with a third party that relates to the
      operation, sales, marketing, development or enhancement of the EPM System,
      and such proposed agreement references the role of AD, AD Holding Corp. or
      their affiliates, then USPS shall:

            (a) as soon as practicable, verbally advise AD of the proposed
            agreement,

            (b) provide AD with an opportunity to negotiate any provisions
            related to its business; and

            (c) furnish AD with a copy of the proposed agreement at least
            fifteen (15) business days prior to the proposed execution of that
            agreement.

      The foregoing provisions specifically apply to any such agreements with
      any other third parties, that may relate to the EPM System, including the
      bundling of the EPM System with other services such as personal
      identification and digital signatures. In the event that an agreement with
      a third party requires that the parties hereto amend the terms and
      conditions of this Agreement, then the parties hereto shall attempt to
      negotiate a mutually agreeable amendment to this Agreement.

      Disclosure of any such agreements or proposed agreements shall be
      considered Confidential Information pursuant to the Nondisclosure
      Agreement attached hereto as Exhibit L.

      Section 7.02 Success Rights. Simultaneously, with the execution of this
Agreement, AD Holding Corp. grants USPS Success Rights in accordance with a

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<PAGE>
                                                                   EXHIBIT 10.23

separate Success Rights Agreement to be mutually negotiated and agreed upon
within thirty (30) days of the Effective Date, and attached hereto as Exhibit O.
USPS shall have the right to freely assign, subject to existing Securities Laws,
its success rights to a third party without the consent of AD Holding Corp.
Success Rights to be completed in Exhibit O will be in accordance with the
following:

                  (1) [ * * * * ]. commencing one (1) year after the Effective
            Date, at an [ * * * * ] of the Execution Date;

                  (2) [ * * * * ] commencing two (2) years after the Effective
            Date, at an [ * * * * ] of the Execution Date; and

                  (3) [ * * * * ] commencing three (3) years after the Effective
            Date, [ * * * * ] of the Execution Date.

Upon the exercise of the Rights granted under the Success Rights Agreement, the
Postal Service shall have one, non-voting observer ("Observer") who shall be
entitled to attend all meetings of AD's Board of Directors ("Board"), including
meetings conducted by telephone or in writing, and special Board meetings. The
Postal Service will designate a Postal Service executive to serve as the
Observer. The Observer is entitled to contribute in an advisory role at all
Board meetings. AD shall provide the observer with notice of all Board meetings,
and all materials circulated to Board members at the same time it provides such
notice or materials to Board members. The Observer is entitled to attend and
participate in all Board meetings for the term of this Agreement.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

ARTICLE VIII. ADVISORY COMMITTEE

      Section 8.01 Establishment. Immediately upon the Effective Date of this
      Agreement, AD and USPS shall establish an Advisory Committee, which shall
      be responsible for coordinating and facilitating the actions of AD and
      USPS in connection with this Agreement.

      Section 8.02 Composition. USPS and AD will each designate [ * * * * ] to
      the Advisory Committee. Each Party may replace its representative at its
      sole discretion at any time. The Advisory Committee will be the body
      responsible for defining decisions that require agreement by AD and USPS.

      [ * Certain information on this page has been omitted and filed separately
      with the Commission. Confidential treatment has been requested with
      respect to the omitted portions.]

Page 25 of 163
<PAGE>
                                                                   EXHIBIT 10.23

      Section 8.03 Guidelines. The Advisory Committee will be governed by the
      Guidelines attached hereto as Exhibit H, and the procedures relating to
      the Pricing Policy Guidelines and Provisional Pricing Schedule attached
      hereto as Exhibit B.

ARTICLE IX. SECURITY AND CERTIFICATION PROVISIONS

      Section 9.01 USPS ISA Process. Prior to both the Service Launch Date and
      the issuance of a USPS EPM to a Customer, AD will successfully complete
      the USPS Information Security Assurance ("ISA") review process with
      standard levels of USPS assistance. AD will assist personnel designated by
      the USPS in conducting a review in accordance with USPS Handbook AS-805,
      and relevant Management instructions and policies. As part of the ISA
      Process, AD shall:

            (a) Designate information security personnel to work with designated
            USPS personnel in evaluating the EPM System;

            (b) Provide all documentation requested by the USPS for the purpose
            of conducting the ISA Process; and

            (c) Provide USPS personnel with access to property and systems as
            requested by the USPS for the purpose of conducting the ISA process.

      Section 9.02 Service Launch Date. AD and USPS shall agree within thirty
      (30) days of the Effective Date, upon a plan for launching the EPM System.
      USPS shall conduct such testing and acceptance processes with respect to
      the EPM System in order to determine that the EPM System meets the
      specifications set forth herein and in the Exhibits attached hereto, and
      that AD has implemented, to the satisfaction of USPS, the Information
      Security Requirements identified in Exhibit M. Once implementation testing
      is successfully completed and USPS completes its acceptance processes,
      USPS shall, within five (5) business days, certify in writing that the EPM
      System meets the requirements necessary for AD to make the EPM System
      available to Customers.

      Section 9.03 Remedial Measures. AD will, upon mutual agreement at its own
      expense, provided such expense is reasonable, remedy any reasonable
      security deficiencies determined by the Postal Service as a result of the
      ISA process to be unacceptable, including the Information Security
      Requirements identified in Exhibit M. Failure to remedy any such material
      security deficiencies, including the Information Security Requirements
      identified in Exhibit M, shall be cause for termination of this Agreement
      at no expense to USPS, notwithstanding

Page 26 of 163
<PAGE>
                                                                   EXHIBIT 10.23

      any other provision of this Agreement provided USPS provides sixty (60)
      days notice to AD and AD has failed to cure such deficiency in such
      period.

      Section 9.04 Suspension of Services. USPS shall have the right to
      temporarily suspend user and Customer access to the EPM System in whole or
      in part, upon written notice to AD, if there is an extreme operational
      problem or significant security risk with respect to the EPM System or
      portion thereof beyond the scope of the USPS ISA process. Upon receipt of
      such written notice from USPS, AD shall take all actions necessary to so
      suspend access to the EPM System and AD and USPS shall cooperate to lift
      the suspension as soon as possible.

      Section 9.05 AD Compliance with USPS Security Regulations. AD will comply
      with all other laws, regulations, policies and procedures applicable to or
      promulgated by the USPS with respect to information security and privacy,
      including the following:

            (a) Certain AD employees and contractors who serve in a trusted
            role, as defined in the Service Level Agreement, will be required to
            pass security clearances, which may include drug testing and
            background checks;

            (b) AD will create and maintain a secured environment to house and
            operate the Servers used to operate the EPM System, in accordance
            with USPS regulations, policies and procedures.

ARTICLE X. PRIVACY PROTECTION In addition to other provisions of this Agreement,
AD agrees to the following:

      Section 10.01 Privacy Act. If AD operates a system of records on behalf of
      the Postal Service, the Privacy Act (5 U.S.C. 552a) and Postal Service
      regulations at 39 CFR Parts 266-267 apply to those records. AD is
      considered to operate a system of records if it manages records (including
      collecting, revising, or disseminating records) from which information is
      retrieved by the name of an individual or by some number, symbol, or other
      identifier assigned to the individual. AD agrees to comply with the
      Privacy Act and the Postal Service regulations in designing, developing,
      and operating the system of records, including ensuring that records are
      current and accurate for their intended use and incorporating adequate
      safeguards to prevent misuse or improper disclosure of personal
      information. Violations of the Privacy Act may subject the violator to
      criminal penalties.

      Section 10.02 Customer or Visitor Data. [ * * * * ] AD must comply with
      the following:

      [ * Certain information on this page has been omitted and filed separately
      with the Commission. Confidential treatment has been requested with
      respect to the omitted portions.]

Page 27 of 163
<PAGE>
                                                                   EXHIBIT 10.23

           (a) General. AD may use such data solely for purposes of this
            Agreement, and may not collect or use such information for
            marketing, promotion, or any other purpose not related to EPM. AD
            must restrict access to such data to those employees who need the
            data to perform work under this contract, and must ensure that each
            such employee (including subcontractors' employees) sign a
            nondisclosure agreement (Exhibit L), in a form suitable to the
            Postal Service, prior to being granted access to the data.

            (b) Data Ownership and Retention. [ * * * * ] retains sole ownership
            and rights to the Customer data, except [ * * * * ] each own the [ *
            * * * ] created by the EPM system. Upon completion of the contract,
            [ * * * * ] must turn over all data in its possession to [ * * * *
            ]. [ * * * * ] may not create or derive personally identifiable
            information about customers or visitors, except as expressly
            provided by the customer or visitor.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

            (c) Legal Demands for Information. If a legal demand is made for
            data (such as by subpoena), AD must immediately notify the Postal
            Service in accordance with the notification provisions in this
            Agreement and the nearest office of the Postal Service Inspection
            Service. After notification, the Postal Service will determine
            whether and to what extent to comply with the legal demand. Should
            the Postal Service agree to or unsuccessfully resist a legal demand,
            AD may, with the written permission of the contracting officer,
            release the data specifically demanded.

      Section 10.03 Online Assistance. If AD has access to customer or visitor
      data obtained from a Postal Service web site, or a web site operated by AD
      on behalf of the Postal Service, or if AD assists in the design,
      development, or operation of a customer web site for the Postal Service,
      the following apply:

            (a) Privacy Policy. AD agrees to act as the agent of the Postal
            Service and to adhere to all provisions of the Postal Service's
            Internet Privacy Policy available at www.usps.com.

            (b) Tracking Devices. Without prior written approval of the Postal
            Service's chief privacy officer, any cookies or other tracking
            devices used by supplier may only be session, not persistent,
            devices; may not collect or

Page 28 of 163
<PAGE>
                                                                   EXHIBIT 10.23

            derive any personally identifiable information regarding the
            customer or visitor; and may only serve to improve the efficiency of
            the customer's or visitor's use of the web site.

            (c) Links and Banners. If, on the Postal Service's behalf, AD places
            a link to a www.usps.com web site, or if it designs or places an ad
            banner, button, or link on a www.usps.com web site or any web site,
            AD must comply with the portion of the Postal Service Privacy Policy
            available at www.usps.com relating to (a) links and banners, and (b)
            use of tracking devices. The placement of any device not permitted
            under the Postal Service's Privacy Policy requires the prior written
            approval of the Postal Service's chief privacy officer.

            (d) Indemnification. AD hereby indemnifies the Postal Service
            against all liability (including costs and fees) for damages arising
            out of violations of this clause.

            (e) Flow-down. AD will flow this clause down to subcontractors that
            will be covered by any portion of this clause if they were AD.

ARTICLE XI. FINANCIAL TERMS

      Section 11.01 Costs. Except as otherwise specifically provided herein,
      each Party will bear its own costs of performing its obligations under
      this Agreement.

      Section 11.02 Gross Revenue. Gross Revenue received from the sale and use
      of EPM shall be paid to USPS and AD as follows:

            (a) [ **** ]

            (b) [ **** ]

            (c) [ **** ]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Section 11.03 Collection and Tracking of Customer Funds. AD shall direct
Customers to make payments directly into a Lockbox account ("Lockbox") in a
financial institution chartered under Federal law that is located in the United
States , controlled by USPS, as designated by USPS. To the extent that Customers
do not act in accordance

Page 29 of 163
<PAGE>
                                                                   EXHIBIT 10.23

with the previous sentence, AD shall immediately forward to the Lockbox any
Customer Funds it receives. AD shall ensure that Customer Funds paid by credit
card are deposited directly into the Lockbox, are processed (including all
activities related to credit card transactions) in conformance with the
procedures concerning credit card acceptance agreed upon by AD and USPS, and
that AD pays all fees imposed in connection with credit card payment
transactions. The Lockbox shall be used solely for the collection of Customer
Funds under this Agreement, and there shall be no commingling of funds in the
Lockbox received from any other USPS or other branded product or service
offering. The Lockbox will be owned and maintained by USPS at its cost and
expense.

USPS shall contract with the Lockbox provider to provide AD with electronic
access to Lockbox account information and copies of all payment information and
correspondence received by the Lockbox. AD will provide an accounts receivable
aging schedule to the USPS on a monthly basis.

Section 11.04 Distribution of Customer Funds. Funds that are collected and
cleared shall be distributed to USPS and AD in accordance with each party's
share of Customer Funds as set forth in Section 11.01. AD shall submit invoices
to USPS for its share of Customer Funds, on a weekly basis to the Program
Manager or other official designated by USPS. The USPS shall process AD's
invoices as follows:

a.    Within two (2) business days of receipt of an invoice from AD, USPS, as
      appropriate, shall take the following actions:

      (1)   Approve the invoice and certify it for payment,

      (2)   Approve the invoice to the extent it is not in dispute. If the
            invoice is in dispute, notify AD of the disputed amount and specify
            the grounds for the dispute. AD may reinvoice the Postal Service for
            the undisputed amount at which time the Postal Service will
            re-process the invoice within two (2) business days as set forth in
            this Section 11.04. Any disputes will be resolved by mutual
            agreement of the parties.

      (3)   Advise AD of necessary adjustments or additional information it
            needs to certify the amount in dispute, or

      (4)   Disapprove the invoice, and so notify AD so stating the grounds for
            the disapproval with specificity.

b.    After USPS certifies the invoice for payment, it shall remit payment to AD
      as soon as practicable in accordance with the Prompt Payment Act.

c.    Notwithstanding the procedures outlined elsewhere in subparagraph (a) and
      (b) of this section, up to twelve (12) times per year, AD may notify USPS
      in writing at the time it submits its invoice that it elects to receive
      the invoiced amount by expedited electronic transfer. USPS, after
      certifying the invoice for payment in accordance with subparagraph a.,
      above, shall initiate an electronic funds transfer for the amount of the
      approved invoice and use its best efforts to

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      electronically transfer to AD the approved and invoiced amount within
      approximately 3 business days, to the extent that such amount reflects
      cleared and collected funds, less fees charged by the USPS-selected
      financial institution for the electronic transfer.

Section 11.05 Return of Customer Funds. USPS and AD shall comply with court
orders requiring return of Customer Funds on account of the bankruptcy or
insolvency of the Customer, according to each party's share of Customer Funds
set forth in Section 11.01 in effect at the time the Customer Funds were
collected and cleared. USPS and AD will jointly determine whether to approve
other requests for return of Customer Funds in accordance with Exhibit P, Return
of Customer Funds, to be completed within 30 days of the Effective Date of this
Agreement and incorporated as if fully set forth herein.

Section 11.06 International Sales. Revenues received by AD or AD Holding Corp.
or their affiliates on account of the sale of any product or service outside the
United States [ * * * * ]; provided, however, by separate written Agreement or
Rider, signed by the parties, the parties [ * * * * ].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

ARTICLE XII. DISPUTE RESOLUTION

      Section 12.01 Mediation. The Parties, for a period of not less than sixty
      (60) days, agree to mediate all controversies, except disputes where a
      party seeks injunctive relief, arising from or relating to this Agreement
      or the performance or breach thereof, and to make a good faith effort to
      resolve such controversies prior to initiating an arbitration proceeding.
      Any resolution signed by the Parties resulting from the mediation shall be
      final and binding on the Parties.

      Section 12.02 Arbitration. Following the Parties' compliance with the
      preceding Section, all controversies, except disputes where a party seeks
      injunctive relief, arising from or relating to this Agreement or the
      performance or breach thereof shall be resolved through non-binding
      arbitration conducted in Washington, D.C., under and subject to the
      commercial Arbitration Rules of the American Arbitration Association
      ("AAA") then in effect. The arbitration shall be conducted before a panel
      of three (3) arbitrators, chosen according to the rules of the AAA from
      among its Panel of Commercial Arbitrators within two (2) weeks of the
      first filing before the AAA, each of whom shall be and remain independent
      of the Parties. The Postal Service shall appoint one arbitrator, AD shall
      appoint one (1) arbitrator, and the two (2) appointed arbitrators shall
      choose the third arbitrator who will act as the chairperson of the
      arbitration. If the two (2) arbitrators appointed by the Parties are not
      able to agree on the third arbitrator

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      within thirty (30) days from the date that the last such arbitrator was
      appointed, the third arbitrator shall be appointed by the AAA. Each of
      such appointees must, however, meet the qualifications set forth in the
      second sentence of this paragraph.

      Section 12.03 Choice of Law. This Agreement will be governed by and
      construed in accordance with federal law. If there is no federal law with
      regard to a particular issue, the issue will be resolved in accordance
      with the laws of the State of New York without regard to the New York
      conflict of laws provisions.

      Section 12.04 Jurisdiction and Venue. With respect to any suit, action or
      other proceedings relating to the Agreement (collectively "Proceedings")
      initiated after the failure of negotiation, mediation or arbitration, the
      parties each irrevocably submit to the exclusive personal jurisdiction of
      the United States District Court for the District of Columbia and waive
      any objection that it may have at any time to the laying of venue of any
      Proceedings brought in such court, waive any claims that such Proceedings
      have been brought in an inconvenient forum and further waive the right to
      object, with respect to such Proceedings, that such court does not have
      personal jurisdiction over such party.

ARTICLE XIII. SERVICE COMMITMENTS

      Section 13.01 Service Level Agreements. AD will be responsible for service
      delivery that meets or exceeds the Service Level Agreement ("SLA")
      attached hereto as Exhibit D.

      Section 13.02 SLA Reports. Except when the data pertaining to SLA
      performance is collected or maintained by the USPS, AD will provide the
      USPS and the Advisory Committee with monthly and/or quarterly reports on
      SLA performance metrics as required by Section 5.08 of this Agreement.

      Section 13.03 Notice of Failure to Meet SLAs. In the event that any SLA
      requirement is not met within the monthly reporting period, the USPS will
      notify AD or AD will notify USPS of the performance violation.

      Section 13.04 Failure to meet SLA Requirements. If AD has not met its SLA
      requirement, AD will correct the performance problem within Thirty (30)
      days after receipt of notice specifying the problem before USPS will
      consider AD to be in material default under this Agreement. If USPS
      reasonably determines that AD is diligently working to correct the
      performance problem, USPS will extend the period for AD to correct the
      performance problem for up to an

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                                                                   EXHIBIT 10.23

      additional thirty (30) days or such extension in accordance with industry
      availability of hardware before USPS considers AD to be in material
      default under this Agreement. Notwithstanding the foregoing, in the event
      USPS reasonably determines that AD is either unable to correct the
      performance problem, or is not diligently working to correct the
      performance problem, USPS may immediately declare AD to be in material
      default under this Agreement.

ARTICLE XIV. INTELLECTUAL PROPERTY RIGHTS

      Section 14.01 General Intellectual Property Rights.

            (a) Individual Rights. Each party will retain during the course of
            this Agreement and after, the rights it possesses in Intellectual
            Property and derivatives thereof respectively upon the Effective
            Date of this Agreement, except that it grants such licenses during
            the term of this Agreement to the other party as set forth in
            various sections of this Agreement.

            (b) Joint Rights. Any Intellectual Property developed during the
            term of this Agreement as part of or as interfacing with the EPM
            System, including the SDK, but excluding the interfaces or interface
            definitions developed for any applications using the EPM System,
            will be [ * * * * ], except as provided in the following paragraphs[
            * * * * ].

            (c) USPS IP Rights. The USPS has sole IP ownership of the following:

                  (i)   The USPS-owned Individual Rights described in subsection
                  (a) above.

                  (ii)  USPS Brands and USPS Marks.

                  (iii) [ **** ]

                  (iv)  Intellectual Property that [ * * * * ].

            (d) AD IP Rights. AD or AD Holding Corp. has sole IP rights to the
            following:

                  (i)   The Individual Rights described in subsection (a) above
                  that are owned by AD or AD Holding Corp.

                  (ii)  [ * * * * ]

                  (iii) AD and AD Holding Corp. Brands and Marks

                  (iv)  Intellectual Property that [ * * * * ].

                  [*Certain information on this page has been omitted and filed
                  separately with the Commission. Confidential treatment has
                  been requested with respect to the omitted portions.]

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                                                                   EXHIBIT 10.23

      Section 14.02 AD and AD Holding Corp Retention of Rights. AD and AD
      Holding Corp. retain all rights, title and interest in and to the AD Core
      Technology and AD Derivatives. At no time during or after the Term shall
      USPS use the rights conferred by AD or AD Holding Corp. under this
      Agreement as a basis to (i) challenge AD or AD Holding Corp.'s rights in
      and to the AD Core Technology or AD Derivatives (to the extent such
      covenant is permitted by law), or (ii) use the AD Technology or AD
      Derivatives in connection with any of its products or services other than
      for the Purposes of this Agreement and otherwise in accordance with this
      Agreement or (iii) allow any other person or entity to use, copy or modify
      the AD Core Technology or AD Derivatives. To the extent the AD Core
      Technology is based on a license(s) granted by a third party(ies), AD and
      AD Holding Corp. shall be obligated to use their best efforts to provide
      the benefits of such license(s) to the USPS.

      Section 14.03 [ * * * * ] Except as provided in Section 14.01, AD, and, AD
      Holding Corp. together as the first party and USPS as the second party
      agree that [ * * * * ]. AD, AD Holding Corp. and USPS further agree that,
      [ * * * * ] to the extent that they are subject to copyrights, shall be
      "works made for hire" (as defined under 17 United States Code Section
      101). Except as provided in Section 14.01, they shall [ * * * * ] in such
      "works made for hire."

      Whether or not such [ * * * * ] constitute a work made for hire [ * * * *]
      by the first party (AD and AD Holding Corp.) and the second party, USPS,
      the first party and the second party hereby assigns, transfers and
      conveys, and agrees to [ * * * * ] to the other party [ * * * * ].

      Each party shall provide to the other such other assistance as it is able
      to provide to establish [ * * * * ] including but not limited to,
      providing assistance in securing and enforcing [ * * * * ] registrations
      and other [ * * * * ] in any and all countries, and signing all documents
      necessary for [ * * * * ] and other applications and registrations, and
      any assignments thereof.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

      Section 14.04 Notice of Development of Improvements. Each party hereto
      shall immediately inform the other party of any developments relating to
      any Joint

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                                                                   EXHIBIT 10.23

      Products and Services to be conceived, developed, created or made by such
      party.

      Section 14.05 Assignment of Rights by Third Parties and Employees. To the
      fullest extent necessary and permitted under applicable contract or law,
      each of the parties hereto shall obtain an assignment from each of its
      employees, contractors, and third parties involved in the conception,
      development, or creation, of any Joint Products and Services of all right,
      title and interest in the Joint Products and Services for the benefit of
      AD, AD Holding Corp. and USPS, in accordance with the foregoing as the
      case may be [ * * * * ] as may be required under this Agreement.

            (a) Customer Data. As between the USPS and AD, [ * * * * ]
            (regardless of the method of collection of such data) will be the
            sole property of [ * * * * ] and shall be at all times, whether in
            the possession of AD, AD Holding Corp. or the [ * * * * ], subject
            to the USPS's privacy policies, 39 U.S.C. Section 412 and all other
            statutes, rules and regulations applicable to the protection of
            similar information [ * * * * ]. To the extent that [ * * * * ]. AD
            and AD Holding Corp. agree to abide by all relevant privacy
            regulations specified by the USPS.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

ARTICLE XV. LICENSE GRANTS - MARKS

      Section 15.01 Branding and Trademarks. AD is licensed and authorized to
      use USPS Marks only to the extent and in a manner specifically approved in
      writing by USPS. AD shall always use USPS Marks in accordance with the
      Usage Guidelines in Exhibit I or as otherwise approved in writing by USPS.
      AD shall fully and promptly correct and remedy any deficiencies in its use
      of the USPS Marks, upon reasonable notice from USPS. The license to AD is
      limited to use of USPS Marks solely in reference to EPM services and
      products of a quality approved by USPS.

      Section 15.02 Ownership of USPS Marks. AD and AD Holding Corp. acknowledge
      USPS's sole ownership of the USPS Marks worldwide and all associated
      goodwill. Nothing in this Agreement or in the performance thereof, or that
      might otherwise be implied by law, shall operate to grant AD or AD Holding
      Corp. any right, title, or interest in or to the USPS Marks other than as
      specified in this Agreement. AD's use of the USPS Marks inure solely to
      the benefit of USPS. AD and AD Holding Corp. hereby assign and shall
      assign in the future to USPS all rights it may acquire by operation of law
      or otherwise in the USPS

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                                                                   EXHIBIT 10.23

      Marks, including all applications or registrations therefore, along with
      the goodwill associated therewith.

      Section 15.03 USPS shall have the sole right to and in its sole discretion
      may commence, prosecute or defend, and control any action concerning the
      USPS Marks. To the extent permitted by law, AD and AD Holding Corp.
      promise not to contest the validity of, by act or omission jeopardize, or
      take any action inconsistent with, USPS's rights or goodwill in the USPS
      Marks in any country, including attempted registration of the USPS Marks,
      or use or attempted registration of any mark confusingly similar thereto.

      Section 15.04 AD and AD Holding Corp. Materials and Marks License. AD and
      AD Holding Corp. hereby grant USPS for the Term of this Agreement, a
      non-exclusive, non-transferable, personal, US license to use the AD and AD
      Holding Corp. Marks on advertising and promotional material and elsewhere
      as contemplated herein solely in accordance with the terms and conditions
      of this Agreement. USPS is authorized to use the Authentidate Marks and
      other Authentidate Materials only in accordance with the terms of this
      Agreement and with respect to the Authentidate Marks, the Usage Guidelines
      in Exhibit I, or as otherwise approved in writing by AD and AD Holding
      Corp., and USPS shall fully and promptly correct and remedy any
      deficiencies in its use of the Authentidate Materials and Authentidate
      Marks, upon reasonable notice from AD or AD Holding Corp.

      Section 15.05 Ownership of Authentidate Marks. USPS acknowledges the sole
      ownership by AD Holding Corp. and AD of the Authentidate Marks worldwide
      and all associated goodwill. Nothing in this Agreement or in the
      performance thereof, or that might otherwise be implied by law, shall
      operate to grant USPS any right, title, or interest in or to the
      Authentidate Marks other than as specified in the limited license grant
      herein. USPS's use of the Authentidate Marks shall inure solely to the
      benefit of AD and AD Holding Corp. USPS hereby assigns and shall assign in
      the future to AD and AD Holding Corp. all rights it may acquire by
      operation of law or otherwise in the Authentidate Marks, including all
      applications or registrations therefore, along with the goodwill
      associated therewith.

      Section 15.06 AD and AD Holding Corp. shall have the sole right to and in
      their sole discretion may commence, prosecute or defend, and control any
      action concerning the Authentidate Marks. USPS shall not contest the
      validity of, by act or omission jeopardize, or take any action
      inconsistent with, rights or goodwill of AD or AD Holding Corp. in the
      Authentidate Marks in any country, including attempted registration of the
      Authentidate Marks, or use or attempted registration of any mark
      confusingly similar thereto.

      Section 15.07 Notification of Claims. Each Party shall promptly notify the
      other Party in writing of any acts, claims, demands or causes of action of
      which it

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                                                                   EXHIBIT 10.23

      learns, based upon, relating to, or arising from any attempt by any other
      person or entity not a party to this Agreement to use the other party's
      Marks or any colorable imitation thereof, in any unauthorized manner. Each
      Party also shall promptly notify the other Party in writing of any acts,
      claims, demands, causes or action or threatened or pending litigation
      involving the EPM System.

ARTICLE XVI. CHANGES TO SERVICES AND SPECIFICATIONS

   (a) AD or USPS may request a change in the EPM Service or the addition of an
   enhancement to the EPM Service at any time by submitting a request to the
   Advisory Committee.

   (b) Upon receipt of such a change request, the Advisory Committee shall
   promptly conduct such investigations and deliberations with respect to the
   change request as it deems necessary and shall make a recommendation as to
   whether the requested change should be implemented. In the event that the
   Advisory Committee recommends a change request, the Advisory Committee shall
   further recommend the form of amendments, if any, that would be required to
   be made to the terms and conditions of this Agreement, including the Exhibits
   hereto. The Advisory Committee shall submit its recommendations with respect
   to a change request to AD and USPS for their consideration.

   (c) Upon receiving the determination of the Advisory Committee with respect
   to change request, AD and USPS shall determine whether to implement the
   change and shall execute such amendments to this Agreement and enter into any
   additional agreements and approve any amendments to or the addition of any
   Exhibits hereto to effect such change as they shall mutually agree.

ARTICLE XVII. PUBLIC ANNOUNCEMENTS

      Section 17.01 Public Announcements. No party may make a public
      announcement or press release regarding this Agreement or the EPM System
      prior to an initial, agreed, joint announcement or press release, which
      the parties shall issue on a mutually agreed-upon date, such agreement not
      to be unreasonably withheld. Each party shall give the other party
      seventy-two (72) hours prior notice of any proposed public announcements
      or press releases regarding the EPM System or this Agreement. Each party
      must agree upon the contents and date of issuance of any future public
      announcements or press releases, such agreement not to be unreasonably
      withheld.

ARTICLE XVIII. CONFIDENTIALITY

      Section 18.01 In order to protect certain confidential information which
      may be provided by one party (hereinafter "Discloser") to the other party
      ("Recipient") pursuant to this Agreement, the Postal Service, AD, and AD
      Holding Corp. intending to be legally bound, agree to this Article 18.

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                                                                   EXHIBIT 10.23

      Section 18.02 The terms of the Non-Disclosure Agreement ("NDA") between AD
      and USPS, Exhibit L are incorporated by reference. The terms and
      conditions of this Agreement are "Confidential Information" as defined in
      the NDA of USPS, AD and AD Holding Corp.

      Section 18.03 Disclosure of Confidential Information. Notwithstanding the
      terms of the NDA, in the event that any party to this Agreement or any of
      its representatives is requested (by deposition, interrogatory, request
      for information or documents, subpoena, civil investigative demand or
      similar process) to disclose any of the Confidential Information as
      defined in the NDA), such party or its representative(s) from whom the
      disclosure is sought shall provide the other party with prompt notice of
      such request or requirement and shall make reasonable efforts to cooperate
      with the other party so that such other party may seek a protective order
      or other appropriate remedy or protection or waive compliance with the
      terms of this Agreement or the NDA concerning such Confidential
      Information. In the event that such protective order or other remedy or
      protection is not obtained, or such other party waives compliance with the
      provisions hereof or of the NDA, the party or its representative(s) from
      whom the disclosure is sought, as the case may be, may disclose only that
      portion of the Confidential Information which such party determines is
      legally required to be disclosed, and the other party can assert no claim
      against the Disclosing Party based upon such disclosure. Recipient's
      duties under this Agreement shall pertain to Confidential Information of
      Discloser which is provided to the Recipient. Such confidential
      information is hereinafter referred to as "Confidential Information."

      Section 18.04 Notwithstanding anything to the contrary in the NDA or in
      this Agreement, a party may disclose Confidential Information:

            (a) If and to the extent such Confidential Information is required
            to be disclosed under the Freedom of Information Act, 5 U.S.C.
            Section 552, because such Confidential Information is not a trade
            secret, or privileged or confidential commercial or financial
            information and is not otherwise entitled to protection from
            disclosure under that Act;

            (b) to the United States Department of Justice pursuant to its
            investigatory jurisdiction or in connection with its legal
            representation of the Postal Service;

            (c) to its independent auditors or accountants for the purpose of
            audits, provided such auditors or accountants agree to maintain the
            confidentiality of such Confidential Information;

            (d) to an entity of the United States government pursuant to its
            oversight or investigatory jurisdiction;

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                                                                   EXHIBIT 10.23

            (e) to the United States Postal Service Office of the Inspector
            General (the "OIG") and to any third parties which the OIG
            determines have a need for such Confidential Information, all in the
            course of the OIG performing audits and investigations under the
            Inspector General Act;

            (f) or to the extent such disclosure otherwise is required by
            applicable Federal law.

            Prior to making any disclosure under subsections (a), (b), (d), (e)
            and (f) of this Section, the Disclosing Party shall provide advance
            notice to the other parties of such disclosure within a reasonable
            time under the circumstances in accordance with Section 18.03. In
            connection with any disclosure of Confidential Information pursuant
            to this Section, in order to protect against further dissemination
            or disclosure of such Confidential Information, the disclosing arty
            shall include a restrictive legend on all released information.

ARTICLE XIX. SOURCE CODE ESCROW

      Section 19.01 The parties simultaneously are entering into a Source Code
      escrow agreement, under which a default by AD shall be deemed to have
      occurred upon the occurrence of any of the following: (i) if [ * * * * ];
      (ii) if [ * * * * ]; (iii) if [ * * * * ] under the Source Code escrow
      agreement; (iv) if [ * * * * ]; or (v) if [ * * * * ]. As used in this
      Paragraph 19.01, "[ * * * * ]" include: (i) any [ * * * * ] in the EPM
      System that causes the Product to [ * * * * ] its Specifications, and (ii)
      any programming [ * * * * ] in the EPM System that substantially [ * * *
      * ] to offer EPM.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

ARTICLE XX. AUDIT AND INSPECTION

      Section 20.01 Audit by a Party. AD and USPS shall have the right to
      inspect the other Party's books and records as they relate to the EPM
      Service and USPS shall have the right to inspect the EPM System, at such
      times as USPS and AD may mutually agree, which times shall be not (a) more
      than fifteen (15) days following one Party's request to conduct an audit
      and (b) (unless otherwise required by applicable statutes, rules,
      regulations or otherwise requested by any governmental agencies or
      instrumentalities) not more frequently than once in each year of this
      Agreement and one time during the twelve (12) month period following the
      end of a term of this Agreement, to the extent necessary to determine and
      confirm financial and other appropriate matters pertaining to the
      activities contemplated by this Agreement, including, without limitation,
      the number of transactions covered by this Agreement, the

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                                                                   EXHIBIT 10.23

      Gross Revenue received, the operation of the EPM System, and other
      activities and matters contemplated by this Agreement. Notwithstanding the
      foregoing, any AD review of USPS books and records shall be limited to the
      review of Gross Revenue received by USPS pursuant to this Agreement. USPS
      also shall have the right to arrange such other audits as requested by any
      governmental agencies and instrumentalities, including the USPS OIG and
      the U.S. Postal Inspection Service.

      Section 20.02 Audit by a Third Party. At any time prior to the termination
      of this Agreement, either AD or USPS may contract with a qualified,
      neutral third-party to audit all of the costs incurred by the other party
      in carrying out the terms of this Agreement. The party whose books are to
      be audited must afford the auditor access during normal business hours to
      any information that is reasonably relevant to such an audit. The party
      that initiates such an audit must bear the full cost of the audit. Prior
      to initiating an audit under this Section, a party must provide the party
      to be audited reasonable advance notice.

ARTICLE XXI. TERM AND TERMINATION

      Section 21.01 Term. The initial term of this Agreement commences on the
      Effective Date and expires five (5) years thereafter, unless terminated
      earlier as provided below. Upon mutual agreement of AD, and USPS, this
      Agreement may be extended for three (3) additional three (3)-year terms,
      unless terminated earlier as provided below. The aggregate term of this
      Agreement shall in no event exceed a total of fourteen (14) years.

      Section 21.02 Events of Termination. This Agreement may be terminated:

            (a). Mutual Agreement. By mutual agreement of AD and USPS.

            (b). Material Breach. By AD (or AD Holding Co.) or USPS if the other
                 Party breaches this Agreement in any material respect and such
                 breach continues for a period of thirty (30) days after the
                 date the non-breaching Party provides written notice of the
                 breach, then the non-breaching Party may terminate this
                 Agreement effective immediately upon a second written notice.
                 Material breach includes any substantial breach of any
                 representation, warranty or obligation. In the event USPS fails
                 to execute a Sales Contract or approve a proposed pricing
                 modification within the time limits set forth in this
                 Agreement, shall not be deemed a material breach of this
                 Agreement.

            (c). Breach of Alliance Metrics. By USPS if USPS reasonably
                 determines that AD or AD Holding Corp. has failed to
                 substantially perform in accordance with metric standards set
                 forth in the Alliance Metrics contained in Exhibit J, USPS
                 provides written notice of the breach to AD and AD Holding
                 Corp., and such breach continues beyond the cure

Page 40 of 163
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                                                                   EXHIBIT 10.23

                 period, if any, specified in the Alliance Metrics, Exhibit J.
                 USPS may terminate this Agreement effective immediately upon
                 delivery of a second written notice to AD.

            (d). Adverse Governmental Action. By USPS, without penalty, at any
                 time upon thirty (30) days written notice if regulatory,
                 legislative or judicial action or inaction occurs which
                 substantially impairs USPS's ability to perform its obligations
                 under this Agreement.

            (e). USPS Convenience. Commencing six (6) months after the Service
                 Launch Date, USPS upon one hundred eighty (180) days written
                 notice, for any reason not otherwise identified in this
                 Section. USPS shall not be entitled to Gross Revenue earned
                 from Customers after providing notice.

            (f). AD Convenience. AD upon three hundred sixty (360) days written
                 notice, for any reason not otherwise identified in this
                 Section. AD shall continue to perform pursuant to the terms of
                 this Agreement from the date of notice through the expiration
                 of the 360-day period.

            (g). Insurance. By USPS at any time upon thirty (30) days written
                 notice in the event AD or Ad Holding Corp. shall notify USPS of
                 any cancellation notice by the insurance carrier with respect
                 to any insurance required pursuant to this Agreement and shall
                 not have presented USPS with satisfactory evidence of
                 replacement coverage within such thirty (30) day period.

      Section 21.03 AD Change of Control. USPS may terminate this Agreement by
      giving thirty (30) days' written notice to AD in the event that there is a
      change in control in AD. AD shall provide USPS with written notice of any
      Change in Control of AD promptly upon AD becoming aware that a Change in
      Control will occur. USPS shall deem a Change in Control of AD to have
      occurred if:

            (a). AD acquires or is acquired by or is merged with or into, or is
                 consolidated with, another person or persons such that AD's
                 shareholders immediately prior to such acquisition, merger or
                 consolidation are entitled to less than 60% of the outstanding
                 voting securities of the surviving entity upon consummation of
                 such acquisition, merger, or consolidation;

            (b). any person or corporation, or more than one person or
                 corporation actively cooperating or acting in concert with each
                 other, in each case who are not shareholders of AD as of the
                 date hereof acquires or becomes entitled, directly or
                 indirectly, to a beneficial interest in 30% or more of the
                 outstanding voting securities of AD;

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                                                                   EXHIBIT 10.23

            (c). AD sells all or substantially all of its assets, or any of its
                 major assets, whether by one or a series of transactions, to
                 another person or persons;

ARTICLE XXII. EFFECT OF TERMINATION

      Section 22.01 Wind Down Strategy. In the event of termination for any
      reason, within sixty (60) days of such notice of termination, the Advisory
      Committee shall propose a wind down plan to minimize financial loss and
      Customer inconvenience in accordance with Exhibit N attached hereto.
      Within thirty (30) days of the Effective Date of this Agreement, USPS and
      AD shall replace the Wind Down Outline attached hereto as Exhibit N with a
      Wind Down/Continuity of Service Plan.

      Section 22.02 AD's Obligations Upon Termination. Upon the discontinuation
      of the EPM System for any reason, AD shall:

            (a)  immediately cease use of all USPS Marks;

            (b)  cooperate with USPS and the Advisory Committee to develop and
                 implement a wind down plan, including but not limited to the
                 termination or transition of customers and archived records.

            (c)  Provide or ensure access to information relating to the EPM
                 System that is stored or archived.

            (d)  Return all customer data to USPS, destroy all other USPS
                 Confidential Information and deliver a certificate to USPS to
                 that effect.

      Section 22.03 USPS's Obligations Upon Termination. Upon termination of
      this Agreement for any reason, USPS shall:

            (a)  immediately cease use of all AD and AD Holding Corp. Marks;

            (b)  cooperate with AD and the Advisory Committee to develop and
                 implement a wind down plan

            (c)  If appropriate, issue an announcement advising Customers and
                 users of any transfer of the EPM System, including any transfer
                 to AD.

            (d)  destroy AD and AD Holding Corp. Confidential Information and
                 deliver a certificate to that effect.

ARTICLE XXIII. BANKRUPTCY

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                                                                   EXHIBIT 10.23

      Section 23.01 In the event that AD or AD Holding Corp. enters into
      proceedings relating to bankruptcy, whether voluntary or involuntary, it
      is required to furnish, by certified mail, written notification of the
      bankruptcy to the USPS. The notification must be furnished within five
      days of the initiation of the bankruptcy proceedings. The notification
      must include the date on which the bankruptcy petition was filed and the
      court in which the petition was filed. This obligation remains in effect
      until USPS receives all Gross Revenue payments. In the event of
      Bankruptcy, AD and AD Holding Corp. will permit the use of the AD Core
      Technology for the EPM System pursuant to a mutually agreeable license or
      technology transfer agreement.

ARTICLE XXIV. REPRESENTATIONS, WARRANTIES, AND UNDERTAKINGS

      Section 24.01 Representations and Warranties. Each party represents,
      warrants and undertakes to the other party that as of the date of
      execution of this Agreement:

            (a) it has full power and authority to execute and deliver this
            Agreement and to carry out the transactions contemplated by this
            Agreement;

            (b) that the execution and/or performance of this Agreement does not
            violate or interfere with any other agreement or contract to which
            it is a party;

            (c) it will not enter into any agreement or contract the execution
            and/or performance of which will violate this Agreement,

            (d) it is not presently the subject of a voluntary or involuntary
            petition in bankruptcy, does not presently contemplate filing any
            such voluntary petition, and is not aware of any intention on the
            part of any other person to file such an involuntary petition
            against it;

            (e) it is not presently the subject of, nor the proponent of, any
            claim that will have a material adverse effect on its ability to
            perform under this Agreement;

            (f) this Agreement has been duly executed and delivered and
            constitutes a legal, valid and binding obligation, enforceable in
            accordance with its terms.

      Section 24.02 Representations and Warranties by AD to USPS. AD and AD
      Holding Corp. represent and warrant to USPS as of the date of execution of
      this Agreement:

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                                                                   EXHIBIT 10.23

            (a) AD is a 95% owned subsidiary of AD Holding Corp. AD Holding
            Corp. has no reason to believe that either it or AD cannot perform
            its obligations under this Agreement.

            (b) AD and AD Holding Corp. are corporations duly organized, validly
            existing and in good standing under the laws of the State of
            Delaware and have all corporate powers and all government licenses,
            authorizations, consents and approvals required to carry on their
            business.

            (c) The execution and delivery of this Agreement by AD and AD
            Holding Corp. and the performance of their obligations hereunder
            have been duly authorized by all necessary corporate action.

            (d) AD and AD Holding Corp. have the full right to use the
            patent-pending technology in accordance with this Agreement, and the
            patent-pending technology does not infringe on any trade secrets,
            copyrights, patents, trademarks or other intellection property
            rights. Neither AD nor AD Holding Corp. has received any notice of
            any alleged infringement of any trade secrets, copyrights, patents,
            trademarks or other intellectual property rights.

            (e) No default has occurred under necessary third party vendor
            licenses.

            (f) AD Holding Corp. has granted AD full right, title and authority
            to use intellectual property owned or controlled by AD Holding Corp.
            in operating the EPM System during the term of this Agreement;

ARTICLE XXV. AMENDMENTS OR MODIFICATIONS

      Section 25.01 In order to be binding upon the USPS or AD, any amendment or
      modification to this agreement must be in writing and signed by the
      official representatives of each party as designated herein. Any alleged
      modification based upon an oral understanding or an oral statement not
      reduced to writing shall fail as not in accordance with this provision.

ARTICLE XXVI. ASSIGNMENT

      Section 26.01 Assignment. This Agreement may not be assigned by any Party
      in whole or in part, without the prior written consent of the other Party.
      Any attempted assignment or transfer in violation of this Section shall be
      void and without legal effect.

ARTICLE XXVII. SUBCONTRACTING

      Section 27.01 Subcontracting. In the event AD desires to employ a
      subcontractor to perform any significant portion of its obligations
      hereunder, AD

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      shall provide advance written notice to USPS and USPS shall have the right
      to approve of any potential subcontracting party within five (5) business
      days, which approval shall not unreasonably be withheld. In the event that
      USPS becomes reasonably dissatisfied with the performance of any
      subcontractor selected by AD, AD shall take all necessary action to remedy
      the problem, including the replacement of such subcontractor. AD shall
      require any subcontractor it employs hereunder to agree in writing to
      comply with the provisions of this Agreement applicable to performing its
      obligations under the subcontract, including but not limited to provisions
      relating to audit, confidentiality, ownership of intellectual property,
      and access to files and records.

ARTICLE XXVIII. GUARANTEE

      Section 28.01 As consideration for [ * * * * ] entering into this
      Agreement, [ * * * * ] hereby irrevocably guarantees the performance by
      [ * * * * ] under this Agreement. This guaranty shall be binding and
      enforceable against [ * * * * ] without regard to any fact that would
      constitute a legal or equitable defense or discharge of a guarantor. This
      guaranty is [ * * * * ]. In the event [ * * * * ] institutes suit to
      collect on this guaranty, [ * * * * ] agrees to pay to [ * * * * ], in
      addition to its obligations, all [ * * * * ] from [ * * * * ] including
      but not limited to [ * * * * ].

      [ * Certain information on this page has been omitted and filed separately
      with the Commission. Confidential treatment has been requested with
      respect to the omitted portions.]

ARTICLE XXIX. NOTICES

      Section 29.01 Notices. All notices and requests in connection with this
      Agreement are effective as of the day they are received by messenger,
      delivery service, or in the United States of America mails, postage
      prepaid, certified or registered, return receipt requested, and addressed
      as follows:

            (a) To USPS
            United States Postal Service
            475 L'Enfant Plaza, SW
            Washington, DC 20260-1100
            Attn: General Counsel
            Phone: 202-268-2951
            Fax: 202-268-5418

            With a copy to:
            Charles Chamberlain, Project Manager
            United States Postal Service
            475 L'Enfant Plaza, SW, Room 1100
            Washington, DC 20260-5130

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                                                                   EXHIBIT 10.23

            Phone: 202-268-5262
            Fax:: 202-268-5526

            (b) To AuthentiDate, Inc.
            2 World Financial Center
            225 Liberty Street, 43rd Floor
            New York, NW  10281
            Attn: Rob Van Naarden
            Phone: 212-329-1110
            Fax: 212-329-1101

            (c) To AuthentiDate Holding Corp.
            2165 Technology Drive
            Schnectady, New York 12308
            Attn: Dennis Bunt
            Phone: 518-346-7799
            Fax: 518-346-3644

            (d) with copy to:
            Goldstein & DiGioia, LLP
            369 Lexington Avenue, 18th Floor
            New York, New York 10017
            Attn: Victor J. DiGioia
            Phone: 212-599-3322
            Fax: 212-557-0295

ARTICLE XXX. SEVERABILITY

      Section 30.01 Construction. If for any reason a court of competent
      jurisdiction finds any provision of this Agreement or portion thereof, to
      be unenforceable, the affected provision of the Agreement will be enforced
      to the maximum extent permissible so as to affect the intent of the
      Parties, and the remainder of this Agreement will continue in full force
      and effect. This Agreement has been negotiated by the Parties and their
      respective counsel and will be interpreted fairly in accordance with its
      terms and without any strict construction in favor of or against either
      party.

      Section 30.02 If a material provision of this agreement is materially
      altered or abridged as a result of an order, request, or direction of a
      Governmental Body having subject matter jurisdiction, then the parties
      will meet to negotiate in good faith a mutually satisfactory modification
      to this agreement based on such material change.

ARTICLE XXXI. EQUAL OPPORTUNITY

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                                                                   EXHIBIT 10.23

      Section 31.01 No Discrimination. AD may not discriminate against employees
      or applicants because of race, color, religion, sex, or national origin,
      and asserts it has taken or will take affirmative action to ensure that
      applicants are employed, and that employees are treated during employment,
      without regard to race, color, religion, sex, or national origin. This
      action must include, but not be limited to, employment, upgrading,
      demotion, or transfer; recruitment or recruitment advertising; layoff or
      termination; rates of pay or other forms of compensation; and selection
      for training, including apprenticeship. AD agrees to post in conspicuous
      places, available to employees and applicants, notices provided by the
      USPS setting forth this policy.

      Section 31.02 Solicitations. AD must, in all solicitations or
      advertisements for employees placed by it or on its behalf, state that all
      qualified applicants will be considered for employment without regard to
      race, color, religion, sex, or national origin.

      Section 31.03 Executive Order 11246. AD agrees to comply with all
      provisions of Executive Order (EO) 11246 of September 24, 1965, as
      amended, and of the rules, regulations, and relevant orders of the
      Secretary of Labor.

      Section 31.04 Audit Requirements. AD agrees to furnish all information and
      reports required by the Executive Order, and by the rules, regulations,
      and orders of the Secretary, and must permit access to AD's books,
      records, and accounts by the Postal Service and the Secretary for purposes
      of investigation to ascertain compliance with these rules, regulations,
      and orders.

      Section 31.05 Cancellation for Failure to Comply. If AD fails to comply
      with this clause or with any of the said rules, regulations, or orders,
      this contract may be canceled, terminated, or suspended, in whole or in
      part; AD may be declared ineligible for further contracts in accordance
      with the Executive Order; and other sanctions may be imposed and remedies
      invoked under the Executive Order, or by rule, regulation, or order of the
      Secretary, or as otherwise provided by law.

      Section 31.06 Inclusion in Subcontracts. AD must insert this clause,
      including this paragraph, in all subcontracts or purchase orders under
      this contract unless exempted by Secretary of Labor rules, regulations, or
      orders issued under the Executive Order, and must take such action with
      respect to any such subcontract or purchase order as the Postal Service
      may direct as a means of enforcing the terms and conditions of this clause
      (including sanctions for noncompliance), provided, however, that if AD
      becomes involved in, or is threatened with, litigation as a result, AD may
      request the Postal Service to enter into the litigation to protect the
      interest of the Postal Service.

ARTICLE XXXII. AFFIRMATIVE ACTION FOR HANDICAPPED WORKERS

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      Section 32.01 Discrimination against Handicapped Workers. AD agrees hereby
      to not discriminate against any employee or applicant because of physical
      or mental handicap, in regard to any position for which the employee or
      applicant is qualified. AD agrees to take affirmative action to employ,
      advance in employment, and otherwise treat qualified handicapped
      individuals without discrimination in all employment practices, such as
      employment, upgrading, demotion or transfer, recruitment, advertising,
      layoff or termination, rates of pay or other forms of compensation, and
      selection for training (including apprenticeship).

      Section 32.02 Compliance with Regulations. AD agrees to comply with the
      rules, regulations, and relevant orders of the Secretary of Labor issued
      pursuant to the Rehabilitation Act of 1973, as amended.

      Section 32.03 Failure to Comply with Regulations. In the event of AD's
      noncompliance with this clause, action may be taken in accordance with the
      rules and regulations and relevant orders of the Secretary of Labor.

      Section 32.04 Posting Notices. AD agrees to post in conspicuous places,
      available to employees and applicants, notices concerning Affirmative
      Action for Handicapped Workers. These notices state AD's obligation under
      the law to take affirmative action to employ and advance in employment
      qualified handicapped employees and applicants, and the rights of
      applicants and employees.

      Section 32.05 Inclusion of Clause in Subcontracts. AD must include this
      clause in every subcontract or purchase order over $2,500 under this
      contract unless exempted by rules, regulations, or orders of the Secretary
      issued pursuant to section 503 of the Act, so its provisions will be
      binding upon each subcontractor or vendor as applicable.

ARTICLE XXXIII. AFFIRMATIVE ACTION FOR DISABLED VETERANS AND VETERANS OF THE
VIETNAM ERA

      Section 33.01 No Discrimination. AD may not discriminate against any
      employee or applicant because that employee or applicant is a disabled
      veteran or veteran of the Vietnam era, in regard to any position for which
      the employee or applicant is qualified. AD agrees to take affirmative
      action to employ, advance in employment, and otherwise treat qualified
      disabled veterans and veterans of the Vietnam era without discrimination
      in all employment practices, such as employment, upgrading, demotion or
      transfer, recruitment, advertising, layoff or termination, rates of pay or
      other forms of compensation, and selection for training (including
      apprenticeship).

      Section 33.02 Recruitment. AD agrees to list employment openings which
      exist at the time of the execution of this contract and those which occur
      during the performance of this contract, in appropriate local publications
      and public

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      places and otherwise actively recruit from applicant sources which will
      include veterans and veterans of the Vietnam era.

      Section 33.03 Listings. Any listing of employment openings with an
      employment service system will be made at least concurrently with the use
      of any recruitment source or effort and will involve the normal
      obligations attaching to the placing of a bona fide job order, including
      the acceptance of referrals of veterans and non-veterans. Any listing of
      employment openings does not require the hiring of any particular
      applicant or hiring from any particular group of applicants, and nothing
      herein is intended to relieve AD from any other requirements regarding
      nondiscrimination in employment.

      Section 33.04 Vietnam Era Veterans. AD agrees to comply with the rules,
      regulations, and relevant orders of the Secretary of Labor issued pursuant
      to the Vietnam Era Veterans Readjustment Assistance Act of 1972, as
      amended. In the event of noncompliance with this clause, action may be
      taken in accordance with the rules, regulations, and relevant orders of
      the Secretary.

ARTICLE XXXIV. THIRD-PARTY AGREEMENTS

      Section 34.01 Right of Termination. USPS and AD each agree and acknowledge
      that in the event that either party enters into any agreement with any
      third party in connection with this Agreement (a "third-party agreement"),
      such party to this Agreement shall include in the third-party agreement
      the right to terminate the third-party agreement upon the termination of
      this Agreement with no cost to it.

      Section 34.02 Limitation on Indemnification. In the event either party
      enters into a third-party agreement that does not contain a right of
      termination as set forth in Section 34.01, or it fails to enforce such a
      right, such party shall have no right to seek indemnification for any
      claims arising out of such inability to terminate a third-party agreement.

ARTICLE XXXV. EFFECT OF VARIOUS LAWS

      Section 35.01 Procurement Laws. USPS, AD Holding Corp. and AD hereby agree
      and acknowledge that this Agreement shall not be governed by the
      provisions of the USPS Purchasing Manual or the Contract Disputes Act. In
      addition, USPS, AD Holding Corp. and AD agree that this is a contractual
      agreement to pursue a business arrangement and does not constitute a USPS
      Purchasing Manual procurement. This Agreement shall not in any way
      prohibit any Federal governmental authority, excluding the USPS, from
      taking or failing to take any action.

      Section 35.02 In the event that any branch, agency, or independent
      establishment of the United States Government takes or fails to take any
      action

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                                                                   EXHIBIT 10.23

      and this action or failure to take action would substantially impair the
      USPS from offering the services contemplated by this Agreement, such
      substantial impairment shall not deprive the Parties of any rights under
      this Agreement, including the USPS's rights of termination as set forth
      above. USPS, AD Holding Corp. and AD acknowledge and agree that this
      Agreement is subject to any legislation that might be enacted by the
      Congress of the United States or any regulations that might be promulgated
      by any agency or independent establishment of the United States other than
      USPS.

      Section 35.03 In the event that USPS is required by any other branch,
      agency or independent establishment of the United States Government to
      terminate or fail to perform its obligations under this Agreement within a
      period of fewer than thirty (30) days from the date such requirement is
      imposed, the USPS may give a notice of termination pursuant to the
      termination provisions set forth above, which notice shall be effective
      immediately or at such other time as specified therein by USPS.

      Section 35.04 In the event that AD, AD Holding Corp. or USPS is enjoined
      from proceeding with this Agreement by a court of competent jurisdiction,
      such Party may give a notice of termination after the exhaustion of all
      appeals pursuant to the termination provisions set forth above, which
      notice shall be effective immediately or at such other time as specified
      therein by USPS.

      Section 35.05 Sovereign Acts. USPS, AD Holding Corp. and AD acknowledge
      and agree that this Agreement in no way waives USPS's authority to act in
      its sovereign capacity and that, pursuant to the sovereign acts doctrine,
      USPS shall not be held liable for any acts performed in its sovereign
      capacity, or for any acts performed by any branch, agency or independent
      establishment of the United States in its sovereign capacity that may
      directly or indirectly affect the terms of this Agreement. USPS
      acknowledges that none of the USPS activities contemplated by this
      Agreement constitute sovereign acts.

      Section 35.06 Force Majeure. Should any circumstance beyond the reasonable
      control of AD, AD Holding Corp. or USPS occur which delays or renders
      impossible the performance of its obligations under this Agreement on the
      dates herein provided for, such obligations shall be postponed for such
      time as such performance necessarily has had to be suspended or delayed on
      account thereof. In either such event, AD, AD Holding Corp. or USPS shall
      promptly meet to determine the equitable solution to the effects of any
      such event, provided that any of them who fails because of force majeure
      to perform its obligations hereunder will upon the cessation of the force
      majeure take all reasonable steps within its power to resume with the
      least possible delay, compliance with its obligations. None of the parties
      hereto shall be liable for any delay or other failure of performance
      because of force majeure. Events of force majeure shall include, without
      limitation, war, revolution, invasion, insurrection, riots, mob violence,
      sabotage or other civil disorders, fires, floods or other acts of

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      God or nature, utility failures, strikes or other labor disputes, acts,
      laws, regulations or rules of any government or governmental agency and
      any other similar cause or event beyond the reasonable control of the
      party, the obligations of which are affected thereby.

      Section 35.07 Compliance and Cooperation. Each of the parties agrees to
      cooperate in good faith to seek to comply with all applicable laws and
      regulations as they apply to the activities of this Agreement and to
      cooperate in good faith and to use best efforts to carry out the purposes
      of this Agreement, including without limitation, to cooperate in
      connection with any public inquiries or proceedings relating to this
      Agreement.

ARTICLE XXXVI  LEGAL RESPONSIBILITIES

      Section 36.01 Indemnification of USPS. AD and AD Holding Corp. agree to
      indemnify USPS, its officer, directors, and employees from and against any
      and all loss, liability, cost and expense, including reasonable legal
      fees, incurred by any one or more of them by reason of any and all claims,
      demands, suits, or proceedings made or brought against any one of them
      arising from or related to: (a) any act or omission of AD or AD Holding
      Corp. or their affiliates, employees, agents or contractors, which caused
      physical property damage, personal injury, wrongful death or any business
      harm; (b) the development, operation, promotion or use of the EPM System
      caused by a violation of this Agreement by AD and AD Holding Corp.; (c)
      the breach of any covenant, obligation, responsibility, warranty, or
      representation of AD or AD Holding Corp. to USPS related to the
      development, operation, promotion or use of the EPM System; (d) a
      violation of the Privacy Act and/or its implementing regulations or the
      disclosure of any USPS data or data contained in the EPM System to any
      third party in violation of the terms of this Agreement by AD, AD Holding
      Corp., or subcontractors; or (e) any claim that any product, service or
      other item is so provided by AD or AD Holding Corp. pursuant to this
      Agreement infringes the claimant's United States patent issued as of the
      time such product, service or other item so provided or the claimant's
      copyright, trade secret, trademark or other non-patent proprietary right
      under the laws of the United States. Without limiting the generality of
      the foregoing, if, as a result of any claim made by any third party
      against any of the parties to this Agreement or their affiliates, a
      royalty or fee of any kind is required in connection with the ongoing
      operation of the EPM System, then AD and AD Holding Corp. shall indemnify
      USPS for the amount of such royalty or fee unless such royalty or fee is
      due to the use of intellectual property rights described in subparagraphs
      14.01(c) (i) and (ii).

      Section 36.02 Indemnification of AD. USPS agrees to indemnify AD and AD
      Holding Corp., its officers, directors, and employees from and against any
      and all loss, liability, cost and expense, including reasonable attorneys'
      fees, incurred by any one or more of them by reason of any and all claims,
      demands, suits or proceedings, made or brought against any one or more of
      them arising

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      from or related to: (a) any act or omission of the USPS, its employees,
      agents or contractors, which cause physical property damage, personal
      injury, wrongful death, or any business harm; (b) the breach of any
      covenant, obligation, responsibility, warranty, or representation of USPS
      to AD related to the operation, promotion, or use of the EPM System
      pursuant to this Agreement; or (c) any claim that any product, service or
      other item provided by USPS pursuant to this Agreement infringes the
      claimant's United States patent issued as of the time such product,
      service or other item is so provided or the claimant's copyright, trade
      secret, trademark or other non-patent proprietary right under the laws of
      the United States. Without limiting the generality of the foregoing, if,
      as a result of any claim made by any third party against any of the
      parties to this Agreement or their affiliates based on intellectual
      property rights as described in subparagraphs 14.01(c) (i) and (ii), a
      royalty or fee of any kind is required in connection with the ongoing
      operation of the EPM System, then USPS shall indemnify AD or AD Holding
      Corp. for the amount of such royalty or fee.

      Section 36.03 Indemnification Procedure. In any case under this Agreement
      where a party has indemnified the other against any claim or legal action,
      indemnification shall be conditioned on the compliance with the procedures
      outlined below. Provided that prompt written notice is given of a claim or
      suit for which indemnification might be claimed, the indemnifying party
      promptly will defend, contest or otherwise may protect against any such
      claim or suit at its own cost and expense. The indemnified party may, but
      will not be obligated to, participate at its own expense in a defense
      thereof by counsel of its own choosing, but to the extent permitted by 39
      U.S.C. 409(d), the indemnifying party shall be entitled to control the
      defense unless the indemnified party has relieved the indemnifying party
      from liability with respect to the particular matter. In the event the
      indemnifying party fails to timely defend, contest or otherwise protect
      against any such claim or suit, the indemnified party may, but will not be
      obligated to, defend, contest or otherwise protect against the same, and
      make any compromise or settlement thereof and recover the entire costs
      thereof from the indemnifying party including reasonable attorneys' fees,
      disbursements and all amounts paid as a result of such claim or suit or
      the compromise or settlement thereof; provided, however, that, if the
      indemnifying party undertakes the defense of such matter, the indemnified
      party shall not be entitled to recover from the indemnifying party its
      costs incurred in the defense thereof other than the reasonable costs of
      investigation undertaken by the indemnified party and reasonable costs of
      providing assistance. The indemnified party shall cooperate and provide
      such assistance as the indemnifying party may reasonably request in
      connection with the defense of the matter subject to indemnification.

      The party providing indemnification shall have control of the defense and
      all related settlement negotiations, provided, however, that any
      settlement be made with the consent of the indemnified Party, such consent
      not to be unreasonably withheld, and that such settlement include as an
      unconditional term thereof the giving by the claimant of an unconditional
      release from all liability in favor of the

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      indemnified Parties. Further, in the case of indemnification for
      infringement, if the infringement results from (1) the indemnified Party's
      modification of the allegedly infringing product; (2) the combination,
      operation or use of the allegedly infringing product with software,
      hardware or other materials not furnished or recommended by the
      indemnifying Party; or (3) the indemnified Party's use of a superseded or
      altered release of the allegedly infringing product, where such an update
      was promptly made available, than in any such event, the Party which would
      otherwise be entitled to be indemnified shall defend, hold harmless and
      indemnify the other Party on the terms contained herein.

      Section 36.04 Limitations on Liability. Nothing in this Agreement shall be
      construed as an acknowledgment or concession as to the validity of any
      claim or the entitlement of either party to any amount of damages. In no
      event shall either party be liable under this Agreement to another party
      to this Agreement party under any theory of tort, contract, strict
      liability or other legal or equitable theory for any lost profits or
      exemplary, punitive, special, incidental, indirect, or consequential
      damages. Provided, however, that this limitation shall not limit the
      indemnification obligations of any party under the Section entitled
      "Indemnification" above , for any amount of damages, including loss of
      profits, consequential, exemplary, incidental or punitive damages
      recovered by a third party.

ARTICLE XXXVII NO JOINT VENTURE

      Section 37.01 This is a contractual relationship that does not create
either a wholly-owned subsidiary of any party or a joint venture with AD or AD
Holding Corp. The parties do not intend that any partnership relationship be
created between them by this Agreement.

ARTICLE XXXVIII COUNTERPARTS

      Section 38.01 This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original, but all such
counterparts shall together constitute but one and the same instrument.

ARTICLE XXXIX SEVERABILITY

      Section 39.01 If any provision of this Agreement is finally held by a
court of competent jurisdiction to be invalid, illegal or unenforceable, then,
to the extent such invalidity, illegality or unenforceability shall not deprive
any party of any material benefit intended to be provided by this Agreement, all
of the remaining provisions of this Agreement shall remain in full force and
effect and shall be binding upon the parties.

ARTICLE XL ENTIRE AGREEMENT

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                                                                   EXHIBIT 10.23

      Section 40.01 This Agreement contains the entire agreement between the
      parties, and no statements, promises, or inducements made by either party
      or agent of either party that are not contained in this written agreement
      shall be valid or binding. All previous communications and negotiations
      between the parties, either verbal or written, that are not memorialized
      in this Agreement are null and void.

ARTICLE XLI EFFECTIVE DATE

      Section 41.01 This Agreement shall become effective as of the date of
      signature of the last party to sign this Agreement.

ARTICLE XLII SURVIVAL

      Section 42.01 Articles X, XII, XIV, XVIII, XX, XXIX and XXXVI are intended
      to survive the expiration or termination of this Agreement and to continue
      in full force and effect indefinitely.

ARTICLE XLIII HEADINGS

      Section 43.01 The headings and subheadings of the articles and paragraphs
      in this Agreement are inserted for convenience only and are not intended
      to affect the meaning or interpretation of this Agreement.

Page 54 of 163
<PAGE>
                                                                   EXHIBIT 10.23

ARTICLE XLIV SIGNATURE BLOCK

AuthentiDate, Inc.

BY:
   ---------------------------
            Rob Van Naarden
            President

Date: July 31, 2002

AuthentiDate Holding Corp.

BY:
   ---------------------------
            President
Date: July 31, 2002

United States Postal Service

BY:
   ---------------------------
            Nicholas F. Barranca
            Vice President
            Product Development

Date: July 31, 2002

Page 55 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBITS

EXHIBIT A:  SALES AND MARKETING PROPOSAL: TO BE REPLACED BY SALES AND MARKETING
            PLAN

EXHIBIT B:  PRICING POLICY GUIDELINES AND PROVISIONAL PRICING SCHEDULE

EXHIBIT C:  DRAFT EPM PRACTICE STATEMENT

EXHIBIT D:  SERVICE LEVEL AGREEMENT BETWEEN USPS AND AUTHENTIDATE

EXHIBIT E:  TECHNICAL DESCRIPTION

EXHIBIT F:  SALES CONTRACTS: TO BE ATTACHED

EXHIBIT G:  LIST OF EXISTING CUSTOMERS

EXHIBIT H:  ADVISORY COMMITTEE GUIDELINES

EXHIBIT I:  USPS TRADEMARK USAGE GUIDELINES

EXHIBIT J:  ALLIANCE METRICS

EXHIBIT K:  CONCEPT OF OPERATIONS

EXHIBIT L:  NONDISCLOSURE AGREEMENT

EXHIBIT M:  INFORMATION SECURITY REQUIREMENTS

EXHIBIT N:  WIND DOWN OUTLINE: TO BE REPLACED

EXHIBIT O:  SUCCESS RIGHTS AGREEMENT: TO BE ATTACHED

EXHIBIT P:  RETURN OF CUSTOMER FUNDS: TO BE ATTACHED

EXHIBIT Q:  SOURCE CODE ESCROW AGREEMENT: TO BE ATTACHED

Page 56 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT A

                          SALES AND MARKETING PROPOSAL

Page 57 of 163
<PAGE>
                                                                   EXHIBIT 10.23

ARTICLE VI. MARKETING PROPOSITION OUTLINE

    1.   MARKET SITUATION AND COMPETITIVE OVERVIEW

                  Security is the single largest factor inhibiting the growth of
electronic commerce and the acceptance of digital transactions and digital
documents. The rate of adoption of digital documents is expected to increase
exponentially with Congress having recently passed legislation allowing digital
signatures to be used in place of physical signatures. Using digital
certificates, the AuthentiDate Service provides non-repudiation of content,
time, and the identity of the user

         AuthentiDate's products enable customers to verify that an electronic
file was created at a particular point in time and, if necessary, ensure that
the content can be securely verified with a proper chain of evidence.
AuthentiDate believes that all electronic transactions, information and data
require security, trust, and proof. Even an unsophisticated user can alter any
electronic file at any time. The AuthentiDate service eliminates the possibility
of alteration of any electronic file without detection, enabling users to
authenticate a file's originality with true evidentiary status, insured to
protect all parties. As businesses move toward a rapidly increasing number of
paperless transactions, AuthentiDate is positioning itself as the Trusted
Content Authority for verifying the authenticity of electronic files.

         AuthentiDate's patent-pending technology addresses the need for the
         verification of digital information in all business processes.
         "AuthentiDating" electronic files provide customers with a time and
         date stamped signature of a file's content. This provides a trusted,
         non-repudiated, legally admissible audit trail and file/transactional
         integrity service for issues such as securing electronic transactions,
         e-mail intellectual property protection, regulatory compliance, fraud
         prevention, and litigation support.

         COMPETITION AND AUTHENTIDATE COMPETITIVE ADVANTAGE

         [****] AuthentiDate has five pending patents, which would provide an
         additional barrier to entry for an organization attempting to duplicate
         the functionality provided by the AuthentiDate service. [****].

         The competitive matrix below outlines the competitive advantages of
         AuthentiDate's service over that of our competitors. [****] . We have
         developed this technology continuously since 1998 and continue to
         develop it. Any company attempting to compete with AuthentiDate would
         find that it takes significant time and resources to do so and in fact
         they probably would not be

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

Page 58 of 163
<PAGE>
                                                                   EXHIBIT 10.23

         able to catch up to AuthentiDate as we will continue to advance our
         technology. [****]. Of the competitors listed, only AuthentiDate have
         [****]. These [****], the official source [****].

         The fundamental competitive advantage is both in the technology and the
         complete business process as a non-repudiation service [****]

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

Page 59 of 163
<PAGE>
                                                                   EXHIBIT 10.23

AUTHENTIDATE COMPETITIVE MATRIX

         [****]

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

    2.   TARGET CUSTOMERS

         [****]

    3.   MARKETING OBJECTIVE

         [****]

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

    4.   MARKETING STRATEGY

         4.1  PRODUCT/SERVICE POSITIONING

                  We are establishing AuthentiDate as the leading provider for
                  authentication and time stamping of any type of electronic
                  file that is transmitted over any type of network. In order to
                  help our customers move from a paper world to a "paperless"
                  world, we are positioning AuthentiDate as being "The Trusted
                  Content Authority." We are also positioning the service as
                  "Paperless Proof".

                  Current and planned marketing programs
              [****]

              [ * Certain information on this page has been omitted and filed
              separately with the Commission. Confidential treatment has been
              requested with respect to the omitted portions.]

         4.2  CHANNEL STRATEGY

                  An indirect or partner centric channel strategy [****].
                  This is because it is [****]. Customer relationships are
                  being established with channel partners in their respective
                  markets while the messaging and branding efforts are being
                  directed towards an end-user vertical market. [****]

              [ * Certain information on this page has been omitted and filed
              separately with the Commission. Confidential treatment has been
              requested with respect to the omitted portions.]

Page 60 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                  Our channel strategy combines the [****]. We believe that
                  we can penetrate the consumer market through our distribution
                  partners. This will happen after the [****] takes hold
                  through our [****].

         4.3  PRICING STRATEGY
      [****]

         4.4  SERVICE AREAS
      [****]

         4.5  ADVERTISING AND PROMOTION

         The AuthentiDate marketing team, as well as, our PR firm will work very
closely with the USPS to build a campaign to educate the public as to the
benefits of this New service. [****]

         4.6  DIRECT SALES
              [****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

         4.7  MARKETING SPENDING ASSUMPTIONS

                           To be determined in conjunction with the USPS.

    A.   MARKETING AND SALES BUDGET FORECAST

                           To be determined in conjunction with the USPS.

    B.   PUBLIC RELATIONS

                           AuthentiDate, working with the USPS PR firm(s) and
                           our PR firm, will put together an extensive press and
                           technical analyst tour to get the word out on the key
                           value of EPM. We anticipate numerous speaking
                           opportunities to address the need to include
                           non-repudiation in the business process and feel our
                           solution will encourage more electronic workflow
                           business processes.

         4.10 BUSINESS RELATIONSHIPS

                           See paragraph 4.1 above.

                         [****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 61 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT B

           PRICING POLICY GUIDELINES AND PROVISIONAL PRICING SCHEDULE

Page 62 of 163
<PAGE>
                                                                   EXHIBIT 10.23

Exhibit B

                            PRICING POLICY GUIDELINES
                              Marketing Information

Capitalized terms have the same meaning as defined in Article II of the
Agreement.

A Customer for the EPM Service may be an individual, business or governmental
entity that acquires EPMs for their own use or for the use of their customers.
The EPM Customer is the entity that pays the EPM Alliance for the EPM Service.

                               Pricing Methodology

[****]

PRICES FOR EPM SERVICE UNDER THIS AGREEMENT ARE ESTABLISHED BY THE POSTAL
SERVICE, AS SET FORTH IN THIS EXHIBIT. PRICES CHANGES TO THIS EXHIBIT MAY BE
PROPOSED BY EITHER THE POSTAL SERVICE OR AUTHENTIDATE. PRICE CHANGE REQUESTS
WILL CONTAIN EXPECTED FINANCIAL IMPACT FOR THE ALLIANCE, REASONS FOR THE CHANGE
AND THE NATURE OF THE CHANGE. THE [****], UPON RECEIVING AN ADEQUATELY
DOCUMENTED PRICE CHANGE REQUEST, WILL WITHIN [****] WORKING DAYS MAKE A
RECOMMENDATION TO THE POSTAL SERVICE. IF THE [****] CANNOT REACH A
RECOMMENDATION, OR FAILS TO TAKE ANY ACTION, THEN [****]MAY ACT ON THE SUGGESTED
PRICE CHANGE WITHOUT A [****]. THE [****] WILL ATTEMPT TO EITHER ACCEPT OR
REJECT THE RECOMMENDATION OF THE [****]DAYS, BUT MUST DO SO [****]. FAILURE OF
THE [****] TO ACT [****]WILL START AN [****] WITH AN EXECUTIVE OF THE [****]ONE
LEVEL ABOVE THE MOST SENIOR MEMBER OF THE [****] REPRESENTED BY THE [****].
THERE ARE SEVERAL COURSES OF ACTION THAT MAY BE PURSUED FOLLOWING [****] REVIEW:

   (a)   IF [****]ACCEPTS THE [****] RECOMMENDATION, THEN ALLIANCE
         WILL IMPLEMENT PRICE CHANGE AS PROPOSED,

   (b)   IF [****]ACCEPTS THE [****] RECOMMENDATION WITH MODIFICATIONS, THEN
         THE ALLIANCE MUST EITHER:

            a.    IMPLEMENT THE REVISED RECOMMENDATION,

            b.    NEGOTIATE A COMPROMISE SOLUTION WITH THE POSTAL SERVICE, OR

            c.    REVISE AND RESUBMIT RECOMMENDED PRICING OR WITHDRAWAL
                  RECOMMENDATION.

            d.    REJECT THE [****]MODIFICATIONS IF THEY FALL OUTSIDE THE
                  ESTABLISHED MINIMUM REVENUE LEVELS PREVIOUSLY ESTABLISHED BY
                  THE ALLIANCE FOR THE PER EPM PRICE [****]OR WILL CAUSE
                  THE TOTAL AVERAGE PRICE PER EPM TO FALL BELOW THE MINIMUM
                  AVERAGE PRICE [****]

   (c)   IF [****]REJECTS THE [****] RECOMMENDATION, THEN THE [****] MAY EITHER:

            a.    REVISE AND RESUBMIT FOR CONSIDERATION, OR

ACCEPT [****]DECISION

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 63 of 163
<PAGE>
                                                                   EXHIBIT 10.23

General Pricing Policies

Customer Pricing Privacy  -  [****].

No Pricing Discrimination - Similarly situated Customers will be treated in a
like manner. Customer pricing for similar volume(s) and terms will be the same.

Provision for Future Price Changes and Service Changes - sales contracts with
Customers may be written for a maximum period of time [****] but may include
additional [****] beyond that [****] subject to the [****]. Prices for the
[****] will be subject to [****] by [****].

In the event the Postal Rate Commission (PRC) directs changes in the Pricing
Policy and Price Schedule, AD and USPS will implement modifications as necessary
to comply with the PRC directives.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Pricing Plans

A LIMITED NUMBER OF PRICING PLANS WILL BE OFFERED BY THE POSTAL SERVICE TO
ADDRESS THE PARTICULAR REQUIREMENTS AND VALUE PROPOSITION FOR IDENTIFIED MARKET
SEGMENTS. THE DIFFERENCES FROM PLAN TO PLAN WILL BE BASED UPON THE DIFFERENT
COST AND REVENUE SITUATIONS FACED BY THE EPM ALLIANCE.

A. Channel Partner Pricing Plans:   [****].

A.1.  MONTHLY VOLUME-BASED "PAY AS YOU GO" TRANSACTION VOLUMES:

The Transaction Pricing model has been designed to provide pricing to Channel
Partners that can be easily applied to the way they market, sell, and price
their solutions to their target customers. [****].

[****].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

A.2  ANNUAL SINGLE APPLICATION PRE-PAID SUBSCRIPTION LICENSE:

The subscription model is used when the Customer requires the ability to more
accurately budget the cost of the service. The "blocks of transactions" approach
allows this capability.

Page 64 of 163
<PAGE>
                                                                   EXHIBIT 10.23

Customer agrees to purchase "blocks of transactions" in [****], to be used
within [****] of purchase. These "blocks of transactions" are limited [****] as
defined in the sales contract. Customers could then buy additional blocks of
transactions at a reduced rate within that year of use.

Early Adopters will be granted a [****] for the duration of any multi-year
contract term, with a minimum price possible [****]. An Early Adopter is a
customer that signs a multi-year contract within the first 12 months following
the Service Launch Date. This [****] based upon the Alliance receiving
the following benefits:

      -  More rapid creation of the EPM market

      -  Reduced time to build the EPM revenue

      -  Agree to use of [****]

      -  Cooperation in [****] to the EPM

      -  Reduced sales and marketing expenses

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

A.3  ANNUAL MULTI APPLICATION PRE-PAID SUBSCRIPTION LICENSE:

The multi-application license model gives our partners the ability to better
budget in a large volume multiple application environment. Customer agrees to
purchase "blocks of transactions" in [****] to be used within [****]
of purchase. These "blocks of transactions" may be used [****] within the
vendor's application profile.

Early Adopters will be granted [****] rate for the duration of any
multi-year contract term, with a minimum price [****]. An Early Adopter is
a customer that signs a multi-year contract within the first 12 months following
the Service Launch Date. This [* * * *] based upon the Alliance receiving the
following benefits:

      -  More rapid creation of the EPM market

      -  Reduced time to build the EPM revenue

      -  Agree to use of [****]

      -  Cooperation in [****] to the EPM

      -  Reduced sales and marketing expenses

B.  PASS THROUGH PRICING PLAN

END USER SELLING WILL BE DONE THROUGH A THIRD PARTY, SUCH AS A CHANNEL PARTNER,
WITH THE [****] RESPONSIBLE FOR BILLING AND REVENUE COLLECTION FOR
PREPAYMENT OF BLOCKS OF TRANSACTIONS TO BE USED DURING THE CONTRACT TERM.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 65 of 163
<PAGE>
                                                                   EXHIBIT 10.23

C. TECHNOLOGY TRANSFER INTRANET SERVER LICENSE PRICING PLAN

The Technology Transfer License pricing model is used when [****], for a
number of reasons, must [****]. Typically, this will be for [****].
An example would be for use by [****]. Pricing is to be [****].

     [ * Certain information on this page has been omitted and filed separately
     with the Commission. Confidential treatment has been requested with respect
     to the omitted portions.]

                           Provisional Price Schedule

Price Schedule is provisional as it may change from time to time based on market
conditions and demand once the EPM Service is publicly discussed with actual
customers and a better understanding is realized of the economic value of the
service.

A. CHANNEL PARTNER PRICING

A.1.  MONTHLY VOLUME-BASED "PAY AS YOU GO" TRANSACTION PRICING

Customer is invoiced monthly for the actual number of transactions during that
month based upon the transaction volume price schedule in force for that month.

[****]

A.2.  ANNUAL SINGLE APPLICATION PRE-PAID SUBSCRIPTION LICENSE

Customer agrees to purchase "blocks of transactions" in blocks [****] to be
used within [*****] of purchase. These "blocks of transactions" are
limited [****]. Customer may buy additional blocks of transactions at a
reduced rate within [****] use.

Initial purchase:

[****]

Subsequent purchases:

[****]

Early Adopters will be granted [****] for the duration of whatever term
contract (i.e., [****]) that they are willing to commit to, with a minimum
[****]. An Early Adopter is a non-retail customer that signs a multi-year
contract within the first 12 months following the public launch date.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 66 of 163
<PAGE>
                                                                   EXHIBIT 10.23

A.3.  ANNUAL MULTI APPLICATION PRE-PAID SUBSCRIPTION LICENSE

Customer agrees to purchase "blocks of transactions" in blocks [****] to be used
within [****] of purchase. These "blocks of transactions" may be used [****]
within the vendor's application profile.

Initial purchase:

[****]

Subsequent purchases:

[****]

Early Adopters will be granted a [****] for the duration of whatever term
contract (i.e., [****]) that they are willing to commit to, with a minimum
price [****]. An Early Adopter is a non-retail customer that signs a
multi-year contract within the first 12 months following the public launch date.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

B.  PASS THROUGH:

END USER SELLING WILL BE DONE THROUGH THE PARTNER AS PART OF THE PARTNER'S
APPLICATION(S). THE [****] WOULD INVOICE THE END USER. PARTNER SELLS BLOCKS
OF TRANSACTIONS TO END-USER. END-USER IS INVOICED DIRECTLY FOR PREPAY OF BLOCKS
OF TRANSACTIONS TO BE USED OVER AN UNLIMITED TIME FRAME.

[****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

C.  TECHNOLOGY TRANSFER  INTRANET SERVER LICENSE: Case by case TBD

Page 67 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT C

                          DRAFT EPM PRACTICE STATEMENT

 Page 68 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                        USPS ELECTRONIC POSTMARK(R)

                                     (EPM)

                               PRACTICE STATEMENT

                               Draft Version 0.5.4

                           USPS EPM PRACTICE STATEMENT

Page 69 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                                    CONTENTS

<TABLE>
<S>                                                                                        <C>
1.    INTRODUCTION....................................................................     73
   1.1      OVERVIEW..................................................................     73
   1.2      POLICY AND OBJECTIVE......................................................     73
   1.3      COMMUNITY AND APPLICABILITY...............................................     73
   1.4      AUTHORIZED BUSINESS VENDOR................................................     73
   1.5      EPM SERVICE REQUESTOR.....................................................     73
   1.6      APPLICABILITY.............................................................     74
   1.7      CONTACT DETAILS...........................................................     74
2.    GENERAL PROVISIONS..............................................................     75
   2.1      RESPONSIBILITIES..........................................................     75
      2.1.1    USPS Responsibilities..................................................     75
      2.1.2    User Responsibilities..................................................     75
   2.2      LIABILITY.................................................................     76
      2.2.1    Disclaimer.............................................................     76
      2.2.2    Limitations on Reverse Engineering, Decompilation  and Disassembly.....     76
      2.2.3    Loss Limitations.......................................................     76
   2.3      FINANCIAL RESPONSIBILITY..................................................     76
      2.3.1    Indemnification By EPM service requesters..............................     76
      2.3.2    Governing Law..........................................................     77
   2.4      FEES......................................................................     77
   2.5      SECURITY AUDIT AND CUSTOMER ACCEPTANCE TESTING (CAT)......................     77
      2.5.1    Frequency of Security Review...........................................     77
      2.5.2    Identity/Qualifications of Auditor.....................................     77
      2.5.3    Auditor's Relationship to Audited Party................................     77
      2.5.4    Scope of the Review....................................................     77
      2.5.5    Actions Taken as a Result of Deficiency................................     77
      2.5.6    Communication of Results...............................................     77
   2.6      SECURITY PROVISIONS.......................................................     77
      2.6.1    Policy.................................................................     78
      2.6.2    Interception, Searching or Reading Messages............................     78
3.    OPERATIONAL REQUIREMENTS........................................................     78
   3.1      ELECTRONIC POSTMARK(R) SERVICE............................................     78
   3.2      ELECTRONIC POSTMARK(R) VERIFICATION.......................................     78
   3.3      TRANSACTION LOGGING.......................................................     78
   3.4      DATA CENTER SECURITY MEASURES.............................................     78
   3.5      COMPUTER SECURITY AUDIT PROCEDURES........................................     78
   3.6      TYPES OF EVENTS RECORDED..................................................     79
   3.7      FREQUENCY OF PROCESSING TRANSACTION TABLES................................
   3.8      RETENTION PERIOD FOR LOGS AND TRANSACTION TABLES..........................     79
      3.8.1    Protection of Logs and Transaction Tables..............................     79
      3.8.2    Audit Log Backup Procedures............................................     79
      3.8.3    Vulnerability Assessments..............................................     79
   3.9      DATABASE..................................................................     79
      3.9.1    Types of Records Archived..............................................     79
      3.9.2    Retention Period For Archives..........................................     79
      3.9.3    Archival Backup........................................................     79
   3.10     COMPROMISE AND DISASTER RECOVERY..........................................     79
   3.11     SUPPORT AND MAINTENANCE...................................................     79
4.    TECHNICAL OVERVIEW..............................................................     80
   4.1      EPM SERVER-SIDE TECHNOLOGY................................................     80
   4.2      EPM CLIENT-SIDE TECHNOLOGY................................................     80
</TABLE>

Page 70 of 163
<PAGE>
                                                                   EXHIBIT 10.23

<TABLE>
<S>                                                                                        <C>
   4.3      EPM CRYPTOGRAPHIC STANDARDS...............................................     80
5.    INDUSTRY STANDARDS..............................................................     80
6.    SECURITY CONTROLS...............................................................     80
   6.1      PHYSICAL CONTROLS.........................................................     80
   6.2      PROCEDURAL CONTROLS.......................................................     80
      6.2.1    Trusted Roles..........................................................     80
      6.2.2    Background and Qualifications/Background Investigation.................     80
      6.2.3    Sanctions For Unauthorized Actions.....................................     80
      6.2.4    Contractor Personnel Requirements......................................     81
   6.3      COMPUTER SECURITY CONTROLS................................................
   6.4      LIFE CYCLE TECHNICAL CONTROLS.............................................     81
      6.4.1    System Development Controls............................................     81
   6.5      NETWORK SECURITY CONTROLS.................................................     81
7.    DEFINITIONS.....................................................................     81
</TABLE>

Page 71 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                                     PREFACE

The Electronic Postmark(R) (EPM) Practice Statement (PS) is being developed to
detail the practices of the Electronic Postmark(R) service and the integration
of the EPM within multiple product offerings. This current version of the PS
focuses primarily on the practices surrounding the basic operation of the EPM
integrated with specific applications or products.

This version of the PS may be [****] for integration with the EPM service.
In addition, this version of this PS may also be [****] at the discretion
of USPS management, but is not intended for publication to the general public or
use in actual operations without prior approval and consensus of the USPS EPM
Policy review team. The EPM PS identifies the technical, business, and legal
processes followed in operating the EPM service. The USPS EPM Policy review team
includes the following entities: USPS Legal, IS Security, Business Development
and USPS Inspection Service.

BUSINESS-SPECIFIC AND APPLICATION-SPECIFIC PRACTICES ARE NOT INCLUDED IN THIS
VERSION. THE SECTIONS AND DETAILS THAT ARE APPLICABLE TO SYSTEM AND/OR
PRODUCT-SPECIFIC ACTIVITIES WILL BE PERIODICALLY UPDATED ACCORDINGLY.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 72 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                           USPS EPM PRACTICE STATEMENT

         1.       INTRODUCTION

         1.1      OVERVIEW

This Electronic Postmark(R) Practice Statement describes the practices the
United States Postal Service (USPS) employs in issuing and managing Electronic
Postmarks(TM) (EPM). These policies and procedures provide management with
enforceable mechanisms to safely operate the EPM components in such a way to
assure due diligence and prudent business practices.

         1.2      POLICY AND OBJECTIVE

The Postal Service seeks to offer Electronic Postmark(R) Services that will
offer customers a trusted third-party validation of the time and date that an
electronic hash was received by the Postal Service, and that will validate the
existence of the electronic hash by enabling recipients to determine whether it
was changed after its' processing by the Postal Service.

         1.3      COMMUNITY AND APPLICABILITY

The United States Postal Service is developing services to further its mission
of "binding the Nation together through the correspondence of the people". These
new services will enable and enhance the development of commerce by electronic
means, by extending the USPS traditional paper mail services. These Postal
services will provide tamper detection and timestamp security and proof of
originality to electronic correspondence and transactions, giving some of the
attributes usually associated with first-class Mail.

         1.4      AUTHORIZED BUSINESS VENDOR

The authorized business vendors are designated to accept and process electronic
files to be electronically postmarked via integration of the Electronic
Postmark(R) application with their new or existing systems or product offerings.

         1.5      EPM SERVICE REQUESTOR

An EPM service requester is any individual or entity that submits an electronic
hash to the EPM server via a public or private network for Electronic
Postmarking.

Page 73 of 163
<PAGE>
                                                                   EXHIBIT 10.23

         1.6      APPLICABILITY

         This practice statement is applicable to all Electronic Postmark
services offered by the Postal Service.

         1.7      CONTACT DETAILS

This Practice statement was developed by the United States Postal Service.
Questions should be directed to:

         The United States Postal Service
         Attn:  Manager, Business Development
         475 L'Enfant Plaza SW
         Washington DC 20260
         (202) 268-5262

         1.8      USPS PRIVACY ONLINE

For over two centuries the Postal Service has served the American public as a
trusted third party in delivering private, secure communications. Today, the
Information Age presents new challenges to protecting the privacy of personal
information. The Postal Service appointed a Chief Privacy Officer who developed
a comprehensive privacy framework that combines Federal laws, public and private
sector best practices, leading technologies and strong security to protect your
privacy.

      -  Federal Laws
      -  USPS Privacy Policies
      -  Leading Technologies
      -  Strong Security and Oversight

                  1.8.1 Federal Laws

The Postal Service adheres to the Privacy Act and the Freedom of Information Act
(FOIA). These laws apply specifically to Federal government institutions and
provide unique privacy protections that commercial institutions are not required
to follow. The Postal Service also voluntarily complies with several additional
privacy laws including the Gramm-Leach-Bliley Act (GLB), the Children's Online
Privacy Policy Act (COPPA), and certain Office of Management and Budget (OMB)
guidelines to ensure that it is at the forefront of protecting the privacy of
its customers. (link to Parents' Resources Landing page)

                  1.8.2 USPS Privacy Policies

Page 74 of 163
<PAGE>
                                                                   EXHIBIT 10.23

Our online privacy policy is based on best practices in both the public and
private sector to provide users with privacy protections while using usps.com.

      -  Personal information will be collected only if specifically and
         knowingly provided by the user;
      -  The USPS will not sell or otherwise provide your personal
         information to outside parties;
      -  Users will have access to usps.com without personally identifying
         themselves;
      -  Users will receive additional features and conveniences if they provide
         some personally identifiable information;
      -  Personal information will be protected in a secure manner if users
         choose to provide it; and,
      -  Users will have the ability to review data collected about them and to
         modify it if necessary.

                  1.8.3 Strong Security

To protect your data, the Postal Service has implemented industry standard data
security measures as well as software programs to monitor network traffic that
identifies unauthorized attempts to upload or change information, or otherwise
cause damage. To secure your information in transit to usps.com, the Postal
Service uses industry standard encryption software, Secured Socket Layer (SSL).

2        GENERAL PROVISIONS

         2.1      RESPONSIBILITIES

                  2.1.1 USPS Responsibilities

The Postal Service provides the following services for an electronic hash sent
to an EPM server for Electronic Postmarking:
     [****]

The Postal Service provides the following services for the implementation of the
Electronic Postmarking application.
[****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

                  2.1.2 User Responsibilities

Page 75 of 163
<PAGE>
                                                                   EXHIBIT 10.23

The User must follow the processes and procedures for the purpose of obtaining
Electronic Postmarks and must pay the appropriate fee. A User shall not submit
electronic files or otherwise use Electronic Postmark Services in any manner
that violates any federal or state law or regulations.

[****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

         2.2 LIABILITY

[****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

                  2.2.1 Disclaimer

[****]

                  2.2.2 Limitations on Reverse Engineering, Decompilation and
                        Disassembly

      [****]

                  2.2.3 Loss Limitations

         [****]

         2.3 FINANCIAL RESPONSIBILITY

                  2.3.1 Indemnification By EPM service requesters

[****]

                  [ * Certain information on this page has been omitted and
                  filed separately with the Commission. Confidential treatment
                  has been requested with respect to the omitted portions.]

Page 76 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                  2.3.2 Governing Law

[****]

         2.4 FEES [****]

         2.5 SECURITY AUDIT AND CUSTOMER ACCEPTANCE TESTING (CAT)

                  2.5.1 Frequency of Security Review

[****]

                  2.5.2 Identity/Qualifications of Auditor

[****]

                  2.5.3 Auditor's Relationship to Audited Party

[****]

                  2.5.4 Scope of the Review

[****]

                  2.5.5 Actions Taken as a Result of Deficiency

                           [****]

                  2.5.6 Communication of Results

[****]

         2.6 SECURITY PROVISIONS

[****].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 77 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                  2.6.1 Policy

[****]

                  2.6.2 Interception, Searching or Reading Messages

[****]

3        OPERATIONAL REQUIREMENTS

The Electronic Postmarking Service will be available [****].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

         3.1 ELECTRONIC POSTMARK(R) SERVICE

[****]

         3.2 ELECTRONIC POSTMARK(R) VERIFICATION

[****]

         3.3 TRANSACTION LOGGING

[****]

         3.4 DATA CENTER SECURITY MEASURES

     [****]

         3.5 COMPUTER SECURITY AUDIT PROCEDURES

[****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 78 of 163
<PAGE>
                                                                   EXHIBIT 10.23

         3.6  TYPES OF EVENTS RECORDED

[****]

         3.7  RETENTION PERIOD FOR LOGS AND TRANSACTION TABLES

[****]

                  3.7.1 Protection of Logs and Transaction Tables

[****]

                  3.7.2 Audit Log Backup Procedures

[****]

                  3.7.3 Vulnerability Assessments

[  * * * * ]

         3.8  DATABASE

                  3.8.1 Types of Records Archived

         [****]

                  3.8.2 Retention Period For Archives

 [****]

                  3.8.3 Archival Backup

[****]

         3.9  COMPROMISE AND DISASTER RECOVERY

[****]

         3.10 SUPPORT AND MAINTENANCE

                  [****]

                  [ * Certain information on this page has been omitted and
filed separately with the Commission. Confidential treatment has been requested
with respect to the omitted portions.]

Page 79 of 163
<PAGE>
                                                                   EXHIBIT 10.23

4        TECHNICAL OVERVIEW

         4.1 EPM SERVER-SIDE TECHNOLOGY

[****]

         4.2 EPM CLIENT-SIDE TECHNOLOGY

         [****]

         4.3 EPM CRYPTOGRAPHIC STANDARDS

                  [****]

5        INDUSTRY STANDARDS

                  [****]
6         SECURITY CONTROLS

[****]

         6.1 PHYSICAL CONTROLS

[****]

         6.2 PROCEDURAL CONTROLS

                  6.2.1 Trusted Roles

[****]

                  6.2.2 Background and Qualifications/Background Investigation

[****]

                  6.2.3 Sanctions For Unauthorized Actions

[****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 80 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                  6.2.4 Contractor Personnel Requirements

[****]

         6.3 LIFE CYCLE TECHNICAL CONTROLS

                  6.3.1 System Development Controls

[****]

         6.4 NETWORK SECURITY CONTROLS

[****]

7        DEFINITIONS

         AGENT  [****]

         ALGORITHM [****]

         AUDIT LOG [****].

         AUDIT TRAIL same as audit log.

         AUTHORIZED BUSINESS VENDOR [****]

         BRANDING FILE [****].

         CERTIFICATE [****]

         CLEARTEXT [****].

         CONTINGENCY PLAN [****].

         CRYPTOGRAPHY [****]

         CRYPTOGRAPHICALLY-SEALED [****].

         DIGITAL DOCUMENT [****]

         DIGITAL SIGNATURE [****]

         DIGITALLY SIGN [****].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 81 of 163
<PAGE>
                                                                   EXHIBIT 10.23

         DIGITAL SIGNATURE STANDARD (DSS) [****]

         ELECTRONIC ADDRESS [****]

         ELECTRONIC MAIL SOFTWARE [****].

         ELECTRONIC POSTMARK(R)  [****]

         EPM PRACTICE STATEMENT (PS) [****]

         EPM SERVICE REQUESTER [****].

         EVENT [****]

         GLOBAL POSITIONING SYSTEM [****].

         HASH [****]

         IETF (INTERNET ENGINEERING TASK FORCE) [****]

         KB  (Kilobit) [****].

         KEY PAIR A [****]

         MAIL PROCESSOR [****].

         MESSAGE [****]

         MONITORING [****]

         MONOTONICALLY INCREASING [****]

         POSTMARKED MESSAGE [****]

         PUBLIC KEY CRYPTOGRAPHY [****]

         RECIPIENT(S) [****]

         SECURITY POLICY [****]

         SPOOFING [****]

         [ * Certain information on this page has been omitted and filed
separately with the Commission. Confidential treatment has been requested with
respect to the omitted portions.]

Page 82 of 163
<PAGE>
                                                                   EXHIBIT 10.23

         TRUSTED TIME [****]

         TSA [****]

         VALIDATION TOOL [****]

X.509 VERSION 3 CERTIFICATES [****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 83 of 163
<PAGE>
                                                                   EXHIBIT 10.23

EXHIBIT D

              SERVICE LEVEL AGREEMENT BETWEEN USPS AND AUTHENTIDATE

Page 84 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                      [UNITED STATES POSTAL SERVICE LOGO]

                            SERVICE LEVEL AGREEMENT

                           USPS ELECTRONIC POSTMARK(R)

                                      (EPM)

                                   VERSION 0.8

                                  JUNE 21, 2002

                           United State Postal Service

                         Office of Business Development

                              475 L'Enfant Plaza SW

                               Washington DC 20260

Page 85 of 163
<PAGE>
                                                                   EXHIBIT 10.23

                         SERVICE LEVEL AGREEMENT SUMMARY

SLA: EPM (USPS ELECTRONIC POSTMARK(R))

PLATFORM: WEB Client/Server
PROGRAM MANAGER: [ * * * * ]
STATUS: Draft
HOURS OF OPERATION: 24X7
RTO (RECOVERY TIME OBJECTIVE) FROM THE BIA (BUSINESS IMPACT ASSESSMENT):
      -  LOSS OF FACILITY: [ * * * * ]
      -  SERVICE OR CONNECTIVITY OUTAGE: [ * * * * ]
AVAILABILITY OBJECTIVE: [ * * * * ]

SECTION 508 COMPLIANCE STATUS:

Authentidate agrees that all systems/applications submitted, as well as changes
to existing systems/applications, covered under this SLA must be in compliance
with Section 508 of the Rehabilitation Act. Section 508 requires that federal
agencies make EIT (Electronic and Information Technology) accessible to persons
with disabilities.

SUMMARY:

This SLA documents the roles and responsibilities of Authentidate, Inc. as the
Postal EPM Service Provider. [****]

SERVICE LEVELS METRICS:

AuthentiDate will display static web pages outlining the agreed-upon service
levels at http://www.authentidate.com/usps/sla.html. This page or pages will
describe support times, availability, responsibilities, contact information and
other metrics, and where available will include links to support partner sites
showing their service offerings. [****]

SPECIAL TERMS & CONDITIONS:

The USPS NISS (National Information Security Systems) BIA is a process to
determine the criticality, sensitivity, and RTO for all information resources.
The criticality rating and RTO from the BIA process has been determined to be
"Business Sensitive" with a [****]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

Page 86 of 163
<PAGE>
                                                                   EXHIBIT 10.23

SLA ACKNOWLEDGMENT

USPS:

--------------------------------                             -----------------
Nicholas F. Barranca                                         Date
Vice President
Product Development

AUTHENTIDATE:

--------------------------------                             -----------------
Rob Van Naarden                                              Date
President

AUTHENTIDATE HOLDING CORP.:

--------------------------------                             -----------------
Name                                                         Date
Title, AuthentiDate Holding Corp.

Page 87 of 163
<PAGE>
                                                                   EXHIBIT 10.23

CUSTOMER DOCUMENT HISTORY

         [****]

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

Page 88 of 163
<PAGE>

                                                                   EXHIBIT 10.23

PLANNED FUTURE REVISIONS

1. Revise the SLA to incorporate additional applications that may use EPM.

2. Revise the SLA to include additional support groups as needed.

3. Review and revise the SLA for each major application release to ensure the
   application's support needs are properly addressed.

Page 89 of 163

<PAGE>
                                                                   EXHIBIT 10.23

                                TABLE OF CONTENTS

<TABLE>
<S>                                                                       <C>
SLA Acknowledgment
Customer Document History
   Planned Future Revisions                                                  89
1.0      System Overview                                                     91
   1.1   Purpose                                                             91
   1.2   System Availability                                                 91
   1.3   Locations Serviced                                                  91
   1.4   Technical Architecture Overview                                     91
   1.5   Software Description                                                92
   1.6   Hardware Description                                                92
   1.7   Service Providers/Hours of Service                                  92
   1.8   SystemBackup                                                        93
   1.9   Archival of Data                                                    93
2.0      Introduction                                                        93
   2.1   Duration of Agreement                                               93
   2.2   Cancellation Clause                                                 93
   2.3   Change Management                                                   94
   2.4   Problem Management                                                  94
      2.4.1    TIER 1 support - Partner                                      94
      2.4.2    TIER 2 support - AuthentiDate                                 95
      2.4.3    Severity Level Definitions                                    95
      2.4.4    Problem Resolution Requirements                               96
3.0      Scope of Work                                                       97
   3.1   Authorized EPM Provider - TIER 1                                    97
   3.2   AuthentiDate - TIER 2                                               97
4.0      Business Operations                                                 98
   4.1   4.1 Customer Profile Management                                     98
   4.2   Billing                                                             98
   4.3   Revenue Collection                                                  99
   4.4   Revenue Distribution                                                99
5.0      Reporting                                                           99
6.0      Service Level Metrics                                              100
7.0      Conflict                                                           100
Appendix A:    EPM Call Flow                                                101
Appendix B:    Management Notification                                      102
   USPS Management Notification                                             102
   Authentidate Management Notification                                     102
Appendix C:    Acronyms                                                     103
</TABLE>

                                 LIST OF FIGURES

Figure 3-1. Definitions..............................................        94
Figure 3-2. Severity Levels..........................................        95
Figure 3-3. Problem Resolution Goals.................................        96

Page 90 of 163
<PAGE>
                                                                   EXHIBIT 10.23

1.0      SYSTEM OVERVIEW

The USPS Electronic Postmark (EPM) will be provided through an environment
developed and maintained by AuthentiDate, Inc. and hosted [ * * * * ]. This
web-based service accepts and stores information describing electronic files for
later non-repudiation. The electronic file, [ * * * * ], and then transmitted to
the central server, where it is time stamped using a secure auditable time
stamping master clock provided by a third-party vendor, [ * * * * ]. The [ * * *
* ], and a receipt is then returned to the client. The receipt consists of: an
electronic object returned to the User after postmarking that incorporates the
EPM time stamp and the hash code of the postmarked file. Later, [ * * * * ].

      1.1 PURPOSE

This SLA documents the roles and responsibilities of Authentidate, Inc., as the
Service Provider, defines the level at which Authentidate must provide these
services, and defines the interactions between Authentidate, Inc., and the
Postal Service. Unless specifically noted, resolution of service level
shortcomings defined in this Agreement are to be resolved in no more than [ * *
* * ].

      1.2 SYSTEM AVAILABILITY

24 X 7 (24 hours a day, 7 days a week)

      1.3 LOCATIONS SERVICED

Nationwide

      1.4 TECHNICAL ARCHITECTURE OVERVIEW

The AuthentiDate non-repudiation service is implemented as a [ * * * * ] service
running in a secure hosted facility [ * * * * ] The [ * * * * ].

At the client side [ * * * * ] are supported, based [ * * * * ], and implemented
in two libraries. The [ * * * * ] communicates with the [ * * * * ] while the [
* * * * ] communicates using [ * * * * ], a relatively new [ * * * * ] protocol
supported by companies such [ * * * * ].

These [ * * * * ]are designed to simplify partner integration by allowing
partners and customers [ * * * * ] in their own applications.

On the following page is a diagram showing the AuthentiDate data center
environment.

[ * * * * ]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

91
<PAGE>
                                                                   EXHIBIT 10.23

      1.5 SOFTWARE DESCRIPTION

The AuthentiDate service is [ * * * * ] as its current application server
environment. AuthentiDate makes full use [ * * * * ]. Static web pages and the
corporate web site [ * * * * ], while some dynamic pages come from [ * * * * ].
Persistence is maintained in [ * * * * ].

At the client side, AuthentiDate provides to customers and partners [ * * * * ].
Using the [ * * * * ], the EPM can be embedded in [ * * * * ] directly. These
client libraries perform such functions as [ * * * * ]. The [ * * * * ]
communicates directly with the [ * * * * ] via [ * * * * ], while the [ * * * *
] communicates via [ * * * * ], an industry standard which is supported by many
companies [ * * * * ]. [ * * * * ] is currently implemented at the server using
[ * * * * ] library.

Time stamping functions are implemented [ * * * * ] using dedicated hardware
with embedded software interfaces that conform to [ * * * * ].

Baseline software lists have been provided in the technical due diligence
documentation provided to USPS previously. Authentidate will provide updated
software configuration documentation to USPS within 30 days of change.

      1.6 HARDWARE DESCRIPTION

The AuthentiDate central server runs behind [ * * * * ]. [ * * * * ] do load
balancing. Three of the four [ * * * * ] ([ * * * * ] database) run on redundant
[ * * * * ] equipment, while the [ * * * * ] runs on dedicated [ * * * * ]
devices provided by the vendor.

Storage is provided via [ * * * * ]array and a [ * * * * ] backup device
implements tape backup. There are also several utility servers running [ * * * *
] for monitoring, messaging and remote management.

The baseline hardware configuration has been provided in the technical due
diligence documentation provided to USPS previously. Authentidate will provide
updated hardware configuration documentation to USPS within 30 days of change.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

      1.7 SERVICE PROVIDERS/HOURS OF SERVICE

      AuthentiDate  212-329-1100,or other number to be supplied prior to launch
      date

      -  Service Description: Provides support for all questions/problems
         regarding EPM.

      -  Hours of Support: 8:30 a.m. to 6:00 p.m. ET, Monday through Friday.

92
<PAGE>
                                                                   EXHIBIT 10.23

      1.8 SYSTEMBACKUP

Backups will be performed by Authentidate, Inc.on a daily basis at [ * * * * ]
in a manner sufficient to satisfy the Service Metrics defined in Section 6.0.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

      1.9 ARCHIVAL OF DATA

The Electronic Postmarking Services do not include any undertaking by the either
AuthentiDate or the Postal Service to store the original electronic file as part
of the USPS EPM service. AuthentiDate's obligation is limited to communicating
the Electronic Postmarked Receipt back to the sender and maintaining an online
archive of each receipt for a period of seven (7) years from the date of
issuance as defined in the USPS EPM Practice Statement document.

2.0      INTRODUCTION

The United States Postal Service is developing services to further its mission
of "binding the Nation together through the correspondence of the people". These
new services enable and enhance the development of commerce by electronic means,
by extending the trust of USPS traditional paper mail services. These Postal
services will provide tamper detection, timestamp security and proof of
originality to electronic correspondence and transactions, providing many of the
attributes usually associated with first-class Mail. This is a service level
agreement for the production environment of the USPS EPM service.

      2.1 DURATION OF AGREEMENT

Postal Service may schedule and conduct a review of this agreement one year from
the acceptance date (the date the last signature is received and the SLA status
is changed from "Final" to "Accepted"). Renewal/cancellations will be based upon
information received from the USPS Program Manager.

Additionally, this agreement may also be altered when a scope adjustment (i.e.,
funding, support services, etc.) is required.

      2.2 CANCELLATION CLAUSE

This SLA may be canceled by mutual agreement of all signatories with 90 days
notice, but in no event may this SLA be cancelled unless it is superseded by
another SLA prior to the expiration or termination of the Alliance Agreement
between the Parties

93
<PAGE>

                                                                   EXHIBIT 10.23

Inherent Processes

                            Figure 2-1. Definitions.

           The following definitions apply throughout this document:

TICKET: A ticket is an electronic or paper representation of a request for
support.

HOT TRANSFER: A hot transfer is a transfer of a trouble ticket from one tier
analyst to an analyst in another tier while the customer is still on the
telephone line.

WARM TRANSFER: A warm transfer is a transfer of a trouble ticket from one tier
to another in which the customer has disconnected or is not on the telephone
line.

COLD TRANSFER: A cold transfer is a transfer of a trouble ticket handled
electronically (through FTP (File Transfer Protocol), fax, or direct connection)
where there is no involvement from the analyst or caller.

OUTAGE: The system is not available during negotiated hours of availability due
to problems with the application, hardware, or software. Maintenance extends
beyond the negotiated maintenance window.

         2.3 CHANGE MANAGEMENT

Normal operational changes will be managed through AuthentiDate's Change
Management process, as described in the AuthentiDate Change Management document
provided to the Postal Service. This will include maintenance and upgrades of
hardware, operating systems, third-party application software, degradations, and
normal feature upgrades and service releases of the AuthentiDate implementation
of the USPS Electronic Postmark. AuthentiDate will provide USPS with reports
showing the status of any of the foregoing changes.

         2.4 PROBLEM MANAGEMENT

Service Description: The USPS EPM service is [ * * * * ] of customers and
partners. Accordingly, license terms will require that customers and technology
partners who integrate the Postal EPM service provide TIER 1 support to ensure
compliance with this SLA. Service levels for TIER 1 support will be defined to
ensure compliance with this SLA, including Section 3.1, below.

AuthentiDate will provide TIER 2 support and problem resolution for users of the
Postal EPM service. Problems are tracked at different tiers using COTS
(commercial off the shelf) or specially developed problem management tools.
Problem resolution is prioritized based on severity. The Customer Support
Manager reviews all open problem tickets daily. The problem ticket is closed
once the problem has been resolved to the satisfaction of the customer.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

                  2.4.1 TIER 1 support - Partner

Authentidate will require that partner operations follow established escalation
procedures in the event tickets are not meeting agreed upon service levels. The
problem ticket is closed once the caller has verified the problem has been
resolved.

94
<PAGE>
                                                                   EXHIBIT 10.23

EPM calls to Partner Operations will be initiated by receiving calls from
customers who may be conferenced with AuthentiDate TIER 2 and via email from the
customer. Tickets can also be initiated through the proactive monitoring of
alerts. Resolution will be completed according to the following guidelines:

1.  A call will be considered received once it has been answered and logged into
    the problem management tool. The technician will troubleshoot the problem or
    question and attempt to identify and resolve it within 5 minutes. If unable
    to diagnose the problem, the technician will transfer the ticket to TIER 2
    for further troubleshooting, resolution, or escalation.

2.  Tickets waiting for long-term resolution will be placed in a "Work On Hold"
    status and the level of service commitments will be suspended. There are two
    "Work On Hold" categories (Internal and External) and both are used by
    agreement of the technician and the customer. This status is removed when
    the problem is resolved or when a determination is made to change the
    request/problem to a developmental effort.

                  2.4.2 TIER 2 support - AuthentiDate

Tickets will be initiated at AuthentiDate TIER 2 by receiving calls from Partner
Operations. Tickets can also be initiated through the proactive monitoring of
alerts. Resolution will be completed according to the following guidelines and
Problem Resolution Requirements (see Section 2.4.4):

1.  TIER 2 will troubleshoot the problem or question and attempt to resolve it.
    If unable to resolve the problem or no progress is being made, TIER 2 will
    consult with the the appropriate group for additional troubleshooting.

2.  Tickets will be prioritized according to the assigned severity level.

3.  TIER 2 will assign severity levels for calls that reach TIER 2.

4.  The level of service measurements and commitments will be suspended for
    problems sent back to TIER 2 due to non-cooperation from the caller.

5.  Tickets waiting for long-term resolution will be placed in a "Work On Hold"
    (Internal or External) status and the level of service commitments will be
    suspended.

6.  The site contact (if applicable) is expected to be available for assistance
    in problem resolution or the problem resolution timer will be suspended
    until the site contact is available.

7.  TIER 2 will maintain ownership of the ticket until its final resolution.
    Upon resolution, TIER 2 will verify resolution with customer and close
    ticket.

                  2.4.3 Severity Level Definitions

                          Figure 2-2. Severity Levels.

    Problem severity levels are nationally defined and examples of each are
                                displayed below.

SEVERITY LEVEL 1 - HIGH

         SEVERITY DEFINITION: NATIONAL IMPACT - DISTRIBUTED system sites are
         down or seriously affected. Host-based national application is down or
         being seriously affected. No alternative is available.

         EPM EXAMPLES:

95
<PAGE>
                                                                   EXHIBIT 10.23

         -    EPM is inaccessible nationally due to loss of facility

         -    EPM is inaccessible nationally due to connectivity or central
              application failure

         -    EPM Database is down.

         -    [ * * * * ] hardware is down.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

SEVERITY LEVEL 2 - MEDIUM

         SEVERITY DEFINITION: CUSTOMER IMPACT - ONE OR MORE customers are
         impacted, excluding client-side hardware or system failures.

         EPM EXAMPLES:

         -    EPM is inaccessible by a single customer or is seriously affected.

         -    EPM service performance or response time is reduced below service
              level guarantees

         -    Noncritical application or transaction error

         -    Customer reporting or account maintenance failure

SEVERITY LEVEL 3 - LOW

         SEVERITY DEFINITION: MINIMAL IMPACT - CUSTOMER, SYSTEM OR APPLICATION
         is able to continue to work with bypass or fallback. Also requests for
         information or upgrade suggestions. Excludes client-side hardware or
         system failures

         EPM EXAMPLES:

         -    An EPM customer is experiencing difficulties, but a workaround is
              available.

         -    Requests for information or help with application usage

         -    Suggestions for upgrades or improvements to the service.

         -    Requests for customer service assistance or direct account
              maintenance

                  2.4.4 Problem Resolution Requirements

                   Figure 2-3. Problem Resolution Requirements

 Problem Resolution Requirements indicate when escalation begins, the expected
      resolution time, and when status updates are provided to the caller.

SEVERITY LEVEL 1 - HIGH

         ESCALATION BEGINS: Immediately

         TICKET UPDATES: Hourly

         EXPECTED RESOLUTION TIME: Within 8 hours

         FIRST/SECOND/THIRD LEVEL MANAGEMENT NOTIFICATION:

         1st      Within 1 hour Management and all affected organizations

         2nd      Verbally within 2 hours

         3rd      Verbally within 3 hours

96
<PAGE>
                                                                   EXHIBIT 10.23

SEVERITY LEVEL 2 - MEDIUM

         ESCALATION BEGINS: Immediately

         TICKET UPDATES: 2 to 4 hours

         EXPECTED RESOLUTION TIME: Within 24 hours

         FIRST/SECOND/THIRD LEVEL MANAGEMENT NOTIFICATION:

         1st      Within 4 hours Management and all affected organizations

         2nd      Verbally within 8 hours

         3rd      Verbally within 12 hours

SEVERITY LEVEL 3 - LOW

         ESCALATION BEGINS: Not to exceed 4 hours

         TICKET UPDATES: Daily

         EXPECTED RESOLUTION TIME: Within 3 business days for problems or
         account assistance, indefinite for service suggestions

         FIRST/SECOND/THIRD LEVEL MANAGEMENT NOTIFICATION:

         1st      Management/Status Report

         2nd      After 3 days, Weekly Status Report

         3rd      Status Report

3.0 SCOPE OF WORK

Service Providers will furnish base services and service levels as described in
each subsection. The figures following each subsection define the service levels
for all applicable services.

         3.1 AUTHORIZED EPM PROVIDER - TIER 1

Authorized EPM Partner TIER 1 Operations will answer basic questions using FAQs
(Frequently Asked Questions) and provide the following services:

1.  CUSTOMER SUPPORT. PARTNER OPERATIONS will provide the POC (Point of Contact)
    for customer problems. Tickets not meeting Strategic Alliance severity
    level, escalation, or expected resolution timeframe goals will be escalated.

2.  TICKET TRANSFERS. Authorized EPM Provider TIER 1 Operations will warm
    transfer tickets to the AuthentiDate TIER 2 for additional support if they
    are unable to resolve the caller's problem.

3.  SURVEY. Partner Operations will notify callers that they may receive a
    survey.

-        Email customer satisfaction survey

-        Analysis of customer satisfaction surveys

         3.2 AUTHENTIDATE - TIER 2

AuthentiDate TIER 2 will be responsible for performing the following services:

1.  CUSTOMER SUPPORT: AuthentiDate TIER 2 will accept problem tickets escalated
    from Partner TIER 1 Operations and resolve in accordance with the Service
    Metrics defined in Section 6.0.

2.  CALL BACKS. AuthentiDate TIER 2 will assure that the customer is called back
    with the trouble ticket status as defined in Figure 2-3 Problem Resolution
    requirements under Ticket Updates. TIER 2 is also responsible for closing
    trouble tickets escalated to TIER 2 or higher.

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<PAGE>
                                                                   EXHIBIT 10.23

3.  TICKET UPDATES. TIER 2 will update the ticket status as defined in Figure
    2-3 Problem Resolution Goals under Ticket Updates and keep the customer
    informed of the trouble ticket's status.

4.  CHANGE MANAGEMENT. AuthentiDate TIER 2 will follow the Change Management
    processes described in the AuthentiDate Change Management process document
    provided to USPS as part of the initial Technical Due Diligence.

4.0 BUSINESS OPERATIONS

Authentidate will be responsible for the development, maintenance, and
operations of data systems required to meet compliance with the metrics defined
in section 6.0 Service Level Metrics.

         4.1 CUSTOMER PROFILE MANAGEMENT

         All Customer Profile Data that will be collected and used by
         AuthentiDate and will be managed according to the security and privacy
         methodologies that are defined in this document and the Alliance
         Agreement between the Parties. The profile data that may be collected
         will include, but not be limited to:

         -        Name

         -        Address

         -        Customer account number

         -        Contact information

         -        Business profile (industry, markets addressed, applications
                  that use EPM, etc.)

         -        Other information as necessary to provide the highest level of
                  customer service

         4.2 BILLING

         Billing will be done either directly by AuthentiDate, through certified
         partners, or through the use of credit cards by selected banking
         partners

                  -        Direct Billing by AuthentiDate

                           AuthentiDate will invoice the partner/user pursuant
                           to the agreement between USPS and the partner/user

                  -        Credit Card Billing

                           When offered, credit card payments will be settled by
                           the collecting bank in accordance with an agreement
                           with that bank, the terms of which shall be mutually
                           acceptable to AuthentiDate and USPS. . AuthentiDate
                           shall forward reports to USPS pursuant to the
                           Alliance Agreement between the parties.

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<PAGE>
                                                                   EXHIBIT 10.23

                  -        Partner Billing

                           Partner billing will conform to the agreement between
                           USPS and the partner.

         4.3 REVENUE COLLECTION

             Revenue collection for the USPS EPM direct invoice customers will
             be collected according to the terms and conditions as stated in the
             EPM Sales Contract. Revenue collected for credit card sales will be
             forwarded to the Alliance according to the terms negotiated with
             the partner bank. Notwithstanding the foregoing, all revenue
             collection and distribution shall comply with the Alliance
             Agreement between the parties.

         4.4 REVENUE DISTRIBUTION

             The revenue collected from users of the USPS EPM will be split and
             distributed in accordance with the Alliance Agreement between the
             parties.

5.0 REPORTING

Management reports will be produced by Authentidate and made available to USPS
and the EPM Advisory Committee to track SLA TIER 2 service metrics as outlined
in section 2.4.4 of this document. The management reports must be available no
later than the 5th business day of each month.

Additional reports will be produced by Authentidate and made available to the
USPS EPM program manager (or designee) which summarize the following:

         -        Open tickets report by week, month, and year.

         -        Closed tickets report by week, month, and year.

         -        Escalation report

         -        Call wait times report

         -        Service response time

         -        New Customers

         -        Transactions Processed

         -        Alliance Revenue by month, and YTD

         -        Customer Satisfaction Survey Score by month and YTD

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                                                                   EXHIBIT 10.23

6.0 SERVICE LEVEL METRICS

                  1) [ * * * * ]

                  2) [ * * * * * ] closure on customer calls within timeframes
                  based on severity level.

                  3) Degradation of service not to [ * * * * ]averaged over a [
                  * * * *] (turnaround from time hash received to hash
                  transmitted w/in AD facility).

                  4) Registration pages for EPM services and the purchase of
                  additional EPMs - [ * * * * ] starting at service launch date.

                  5) Billing - Invoicing, credit card settlements, and partner
                  billing will occur within 2 days of scheduled date an average
                  of [ * * * * ] over a [ * * * * ] period starting at service
                  launch date. Invoicing error rate no more than [ * * * * ] of
                  total invoices processed over [ * * * * ]starting at service
                  launch date.

                  6) Revenue Distribution - The revenue will be distributed
                  within 2 days of receipt of funds an average of [ * * * * * ]
                  over a [ * * * * ] starting at service launch date.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

7.0 CONFLICT

         In the event of a conflict between this SLA and the Alliance Agreement
         between the parties. The terms of the Alliance Agreement govern and
         supersede the terms of this SLA.

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                                                                   EXHIBIT 10.23

APPENDIX A: EPM CALL FLOW

[FLOW CHART GRAPHIC]

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                                                                   EXHIBIT 10.23

APPENDIX B: MANAGEMENT NOTIFICATION

                          USPS MANAGEMENT NOTIFICATION

NOTIFICATION LEVEL: Manger, Business Development
         NAME: [ * * * * ]
         PHONE: [ * * * * *]
         PAGER: [ * * * * *]
         RESPONSE TIME: 15 minutes, re-page

NOTIFICATION LEVEL: Project Manager
         NAME: [ * * * * ]
         PHONE: [ * * * * ]
         CELL: [ * * * * ]
         RESPONSE TIME: 15 minutes, re-page; 15 minutes, escalate

                      AUTHENTIDATE MANAGEMENT NOTIFICATION

NOTIFICATION LEVEL: Operations
         NAME: [ * * * * ]
         PHONE: [ * * * * ]
         CELL PHONE: [ * * * * ]
         PAGER: [ * * * * ]
         RESPONSE TIME: 15 minutes, re-page; 15 minutes, escalate

NOTIFICATION LEVEL:  Chief Technology Officer
         NAME: [ * * * * ]
         PHONE: [ * * * * ]
         CELL PHONE: [ * * * * ]
         PAGER: [ * * * * ]
         RESPONSE TIME: 15 minutes, re-page; 15 minutes, escalate

NOTIFICATION LEVEL: AuthentiDate CEO
         NAME: [ * * * * ]
         PHONE: [ * * * * ]
         CELL PHONE: [ * * * * ]
         RESPONSE TIME: 15 minutes, re-page

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

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                                                                   EXHIBIT 10.23

APPENDIX C: ACRONYMS

24X7          24 hours a day, 7 days a week
BIA           Business Impact Assessment
BPL           Business Project Leader
C/CM          Change/Configuration Management
CAPS          Centralized Account Processing System
CCO           Customer Care Operations
CICS          Customer Information Control System
CMB           Change Management Board
COSC          Computer Operations Service Center
COTS          Commercial Off The Shelf
CSS           Content Smart Switches
DNS           Domain Name Server
DR            Disaster Recovery
DSSC          Distributed Systems Service Center
EDI           Electronic Data Interchange
EIT           Electronic and Information Technology
EJB           Enterprise Java Beans
EPM           Electronic PostMark(R)
EST           Eastern Standard Time Zone
FAQS          Frequently Asked Questions
FTP           File Transfer Protocol
HQ            Headquarters
IBSSC         Integrated Business Systems Solutions Center
IDMS          Integrated Database Management System
IT            Information Technology
LAN           Local Area Network
NISS          National Information Security Systems
POC           Point of Contact
RMI           Remote Method Invocation
RTO           Recovery Time Objective
SLA           Service Level Agreement
SOAP          Simple Object Access Protocol
TRID          Transaction Identification Designators
URL           Uniform Resource Locator
US            United States
USPS          United States Postal Service

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                                                                   EXHIBIT 10.23

                                    Exhibit E

                              TECHNICAL DESCRIPTION

                        USPS ELECTRONIC POSTMARK(R) (EPM)

USPS EPM is a content integrity and time and date service. The service uses [ *
* * * ] to provide trusted proof of the content of any digital file as of a
specific point in time.

The service includes:

    -    Access to the USPS EPM Central Server for applying a [ * * * * ],
         storage of [ * ** * ], and centralized [ * * * * ]. Each transaction
         consists of the [ * * * * ].

    -    License to use two client-side [ * * * * ] that allow any electronic
         file, group of files, or memory object to be submitted to the EPM
         process (described below). Both of these [ * * * * ] contain two
         primary functions - [ * * * * ]

              o   [ * * * * ] to seamlessly integrate the USPS EPM process into
                  [ * * * * ]e.

              o   A [ * * * * ] to integrate the [ * * * * ].

EPM PROCESS DESCRIPTION

There are two primary processes:

THE EPM PROCESS

When a file is submitted to the EPM process, first a [ * * * * ] of the file is
produced. In an EPM transaction the [ * * * * ] by the requestor and then sent
to the Central Server where the [ * * * * ] in the USPS EPM Central Server
database for [ * * * * ]. This proves WHAT file(s) were submitted for
Postmarking and WHEN. If signed by the requestor, with a certificate acceptable
to USPS, the transaction identifies WHO hashed the original file as well and the
signing certificate will be checked for validity. A Transaction ID is returned
that uniquely identifies the stored transaction. Using the Transaction ID, a [ *
* * * ] receipt can be retrieved and stored locally that contains the [ * * * *
] issued by the USPS EPM Central Server.

THE EMP [* * * *]

EPM [* * * *] can be done in 3 ways.

104

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

<PAGE>
                                                                   EXHIBIT 10.23

    1)   [ * * * * ] - If the receipt is [ * * * * ], it can be
         used [ * * * * ] the file has not been altered since the
         receipt was created. No connection is needed to [ * * * * ] .

    2)   [ * * * * ] - If the receipt is [ * * * * ], it can be submitted
         to [ * * * * ] that neither the original file nor the receipt
         has been altered, since they were created by the USPS EPM Central
         Server . If only the [ * * * * ] has been stored [ * * * * ], it can be
         used to pull the receipt down as needed from the USPS EPM Central
         Server and then a [ * * * *] can be performed. If the transaction was
         signed, using a certificate acceptable to USPS, then the [* * * *]
         includes [ * * * * ].

    3)   [ * * * * ] - If only the [ * * * * ] has been [ * * * * ], its
         hash code is calculated [ * * * * ]to the [ * * * * ]. A lookup is then
         performed in the USPS EPM Central Server for any published transaction
         that has a [ * * * * ]. The [ * * * * ] of all matching transactions
         will be returned.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

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                                                                   EXHIBIT 10.23

                                    EXHIBIT F
                                 SALES CONTRACT

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<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT G
                           LIST OF EXISTING CUSTOMERS

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<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT G
                           LIST OF EXISTING CUSTOMERS

                                    [ **** ]

 [* Certain information on this page has been omitted and filed separately with
 the Commission. Confidential treatment has been requested with respect to the
                               omitted portions.]

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                                                                   EXHIBIT 10.23

                                    EXHIBIT H
                          ADVISORY COMMITTEE GUIDELINES

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<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT H

                          ADVISORY COMMITTEE GUIDELINES

                                  CONFIDENTIAL

                          ADVISORY COMMITTEE GUIDELINES

The following guidelines shall apply to The Advisory Committee ("Committee")
meetings ("Meetings") held pursuant to the Alliance Agreement ("Agreement"),
between the United States Postal Service ("USPS"), AuthentiDate, Inc. ("AD")
Holding Corp. and Authentidate Holding Corp. (hereinafter AD and USPS are
sometimes together referred to as "Parties")

A.   MEMBERSHIP

1.   The Committee shall be composed of [ * * * * ].

2.   [ * * * * ].

B.   MEETINGS

     1.   Unless otherwise agreed by the Parties, [ * * * * ] Individual members
          may participate in meetings through a telephonic hookup.

     2.   Unless otherwise agreed to by the Committee [ * * * * ].

     3.   Upon agreement of the Committee, [ * * * * ].

     4.   Upon agreement of the Committee[ * * * * ].

C.   QUORUM

     1.   A quorum [ * * * * ].

     2.   [ * * * * ].

D.   VOTING

     1.   Each Party shall [ * * * * ]

     2.   If fewer [ * * * * ].

     [ * Certain information on this page has been omitted and filed separately
     with the Commission. Confidential treatment has been requested with respect
     to the omitted portions.]

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                                                                   EXHIBIT 10.23

D.   CHAIR

     1.   Each meeting [ * * * * ].

     2.   The Chair is responsible for [ * * * * ].

E.   SUBCOMMITTEES

     1.   From time to time the Committee may [ * * * * ].

     2.   Unless agreed to by the Committee, [ * * * * ].

     3.   In establishing a subcommittee, [ * * * * ].

F.   GUESTS

     1.   Upon agreement by the Committee [ * * * * * ]

G.   AGENDA

     1.   An agenda [ * * * * ].

     2.   It is the responsibility of the Chair [ * * * * ]

     3.   The agenda shall contain [ * * * * ].

H.   REPORTS

     1.   The Committee shall [ * * * * ].

     2.   Special reports [ * * * * ].

I.    ACTIONS & TASKS

     1.   All proposed actions to be taken by the Committee and all proposals
          for tasks to be performed for the Committee [ * * * * ]

     2.   Unless otherwise specified in an agreement of the Parties, [ * * * * ]

     3.   No tasks can be assigned [ * * * * ].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

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                                                                   EXHIBIT 10.23

J.   NOTES & MINUTES

     1.   The Chair for each meeting [ * * * * ].

     2.   The Chair shall also be responsible for [ * * * * ].

     3.   The Chair shall [ * * * * ]

     4.   The Chair will [ * * * * ]

     5.   All minutes shall [ * * * * ].

K.   RESOLUTION OF DISPUTES

     1.   The Committee may [ * * * * ].

L.   SCOPE OF COMMITTEE ACTION

     1.   The Advisory Committee shall [ * * * * ]. The Advisory Committee shall
          [ * * * * ] . The Advisory Committee may [ * * * * ].

     2.   The performance management program shall:

          a.   [ * * * * ]

          b.   [ * * * * ].

          c.   [ * * * * ].

          d.   [ * * * * ].

     3.   The marketing management program shall:

          a.   [ * * * * ]

          b.   [ * * * * ]

          c.   [ * * * * ]

2.   The Committee may also [ * * * * ].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

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                                                                   EXHIBIT 10.23

                                    EXHIBIT I

                         USPS TRADEMARK USAGE GUIDELINES

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                                                                   EXHIBIT 10.23

                                    EXHIBIT I

                           MARKS AND USAGE GUIDELINES

    -    AD may use USPS Marks solely on the EPM Web Pages, and in related
         advertising, marketing, and collateral materials, solely as approved by
         USPS in writing, and insofar as the use is consistent with this
         Agreement.

    -    USPS's name, logo, or trademark must appear on all USPS EPM materials.
         AD's name, logo, or trademark may be used in web-pages and advertising
         related to the EPM in accordance with Section 3.01 of this Agreement,
         as may be approved by USPS, which approval will not be unreasonably
         withheld.

    -    USPS Marks may not be used in any manner that expresses or might imply
         USPS's affiliation, sponsorship, endorsement, certification, or
         approval, other than as contemplated by this Agreement.

    -    AD shall not use USPS Marks in association with any third party
         trademarks in a manner that might suggest co-branding and/or
         co-marketing with the third party or is otherwise likely to create
         confusion as to source or sponsorship of the USPS EPM Service, or
         ownership of USPS Marks.

    -    USPS Marks may not be incorporated into or used as part of any non-USPS
         trade name, business name, domain name, product or service name, logo,
         trade dress, design, slogan, or other trademark. This restriction
         applies whether the USPS Mark(s) are used alone or are combined with
         any other symbols, be they words, logos, icons, graphics, photos,
         slogans, numbers, or other design elements.

    -    AD may use the USPS logo only in the forms provided by USPS
         electronically or in hard copy. Except for size and subject to the
         restrictions herein, the logo may not be altered in any manner, be it
         in proportion, color, movement, element, etc., or animated, morphed, or
         otherwise distorted in perspective or dimensional appearance.

    -    The USPS logo must stand alone. A minimum amount of empty space must
         surround the logo, separating it from any other object, such as type,
         photography, borders, edges, and so on. The amount of empty space
         around the logo must be 2x, where x equals the distance from the top of
         the angled box to the top of the Eagle's back on the logo.

         USPS Marks must include the appropriate (R) or (TM) symbol as they
appear in accordance with the materials that have been provided, at least at the
first and most prominent mention on each visually distinguishable page (or Web
Page) of material. All of the United States Postal Service marks of any kind
must be used without any alterations. The first use of the trademarks in copy
must be designated by a (R), TM, or SM, as appropriate. When the used within
text of the marketing and communications materials the proper symbol place at
the end in the right-hand corner as indicated below. The TM and (R) should be
set in Helvetica or Arial.

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                                                                   EXHIBIT 10.23

UNITED STATES POSTAL SERVICE (R)

U.S. POSTAL SERVICE(TM)

POSTAL SERVICE(TM)

USPS(TM)

UNITED STATES POST OFFICE(R)

POST OFFICE(TM)

When using the corporate signature on signage, billboards, or any large display,
be sure to enlarge the r proportionately to the size of the signature used. The
(R) must not exceed the height of the lower bar (1/2 inch or larger) of the "E."

However, when the corporate signature is reduced to the minimum size (7/32 inch
up to 3/8 inch), the (R) should be replaced with the legal phrase below in an
appropriate place.

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                                                                   EXHIBIT 10.23

                                    Exhibit J
                                ALLIANCE METRICS

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<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT J

                              EPM ALLIANCE METRICS

Definitions

EFFECTIVE DATE - The date of signature of the last party to sign the "STRATEGIC
ALLIANCE AGREEMENT BETWEEN AUTHENTIDATE HOLDING CORP., AUTHENTIDATE, INC. AND
THE UNITED STATES POSTAL SERVICE REGARDING THE USPS ELECTRONIC POSTMARK(R)
SERVICE" ("Alliance Agreement"). ("Effective Date" is defined in 2.08, Alliance
Agreement.)

SERVICE LAUNCH DATE - The date on which the EPM System is made available to the
public pursuant to the Alliance Agreement. ("Service Launch Date" is defined in
Section 2.24, Alliance Agreement)

MEASUREMENT START DATE - Commencement of the measurement period for the metric
in question.

METRIC #1 - SERVICE LAUNCH DATE

Tracks the [ * * * *].

The Service Launch Date is within 120 days after the Effective Date, provided
that the requirements of Section 9.02 of the Alliance Agreement are met.

Approval of Launch Plan is within 30 days of the Effective Date, as set forth in
Section 9.02 of the Alliance Agreement.

Approval of the Service Launch Date is within ninety (90) days of the Effective
Date, provided, however, [ * * * * ] Failure of AD to implement the Information
Security Requirements to the satisfaction of USPS [ * * * *] of the Effective
Date, shall constitute a Breach of Alliance Metrics, and shall be cause for
termination of the Alliance Agreement in accordance with Section 9.03 of the
Alliance Agreement.

METRIC #2 - CUSTOMER SATISFACTION

Tracks customer satisfaction. Surveys will be conducted [ * * * * ] with a
follow-up survey [ * * * * ] later. Additional follow-up surveys are conducted [
* * * * ]. The average score of the surveys [ * * * * ] over time.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

USPS and Authentidate will jointly develop a customer survey based on industry
best practices. The concept of "Top box scores" will be used to manage the
desired results from the customer survey. The survey will be based on diagnostic
questions that

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<PAGE>
                                                                   EXHIBIT 10.23

provide focus on areas of the EPM service that require improvement to drive a
higher level of customer satisfaction. Overall weighting of "top box scores"
will be based on [ * * * * ] responses to each survey. Each survey will use the
following set of standard responses.

[ * * * * ]

A score of [ * * * * ] means that [ * * * * ] of all respondents to the survey
during the specified time period rated their overall experience as either [ * *
* * ].

Measurement Start Date is date of first customer install.

    -    "Top Box Score" at first anniversary after Service Launch Date must [ *
         * * * ].

    -    "Top Box Score" at second anniversary after Service Launch Date must [
         * * * * ]

    -    "Top Box Score" at third anniversary after Service Launch Date must be
         [ * * * * ]

Customer Satisfaction will be reported [ * * * * ] to gain regular insight into
progress towards meeting these standards.

Failure to accomplish the standard constitutes a Breach of Alliance Metrics as
set forth in Section 21.02 of the Alliance Agreement and results in the start of
a 6 month cure period. [ * * * * ] Therefore, any slippage that [ * * * * ] also
moving to meet the next progressive service standard.

METRIC #3 - RECOGNIZABLE REVENUE ATTAINMENT

Tracks revenue of Electronic PostMark(R) service. Revenue is recognized upon [ *
* * * ]. Tracking begins [ * * * * ] after the Service Launch Date.

Billing level at end of 1st 12 months - [ * * * * ]

Billing Level at end of 18 months - [ * * * * ]

Billing Level at end of 24 months - [ * * * * ]

Billing Level at end of 30 months - [ * * * * ]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

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<PAGE>
                                                                   EXHIBIT 10.23

Failure to accomplish a required revenue attainment billing level within the
time period set forth above constitutes a Breach of Alliance Metrics as set
forth in Section 21.02 of the Alliance Agreement and results in the start of a 6
month cure period. A slippage in [ * * * * ] does not reset expectations for [ *
* * * ]. Therefore, any slippage that has to be [ * * * * ] in addition to also
moving [ * * * * ].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

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                                                                   EXHIBIT 10.23

                                    EXHIBIT K

                              CONCEPT OF OPERATIONS

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                                                                   EXHIBIT 10.23

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<PAGE>
                                                                   EXHIBIT 10.23

                                  AUTHENTIDATE
                           CONCEPT OF OPERATIONS PLAN

                               [AUTHENTIDATE LOGO]

                      Author:                     R. Visnov
                      Creation Date:              Mar. 12, 2002
                      Last Updated:               May. 29, 2002
                      Version:                    Draft

                  CONTROL NUMBER and VERSION are marked by a Word Bookmark so
                           that they can be easily reproduced in the header and
                           footer of documents. When you change either of these
                           values, be careful not to accidentally delete the
                           bookmark. You can make bookmarks visible by selecting
                           Tools->Options...View and checking the Bookmarks
                           option in the Show region.

                     APPROVALS:

To add additional approval lines, Press [Tab] from the last cell in the table
above.

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<PAGE>
                                                                   EXHIBIT 10.23

DOCUMENT CONTROL

CHANGE RECORD

<TABLE>
<CAPTION>
DATE          AUTHOR                 VERSION   CHANGE REFERENCE
----          ------                 -------   ----------------
<S>           <C>                    <C>       <C>
03/15/2002    R. Visnov              1         Initial Document
5/29/2002     R Visnov               2

</TABLE>

REVIEWERS

<TABLE>
<CAPTION>
NAME                                              POSITION
----                                              --------
<S>                                               <C>
ADUS Operations Team
ADUS Development Team

</TABLE>

DISTRIBUTION

<TABLE>
<CAPTION>
COPY NO.     NAME                                      LOCATION / POSITION
--------     ----                                      -------------------
<S>          <C>                                       <C>
1            Robert Van Naarden                        CEO
2            ADUS Ops. Team                            NY
3            ADUS Dev. Team                            NY
4
</TABLE>

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<PAGE>
                                                                   EXHIBIT 10.23

CONTENTS
<TABLE>
<S>       <C>                                                                                                                <C>
1    Overview................................................................................................................125
   1.1    DOCUMENT PURPOSE...................................................................................................125
   1.2    SCOPE..............................................................................................................126
   1.3    STAFF GROUPS.......................................................................................................127
2    Data Center Operations..................................................................................................128
   2.1    OPERATING SYSTEM ADMINISTRATION....................................................................................128
   2.2    DATABASE ADMINISTRATION............................................................................................129
   2.3    HARDWARE MAINTENANCE AND REPAIR....................................................................................129
   2.4    THIRD-PARTY PACKAGED SYSTEMS.......................................................................................130
   2.5    COMMUNICATIONS SERVICES............................................................................................130
3    Physical Security.......................................................................................................130
   3.1    DATA CENTER PHYSICAL SECURITY......................................................................................130
   3.2    OFFICE ENVIRONMENT PHYSICAL SECURITY...............................................................................131
4    Network Security and Monitoring.........................................................................................131
   4.1    FIREWALL AND NETWORK DEVICES ......................................................................................
   4.2    SYSTEM MONITORING..................................................................................................132
   4.3    INTRUSION DETECTION................................................................................................132
5    Backup, Recovery and Archiving..........................................................................................132
   5.1    BACKUP AND RECOVERY................................................................................................132
   5.2    EXTERNAL STORAGE...................................................................................................133
6    Incident Response, Tracking and Reporting...............................................................................133
   6.1    INCIDENT AWARENESS, COMMUNICATION AND ESCALATION...................................................................133
   6.2    INCIDENT TRACKING , REPORTING AND FOLLOWUP.........................................................................134
7    Software Development Life Cycle.........................................................................................134
   7.1    PROJECT INITIATION AND APPROVAL....................................................................................134
   7.2    SCOPING ...........................................................................................................
   7.3    SOFTWARE LIFE CYCLE................................................................................................135
8    Software and Data Security..............................................................................................135
   8.1    VERSION CONTROL....................................................................................................135
   8.2    ACCESS CONTROL.....................................................................................................135
   8.3    [ * * **  ]........................................................................................................135
9    Change Control / Change Management......................................................................................135
   9.1    RELEASE MANAGEMENT.................................................................................................135
   9.2    APPROVAL, TRACKING AND REPORTING...................................................................................136
10      Office Network Operations............................................................................................136
   10.1      [ * * * * ] ....................................................................................................
</TABLE>

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

124
<PAGE>
                                                                   EXHIBIT 10.23

       1. Overview

1.1 Document Purpose

         AuthentiDate Inc. develops and maintains an Internet-based service for
         electronic non-repudiation and legal electronic signing. AuthentiDate's
         applications and the operation that supports them must meet the highest
         standards of reliability and performance. The purpose of this Concept
         of Operations Plan is to summarize AuthentiDate's technical and
         operational processes and indicate where responsibility lies for their
         implementation.

         Suggestions as to corrections and/or improvements are greatly
         appreciated and should be directed to the author [ * * * * ].

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

125
<PAGE>
                                                                   EXHIBIT 10.23

            1.2 SCOPE

         The following areas are addressed:

                  -        DATA CENTER OPERATIONS: [ * * * * ]

                  -        PHYSICAL SECURITY: [ * * * * ]

                  -        NETWORK SECURITY AND MONITORING: [ * * * * ]
                  -        BACKUP, RECOVERY AND ARCHIVING: [ * * * * ]

                  -        INCIDENT RESPONSE, TRACKING AND REPORTING:
                           [ * * * * ]

                  -        SOFTWARE DEVELOPMENT LIFE CYCLE: [ * * * * ]
                  -        SOFTWARE AND DATA SECURITY: [ * * * *].

                  -        CHANGE CONTROL / CHANGE MANAGEMENT [ * * * * ]
                  -        OFFICE NETWORK OPERATIONS: [ * * * * ]

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

126
<PAGE>
                                                                   EXHIBIT 10.23

         1.3 STAFF GROUPS

         AuthentiDate technical staff consists of two primary groups, Operations
         and Development. There are also external groups who provide operational
         services.

                  -        OPERATIONS

                           The operations team includes staff responsible [ * *
                           * * ]. The operations team includes both full-time
                           staff and contract professionals, and serves as the
                           first tier response team for incidents.

                  -        DEVELOPMENT

                           The development team is responsible for the design
                           and development of AuthentiDate's application code.
                           This includes [ * * * * ]. Developers are the second
                           tier response team for application-related incidents.
                           This team consists of people fulfilling the following
                           roles: [ * * * * ]. Some team members are contract
                           professionals also.

                  -        [ * * * * ] SECURITY MONITORING AND MANAGED SERVICES
                           PROVIDER (MSP)

                           In order to provide a high service level,
                           AuthentiDate is [ * * * * ]. This is needed in order
                           to assure round-the-clock availability of the
                           AuthentiDate service.

                           AuthentiDate will [ * * * * ], and an [ * * * * ].
                           Both [ * * * * ] will be under the direction of the
                           AD Ops team.

                           It will be the responsibility of the [ * * * * ] to
                           provide [ * * * * ] directly, including direct
                           administrative tasks, depending on severity, time of
                           day and other considerations.

                           Specifications and quotations for the [ * * * * ]
                           that AuthentiDate is reviewing may be provided on
                           request. It is expected that an [ * * * * ].

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

127
<PAGE>
                                                                   EXHIBIT 10.23

                  -        [ * * * * ]STAFF

                           A key partner company of AuthentiDate is [ * * * * ],
                           which provides specialized [ * * * * ] for the
                           generation of [ * * * * ] based on time provided by [
                           * * * * ]. [ * * * * ]servers are tamper-proof
                           enhanced [ * * * * ] that reside in the [ * * * * ]
                           other servers, and they are in communication with [ *
                           * * * ]for audit purposes through dedicated
                           communication channels.

                           While it is the responsibility of AuthentiDate staff
                           to provide normal maintenance of the [ * * * * ]
                           servers, there are certain forms of maintenance that
                           need to be done by [ * * * * ] staff. Therefore, [ *
                           * * * ] operational staff acts as another outsourced
                           operational resource with certain rights of access to
                           the AuthentiDate production environment.

                  -        [ * * * * ] CENTER

                           Currently AuthentiDate maintains [ * * * * ] data
                           center in the U.S. located at [ * * * * ] colocation
                           network operation center (NOC) environment at [ * * *
                           * ]. This hosting environment provides power, air
                           conditioning, communication, backup environmental
                           systems and physical security. On an emergency basis,
                           [ * * * * ] NOC staff will if necessary provide
                           controlled system and network administration tasks.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

2 DATA CENTER OPERATIONS

         2.1 OPERATING SYSTEM ADMINISTRATION

         AuthentiDate Operations (Ops) team personnel are responsible for
         administration and service of server operating systems including

                  -        [ * * * * ]

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

128
<PAGE>
                                                                   EXHIBIT 10.23

         The EPM Service is a 24 X 7, round the clock service. Maintenance and
         administration will be performed by AD Ops personnel [ * * * * ]. At
         all other times maintenance and administration will be performed by [ *
         * * * ] personnel, under the direction of the AD Ops team. Furthermore,
         on an emergency basis the [ * * * *] NOC staff may perform rapid
         administrative tasks. Any non-routine maintenance undertaken by all
         parties will be captured in AuthentiDate's incident reporting system,
         described in Section 6.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

         In addition, the Ops team will direct the administration of [ * * * * ]
         network gear as needed through outsourced network services.

         Normal maintenance occurs during off-peak scheduled maintenance
         windows, which time will depend on the criticality and production
         status of the system being maintained. The [ * * * * ] will determine
         the specific appropriate normal maintenance schedule.

         2.2 DATABASE ADMINISTRATION

         The Authentidate Ops team will provide database administration (DBA)
         tasks, including [ * * * * ] The Ops team includes a staff member
         dedicated to database administration.

         On an emergency basis, database administration will be performed by
         development team members or staff of the outsourced managed serviced
         provider.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

         2.3 HARDWARE MAINTENANCE AND REPAIR

         AuthentiDate maintains service agreements with hardware vendors that
         provide for repair and support. For routine tasks, the Ops team will
         maintain hardware, calling on the vendor for cases where there is a
         problem requiring their specialized knowledge. Normal maintenance will
         occur during predefined off-peak scheduled maintenance windows.

         The [ * * * * ] hardware is a special case. [ * * * * ] and
         AuthentiDate have a support agreement providing for specialized
         software, firmware and hardware technical support.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

129
<PAGE>
                                                                   EXHIBIT 10.23

         2.4 THIRD-PARTY PACKAGED SYSTEMS

         Several third-party packaged products play a key role in the delivery
         of the AuthentiDate production service. These include:

                  -        [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

         Maintenance of these systems is the responsibility of the Ops team. On
         an emergency basis the AuthentiDate development team or the outsourced
         managed services provider may do maintenance on these systems, under
         the direction of Ops staff. When this occurs, these events will be
         captured in AuthentiDate's incident reporting system, described in
         Section 6.

         2.5 COMMUNICATIONS SERVICES

         Communications services such as:

                  -        [ * * * * ]

         are critical for notification of incidents and recovery processes. It
         is the responsibility of the Ops team to maintain these services.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

3 PHYSICAL SECURITY

         3.1 DATA CENTER PHYSICAL SECURITY

         It is the responsibility of [ * * * * ], whose colocation facility
         hosts AuthentiDate's site, to provide physical security and access
         control. The [ * * * * ] NOC is highly secure.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

130
<PAGE>
                                                                   EXHIBIT 10.23

                  -        Access to the facility is controlled from a separate
                           location. Only authorized AuthentiDate staff may
                           modify the access list, through a ticketing process
                           with a record.

                  -        Servers are located in a locked and separated cage,
                           with access controlled by the NOC staff

                  -        All visitors are escorted to the cage by NOC staff.

         3.2 OFFICE ENVIRONMENT PHYSICAL SECURITY

         AuthentiDate's office is currently located in 2 World Financial Center,
         also the world headquarters of Merrill Lynch. Because it is the
         headquarters of a major financial service firm, this building is one of
         the most secure office buildings in New York.

                  -        Employees have photo IDs which are tightly managed.

                  -        Guest visits must be arranged with the guard desk by
                           AuthentiDate staff or guests will not be allowed
                           access. Guests wear identification tags, good for a
                           predefined length of time.

                  -        Since the disaster at the nearby World Trade Center,
                           screening has tightened further so that both guests
                           and employees are X-rayed on entry.

4 NETWORK SECURITY AND MONITORING

         4.1 [ * * * * ]

         The AuthentiDate Ops team will administer network devices, including [
         * * * * ]. Currently there is [ * * * * ] on the Ops team dedicated to
         network and security administration during business hours.

         The network configuration is [ * * * * ].

         On an emergency basis, network administration will be performed by
         development team members or staff of the outsourced managed serviced
         provider. When this occurs, these events will be captured in
         AuthentiDate's incident reporting system, described in Section 6.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

131
<PAGE>
                                                                   EXHIBIT 10.23

         4.2 SYSTEM MONITORING

         AuthentiDate has licensed the third-party monitoring package [ * * * *
         ] from [ * * * * ]. [ * * * * ] continuously monitors the status of all
         servers and collects them in a utility server at the data center. At
         any time [ * * * * ] displays a comprehensive diagnostic image of the
         current status of all monitored systems. When [ * * * * ] detects an
         error or warning condition a message will be sent via email to a
         mailing list, which may include operation's pagers.

         In addition, AuthentiDate is negotiating with several [ * * * * ],
         including those who specialize in security monitoring, to provide
         system monitoring services. It is expected that they will install
         separate monitoring services in the hosted environment.

         4.3 INTRUSION DETECTION

         AuthentiDate is negotiating with [ * * * * ] to become the outsourced
         provider of security monitoring and intrusion detection services. When
         this arrangement is implemented, [ * * * * ] will provide dedicated
         "black boxes" in the [ * * * * ] center which will perform intrusion
         detection and security monitoring. [ * * * * ] staff will notify
         AuthentiDate's Ops team of any security incidents according to a
         predefined escalation policy, and also provide reporting on a regular
         basis.

         In addition, AuthentiDate's Ops team will perform security sweeps
         directly on a regular basis. AuthentiDate is evaluating intrusion
         detection software such as [ * * * * ] and the [ * * * * *] , as well
         as the open source package [ * * * * ].

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

5 BACKUP, RECOVERY AND ARCHIVING

         5.1 BACKUP AND RECOVERY

         Backup and recovery is the responsibility of the Operations team.

         Backup is currently being migrated from a managed backup solution
         provided by [ * * * * ] to [ * * * * ] procedure. A [ * * * *] library
         has been purchased and [ * * * * ].

         All production [ * * * * ] are backed up using [ * * * * ]. In
         particular, we will be using the [ * * * * ] to allow hot,
         non-disruptive backups of the live database.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

132
<PAGE>
                                                                   EXHIBIT 10.23

         5.2 EXTERNAL STORAGE

         Offsite storage of backup tapes is provided by [ * * * * ], located at
         [ * * * * ]. Tapes are retrieved through a 24 X 7 service [ * * * * ].

6 INCIDENT RESPONSE, TRACKING AND REPORTING

         6.1 INCIDENT AWARENESS, COMMUNICATION AND ESCALATION

         Incidents at the production site may be first reported in any of
         several different ways:

         -        Monitoring software may respond to a trap and forward a
                  message to an email mailing list, which in turn forwards to a
                  set of pagers.

         -        Devices managed by [ * * * * ] may raise an alarm.

         -        An error may become visible to a staff member.

         -        An error may become visible to a customer who reports it to
                  the AuthentiDate customer service area.

         Primary responsibility rests with the Ops team. This does not mean
         however that they directly act on all incidents. The [ * * * * ] will
         have a run book developed by them and the Ops team, and it is expected
         that many incidents will be handled routinely by { * * * * ].

         For severe errors not manageable by the [ * * * * ], their staff will
         notify AuthentiDate Ops personnel, who will directly evaluate the
         incident.

         -        The problem may be within the direct responsibility of the Ops
                  team. For example it could be at the operating system,
                  hardware or third-party package level. In this case the Ops
                  team will deal with the problem directly.

         -        It may also involve communication or other issues involving [
                  * * * * ] hosting environment. In this case the Ops team will
                  work directly with NOC personnel on a repair.

         -        Finally, the Ops team may determine that an incident may be
                  due to an unforeseen application failure requiring the
                  assistance of members of the development staff. In this case
                  developers will be contacted via phone or pager to repair the
                  problem.

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

133
<PAGE>
                                                                   EXHIBIT 10.23

         6.2 INCIDENT TRACKING , REPORTING AND FOLLOWUP

AuthentiDate uses a [ * * * * ] project tracking tool [ * * * * ] for [ * * * *
]. This tool allows incident tasks to be assigned, discussed, escalated and
reported on later. It will also serve as a document repository and a knowledge
base for retaining information on incidents.

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

7 SOFTWARE DEVELOPMENT LIFE CYCLE

         7.1 PROJECT INITIATION AND APPROVAL

         Software and service development projects come about as a result of
         product discussions held frequently within AuthentiDate. There is a
         regularly scheduled product meeting where members of the Business
         Development, Marketing, Sales and Development staffs review
         opportunities, current projects and new development proposals.

         This group is the approving body for major development projects. Minor
         projects may initiate within the technical team for the purpose of
         improving performance or other straightforward benefit.

         7.2 REQUIREMENTS DEFINITION

         Once a project is approved, a development team member is assigned to
         create a requirements document outlining the nature of the document. At
         the same time, the DevTrack administrator creates a project environment
         that will be the repository for project tasks and the source of project
         reporting.

         Any development team member may be assigned the task of generating a
         requirements document, and that person will be responsible to confer
         with anyone in the company who can provide needed information.

         Project requirements are reviewed by the development team, development
         management (Director or CTO), partner integration manager and possibly
         others, and approved by development management.

134
<PAGE>
                                                                   EXHIBIT 10.23

            7.3 SOFTWARE LIFE CYCLE

         AuthentiDate follows a typical software life cycle process that
         includes [ * * * * ]

         Source code control [ * * * * ].

8 SOFTWARE AND DATA SECURITY

            8.1 VERSION CONTROL

         Source code control [ * * * * * ]. For reliability [ * * * * ], and
         AuthentiDate makes extensive use of [ * * * * ]. At any time previous
         versions, internally designated Release Candidates, can be reproduced.
         AuthentiDate [ * * * * ], although other static versions for
         demonstration, etc. may be preserved and maintained as well.

            8.2 ACCESS CONTROL

         AuthentiDate's service is at the core a data retention service in which
         non-repudiation records are maintained securely in a database. This
         data is protected by access control and authentication in several
         layers:

                  -        Distributed application layer - [ * * * * ].

                  -        Firewall / network device protection:
                           [ * * * * ].

                  -        Operating system security: [ * * * * ].

                  -        Database level security: [ * * * * ]

            8.3 CODE [ * * * ]

         [ * * * * ]

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

9 CHANGE CONTROL / CHANGE MANAGEMENT

            9.1 RELEASE MANAGEMENT

            AuthentiDate has instituted rigorous policies and procedures for
            change control, including but not limited to documentation, project
            development, task management, situation handling, and source code
            controls. The approach taken is unified from project and feature
            concept inception, and continues in a formal manner through
            development, testing, staging, and ultimately production deployment.
            This same methodology is

135
<PAGE>
                                                                   EXHIBIT 10.23

         applied to exception (bug) logging, resulting in a single, unified
         approach to engineering and support.

         The primary tool for managing releases is [ * * * * * ] described in
         other sections of this document. [ * * * * ] secure [ * * * * ] control
         system with extensive access control features, and good branching and
         tagging abilities. [ * * * * ].

         9.2 APPROVAL, TRACKING AND REPORTING

         The primary tool for managing workflow is [ * * * * ], described in
         other sections of this document. This is a [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

                  -        [ * * * * ]

         It also is highly customizable and comes with a variety of useful
         reports.

         [ * * * * ] capabilities extend to the routing of tasks or other items,
         [ * * * * ].

         [ * Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

10 OFFICE NETWORK OPERATIONS

         10.1 [ * * * * ]

         In addition to their data center responsibilities, AuthentiDate
         Operations staff also is responsible [ * * * * * ]:

                  -        [ * * * * ].

                  -        [ * * * * ].

                  -        [ * * * * *]

                  -        [ * * * * ]

                  -        [ * * * * ]

                  [ * Certain information on this page has been omitted and
                  filed separately with the Commission. Confidential treatment
                  has been requested with respect to the omitted portions.]

136
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT L

                             NONDISCLOSURE AGREEMENT

137
<PAGE>
                                                                   EXHIBIT 10.23

               FIRST AMENDMENT TO MUTUAL NON-DISCLOSURE AGREEMENT

         WHEREAS, the United States Postal Service ("USPS") and AuthentiDate,
Inc. ("AD") entered into the Mutual Non-Disclosure Agreement attached hereto on
May 15, 2001; and

         WHEREAS, USPS and AD desire that AuthentiDate Holding Corp. be bound by
the Mutual Non-Disclosure Agreement, and AuthentiDate Holding Corp. so desires
to be bound;

         NOW THEREFORE, the parties hereto amend said Mutual Non-Disclosure
Agreement as follows:

1.       Paragraph 1 is amended by deleting "May 15, 2001" and substituting
         therefore the Effective Date of the Strategic Alliance Agreement among
         the parties so that the Effective Date of the Strategic Alliance
         Agreement and the Mutual Non-Disclosure Agreement is the same.

2.       Paragraph 2 is amended by deleting the period at the end and adding the
         following: "and AuthentiDate Holding Corp., which has a principal place
         of business at 2165 Technology Drive, Schenectedy, New York 12308.
         Hereinafter, the term "party" refers to USPS as one party, and AD and
         AuthentiDate Holding Corp. together as one party."

3.       Paragraph 7 is amended by deleting "one year after the Effective Date"
         and substituting the following: "prior to and during the Strategic
         Alliance Agreement between the parties."

4.       Paragraph 8 is amended by deleting "Effective Date" and substituting
         "termination of the Strategic Alliance Agreement between the parties."

         IN WITNESS WHEREOF, the parties hereto, intending legally to be bound
         execute this agreement as of the 31st day of July, 2002.

         UNITED STATES POSTAL SERVICE                AuthentiDate, Inc.

         By:___________________________              By:______________________
               Nicholas F. Barranca                         Rob Van Naarden
               Vice President                               President

         AuthentiDate Holding Corp.

         By:___________________________
               President

138
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT M

                        INFORMATION SECURITY REQUIREMENTS

139
<PAGE>
                                                                   EXHIBIT 10.23

                       [UNITED STATES POSTAL SERVICE LOGO]

                                    EXHIBIT M

                        INFORMATION SECURITY REQUIREMENTS

         INFORMATION RESOURCE NAME: AUTHENTIDATE

                                   Version 2.9
                                January 23, 2002

140
<PAGE>
                                                                   EXHIBIT 10.23

REQ.     INFORMATION SECURITY REQUIREMENTS
NO.      (HANDBOOK AS-805, INFORMATION SECURITY REFERENCE)

[ **** ]

[* Certain information on this page has been omitted and filed
         separately with the Commission. Confidential treatment has been
         requested with respect to the omitted portions.]

141

<PAGE>

                                                                   EXHIBIT 10.23

                                    EXHIBIT N
                                WIND DOWN OUTLINE

142
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT N

                                WIND DOWN OUTLINE

The following is a preliminary list of the responsibilities of the Postal
Service and Authentidate, Inc. at the termination of the Strategic Alliance
Agreement:

Postal Responsibilities

    1.   Archive 3 copies of Final Backup Data (To be stored at Eagan, Raleigh,
         HQ).

    2.   Send memo to users outlining Postal intent to discontinue current
         service offering.

    3.   Verify receipt of Customer Data from Authentidate.

    4.   Perform financial analysis of shutdown regarding the reimbursement of
         revenue for services not yet performed.

    5.   Suspend the current EPM Practice Statement.

    6.   Will act in accordance with the provisions of the "Effect of
         Termination" clause, Article XXII, in the "Strategic Alliance Agreement
         Between Authentidate Holding Corp., Authentidate, Inc. and The United
         States Postal Service Regarding The USPS Electronic Postmark Service."

Authentidate Responsibilities

    1.   Perform Final Backup of EPM Customer Data and deliver to Postal
         Service.

    2.   [ **** ]

    3.   [ **** ]

    4.   Perform Final Backup of EPM Transaction Data and deliver to Postal
         Service.

    5.   Develop report to identify pre-paid revenue collected from customers to
         be reimbursed for period of performance whereby services will not be
         performed.

    6.   Send final invoices for any outstanding account balances.

    7.   Make final payment to Postal Service with declaration that no further
         revenue is expected.

    8.   Will act in accordance with the provisions of the "Effect of
         Termination" clause, Article XXII, in the "Strategic Alliance Agreement
         Between Authentidate Holding Corp., Authentidate, Inc. and The United
         States Postal Service Regarding The USPS Electronic Postmark Service."

    The Wind Down/Continuation of Service Plan shall contain provisions for
    continuity of service in the event USPS elects to provide USPS EPM to
    Customers upon termination, or insolvency or bankruptcy of AD or AD Holding
    Corp., including as referenced in Articles XIX and XXIII. The Wind
    Down/Continuation of Service Plan shall ensure that USPS policies governing
    the retirement of information resources are addressed. These policies are
    contained with the AS-805, Section 8-6.5.7 and the ASM Manual, Section 35.

    *Certain information on this page has been omitted and filed separately
    with the Commission. Confidential treatment has been requested with respect
    to the omitted portions.

143
<PAGE>
                                                                   EXHIBIT 10.23

                                    EXHIBIT O
                            SUCCESS RIGHTS AGREEMENT

144
<PAGE>
                                                                   EXHIBIT 10.23

                            SUCCESS RIGHTS AGREEMENT

         This Success Rights Agreement (the "Success Rights Agreement"), is
dated as of the 31st day of July, 2002 (the "Effective Date"), between
Authentidate Holding Corp., a Delaware corporation (the "Company") and the
United States Postal Service (hereinafter referred to variously as the "Holder"
or "USPS").

                              W I T N E S S E T H:

         WHEREAS, the Company, Authentidate, Inc., and USPS have entered into
that certain Strategic Alliance Agreement (the "Alliance Agreement") dated as of
even date herewith, pursuant to which the parties thereto have agreed to develop
and market the USPS Electronic Postmark Service as described and on the terms
and conditions set forth in the Alliance Agreement; and

         WHEREAS, [ **** ]

         WHEREAS, [ **** ]

         NOW, THEREFORE, in consideration of the premises made herein, the
agreements herein set forth, and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

         1. Grant of Warrants. For good and valuable consideration, the receipt
of which is hereby acknowledged by the Company, the Holder or its designees are
hereby [ **** ]:

                  (a) Provided that the Alliance Agreement has not been
                  terminated, and no notice to terminate has been served by
                  either party, commencing on the first anniversary of the
                  Effective Date of the Alliance Agreement [ **** ];

                  (b) Provided that the Alliance Agreement has not been
                  terminated, and no notice to terminate has been served by
                  either party, commencing on the second anniversary of the
                  Effective Date of the Alliance Agreement, [ **** ]

                  (c) Provided that the Alliance Agreement has not been
                  terminated, and no notice to terminate has been served by
                  either party, commencing on the third anniversary of the
                  Effective Date of the Alliance Agreement, [ **** ].

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

145
<PAGE>
                                                                   EXHIBIT 10.23

For purposes of this Agreement, the term "Effective Date" shall mean July 31,
 2002. [ **** ]

         2. [ **** ]

[ * Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.]

         3.1 Method of Exercise. The Warrants initially are exercisable at the
Exercise Price (subject to adjustment as provided in Section 8 hereof) set forth
in Section 1 hereof, payable in cash or by certified or official bank check in
New York Clearing House funds. Upon surrender of a Warrant Certificate with the
annexed Form of Election to Purchase duly executed, together with payment of the
Exercise Price for the shares of Common Stock purchased at the Company's
principal offices (presently located at 2165 Technology Drive, Schenectady, New
York 12308) the registered Holder of a Warrant Certificate shall be entitled to
receive a certificate or certificates for the shares of Common Stock.

         3.2 The purchase rights represented by each Warrant Certificate are
exercisable at the option of the Holder thereof, in whole or in part (but not as
to fractional shares of the Common Stock underlying the Warrants) during any
period in which this Warrant may be exercised as set forth above. Warrants may
be exercised to purchase all or part of the shares of Common Stock. In the case
of the purchase of less than all the shares of Common Stock purchasable under
any Warrant Certificate, the Company shall cancel said Warrant Certificate upon
the surrender thereof and shall execute and deliver a new Warrant Certificate of
like tenor for the balance of the shares of Common Stock purchasable thereunder.

         4. Issuance of Certificates. Upon the exercise of the Warrants, the
issuance of certificates for shares of Common Stock or other securities,
properties or rights underlying such Warrants, shall be made forthwith without
charge to the Holder thereof including, without limitation, any tax which may be
payable in respect of the issuance thereof, and such certificates shall (subject
to the provisions of Sections 5 and 7 hereof) be issued in the name of, or in
such names as may be directed by, the Holder thereof; provided, however, that
the Company shall not be required to pay any tax which may be payable in respect
of any transfer involved in the issuance and delivery of any such certificates
in a name other than that of the Holder and the Company shall not be required to
issue or deliver such certificates unless or until the person or persons
requesting the issuance thereof shall have paid to the Company the amount of
such tax or shall have established to the satisfaction of the Company that such
tax has been paid.

         The Warrant Certificates and the certificates representing the shares
of Common Stock (and/or other securities, property or rights issuable upon the
exercise of the Warrants) shall be executed on behalf of the Company by the
manual or facsimile

146
<PAGE>
                                                                   EXHIBIT 10.23

signature of the then present Chairman or Vice Chairman of the Board of
Directors or President or Vice President of the Company under its corporate seal
reproduced thereon, attested to by the manual or facsimile signature of the then
present Secretary or Assistant Secretary of the Company. Warrant Certificates
shall be dated the date of execution by the Company upon initial issuance,
division, exchange, substitution or transfer.

         5. Restrictions on Transfer of Warrants.

         5.1 Warrant Acquired for Investment. The Holder of a Warrant
Certificate, by its acceptance thereof, covenants and agrees that it has
acquired this Warrant and will acquire the Securities (as defined below) for its
own account for investment and not with a view to the sale or distribution
thereof or the granting of any participation therein, and that it has no present
intention of distributing or selling to others any of such interest or granting
any participation therein. The Holder acknowledges that it has been advised by
the Company that this Warrant and the shares of Common Stock (the "Warrant
Shares") issuable upon exercise thereof (collectively the "Securities") have not
been registered under the Securities Act of 1933, as amended (the "Securities
Act"), that the Warrant is being issued, and the Warrant Shares will be issued,
on the basis of the statutory exemption provided by Section 4(2) of the
Securities Act relating to transactions by an issuer not involving any public
offering, and that the Company's reliance upon this statutory exemption is based
in part upon the representations made by the Holder contained herein. The Holder
acknowledges that he has been informed by the Company of, or is otherwise
familiar with, the nature of the limitations imposed by the Securities Act and
the rules and regulations thereunder on the transfer of securities.

         5.2 Compliance with the Securities Act. In particular, the Holder
agrees that no sale, assignment or transfer of the Securities shall be valid or
effective, and the Company shall not be required to give any effect to any such
sale, assignment or transfer, unless (i) the sale, assignment or transfer of the
Securities is registered under the Securities Act, and the Company has no
obligations or intention to so register the Securities except as may otherwise
be provided herein, or (ii) the Securities are sold, assigned or transferred in
accordance with all the requirements and limitations of Rule 144 under the
Securities Act or such sale, assignment, or transfer is otherwise exempt from
registration under the Securities Act.

         5.3 Legend Requirement. The Holder acknowledges that the Warrant
Certificate and, upon exercise of the Warrants, in part or in whole,
certificates representing the Warrant Shares shall bear a legend substantially
similar to the following:

                  "These securities have not been registered under the
                  Securities Act of 1933. Such securities may not be sold or
                  offered for sale, transferred, hypothecated or otherwise
                  assigned in the absence of an effective registration statement
                  with respect thereto under such Act or an opinion

147
<PAGE>
                                                                   EXHIBIT 10.23

                  of counsel to the Company that an exemption from registration
                  for such sale, offer, transfer, hypothecation or other
                  assignment is available under such Act."

         5.4 Procedure for Permitted Assignment. In addition to its compliance
with the restrictions set forth on the legend of any Warrant Certificate and as
set forth in Sections 5.1 and 5.2 of this Success Rights Agreement, a Holder
seeking to transfer or assign a Warrant Certificate shall surrender the subject
Warrant Certificate, along with a properly executed Assignment Agreement (in the
form of Assignment attached hereto and made a part hereof) at the principal
office of the Company.

         5.5 Permitted Assignments. As authorized by Section 7.02 of the
Alliance Agreement, the Holder is permitted to freely assign this Success Right
Agreement, subject to the existing Securities Laws, to a third party without the
consent of Authentidate Holding Corp. (a "Permitted Assignment").

         6. Exercise Price.

         6.1 Initial and Adjusted Exercise Price. Except as otherwise provided
in Section 8 hereof, the initial exercise price of each Warrant shall be as set
forth in Section 1 of this Agreement. The adjusted exercise price of each
Warrant shall be the price which shall result from time to time from any and all
adjustments of the initial exercise price in accordance with the provisions of
Section 8 hereof.

         6.2 Exercise Price. The term "Exercise Price" herein shall mean the
initial exercise price or the adjusted exercise price, depending upon the
context.

         7. Registration Rights.

         7.1 Piggyback Registration Rights.

         If, at any time commencing after the date hereof the Company proposes
to register any of its securities under the Act (other than in connection with a
merger or acquisition or pursuant to Form S-8 or such successor form) it will
give written notice by registered mail, at least thirty (30) days prior to the
filing of each such registration statement, to the Holder or Holders of the
Warrants and/or the Warrant Shares of its intention to do so. If such Holder or
Holders of the Warrants and/or Warrant Shares notify the Company within ten (10)
days after receipt of any such notice of its or their desire to include any such
securities in such proposed registration statement, the Company shall afford
such Holder or Holders of the Warrants and/or Warrant Shares the opportunity to
have any such Warrant Shares registered under such registration statement.

         The Company shall supply such number of prospectuses and other
documents as the Holder may reasonably request in order to facilitate the public
sale or other disposition of the Warrant Shares, qualify the Warrant Shares for
sale in such states as

148
<PAGE>
                                                                   EXHIBIT 10.23

any such Holder reasonably designates and do any and all other acts and things
which may be necessary or desirable to enable such Holders to consummate the
public sale or other disposition of the Warrant Shares, and furnish
indemnification in the manner as set forth in Subsection 7.2 of this Section 7.
Such Holders shall furnish information and indemnification as set forth in
Subsection 7.2 of this Section 7. For the purpose of the foregoing, inclusion of
the Warrant Shares by the Holder in a Registration Statement pursuant to this
sub-paragraph 7.l under a condition that the offer and/or sale of such Warrant
Shares not commence until a date not to exceed 90 days from the effective date
of such registration statement shall be deemed to be in compliance with this
sub-paragraph 7.l.

         7.2 The following provisions of this Section 7.2 shall also be
applicable to the exercise of the registration rights granted under this Section
7.l:

         (A) The foregoing registration rights shall be contingent on the
Holders furnishing the Company with such appropriate information (relating to
the intentions of such Holders) as the Company shall reasonably request in
writing. Following the effective date of such registration, the Company shall
upon the request of any owner of Warrants and/or Warrant Shares forthwith supply
such number of prospectuses meeting the requirements of the Act as shall be
requested by such owner to permit such Holder to make a public offering of all
Warrant Shares from time to time offered or sold to such Holder, provided that
such Holder shall from time to time furnish the Company with such appropriate
information (relating to the intentions of such Holder) as the Company shall
request in writing. The Company shall also use its best efforts to qualify the
Warrant Shares for sale in such states as such Holder shall reasonably
designate.

         (B) The Company shall bear the entire cost and expense of any
registration of securities initiated by it under Subsection 7.1 of this
Agreement notwithstanding that Warrant Shares subject to this Warrant may be
included in any such registration. Any Holder whose Warrant Shares are included
in any such registration statement pursuant to Section 7.1 shall, however, bear
the fees of his own counsel and any registration fees, transfer taxes or
underwriting discounts or commissions applicable to the Warrant Shares sold by
him pursuant thereto.

         (C) The Company shall indemnify and hold harmless each such Holder and
each underwriter, if any, within the meaning of the Act, who may purchase from
or sell for any such Holder any Warrant Shares from and against any and all
losses, claims, damages and liabilities caused by any untrue statement or
alleged untrue statement of a material fact contained in the Registration
Statement or any post-effective amendment thereto or any registration statement
under the Act or any prospectus included therein required to be filed or
furnished by reason of this Section 7 or caused by any omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading except insofar as such
losses, claims, damages or liabilities are caused by any such untrue statement
or alleged untrue statement or omission or alleged omission based upon
information furnished or required to be furnished in writing to the Company by
such Holder or underwriter

149
<PAGE>
                                                                   EXHIBIT 10.23

expressly for use therein, which indemnification shall include each person, if
any, who controls any such underwriter within the meaning of such Act; provided,
however, that the Company shall not be obliged to so indemnify any such Holder
or underwriter or controlling person unless such Holder or underwriter shall at
the same time agree to indemnify the Company, its directors, each officer
signing the related registration statement and each person, if any, who controls
the Company within the meaning of such Act, from and against any and all losses,
claims, damages and liabilities caused by any untrue statement or alleged untrue
statement of a material fact contained in any registration statement or any
prospectus required to be filed or furnished by reason of this Section 7 or
caused by any omission to state therein a material fact required to be stated
therein or necessary to make the statements therein not misleading insofar as
such losses, claims, damages or liabilities are caused by any untrue statement
or alleged untrue statement or omission based upon information furnished in
writing to the Company by any such Holder or underwriter expressly for use
therein.

         (D) If the underwriter, if any, managing any underwritten registration
under this Section 7.1 determines in good faith that, because of marketing
factors the number of shares of Common Stock requested to be registered by all
the Company's shareholders holding registration rights, including the Holders of
Warrant Shares, exceed the number of shares of Common Stock to which such
registration should, in the opinion of the managing underwriter, be limited (the
"Underwriters' Maximum Number"), then the Company will be obligated and required
to include in such registration the number of shares of Common Stock requested
to be registered by all of the Company's shareholders holding registration
rights, including the Holders of Warrant Shares, which does not exceed the
Underwriters' Maximum Number. The securities included in the registration
statement, including the Warrant Shares, shall be allocated pro rata among the
Company's shareholders holding registration rights based upon the number of
shares of Common Stock requested to be included by such shareholders.

         (E) Notwithstanding the provisions of Section 7.1, the Company shall
have the right at any time after it shall have given written notice pursuant to
this Section 7.1 (irrespective of whether a written request for inclusion of any
such securities shall have been made) to elect not to file any such proposed
registration statement, or to withdraw the same after the filing but prior to
the effective date thereof.

         (F) The Company shall be entitled to exclude the Warrant Shares of any
Holder who fails to comply with this section from any registration statement
within this Section 7.2.

         8. Adjustments to Exercise Price and Number of Securities.

         8.1 Dividends, Subdivision and Combination. If the Company shall (A)
declare a dividend or make a distribution on its Common Stock in shares of its
Common Stock, (B) subdivide or reclassify the outstanding shares of Common Stock
into a greater number of shares, or (C) combine or reclassify the outstanding
Common Stock into a smaller number of shares, the Exercise Price in effect at
the time of the record

150
<PAGE>
                                                                   EXHIBIT 10.23

date for such dividend or distribution or the effective date of such
subdivision, combination or reclassification shall be proportionately adjusted
so that the Holder after such date shall be entitled to receive the number of
shares of Common Stock which he would have owned or been entitled to receive had
this Warrant been exercised immediately prior to such date. Successive
adjustments in the Exercise Price shall be made whenever any event specified
above shall occur.

         8.2 Consolidation, Merger, Sale or Conveyance. In case of any
consolidation or merger of the Company with any other corporation (other than a
wholly owned subsidiary), or in case of sale or transfer of all or substantially
all of the assets of the Company, or in the case of any share exchange whereby
the Common Stock is converted into other securities or property, the Company
will be required to make appropriate provision so that the Holder will have the
right thereafter to exercise this Warrant into the kind and amount of shares of
stock and other securities and property receivable upon such consolidation,
merger, sale, transfer or share exchange by a holder of the number of shares of
Common Stock for which this Warrant was exercisable immediately prior to such
consolidation, merger, sale, transfer or share exchange.

         9. Exchange and Replacement of Warrant Certificates.

         Each Warrant Certificate is exchangeable without expense, upon the
surrender hereof by the registered Holder at the principal executive office of
the Company, for a new Warrant Certificate of like tenor and date representing
in the aggregate the right to purchase the same number of Warrant Shares in such
denominations as shall be designated by the Holder thereof at the time of such
surrender.

         Upon receipt by the Company of evidence reasonably satisfactory to it
of the loss, theft, destruction or mutilation of any Warrant Certificate, and,
in case of loss, theft or destruction, of indemnity or security reasonably
satisfactory to it, and reimbursement to the Company of all reasonable expenses
incidental thereto, and upon surrender and cancellation of the Warrants, if
mutilated, the Company will make and deliver a new Warrant Certificate of like
tenor, in lieu thereof and any such lost, stolen, destroyed or mutilated warrant
shall thereupon become void.

         10. Elimination of Fractional Interests.

         The Company shall not be required to issue certificates representing
fractions of shares of Common Stock upon the exercise of the Warrants, nor shall
it be required to issue scrip or pay cash in lieu of fractional interests, it
being the intent of the parties that all fractional interests shall be
eliminated by rounding any fraction up or down to the nearest whole number of
shares of Common Stock.

            11. Reservation and Listing of Securities. The Company shall at all
times reserve and keep available out of its authorized shares of Common Stock,
solely for the purpose of issuance upon the exercise of the Warrants, such
number of shares of Common Stock or other securities, properties or rights as
shall be issuable upon the

151
<PAGE>
                                                                   EXHIBIT 10.23

exercise thereof. The Company covenants and agrees that, upon exercise of the
Warrants and payment of the Exercise Price therefor, all shares of Common Stock
and other securities issuable upon such exercise shall be duly and validly
issued, full paid, non-assessable and not subject to the preemptive rights of
any stockholder. As long as the Warrants shall be outstanding, the Company shall
use its best efforts to cause all shares of Common Stock issuable upon the
exercise of the Warrants to be listed (subject to official notice of issuance)
on all securities exchanges, if any, including the Nasdaq Stock Market, on which
the Common Stock issued to the public in connection herewith may then be listed
and/or quoted.

         12. Notices to Warrant Holders. Nothing contained in this Agreement
shall be construed as conferring upon the Holders the right to vote or to
consent or to receive notice as a stockholder in respect of any meetings of
stockholders for the election of directors or any other matter, or as having any
rights whatsoever as a stockholder of the Company. If, however, at any time
prior to the expiration of the Warrants and their exercise, any of the following
events shall occur:

                  (a) the Company shall take a record of the holders of its
shares of Common Stock for the purpose of entitling them to receive a dividend
or distribution payable otherwise than in cash, or a cash dividend or
distribution payable otherwise than out of current or retained earnings, as
indicated by the accounting treatment of such dividend or distribution on the
books of the Company; or

                  (b) the Company shall offer to all the holders of its Common
Stock any additional shares of capital stock of the Company or securities
convertible into or exchangeable for shares of capital stock of the Company, or
any option, right or warrant to subscribe therefor; or

                  (c) a dissolution, liquidation or winding up of the Company
(other than in connection with a consolidation or merger) or a sale of all or
substantially all of its property, assets and business as an entirety shall be
proposed;

then, in any one or more of said events, the Company shall give written notice
of such event at least fifteen (15) days prior to the date fixed as a record
date or the date of closing the transfer books for the determination of the
stockholders entitled to such dividend, distribution, convertible or
exchangeable securities or subscription rights, or entitled to vote on such
proposed dissolution, liquidation, winding up or sale.

         13. Notices. All notices, requests, consents and other communications
hereunder shall be in writing and shall be deemed to have been ------- duly made
when delivered, or mailed by registered or certified mail, return receipt
requested:

                  (a) If to the registered Holder of the Warrants, to the
address of such Holder as shown on the books of the Company; or

                  (b) If to the Company, to the address set forth in Section 3
hereof or to such other address as the Company may designate by notice to the
Holders.

152
<PAGE>
                                                                   EXHIBIT 10.23

         14. Termination. This Agreement shall terminate at the close of
business on July 31, 2007. Notwithstanding the foregoing, the indemnification
provisions of Section 7 hereof shall survive such termination.

1.       Miscellaneous.

         15.1 Supplements and Amendments. The Company and USPS may from time to
time supplement or amend this Success Rights Agreement without the approval of
any Holders of Warrant Certificates (other than USPS) in order to cure any
ambiguity, to correct or supplement any provision contained herein which may be
defective or inconsistent with any provisions herein, or to make any other
provisions in regard to matters or questions arising hereunder which the Company
and USPS may deem necessary or desirable and which the Company and USPS deem
shall not adversely affect the interests of the Holders of Warrant Certificates.

         15.2 Successors. All the covenants and provisions of this Agreement
shall be binding upon and inure to the benefit of the Company, the Holders and
their respective successors and assigns hereunder.

         15.3 Governing Law; Submission to Jurisdiction. This Agreement and each
Warrant Certificate issued hereunder shall be deemed to be a contract made under
the laws of the State of New York and for all purposes shall be construed in
accordance with the laws of said State, without giving effect to the rules of
said State governing the conflicts of laws.

         The Company, USPS and the Holders hereby agree that any action,
proceeding or claim against it arising out of, or relating in any way to, this
Agreement shall be brought and enforced in the courts of the State of New York
or of the United States of America for the Southern District of New York, and
irrevocably submits to such jurisdiction, which jurisdiction shall be exclusive.
The Company, USPS and the Holders hereby irrevocably waive any objection to such
exclusive jurisdiction or inconvenient forum. Any such process or summons to be
served upon any of the Company, USPS and the Holders (at the option of the party
bringing such action, proceeding or claim) may be served by transmitting a copy
thereof, by registered or certified mail, return receipt requested, postage
prepaid, addressed to it at the address set forth in Section 13 hereof. Such
mailing shall be deemed personal service and shall be legal and binding upon the
party so served in any action, proceeding or claim.

         15.4 Entire Agreement; Modification. This Agreement contains the entire
understanding between the parties hereto with respect to the subject matter
hereof and may not be modified or amended except by a writing duly signed by the
party against whom enforcement of the modification or amendment is sought.

153
<PAGE>
                                                                   EXHIBIT 10.23

         15.5 Severability. If any provision of this Agreement shall be held to
be invalid or unenforceable, such invalidity or unenforceability shall not
affect any other provision of this Agreement.

         15.6 Captions. The caption headings of the Sections of this Agreement
are for convenience of reference only and are not intended, nor should they be
construed as, a part of this Agreement and shall be given no substantive effect.

         15.7 Benefits of this Agreement. Nothing in this Agreement shall be
construed to give to any person or corporation other than the Company and USPS
any other registered Holder(s) of the Warrant Certificates or Warrant Securities
any legal or equitable right, remedy or claim under this Agreement; and this
Agreement shall be for the sole and exclusive benefit of the Company and USPS
and any other Holder(s) of the Warrant Certificates or Warrant Securities.

         15.8 Counterparts. This Agreement may be executed in any number of
counterparts and each of such counterparts shall for all purposes be deemed to
be an original, and such counterparts shall together constitute but one and the
same instrument.

         15.9 No Recourse. No recourse shall be had for any claim based hereon
or otherwise in any manner in respect hereof, against any incorporator,
stockholder, officer or director, past, present or future, of the Company or of
any predecessor corporation, whether by virtue of any constitutional provision
or statute or rule of law, or by the enforcement of any assessment or penalty or
in any other manner, all such liability being expressly waived and released by
the acceptance hereof and as part of the consideration for the issue hereof.

         15.10 No Waiver. No course of dealing between the Company and the
Holder hereof shall operate as a waiver of any right of any Holder hereof, and
no delay on the part of the Holder in exercising any right hereunder shall so
operate.

       Remainder of page intentionally left blank. Signature page follows.

154
<PAGE>
                                                                   EXHIBIT 10.23

155
<PAGE>
                                                                   EXHIBIT 10.23

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

                                           AUTHENTIDATE HOLDING CORP.

                                           By:
                                              ---------------------------------
                                                       John T. Botti
                                                       President

ATTEST:

-----------------------------
Secretary

                                           UNITED STATES POSTAL SERVICE

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

Confidential                          156                                AD
                                                                           -----
                                                           AD Holding Corp.
                                                                           -----
                                                                       USPS
                                                                           -----
<PAGE>
                                  EXHIBIT 10.23

                                    EXHIBIT A

THE WARRANTS REPRESENTED BY THIS CERTIFICATE AND THE OTHER SECURITIES ISSUABLE
UPON EXERCISE HEREOF MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO (i) AN
EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933, AS AMENDED
(THE "ACT"), (ii) TO THE EXTENT APPLICABLE, RULE 144 UNDER SUCH ACT (OR ANY
SIMILAR RULE UNDER SUCH ACT RELATING TO THE DISPOSITION OF SECURITIES), OR (iii)
AN OPINION OF COUNSEL, IF SUCH OPINION SHALL BE REASONABLY SATISFACTORY TO
COUNSEL FOR THE ISSUER, THAT AN EXEMPTION FROM REGISTRATION UNDER SUCH ACT IS
AVAILABLE.

THE TRANSFER OR EXCHANGE OF THE WARRANTS REPRESENTED BY THIS CERTIFICATE IS
RESTRICTED IN ACCORDANCE WITH THE SUCCESS RIGHTS AGREEMENT REFERRED TO HEREIN.

                            EXERCISABLE ON OR BEFORE
                      5:00 P.M. NEW YORK TIME, _______,2007

NO. W-______

                                                            (Number of )Warrants

                               WARRANT CERTIFICATE

         This Warrant Certificate certifies that ( Name of Holder ), or
registered assigns, is the registered holder of ( Number of ) Warrants to
purchase initially at any time from 12:01 A.M. on _______________ until 5:00
P.M. New York time on __________,2007 (the "Expiration Date"), up to (Number of)
fully-paid and non-assessable shares of common stock, $.001 par value ("Common
Stock") of Authentidate Holding Corp., a Delaware corporation (the "Company"),
at the initial exercise price of $3.65 per share, subject to adjustment in
certain events (the "Exercise Price"), pursuant to the Success Rights Agreement
dated as of July 31, 2002 between the Company and the United States Postal
Service (the "Success Rights Agreement"), upon surrender of this Warrant
Certificate and payment of the applicable Exercise Price at an office or agency
of the Company, but subject to the conditions set forth herein and in the
Success Rights Agreement. Payment of the applicable Exercise Price shall be made
by cash or certified or official bank check in New York Clearing House funds
payable to the order of the Company.

         No Warrant may be exercised after 5:00 P.M., New York time, on the
Expiration Date, at which time all Warrants evidenced hereby, unless exercised
prior thereto, shall thereafter be void.

         The Warrants evidenced by this Warrant Certificate are part of a duly
authorized issue of Warrants issued pursuant to the Success Rights Agreement,
which Success

Confidential                          157                                AD
                                                                           -----
                                                           AD Holding Corp.
                                                                           -----
                                                                       USPS
                                                                           -----
<PAGE>
                                  EXHIBIT 10.23

Rights Agreement is hereby incorporated by reference herein and made a part of
this instrument and is hereby referred to for a description of the rights,
limitation of rights, obligations, duties and immunities thereunder of the
Company and the Holders (the words "Holders" or "Holder" meaning the registered
holders or registered holder) of the Warrants.

         The Success Rights Agreement provides that upon the occurrence of
certain events, the then applicable Exercise Price and the type and/or number of
the Company's securities issuable thereupon may, subject to certain conditions,
be adjusted. In such event, the Company will, at the request of the holder,
issue a new Warrant Certificate evidencing the adjustment in the then applicable
Exercise Price and the number and/or type of securities issuable upon the
exercise of the Warrants; provided, however, that the failure of the Company to
issue such new Warrant Certificates shall not in any way change, alter, or
otherwise impair, the rights of the holder as set forth in the Success Rights
Agreement.

         Upon due presentment for registration of transfer of this Warrant
Certificate at an office or agency of the Company, a new Warrant Certificate or
Warrant Certificates of like tenor and evidencing in the aggregate a like number
of Warrants shall be issued to the transferee(s) in exchange for this Warrant
Certificate, subject to the limitations provided herein and in the Success
Rights Agreement, without any charge except for any tax or other governmental
charge imposed in connection with such transfer.

         Upon the exercise of less than all of the Warrants evidenced by this
Certificate, the Company shall forthwith issue to the holder hereof a new
Warrant Certificate representing such number of unexercised Warrants.

         The Company may deem and treat the registered holder(s) hereof as the
absolute owner(s) of this Warrant Certificate (notwithstanding any notation of
ownership or other writing hereon made by anyone), for the purpose of any
exercise hereof, and of any distribution to the holder(s) hereof, and for all
other purposes, and the Company shall not be affected by any notice to the
contrary.

         All terms used in this Warrant Certificate which are defined in the
Success Rights Agreement shall have the meanings assigned to them in the Success
Rights Agreement.

Confidential                          158                                AD
                                                                           -----
                                                           AD Holding Corp.
                                                                           -----
                                                                       USPS
                                                                           -----
<PAGE>
                                  EXHIBIT 10.23

            IN WITNESS WHEREOF, the Company has caused this Warrant Certificate
to be duly executed under its corporate seal.

Dated as of
            -------------

                                             AUTHENTIDATE HOLDING CORP.

[SEAL]                                       By:
                                                -------------------------------
                                             Name: John T. Botti
                                             Title:   President

Attest:

-------------------------------
Ira C. Whitman, Secretary

Confidential                          159                                AD
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                                  EXHIBIT 10.23

                                  PURCHASE FORM

TO:      Authentidate Holding Corp.
         2165 Technology Drive
         Schenectady, New York 12308

         The undersigned Holder hereby irrevocably elects to exercise the right
to purchase      shares of Common Stock covered by this Warrant according to the
conditions hereof and herewith makes full payment of the Exercise Price of such
shares.

         Kindly deliver to the undersigned a certificate representing the
Shares.

                  INSTRUCTIONS FOR DELIVERY

Name:
     ---------------------------------------------------------------------------
                  (please typewrite or print in block letters)

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

Tax I.D. No. or Social Security No.:
                                    --------------------------------------------

Dated:
      --------------------------

Signature
          --------------------------------

STATE OF           )
         ----------
COUNTY OF          ) ss:
          ---------

            On this __ day of ___________, before me personally came ________,
to me known, who being by me duly sworn, did depose and say that he resides at
__________________, that he is the holder of the foregoing instrument and that
he executed such instrument and duly acknowledged to me that he executed the
same.

                                           ------------------------------------
                                           Notary Public

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                                  EXHIBIT 10.23

                               FORM OF ASSIGNMENT

         (To be executed by the registered holder if such holder desires to
transfer the Warrant Certificate.)

         FOR VALUE RECEIVED

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

hereby sells, assigns and transfers unto

------------------------------------------------
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
------------------------------------------------
(Please print name, address and social security or tax identification number of
transferee)

this Warrant Certificate, together with all right, title and interest therein,
and hereby irrevocably constitutes and appoints _________ Attorney, to transfer
the within Warrant Certificate on the books of the within-named Company, with
full power of substitution.

Dated:
      ---------------------

Signature:
          -----------------

Printed Name:
             -------------------------------
(Name and Signature must confirm in all respects to name of holder as specified
on the face of the Warrant Certificate.)

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

Tax I.D. No. or Social Security No.:
                                    --------------------------------------------

STATE OF            )
         -----------
COUNTY OF           ) ss:
          ----------

         On this __ day of ___________, before me personally came ________, to
me known, who being by me duly sworn, did depose and say that he resides at
__________________, that he is the holder of the foregoing instrument and that
he executed such instrument and duly acknowledged to me that he executed the
same.

                                                -----------------------------
                                                Notary Public

Confidential                          161                                AD
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                                  EXHIBIT 10.23

                                    EXHIBIT P

                            RETURN OF CUSTOMER FUNDS

Confidential                          162                                AD
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                                  EXHIBIT 10.23

                                    EXHIBIT Q

                          SOURCE CODE ESCROW AGREEMENT

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                                                                  Exhibit 10.6.1

May 8, 2002

Edison Schools Inc.
521 Fifth Avenue, 11th Floor
New York, NY 10175

Dear Ladies and Gentlemen:

On June 20, 2000, Edison Schools Inc. (the "Company") and the undersigned
entered into a letter agreement, as amended on March 28, 2002, setting forth the
terms of the undersigned's employment with the Company (the "Letter Agreement as
Amended"). This letter agreement (the "Second Amendment to Letter Agreement")
sets forth an amendment to the Letter Agreement as Amended.

For good an valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the Company and the undersigned, intending to be legally
bound, hereby agree as follows:

1.    The first sentence of paragraph (iv) of the section of the Letter
      Agreement entitled "Termination/Severance Pay" is hereby deleted in its
      entirety and the following sentence inserted in lieu thereof:

      "If Edison terminates your employment without cause or if you terminate
      your employment for "good reason," in addition to any other severance pay
      to which you may be entitled, the Company will pay you a lump sum of $3.2
      million (the "Lump-Sum Severance Payment") within 30 days after the
      Effective Termination Date."

2.    As amended hereby, the Letter Agreement is hereby confirmed to be in full
      force and effect.

3.    This Second Amendment to the Letter Agreement constitutes the entire
      understanding of the parties with respect to the subject matter hereof.

4.    This Second Amendment to the Letter Agreement is governed by the
      substantive laws of the State of New York.

Please sign below to evidence your agreement to the foregoing.

Sincerely,

/s/  Benno C. Schmidt, Jr.
--------------------------
Benno C. Schmidt, Jr.

ACCEPTED AND AGREED:

EDISON SCHOOLS INC.

By: /s/ H. Christopher Whittle
    ----------------------------
    Name:  H. Christopher Whittle
    Title: CEO and President

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