Using the Elliptic Curve Signature Algorithm (ECDSA) for XML Digital Signatures
draft-blake-wilson-xmldsig-ecdsa-09

INTERNET-DRAFT                                      S. Blake-Wilson, BCI
                                               G. Karlinger, CIO Austria
                                                       T. Kobayashi, NTT
                                                           Y. Wang, UNCC
Expires: Sept 2004                                            March 2004

             Using the Elliptic Curve Signature Algorithm (ECDSA) 
                        for XML Digital Signatures
                 <draft-blake-wilson-xmldsig-ecdsa-09.txt>

Status of this Memo

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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or to cite them other than as "work in progress."

The list of current Internet-Drafts may be found at
http://www.ietf.org/ietf/1id-abstracts.txt

The list of Internet-Draft Shadow Directories may be found at
http://www.ietf.org/shadow.html.

Abstract

  This document specifies how to use ECDSA (Elliptic Curve Digital
  Signature Algorithm) with XML Signatures. The mechanism
  specified provides integrity, message authentication, and/or signer
  authentication services for data of any type, whether located 
  within the XML that includes the signature or included by reference.

Table of Contents

  1  Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .  3
  2  ECDSA  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
  3  Specifying ECDSA within XMLDSIG  . . . . . . . . . . . . . . . .  3
     3.1  Version, Namespaces and Identifiers . . . . . . . . . . . .  3
     3.2  XML Schema Preamble and DTD Replacement . . . . . . . . . .  4
          3.2.1 XML Schema Preamble . . . . . . . . . . . . . . . . .  4
          3.2.2 DTD Replacement . . . . . . . . . . . . . . . . . . .  4
     3.3  ECDSA Signatures  . . . . . . . . . . . . . . . . . . . . .  4
     3.4  ECDSA Key Values  . . . . . . . . . . . . . . . . . . . . .  4
          3.4.1  Key Value Root Element . . . . . . . . . . . . . . .  4
          3.4.2  EC Domain Parameters . . . . . . . . . . . . . . . .  5
                 3.4.2.1  Field Parameters  . . . . . . . . . . . . .  6
                 3.4.2.2  Curve Parameters  . . . . . . . . . . . . .  8
                 3.4.2.3  Base Point Parameters . . . . . . . . . . .  8
          3.4.3  EC Points  . . . . . . . . . . . . . . . . . . . . .  9

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  4  Security Considerations  . . . . . . . . . . . . . . . . . . . . 10
  5  Normative References . . . . . . . . . . . . . . . . . . . . . . 10
  6  Informative References . . . . . . . . . . . . . . . . . . . . . 12
  7  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12
  
  Appendix A: Aggregate XML Schema  . . . . . . . . . . . . . . . . . 13
  Appendix B: Aggregate DTD . . . . . . . . . . . . . . . . . . . . . 16

  Authors' addresses. . . . . . . . . . . . . . . . . . . . . . . . . 17
  Intellectual Property Rights. . . . . . . . . . . . . . . . . . . . 17
  Full Copyright Statement. . . . . . . . . . . . . . . . . . . . . . 18

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1. Introduction

This document specifies how to use the Elliptic Curve Digital Signature
Algorithm (ECDSA) with XML signatures as specified in [XMLDSIG]. 
[XMLDSIG] defines only two digital signature methods: RSA signatures 
and DSA (DSS) signatures. This document introduces ECDSA signatures as 
an additional method.

This document uses both XML Schemas [XML-schema] (normative) and DTDs 
[XML] (informational) for specifying the corresponding XML structures.

2. ECDSA 

The Elliptic Curve Digital Signature Algorithm (ECDSA) is the elliptic
curve analogue of the DSA (DSS) signature method [FIPS186-2]. It is
defined in the ANSI X9.62 standard [X9.62]. Other compatible
specifications include FIPS 186-2 [FIPS186-2], IEEE 1363 [IEEE1363], 
IEEE 1363a [IEEE1363a], and SEC1 [SEC1]. [RFC3279] describes the means 
to carry ECDSA keys in X.509 certificates. [FIPS186-2], [SEC2], and 
[X9.62] give recommended elliptic curve domain parameters for use with 
ECDSA. 

Like DSA, ECDSA incorporates the use of a hash function. Currently,the
only hash function defined for use with ECDSA is the SHA-1 message
digest algorithm [FIPS-180-1].

ECDSA signatures are smaller than RSA signatures of similar 
cryptographic strength. ECDSA public keys (and certificates) are smaller
than similar strength DSA keys, resulting in improved communications
efficiency. Furthermore, on many platforms ECDSA operations can be
computed faster than similar strength RSA or DSA operations (see [KEYS]
for a security analysis of key sizes across public key algorithms).
These advantages of signature size, bandwidth, and computational
efficiency may make ECDSA an attractive choice for XMLDSIG
implementations.

3. Specifying ECDSA within XMLDSIG

This section specifies the details of how to use ECDSA with XML 
Signature Syntax and Processing [XMLDSIG]. It relies heavily on the
syntax and namespace defined in [XMLDSIG].

3.1 Version, Namespaces and Identifiers 

This specification makes no provision for an explicit version number in
the syntax. If a future version is needed, it will use a different 
namespace. 

The XML namespace [XML-ns] URI that MUST be used by implementations of
this (dated) specification is: 
  http://www.w3.org/2001/04/xmldsig-more#

Elements in the namespace of the [XMLDSIG] specification are marked as 
such by using the namespace prefix "dsig" in the remaining sections of 

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this document.
  
The identifier for the ECDSA signature algorithm as defined in 
[Eastlake] is:
  http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha1

3.2 XML Schema Preamble and DTD Replacement

3.2.1 XML Schema Preamble

The subsequent preamble is to be used with the XML Schema definitions 
given in the remaining sections of this document.

  <?xml version="1.0" encoding="UTF-8"?>
  <xs:schema 
    targetNamespace="http://www.w3.org/2001/04/xmldsig-more#"
    xmlns:ecdsa="http://www.w3.org/2001/04/xmldsig-more#"
    xmlns:xs="http://www.w3.org/2001/XMLSchema" 
    elementFormDefault="qualified" attributeFormDefault="unqualified"
    version="0.2">

3.2.2 DTD Replacement 

In order to include ECDSA in XML-signature syntax, the following
definition of the entity Key.ANY SHOULD replace the one in [XMLDSIG]:

  <!ENTITY % KeyValue.ANY '| ecdsa:ECDSAKeyValue'>

3.3 ECDSA Signatures

The input to the ECDSA algorithm is the canonicalized representation of 
the dsig:SignedInfo element as specified in Section 3 of [XMLDSIG].

The output of the ECDSA algorithm consists of a pair of integers usually
referred by the pair (r, s). The signature value (text value of element
dsig:SignatureValue - see section 4.2 of [XMLDSIG]) consists of the  
base64 encoding of the concatenation of two octet-streams that  
respectively result from the octet-encoding of the values r and s. This 
concatenation is described in section E3.1 of [IEEE1363].

3.4 ECDSA Key Values

The syntax used for ECDSA key values closely follows the ASN.1 syntax
defined in ANSI X9.62 [X9.62]. 

3.4.1 Key Value Root Element

The element ECDSAKeyValue is used for encoding ECDSA public keys. For 
use with XMLDSIG simply use this element inside dsig:KeyValue, such as
the predefined elements dsig:RSAKeyValue or dsig:DSAKeyValue.

The element consists of an optional subelement DomainParameters and the
mandatory subelement PublicKey. If Domainparameters is missing in an 
instance, this means that the application knows about them from other 
means (implicitly).  

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  Schema Definition:

  <xs:element name="ECDSAKeyValue" type="ecdsa:ECDSAKeyValueType"/>

  <xs:complexType name="ECDSAKeyValueType">
    <xs:sequence>
      <xs:element name="DomainParameters" type="ecdsa:DomainParamsType"
                  minOccurs="0"/>
      <xs:element name="PublicKey" type="ecdsa:ECPointType"/>
    </xs:sequence>
  </xs:complexType>
  
  DTD Definition:
  
  <!ELEMENT ECDSAKeyValue (DomainParameters?, PublicKey)>
  <!ELEMENT PublicKey (X, Y)?>
  <!ELEMENT X EMPTY>
  <!ATTLIST X Value CDATA #REQUIRED>
  <!ELEMENT Y EMPTY>
  <!ATTLIST Y Value CDATA #REQUIRED>

3.4.2 EC Domain Parameters

Domain parameters can be encoded either explicitly using element 
ExplicitParams, or by reference using element NamedCurve. The latter 
simply consists of an attribute named URN, which bears a uniform 
resource name as its value. For the named curves of standards like 
[X9.62], [FIPS-186-2] or [SEC2], the OIDs of these curves SHOULD be used
in this attribute, e. g. URN="urn:oid:1.2.840.10045.3.1.1". The 
mechanism for encoding OIDs in URNs is shown in [RFC3061].

  Schema Definition:
  
  <xs:complexType name="DomainParamsType">
    <xs:choice>
      <xs:element name="ExplicitParams" 
                  type="ecdsa:ExplicitParamsType"/>
      <xs:element name="NamedCurve">
        <xs:complexType>
          <xs:attribute name="URN" type="xs:anyURI" use="required"/>
        </xs:complexType>
      </xs:element>
    </xs:choice>
  </xs:complexType>
  
  DTD Definition:
  
  <!ELEMENT DomainParameters (ExplicitParams | NamedCurve)>
  <!ELEMENT NamedCurve EMPTY>
  <!ATTLIST NamedCurve URN CDATA #REQUIRED>

The element ExplicitParams is used for explicit encoding of domain 

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parameters. It contains three subelements: FieldParams describes the
underlying field, CurveParams describes the elliptic curve, and 
BasePointParams describes the base point of the elliptic curve.

  Schema Definition:
  
  <xs:complexType name="ExplicitParamsType">
    <xs:sequence>
      <xs:element name="FieldParams" type="ecdsa:FieldParamsType"/>
      <xs:element name="CurveParams" type="ecdsa:CurveParamsType"/>
      <xs:element name="BasePointParams" 
                  type="ecdsa:BasePointParamsType"/>
    </xs:sequence>
  </xs:complexType>

  DTD Definition:

  <!ELEMENT ExplicitParams (FieldParams, CurveParams, BasePointParams)>
  
3.4.2.1 Field Parameters  
  
The element FieldParams is used for encoding field parameters. The 
corresponding XML Schema type FieldParamsType is declared abstract and 
will be extended by specialized types for prime field, characteristic
two field and odd characteristic extension fields parameters.

The XML Schema type PrimeFieldParamsType is derived from FieldParamsType
and is used for for encoding prime field parameters. The type contains 
as its single subelement P, the order of the prime field.

The XML Schema type CharTwoFieldParamsType is derived from 
FieldParamsType as well and is used for encoding parameters of a 
characteristic two field. It is again an abstract type and will be 
extended by specialized types for trinomial base fields and pentanomial
base fields. F2m Gaussian Normal Base fields are not supported by this
specification to relieve interoperability. Common to both specialized 
types is the element M, the extension degree of the field.

The XML Schema type TnBFieldParamsType is derived from 
CharTwoFieldParamsType and is used for encoding trinomial base fields. 
It adds the single element K, which represents the integer k, where 
x^m + x^k + 1 is the reduction polynomial.

The XML Schema type PnBFieldParamsType is derived from 
CharTwoFieldParamsType as well and is used for encoding pentanomial base
fields. It adds the three elements K1, K2 and K3, which represent the 
integers k1, k2 and k3 respectively, where x^m + x^k3 + x^k2 + x^k1 + 1 
is the reduction polynomial.

The XML Schema type OddCharExtensionFieldParamsType is derived from 
FieldParamsType as well and is used for encoding parameters of an 
odd characteristic extension field. The type contains two elements M, 
which represents the extension degree of the field m, and W, which
represents the integer w, where x^m - w is the reduction polynomial.

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  Schema Definition:
  
  <xs:complexType name="FieldParamsType" abstract="true"/>
  
  <xs:complexType name="PrimeFieldParamsType">
    <xs:complexContent>
      <xs:extension base="ecdsa:FieldParamsType">
        <xs:sequence>
          <xs:element name="P" type="xs:positiveInteger"/>
        </xs:sequence>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="CharTwoFieldParamsType" abstract="true">
    <xs:complexContent>
      <xs:extension base="ecdsa:FieldParamsType">
        <xs:sequence>
          <xs:element name="M" type="xs:positiveInteger"/>
        </xs:sequence>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="OddCharExtensionFieldParamsType">
    <xs:complexContent>
      <xs:extension base="ecdsa:FieldParamsType">
        <xs:sequence>
          <xs:element name="M" type="xs:positiveInteger"/>
          <xs:element name="W" type="xs:positiveInteger"/>
        </xs:sequence>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="TnBFieldParamsType">
    <xs:complexContent>
      <xs:extension base="ecdsa:CharTwoFieldParamsType">
        <xs:sequence>
          <xs:element name="K" type="xs:positiveInteger"/>
        </xs:sequence>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="PnBFieldParamsType">
    <xs:complexContent>
      <xs:extension base="ecdsa:CharTwoFieldParamsType">
        <xs:sequence>
          <xs:element name="K1" type="xs:positiveInteger"/>
          <xs:element name="K2" type="xs:positiveInteger"/>
          <xs:element name="K3" type="xs:positiveInteger"/>

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        </xs:sequence>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>
  
  DTD Definition:

  <!ELEMENT FieldParams (P | (M, K) | (M, K1, K2, K3) | (M, W))>
  <!ELEMENT P (#PCDATA)>
  <!ELEMENT M (#PCDATA)>
  <!ELEMENT K (#PCDATA)>
  <!ELEMENT K1 (#PCDATA)>
  <!ELEMENT K2 (#PCDATA)>
  <!ELEMENT K3 (#PCDATA)>
  <!ELEMENT W (#PCDATA)>

3.4.2.2 Curve Parameters

The element CurveParams is used for encoding parameters of the elliptic
curve. The corresponding XML Schema type CurveParamsType bears the 
elements A and B representing the coefficients a and b of the elliptic
curve, while the optional element Seed contains the value used to derive
the coefficients of a randomly generated elliptic curve, according to 
the algorithm specified in annex A3.3 of [X9.62].

  Schema Definition:
  
  <xs:complexType name="CurveParamsType">
    <xs:sequence>
      <xs:element name="A" type="ecdsa:FieldElemType"/>
      <xs:element name="B" type="ecdsa:FieldElemType"/>
      <xs:element name="Seed" type="xs:hexBinary" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>

  DTD Definition:
  
  <!ELEMENT CurveParams (A, B, Seed?)>
  <!ELEMENT A EMPTY>
  <!ATTLIST A Value CDATA #REQUIRED>
  <!ELEMENT B EMPTY>
  <!ATTLIST B Value CDATA #REQUIRED>
  <!ELEMENT Seed (#PCDATA)>

3.4.2.3 Base Point Parameters

The element BasePointParams is used for encoding parameters regarding  
the base point of the elliptic curve. BasePoint represents the base 
point itself, Order provides the order of the base point, and Cofactor 
optionally provides the cofactor of the base point.

  Schema Definition:
  
  <xs:complexType name="BasePointParamsType">

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    <xs:sequence>
      <xs:element name="BasePoint" type="ecdsa:ECPointType"/>
      <xs:element name="Order" type="xs:positiveInteger"/>
      <xs:element name="Cofactor" type="xs:positiveInteger" 
                  minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>

  DTD Definition:
  
  <!ELEMENT BasePointParams (BasePoint, Order, Cofactor?)>
  <!ELEMENT BasePoint (X, Y)?>
  <!ELEMENT Order (#PCDATA)>
  <!ELEMENT Cofactor (#PCDATA)>

3.4.3 EC Points

The XML Schema type ECPointType is used for encoding a point on the 
elliptic curve. It consists of the subelements X and Y, providing the
x and y coordinates of the point. Point compression representation is
not supported by this specification for the sake of simple design. 

The point at infinity is encoded by omitting both elements X and Y.

The subelements X and Y are of type FieldElemType. This is an abstract
type for encoding elements of the elliptic curves underlying field and
is extended by specialized types for prime field elements and 
characteristic two field elements.

The XML Schema type PrimeFieldElemType is used for encoding prime field
elements. It contains a single attribute named Value, whose value 
represents the field element as an integer.

The XML Schema type CharTwoFieldElemType is used for encoding 
characteristic two field elements. It contains a single attribute named 
Value, whose value represents the field element as an octet string. The
octet string must be composed as shown in paragraph 2 of section 4.3.3
of [X9.62].

The XML Schema type OddCharExtensionFieldElemType is used for encoding 
odd characteristic extension field elements. It contains a single 
attribute named Value, whose value represents the field element as an 
integer. The integer must be composed as shown in section
5.3.3 of [IEEE1363a].

  Schema Definition:
  
  <xs:complexType name="ECPointType">
    <xs:sequence minOccurs="0">
      <xs:element name="X" type="ecdsa:FieldElemType"/>
      <xs:element name="Y" type="ecdsa:FieldElemType"/>
    </xs:sequence>
  </xs:complexType>

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  <xs:complexType name="FieldElemType" abstract="true"/>
  
  <xs:complexType name="PrimeFieldElemType">
    <xs:complexContent>
      <xs:extension base="ecdsa:FieldElemType">
        <xs:attribute name="Value" type="xs:nonNegativeInteger" 
                      use="required"/>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="CharTwoFieldElemType">
    <xs:complexContent>
      <xs:extension base="ecdsa:FieldElemType">
        <xs:attribute name="Value" type="xs:hexBinary" 
                      use="required"/>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="OddCharExtensionFieldElemType">
    <xs:complexContent>
      <xs:extension base="ecdsa:FieldElemType">
        <xs:attribute name="Value" type="xs:nonNegativeInteger" 
                      use="required"/>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

4. Security Considerations

Implementers should ensure that appropriate security measures are in
place when they deploy ECDSA within XMLDSIG. In particular, the security
of ECDSA requires the careful selection of both key sizes and elliptic
curve domain parameters. Selection guidelines for these parameters and
some specific recommended curves that are considered safe are provided
in [X9.62], [NIST-ECC], and [SEC2]. For further security discussion,
see [XMLDSIG].

5. Normative References

  [Eastlake] Eastlake, D. Additional XML Security URIs. IETF 
             Internet-Draft. March 2004.
             http://www.ietf.org/internet-drafts/
             draft-eastlake-xmldsig-uri-06.txt.

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  [X9.62] American National Standards Institute. ANSI X9.62-1998,
          Public Key Cryptography for the Financial Services Industry:
          The Elliptic Curve Digital Signature Algorithm. January 1999.

  [XMLDSIG] Eastlake, D., Reagle, J., and Solo, D., RFC 3275, 
            XML-Signature Syntax and Processing. IETF RFC, March 2002.
            http://www.ietf.org/rfc/rfc3275.txt. 
            (Also W3C Recommendation, February 2002.
            http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/.) 

  [XML-schema] Beech, D., Maloney, M., Mendelsohn, N., and Thompson, 
               H., XML Schema Part 1: Structures, W3C Recommendation,
               May 2001.
               http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/
               Biron, P., and Malhotra, A., ML Schema Part 2: 
               Datatypes, W3C Recommendation, May 2001.
               http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/ 

6. Informative References

  [FIPS-180-1] Federal Information Processing Standards Publication
               (FIPS PUB) 180-1, Secure Hash Standard, April 1995.

  [FIPS-186-2] Federal Information Processing Standards Publication
               (FIPS PUB) 186-2, Digital Signature Standard, January
               2000. 

  [IEEE1363] Institute for Electrical and Electronics Engineers (IEEE)
             Standard 1363-2000, Standard Specifications for Public Key
             Cryptography, January 2000. 

  [IEEE1363a] Institute for Electrical and Electronics Engineers (IEEE)
              Standard 1363, Draft Standard Specifications for Public 
              Key Cryptography -- Amendment 1: Additional Techniques, 
              October 2002.

  [KEYS] Lenstra, A.K. and Verheul, E.R., Selecting Cryptographic Key
         Sizes. October 1999. Presented at Public Key Cryptography 
         Conference, Melbourne, Australia, January 2000.
         http://www.cryptosavvy.com/

  [RFC3061] Mealling, M., RFC 3061, A URN Namespace of Object 
            Identifiers. IETF Informational RFC, February 2001.
            http://www.ietf.org/rfc/rfc3061.txt

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  [RFC3279] Bassham, L., Housley, R., and Polk, W., RFC 3279, Algorithms  
            and Identifiers for the Internet X.509 Public Key 
            Infrastructure Certificate and Certificate Revocation List 
            (CRL) Profile. IETF Proposed Standard, April 2002. 
            http://www.ietf.org/rfc/rfc3279.txt

  [SEC1] Standards for Efficient Cryptography Group, SEC 1: Elliptic 
         Curve Cryptography, Version 1.0, September 2000.
         http://www.secg.org

  [SEC2] Standards for Efficient Cryptography Group, SEC 2: Recommended
         Elliptic Curve Domain Parameters, Version 1.0, September 2000.
         http://www.secg.org

  [XML] Bray, T., Maler, E., Paoli, J. , and Sperberg-McQueen, C. M., 
        Extensible Markup Language (XML) 1.0 (Second Edition), W3C 
        Recommendation, October 2000.
        http://www.w3.org/TR/2000/REC-xml-20001006 

  [XML-ns] Bray, T., Hollander, D., and Layman, A., Namespaces in XML,
           W3C Recommendation, January 1999. 
           http://www.w3.org/TR/1999/REC-xml-names-19990114/

7. Acknowledgements

  The authors would like to acknowledge the many helpful comments of
  Wolfgang Bauer, Donald Eastlake, Tom Gindin, Chris Hawk, Akihiro Kato,
  Shiho Moriai, Joseph M. Reagle Jr., and Francois Rousseau.

   

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Appendix A: Aggregate XML Schema

  <?xml version="1.0" encoding="UTF-8"?>
  <xs:schema targetNamespace="http://www.buergerkarte.at/namespaces/
                              ecdsa/200206030#"
             xmlns:dsig="http://www.w3.org/2000/09/xmldsig#" 
             xmlns:xs="http://www.w3.org/2001/XMLSchema" 
             xmlns:ecdsa="http://www.buergerkarte.at/namespaces/
                          ecdsa/200206030#"
             elementFormDefault="qualified" 
             attributeFormDefault="unqualified" version="0.3">

    <!--ECDSA key value root element-->

    <xs:element name="ECDSAKeyValue" type="ecdsa:ECDSAKeyValueType"/>
    <xs:complexType name="ECDSAKeyValueType">
      <xs:sequence>
        <xs:element name="DomainParameters" 
                    type="ecdsa:DomainParamsType" minOccurs="0"/>
        <xs:element name="PublicKey" type="ecdsa:ECPointType"/>
      </xs:sequence>
    </xs:complexType>

    <!--EC domain parameters-->

    <xs:complexType name="DomainParamsType">
      <xs:choice>
        <xs:element name="ExplicitParams" 
                    type="ecdsa:ExplicitParamsType"/>
        <xs:element name="NamedCurve">
          <xs:complexType>
            <xs:attribute name="URN" type="xs:anyURI" use="required"/>
          </xs:complexType>
        </xs:element>
      </xs:choice>
    </xs:complexType>
    <xs:complexType name="FieldParamsType" abstract="true"/>

    <xs:complexType name="PrimeFieldParamsType">
      <xs:complexContent>
        <xs:extension base="ecdsa:FieldParamsType">
          <xs:sequence>
            <xs:element name="P" type="xs:positiveInteger"/>
          </xs:sequence>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>

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    <xs:complexType name="CharTwoFieldParamsType" abstract="true">
      <xs:complexContent>
        <xs:extension base="ecdsa:FieldParamsType">
          <xs:sequence>
            <xs:element name="M" type="xs:positiveInteger"/>
          </xs:sequence>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
    <xs:complexType name="OddCharExtensionFieldParamsType">
      <xs:complexContent>
        <xs:extension base="ecdsa:FieldParamsType">
          <xs:sequence>
            <xs:element name="M" type="xs:positiveInteger"/>
            <xs:element name="W" type="xs:positiveInteger"/>
          </xs:sequence>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
    <xs:complexType name="TnBFieldParamsType">
      <xs:complexContent>
        <xs:extension base="ecdsa:CharTwoFieldParamsType">
          <xs:sequence>
            <xs:element name="K" type="xs:positiveInteger"/>
          </xs:sequence>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
    <xs:complexType name="PnBFieldParamsType">
      <xs:complexContent>
        <xs:extension base="ecdsa:CharTwoFieldParamsType">
          <xs:sequence>
            <xs:element name="K1" type="xs:positiveInteger"/>
            <xs:element name="K2" type="xs:positiveInteger"/>
            <xs:element name="K3" type="xs:positiveInteger"/>
          </xs:sequence>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>

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    <xs:complexType name="ExplicitParamsType">
      <xs:sequence>
        <xs:element name="FieldParams" type="ecdsa:FieldParamsType"/>
        <xs:element name="CurveParams" type="ecdsa:CurveParamsType"/>
        <xs:element name="BasePointParams" 
                    type="ecdsa:BasePointParamsType"/>
      </xs:sequence>
    </xs:complexType>
    <xs:complexType name="CurveParamsType">
      <xs:sequence>
        <xs:element name="A" type="ecdsa:FieldElemType"/>
        <xs:element name="B" type="ecdsa:FieldElemType"/>
        <xs:element name="Seed" type="xs:hexBinary" minOccurs="0"/>
      </xs:sequence>
    </xs:complexType>
    <xs:complexType name="BasePointParamsType">
      <xs:sequence>
        <xs:element name="BasePoint" type="ecdsa:ECPointType"/>
        <xs:element name="Order" type="xs:positiveInteger"/>
        <xs:element name="Cofactor" type="xs:positiveInteger" 
                    minOccurs="0"/>
      </xs:sequence>
    </xs:complexType>

    <!--EC point-->

    <xs:complexType name="ECPointType">
      <xs:sequence minOccurs="0">
        <xs:element name="X" type="ecdsa:FieldElemType"/>
        <xs:element name="Y" type="ecdsa:FieldElemType"/>
      </xs:sequence>
    </xs:complexType>

    <!--Field element-->

    <xs:complexType name="FieldElemType" abstract="true"/>
    <xs:complexType name="PrimeFieldElemType">
      <xs:complexContent>
        <xs:extension base="ecdsa:FieldElemType">
          <xs:attribute name="Value" type="xs:nonNegativeInteger" 
                        use="required"/>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>

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    <xs:complexType name="CharTwoFieldElemType">
      <xs:complexContent>
        <xs:extension base="ecdsa:FieldElemType">
          <xs:attribute name="Value" type="xs:hexBinary" 
                        use="required"/>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
    <xs:complexType name="OddCharExtensionFieldElemType">
      <xs:complexContent>
        <xs:extension base="ecdsa:FieldElemType">
          <xs:attribute name="Value" type="xs:nonNegativeInteger" 
                        use="required"/>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
  </xs:schema>

Appendix B: Aggregate DTD

  <!ELEMENT ECDSAKeyValue (DomainParameters?, PublicKey)>
  <!ELEMENT PublicKey (X, Y)?>
  <!ELEMENT X EMPTY>
  <!ATTLIST X Value CDATA #REQUIRED>
  <!ELEMENT Y EMPTY>
  <!ATTLIST Y Value CDATA #REQUIRED>
  <!ELEMENT DomainParameters (ExplicitParams | NamedCurve)>
  <!ELEMENT NamedCurve EMPTY>
  <!ATTLIST NamedCurve URN CDATA #REQUIRED>
  <!ELEMENT ExplicitParams (FieldParams, CurveParams, BasePointParams)>
  <!ELEMENT FieldParams (P | (M, K) | (M, K1, K2, K3) | (M, W))>
  <!ELEMENT P (#PCDATA)>
  <!ELEMENT M (#PCDATA)>
  <!ELEMENT W (#PCDATA)>
  <!ELEMENT K (#PCDATA)>
  <!ELEMENT K1 (#PCDATA)>
  <!ELEMENT K2 (#PCDATA)>
  <!ELEMENT K3 (#PCDATA)>
  <!ELEMENT CurveParams (A, B, Seed?)>
  <!ELEMENT A EMPTY>
  <!ATTLIST A Value CDATA #REQUIRED>
  <!ELEMENT B EMPTY>
  <!ATTLIST B Value CDATA #REQUIRED>
  <!ELEMENT Seed (#PCDATA)>
  <!ELEMENT BasePointParams (BasePoint, Order, Cofactor?)>
  <!ELEMENT BasePoint (X, Y)?>
  <!ELEMENT Order (#PCDATA)>
  <!ELEMENT Cofactor (#PCDATA)>

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Authors' Addresses

   Simon Blake-Wilson
   BCI
   96 Spadina Ave, Unit 606
   Toronto, ON, M5V 2J6, Canada
   e-mail: sblakewilson@bcisse.com

   Gregor Karlinger
   Federal Staff Office for IT Strategies/Federal Chancellery
   Ballhausplatz 2
   1014 Wien, Austria
   e-mail: gregor.karlinger@cio.gv.at

   Tetsutaro Kobayashi
   NTT Laboratories
   1-1 Hikarinooka, Yokosuka, 239-0847, Japan
   e-mail: kotetsu@isl.ntt.co.jp
   
   Yongge Wang
   University of North Carolina at Charlotte
   9201 University City Blvd
   Charlotte, NC 28223, USA
   e-mail: yonwang@uncc.edu

Intellectual Property Rights

The IETF has been notified of intellectual property rights claimed in
regard to the specification contained in this document.
For more information, consult the online list of claimed rights
(http://www.ietf.org/ipr.html).

The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
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might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementers or users of this specification can
be obtained from the IETF Secretariat.

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Full Copyright Statement

  Copyright (C) The Internet Society (1999).  All Rights Reserved.
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