Network Working Group                                        K. Fujimura
Request for Comments: 4153                                           NTT
Category: Informational                                        M. Terada
                                                              NTT DoCoMo
                                                         D. Eastlake 3rd
                                                   Motorola Laboratories
                                                          September 2005

XML Voucher: Generic Voucher Language

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2005).

Abstract

   This document specifies rules for defining voucher properties in XML
   syntax.  A voucher is a logical entity that represents a right to
   claim goods or services.  A voucher can be used to transfer a wide
   range of electronic values, including coupons, tickets, loyalty
   points, and gift certificates, which often have to be processed in
   the course of payment and/or delivery transactions.

   1.  Introduction .................................................  2
   2.  Processing Model .............................................  2
   3.  Trust Model ..................................................  4
   4.  Component Structure ..........................................  4
   5.  Syntax Overview and Examples .................................  6
   6.  Syntax and Semantics .........................................  8
       6.1. <Voucher> ...............................................  8
       6.2. <Title> .................................................  9
       6.3. <Description> ...........................................  9
       6.4. <Provider> ..............................................  9
       6.5. <Issuer> ................................................ 10
       6.6. <Holder> ................................................ 10
       6.7. <Collector> ............................................. 11
       6.8. <Value> ................................................. 11
            6.8.1. <Ratio> .......................................... 13
            6.8.2. <Fixed> .......................................... 13

       6.9. <Merchandise> ........................................... 14
       6.10. <ValidPeriod> .......................................... 14
       6.11. <Conditions> ........................................... 15
   7.  IANA Considerations .......................................... 15
   8.  VTS Schema Example ........................................... 18
   9.  Security Considerations ...................................... 18
   10. Acknowledgements ............................................. 19
   11. Normative References ......................................... 19
   12. Informative References ....................................... 20

1. Introduction

   This document specifies rules for defining voucher properties in XML
   syntax.  The motivation and background of the specification are
   described in [VTS].

   A voucher is a logical entity that represents a certain right and
   that is logically managed by the Voucher Trading System (VTS).  A
   voucher is generated by the issuer, traded among users, and finally
   collected by the collector using VTS.

   This document defines the syntax and semantics of the Voucher
   Component, which defines voucher meaning and processing rules in XML
   syntax [XML].  A Voucher Component defines the properties that must
   be satisfied to allow the voucher to be processed by VTS or other
   trading systems; e.g., a wallet or merchant system.  VTS definitions
   and models are also defined in [VTS].

   Note: This document uses "voucher" as an "instance of voucher", whose
   meaning is defined by the Voucher Component.  In other words, a
   Voucher Component is NOT a voucher, and multiple vouchers can be
   issued and managed by the VTS using the same Voucher Component.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119]

2. Processing Model

   There are several ways of implementing VTS and technologies are
   continually changing.  For discount coupons or event tickets, for
   example, the smartcard-based offline VTS is often preferred, whereas
   for bonds or securities, the centralized online VTS is preferred.  It
   is impractical to define standard protocols for issuing,
   transferring, or redeeming vouchers at this time.

   To provide implementation flexibility, this document assumes a
   modular wallet architecture that allows multiple VTSes to be added as
   plug-ins.  In this architecture, instead of specifying a standard
   voucher transfer protocol, two specifications, Voucher Component and
   VTS-API, are standardized (Figure 1).

   After the sender and receiver agree on which vouchers are to be
   traded and which VTS is to be used, the issuing system or wallet
   system requests the corresponding VTS plug-in to permit the issue,
   transfer, or redeem transactions to be performed via the VTS API.
   The VTS then rewrites the ownership of the vouchers using the VTS-
   specific protocol.  Finally, a completion event is sent to the wallet
   systems or issuing/collecting systems.

   This document describes the Voucher Component specification.  The
   VTS-API specification is defined in [VTS-API].

   Sender wallet/Issuing system      Receiver wallet/Collecting system
   +---------------------------+       +---------------------------+
   |                           |       |                           |
   |  |                    Voucher Component                    |  |
   |  |            (Specifies VTS Provider and Promise)         |  |
   |  |-------------------------------------------------------->|  |
   |  |                        |       |                        |  |
   |  |         Intention to receive and payment (option)       |  |
   |  |<- - - - - - - - - - - - - - - - - - - - - - - - - - - - |  |
   |  |                        |       |                        |  |
   |  |                        |       |                        |  |
   |  | Issue/transfer/  VTS   |       |   VTS      Register    |  |
   |  | redeem request   plug-in       |   plug-in  Listener(*1)|  |
   |  |------------------>|    |       |    |<------------------|  |
   |  | (VTS-API)         |<- - - - - - - ->|         (VTS-API) |  |
   |  |                   | VTS-specific    |                   |  |
   |  |                   | protocol if VTS |                   |  |
   |  |                   | is distributed  |                   |  |
   |  |  Result           |<- - - - - - - ->|       Notify(*2)  |  |
   |  |<------------------|    |       |    |------------------>|  |
   +---------------------------+       +---------------------------+

   (*1) Registration is optional.  Note also that the VTS plug-ins are
        usually pre-registered when the wallet or collecting system
        is started.

   (*2) If a listener is registered.

           Figure 1. Wallet architecture with VTS plug-ins

3. Trust Model

   A voucher is trusted if the Issuer and VTS Provider are trusted, as
   the Issuer is responsible for the contents of the voucher and the VTS
   Provider is responsible for preventing ownership from being assigned
   to multiple users.

   The trust level required for the Issuer and VTS Provider depends on
   the type (or Promise) of the voucher.  To provide the information
   needed for verification, the conditions of the Issuer and VTS
   Provider are specified in the Voucher Component and given as input to
   the verifier; e.g., wallet system or other software.  The trust of a
   voucher is thus verified through the Voucher Component.  This model
   enables trading partners to verify their trust in the voucher
   regardless of their trust in the partners.

   This document assumes that the Voucher Component is the root of
   trust.  If a malicious user could alter the Voucher Component, a
   forged voucher could be verified as valid.

   When a Voucher Component is delivered from the trusted VTS Provider,
   Issuer, or trusted third party, a secure communication channel (e.g.,
   [TLS], [IPSEC], or object security, such as [XMLDSIG]) should be used
   to prevent alteration during the delivery.

   Note: The Voucher Component does not have to be sent from the sender
   of the voucher.  Note also that a set of trusted Voucher Components
   can be downloaded before a transaction is conducted.

4. Component Structure

   The Voucher Component provides the information needed to identify the
   monetary value or merchandize rendered when the voucher is redeemed.
   It includes

   o how much value/items can be claimed in exchange for the voucher,
      and

   o restrictions applied to the voucher

      - participants (VTS Provider, Issuer, Holder, and Collector),

      - objects (merchandise) to be claimed,

      - time when valid (validity period), and

      - others.

   The Voucher Component also provides common properties useful for
   displaying and manipulating the contents of wallet systems.  It
   includes the title and description of each voucher.

   The Voucher Component contains the following components:

   Title Component

      Provides the title of the voucher.  This is mainly for listing the
      entities stored in a wallet system.

   Description Component

      Provides a short description of the voucher.  This is mainly for
      listing the entities stored in a wallet system.

   Provider Component

      Provides restrictions on which VTS Provider (or VTS plug-in) can
      be used for trading the voucher.

   Issuer Component

      Provides restrictions on the Issuer of the voucher.

   Holder Component

      Provides restrictions on the Holder of the voucher.

   Collector Component

      Provides restrictions on the Collector of the voucher.

   Value Component

      Provides the value of each voucher.  There are two types of
      values: fixed and ratio values.  For a fixed value, the currency
      and the figure is specified.  For a ratio value, the discount
      ratio of the corresponding merchandize is specified.

      The Value Component also indicates the number of vouchers to be
      redeemed for claiming the merchandise or monetary value specified
      in the Merchandise Component or Value Component.  If "n" (>0) is
      specified, the merchandize or monetary value can be claimed in
      exchange for "n sheets of" vouchers.  If "0" is specified, it can
      be used repeatedly.

5. Syntax Overview and Examples

   This section provides an overview and examples of Voucher Components.
   The formal syntax and semantics are found in Sections 6 and 7.

   Voucher Components are represented by the <Voucher> element, which
   has the following structure (where "?" denotes zero or one
   occurrence):

      <Voucher>
        (Title)
        (Description)?
        (Provider)
        (Issuer)?
        (Holder)?
        (Collector)?
        (Value)
        (Merchandise)?
        (ValidPeriod)?
        (Conditions)?
      </Voucher>

   An example of a Voucher Component is described below.  This is an
   example of a five-dollar discount coupon for specific merchandize, a
   book with ISBN number 0071355014.  The coupon is valid from April 1,
   2001, to March 31, 2002.  To claim this offer, one voucher must be
   spent.

      <?xml version="1.0" encoding="UTF-8"?>
      <Voucher xmlns="urn:ietf:params:xml:ns:vts-lang"
               xmlns:vts="http://www.example.com/vts">
        <Title>IOTP Book Coupon</Title>
        <Description>$5 off IOTP Book</Description>
        <Provider name="Voucher Exchanger 2002">
          <vts:Version>VE2.31</vts:Version>
        </Provider>
        <Issuer name="Alice Book Center, Ltd.">
          <vts:KeyInfo>
            1DA8DFCF95521014BBB7171B95545E8D61AE803F
          </vts:KeyInfo>
        </Issuer>
        <Collector name="Alice Book Center, Ltd."/>
        <Value type="discount" spend="1">
          <Fixed amount="5" currency="USD"/>
        </Value>
        <Merchandise>
          <bk:Book xmlns:bk="http://www.example.com/bk"
                   bk:isbn="0071355014"/>
        </Merchandise>
        <ValidPeriod start="2002-04-01" end="2003-03-31"/>
        <Conditions>
          The value of this coupon is subject to tax.
        </Conditions>
      </Voucher>

6. Syntax and Semantics

   The general structure of an XML Voucher Component is described in
   Section 4.  This section details the Voucher Component features.
   Features described in this section MUST be implemented unless
   otherwise indicated.  The syntax is defined via [XML-Schema-1]
   [XML-Schema-2].  For clarity, unqualified elements in schema
   definitions are in the XML schema namespace:

      xmlns="http://www.w3.org/2001/XMLSchema"

   References to XML Voucher schema defined herein use the prefix "gvl"
   and are in the namespace:

      xmlns:gvl="urn:ietf:params:xml:ns:vts-lang"

   This namespace URI for elements defined by this document is a URN
   [URN] that uses the namespace identifier 'ietf', defined by
   [URN-NS-IETF] and extended by [XML-Registry].

   This namespace is also used for unqualified elements in voucher
   examples.

6.1. <Voucher>

   The <Voucher> element contains <Title>, <Provider>, and <Value>
   elements and optionally contains <Description>, <Issuer>, <Holder>,
   <Collector>, <ValidPeriod>, and <Condition> elements.  These sub-
   elements are defined in the following sections.

   The <Voucher> element is defined by the following schema:

      <element name="Voucher" type="gvl:VoucherType"/>
      <complexType name="VoucherType">
       <sequence>
        <element ref="gvl:Title"/>
        <element ref="gvl:Description" minOccurs="0"/>
        <element ref="gvl:Provider"/>
        <element ref="gvl:Issuer" minOccurs="0"/>
        <element ref="gvl:Holder" minOccurs="0"/>
        <element ref="gvl:Collector" minOccurs="0"/>
        <element ref="gvl:Value"/>
        <element ref="gvl:Merchandise" minOccurs="0"/>
        <element ref="gvl:ValidPeriod" minOccurs="0"/>
        <element ref="gvl:Conditions"  minOccurs="0"/>
       </sequence>
      </complexType>

6.2. <Title>

   The <Title> element contains a simpletext title of the voucher.  This
   is mainly for listing the entities stored in a wallet system.

   The <Title> element has no attribute.

   The <Title> element is defined by the following schema:

      <element name="Title" type="string"/>

6.3. <Description>

   The <Description> element contains a simpletext description of the
   voucher.  This is mainly for listing the entities stored in a wallet
   system.

   The <Description> element has no attribute.

   The <Description> element is defined by the following schema:

      <element name="Description" type="string"/>

6.4. <Provider>

   The <Provider> element may contain any element that is used to
   specify or restrict the VTS Provider of the voucher.  The sub-
   elements contained in this element depend on the implementation of
   the VTS.

   An implementation of a wallet system may use this information to
   identify and/or authenticate the VTS Provider when the VTS plug-in is
   registered (see Section 7 of [VTS-API]).  These implementation-
   specific elements of the VTS can be extended using [XML-ns].  An
   example of such a schema definition is described in Section 8.

   The <Provider> element has a string-type "name" attribute that is
   used to specify the name of the VTS Provider.

   The <Provider> element is defined by the following schema:

      <element name="Provider" type="gvl:RoleType"/>
      <complexType name="RoleType" mixed="true">
       <sequence>
        <any namespace="##any" minOccurs="0" maxOccurs="unbounded"/>
       </sequence>
       <attribute name="name" type="string"/>
      </complexType>

6.5. <Issuer>

   The <Issuer> element may contain any element that is used to specify
   or restrict the Issuer of the voucher.

   The Issuer of the voucher is generally managed by the VTS [VTS-API].
   There is no need to specify the Issuer of the voucher using this
   element if there are no restrictions on the Issuer.

   An implementation of a VTS may use this element to describe the
   authentication data and/or qualification information of the Issuer.
   This implementation-specific information can be extended through
   sub-elements using [XML-ns].  An example of such a schema definition
   is described in Section 8.

   The <Issuer> element has a string-type "name" attribute that is used
   to specify the name of the Issuer.

   The <Issuer> element is defined by the following schema:

      <element name="Issuer" type="gvl:RoleType"/>

   The <RoleType> element type is defined in Section 6.4.

   If the <Issuer> element is omitted, it MUST be interpreted that there
   are no restrictions on the Issuer.

6.6. <Holder>

   The <Holder> element may contain any element that is used to specify
   or restrict the Holder of the voucher.

   The Holder of the voucher is generally managed by the VTS [VTS-API].
   There is no need to specify the Holder of the voucher using this
   element if there are no restrictions on the Holder.

   An implementation of a VTS may use this element to describe the
   authentication data and/or qualification information of the Holder.
   This implementation-specific information can be extended through
   sub-elements using [XML-ns].

   The <Holder> element has a string-type "name" attribute that is used
   to specify the name of the Holder.

   The <Holder> element is defined by the following schema:

      <element name="Holder" type="gvl:RoleType"/>

   The <RoleType> element type is defined in Section 6.4.

   If the <Holder> element is omitted, it MUST be interpreted that there
   are no restrictions on the Holder.

6.7. <Collector>

   The <Collector> element may contain any element that is used to
   specify or restrict the Collector of the voucher.

   There is no need to specify the Collector of the voucher using this
   element if there are no restrictions on the Collector.

   An implementation of a VTS may use this element to describe the
   authentication data and/or qualification information of the
   Collector.  This implementation-specific information can be extended
   through sub-elements using [XML-ns].

   The <Collector> element has a string-type "name" attribute that is
   used to specify the name of the Collector.

   The <Collector> element is defined by the following schema:

      <element name="Collector" type="gvl:RoleType"/>

   The <RoleType> element type is defined in Section 6.4.

   If the <Collector> element is omitted, it MUST be interpreted that
   there are no restrictions on the Collector.

6.8. <Value>

   The <Value> element optionally contains a <Fixed> or <Ratio> element
   but not both.  These sub-elements are defined in the following
   sections.

   The <Value> element has a "type" attribute that is used to specify
   the value process type.  This attribute is provided to calculate the
   amount paid when the vouchers are redeemed at Merchant site, etc.

   The following identifiers are defined for the "type" attribute.

   Exchange: Items specified in the <Merchandise> element can be claimed
      in exchange for the voucher.  If this type is selected, neither
      the <Ratio> nor the <Fixed> element MUST be specified.  Note that
      this value process type has the same meaning as:

      <Value type="discount"><Ratio percentage="100"/></Value>

   Discount: Items specified in the <Merchandise> element can be
      purchased at the discount price calculated by the <Ratio> or
      <Fixed> element.

   Monetary: Items specified in the <Merchandise> element can be
      purchased using the value of the voucher.  (Note: if the
      <Merchandise> element is not specified, the voucher can be used
      for any purchase.)  If this type is selected, the <Fixed> element
      MUST be specified.

   The <Value> element also has a "spend" attribute that is used to
   specify the number of vouchers to be redeemed for claiming the goods,
   services, or monetary value specified.  For example, if "n" (>0) is
   specified, goods can be claimed in exchange for "n sheets of"
   vouchers.  (Note: Multiple vouchers for the same Voucher Component
   must exist in this case.)  If "0" is specified, it can be used
   repeatedly.

   If the "spend" attribute or the whole element is omitted, it MUST be
   interpreted that "1" is specified for the "spend" attribute.

   The <Value> element is defined by the following schema:

      <element name="Value" type="gvl:ValueType"/>
      <complexType name="ValueType">
       <sequence minOccurs="0">
        <choice>
         <element name="Ratio" type="gvl:RatioValueType"/>
         <element name="Fixed" type="gvl:FixedValueType"/>
        </choice>
       </sequence>
       <attribute name="type" type="gvl:ValueProcessType"
                  use="required"/>
       <attribute name="spend" type="nonNegativeInteger"
                  default="1"/>
      </complexType>

   The <ValueProcessType> element type is defined by the following
   schema:

      <simpleType name="ValueProcessType">
       <restriction base="string">
        <enumeration value="exchange"/>
        <enumeration value="discount"/>
        <enumeration value="monetary"/>
       </restriction>
      </simpleType>

6.8.1. <Ratio>

   The <Ratio> element does not contain any contents.

   The <Ratio> element has a "percentage" attribute that is used to
   specify the discount ratio of the price of the corresponding
   merchandize in percentage.

   The <RatioValueType> element type is defined by the following schema:

      <complexType name="RatioValueType">
       <attribute name="percentage" use="required">
        <simpleType>
         <restriction base="float">
          <maxInclusive value="100"/>
         </restriction>
        </simpleType>
       </attribute>
      </complexType>

6.8.2. <Fixed>

   The <Fixed> element does not contain any contents.

   The <Fixed> element has "currency" and "amount" attributes and
   optionally a "decimalPower" attribute as follows:

   Currency: Provides the unit of the monetary value in the three letter
      ISO currency code [ISO4217].  For example, US dollars is "USD".

   Amount: Provides the amount of the monetary value per voucher.

   DecimalPower: Provides the number of decimal digits from the decimal
      point applied to the base for the "amount" attribute above.  If
      the "decimalPower" attribute is omitted, it MUST be interpreted
      that "0" is specified for the "decimalPower" attribute.

   For example, with a dollar currency denominated in cents, "1" is
   specified for the "amount" attribute, and "-2" is specified for the
   "decimalPower" attribute.  Alternately, "0.01" is specified for the
   "amount" attribute, and the "decimalPower" attribute is omitted.

   The <FixedValueType> type is defined follows:

      <complexType name="FixedValueType">
       <attribute name="currency" type="string" use="required"/>
       <attribute name="amount" type="float" use="required"/>
       <attribute name="decimalPower" type="short" default="0"/>
      </complexType>

6.9. <Merchandise>

   The <Merchandise> element may contain any element used to specify or
   restrict the goods or services rendered when the voucher is redeemed.
   The sub-elements contained in this element depend on the application
   of the voucher and are left to the other domain-specific
   specifications.  Domain-specific elements can be extended as sub-
   elements using [XML-ns].

   This element is intended to be interpreted by a collecting system.
   An implementation of a wallet system does not have to use this
   element.  Any restrictions applied should also be described in the
   <Description> element or the <Conditions> elements in natural
   language form to enable users to check the restrictions.

   The <Merchandise> element does not have any attribute.

   The <Merchandise> element is defined by the following schema:

      <element name="Merchandise" type="gvl:MerchandiseType"/>
      <complexType name="MerchandiseType" mixed="true">
       <sequence>
        <any namespace="##any" minOccurs="0" maxOccurs="unbounded"/>
       </sequence>
      </complexType>

6.10. <ValidPeriod>

   The <ValidPeriod> element does not contain any contents.

   The <ValidPeriod> element has dateTime-type "start" and "end"
   attributes that are used to place limits on the validity of the
   voucher.

   The <ValidPeriod> element is defined by the following schema:

      <element name="ValidPeriod" type="gvl:ValidPeriodType"/>
      <complexType name="ValidPeriodType">
        <attribute name="start" type="dateTime"/>
        <attribute name="end" type="dateTime"/>
      </complexType>

   If the "start" attribute is omitted, it MUST be interpreted that the
   voucher is valid on any date up to that specified by the end
   attribute (inclusive).  If the "end" attribute is omitted, it MUST be
   interpreted that the voucher is valid from the start attribute with
   no expiry.  If neither attribute is specified or the whole element is
   omitted, it MUST be interpreted that the voucher is valid at any
   time.

6.11. <Conditions>

   The <Conditions> element contains any other restrictions or
   conditions applied.  This is intended to cover contracts between the
   issuer and the holder of the voucher in natural language form.

   An implementation of a wallet system SHOULD provide a means of
   displaying the text in this element.

   The <Conditions> element has no attribute.

   The <Conditions> element is defined by the following schema:

      <element name="Conditions" type="string"/>

7. IANA Considerations

   This document uses URNs to describe XML namespaces and XML schemas
   conforming to a registry mechanism described in [XML-Registry].  IANA
   has registered two URI assignments.

   Registration request for the vts-lang namespace:

   URI: urn:ietf:params:xml:ns:vts-lang

   Registrant Contact: See the "Authors' Addresses" section of this
   document.

   XML: None.  Namespace URIs do not represent an XML specification.

   Registration request for the vts-lang XML schema:

   URI: urn:ietf:params:xml:schema:vts-lang

   Registrant Contact: See the "Authors' Addresses" section of this
   document.

   XML:
      BEGIN
      <?xml version="1.0" encoding="UTF-8"?>

      <schema
        targetNamespace="urn:ietf:params:xml:ns:vts-lang"
        xmlns:gvl="urn:ietf:params:xml:ns:vts-lang"
        xmlns="http://www.w3.org/2001/XMLSchema"
        elementFormDefault="qualified">

      <element name="Voucher" type="gvl:VoucherType"/>
      <complexType name="VoucherType">
       <sequence>
        <element ref="gvl:Title"/>
        <element ref="gvl:Description" minOccurs="0"/>
        <element ref="gvl:Provider"/>
        <element ref="gvl:Issuer" minOccurs="0"/>
        <element ref="gvl:Holder" minOccurs="0"/>
        <element ref="gvl:Collector" minOccurs="0"/>
        <element ref="gvl:Value"/>
        <element ref="gvl:Merchandise" minOccurs="0"/>
        <element ref="gvl:ValidPeriod" minOccurs="0"/>
        <element ref="gvl:Conditions"  minOccurs="0"/>
       </sequence>
      </complexType>

      <element name="Title" type="string"/>

      <element name="Description" type="string"/>

      <element name="Provider" type="gvl:RoleType"/>
      <element name="Issuer"   type="gvl:RoleType"/>
      <element name="Holder"   type="gvl:RoleType"/>
      <element name="Collector"   type="gvl:RoleType"/>
      <complexType name="RoleType" mixed="true">
       <sequence>
        <any namespace="##any" minOccurs="0" maxOccurs="unbounded"/>
       </sequence>
       <attribute name="name" type="string"/>
      </complexType>

        <attribute name="end" type="dateTime"/>
      </complexType>

      <element name="Conditions" type="string"/>
     </schema>
     END

8. VTS Schema Example

   An example of the schema definition for a VTS implementation is
   described below.

      <?xml version="1.0"?>

      <schema
       targetNamespace="http://www.example.com/vts"
       xmlns:vts="http://www.example.com/vts"
       xmlns="http://www.w3.org/2001/XMLSchema"
       elementFormDefault="qualified">

       <element name="Version" type="string"/>
       <element name="KeyInfo" type="hexBinary"/>
      </schema>

   Using this schema definition, the <vts:Version> can be used for
   specifying the VTS version number, and the <vts:KeyInfo> element can
   be used for specifying the Issuer in the Voucher Component, as shown
   in Section 5.

9. Security Considerations

   The VTS must provide a means to prevent forgery, alteration,
   duplicate-redemption, reproduction of a voucher, and non-repudiation
   of transactions, as described in Section 3.2 of [VTS].  This will
   commonly require the presence of a unique serial number or the like
   in each Voucher instance, usually outside the Voucher Component.
   These security requirements, however, mainly follow the VTS plug-ins
   and their protocols.  This document assumes that the VTS plug-ins are
   trusted and are installed by some means; e.g., manually checked as
   are other download applications.

   The Voucher Component, however, defines restrictions on the VTS
   Provider (or VTS plug-in), and, if this information is altered,
   incorrect VTS plug-ins not accepted by the issuer could be used,
   allowing a forged voucher to be verified as if it were valid.  To
   prevent this situation, the Voucher Component should be stored and

   acquired securely; e.g., downloaded from a trusted party using a
   secure communication channel, such as [TLS] or [IPSEC], or secured by
   the digital signature of a trusted party [XMLDSIG].

10. Acknowledgements

   The following persons, in alphabetic order, contributed substantially
   to the material herein:

      Ian Grigg
      Renato Iannella
      Yoshiaki Nakajima

11. Normative References

   [ISO4217]      "Codes for the representation of currencies and
                  funds", ISO 4217, 1995.

   [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.

   [URN]          Moats, R., "URN Syntax", RFC 2141, May 1997.

   [URN-NS-IETF]  Moats, R., "A URN Namespace for IETF Documents", RFC
                  2648, August 1999.

   [XML]          "Extensible Mark Up Language (XML) 1.0 (Second
                  Edition)", A W3C Recommendation,
                  <http://www.w3.org/TR/REC-xml>, October 2000.

   [XML-ns]       "Namespaces in XML", A W3C Recommendation,
                  <http://www.w3.org/TR/REC-xml-names>, January 1999.

   [XML-Registry] Mealling, M., "The IETF XML Registry", BCP 81, RFC
                  3688, January 2004.

   [XML-Schema-1] Thompson, H., Beech, D., Maloney, M., and N.
                  Mendelsohn, "XML Schema Part 1: Structures W3C
                  Recommendation.", <http://www.w3.org/TR/xmlschema-1/>,
                  May 2001.

   [XML-Schema-2] Biron, P. and A. Malhotra, "XML Schema Part 2:
                  Datatypes W3C Recommendation.",
                  <http://www.w3.org/TR/xmlschema-2/>, May 2001.

12. Informative References

   [VTS]          Fujimura, K. and D. Eastlake, "Requirements and Design
                  for Voucher Trading System (VTS)", RFC 3506, March
                  2003.

   [IPSEC]        Thayer, R., Doraswamy, N., and R. Glenn, "IP Security
                  Document Roadmap", RFC 2411, November 1998.

   [TLS]          Dierks, T. and C. Allen, "The TLS Protocol Version
                  1.0", RFC 2246, January 1999.

   [VTS-API]      Terada, M. and K. Fujimura, "Voucher Trading System
                  Application Programming Interface (VTS-API)", RFC
                  4154, September 2005.

   [XMLDSIG]      Eastlake 3rd, D., Reagle, J., and D. Solo,
                  "(Extensible Markup Language) XML-Signature Syntax and
                  Processing", RFC 3275, March 2002.

Authors' Addresses

   Ko Fujimura
   NTT Corporation
   1-1 Hikari-no-oka, Yokosuka-shi, Kanagawa, 239-0847 JAPAN

   Phone: +81-(0)46-859-3053
   Fax:   +81-(0)46-855-1730
   EMail: fujimura.ko@lab.ntt.co.jp

   Masayuki Terada
   NTT DoCoMo, Inc.
   3-5 Hikari-no-oka, Yokosuka-shi, Kanagawa, 239-8536 JAPAN

   Phone: +81-(0)46-840-3809
   Fax:   +81-(0)46-840-3705
   EMail: te@rex.yrp.nttdocomo.co.jp

   Donald E. Eastlake 3rd
   Motorola Laboratories
   155 Beaver Street
   Milford, MA 01757 USA

   Phone: 1-508-786-7554 (work)
          1-508-634-2066 (home)
   EMail: Donald.Eastlake@motorola.com

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