XML Key Management Specification (XKMS 2.0)

W3C Editors Copy 1st August 2002

This version:

http://www.w3.org/2001/XKMS/Drafts/XKMS/xkms-part-1.html 

Latest version:

http://www.w3.org/2001/XKMS/Drafts/XKMS/xkms-part-1.html 

Previous version:

http://www.w3.org/2001/XKMS/Drafts/xkms.html

Editor:

Phillip Hallam-Baker VeriSign

Contributors:

See the WG participants list.

[1] Copyright  2001,2002 W3C (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply.

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Table Of Contents

XML Key Management Specification (XKMS 2.0)

W3C Editors Copy 1st August 2002

Abstract

Status of this document

Table Of Contents

1 Introduction

1.1 Editorial and Conformance Conventions

1.2 Definition of Terms

1.3 Namepaces

1.4 Key Information Service Specification Overview (Non-Normative)

1.5 Key Registration Service Specification Overview (Non-Normative)

1.6 Structure of this document

2 Message Format

2.1 Synchronous and Asynchronous Processing

2.2 Security Binding

2.3 Syntax

3 Key Information Service Overview

3.1 XKISS Locate Service

3.2 XKISS: Validate Service

3.3 Using Locate and Validate

4 Key Information Service Message Set

4.1 Key Binding Specification

4.2 Locate Service

4.3 Validate Service

5 Key Registration Service Overview

5.1 Registration

5.2 Reissue

5.3 Revocation

5.4 Key Recovery

5.5 Request Authentication

6 Key Registration Service Message Set

6.1 Registration

7 Cryptographic Algorithm Specific Parameters

7.1 Use of Limited-Use Shared Secret Data

7.2 Private Key Parameters

8 Security Considerations

8.1 Replay Attacks

8.2 Denial of Service

8.3 Recovery Policy

8.4 Security of Limited Use Shared Secret

8.5 Security of Not Bound Authentication Data

9 Acknowledgments

Appendix A Schemas

A.1 XKMS Schema

Appendix B Service Location Configuration

B.1 Domain Name Service (DNS)

Appendix C Sample Protocol Exchanges

C.1 Authentication Computation

C.2 Pass Phrase Computation

C.3 Private Key Parameters

Appendix D References

Appendix E Legal Notices

Appendix F Work In Progress

F.1 Outstanding Issues

F.2 Issues Addressed in this Draft

F.3 Issues Addressed in Draft 9

F.4 Issues Addressed in Draft 8

F.5 Issues Addressed in Previous Drafts

1 Introduction

[9] This document specifies protocols for distributing and registering public keys, suitable for use in conjunction with the proposed standard for XML Signatures [XML-SIG] developed by the World Wide Web Consortium (W3C) and the Internet Engineering Task Force (IETF) and an anticipated companion standard for XML encryption.  The XML Key Management Specification (XKMS) comprises two parts -- the XML Key Information Service Specification (X-KISS) and the XML Key Registration Service Specification (X-KRSS).

[10] These protocols do not require any particular underlying public key infrastructure (such as X.509) but are designed to be compatible with such infrastructures.

[11] This document comprises the following service specifications:

XML Key Information Service Specification: 

A protocol to support the delegation by an application to a service of the processing of Key Information associated with an XML signature, XML encryption, or other public key.  Its functions include the location of required public keys and describing the binding of such keys to identification information.

XML Key Registration Service Specification: 

A protocol to support the registration of a key pair by a key pair holder, with the intent that the key pair subsequently be usable in conjunction with the XML Key Information Service Specification or higher level trust assertion service such as XML Trust Assertion Service Specification [XTASS].

1.1 Editorial and Conformance Conventions

[12] This specification uses XML Schemas [XML-schema] to describe the content model.

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

[14] "they MUST only be used where it is actually required for interoperation or to limit behavior which has potential for causing harm (e.g., limiting retransmissions)"

[15] Consequently, we use these capitalized keywords to unambiguously specify requirements over protocol and application features and behavior that affect the interoperability and security of implementations. These key words are not used (capitalized) to describe XML grammar; schema definitions unambiguously describe such requirements and we wish to reserve the prominence of these terms for the natural language descriptions of protocols and features. For instance, an XML attribute might be described as being "optional." Compliance with the XML-namespace specification [XML-NS] is described as "REQUIRED."

1.2 Definition of Terms

[16] The following terms are used within this document with the particular meaning indicated below:

[17] Service
    An application that provides computational or informational resources on request. A service may be provided by several physical servers operating as a unit.

[18] Web service
    A service that is accessible by means of messages sent using standard web protocols, notations and naming conventions

[19] Client
    An application that makes requests of a service.  The concept of 'client' is relative to a service request; an application may have the role of client for some requests and service for others.

1.3 Namepaces

[20] For clarity, some examples of XML are not complete documents and namespace declarations may be omitted from XML fragments. In this document, certain namespace prefixes represent certain namespaces as follows

[21] These namespaces are declared in the XKMS schema as follows:

<?xml version="1.0"?>
<schema targetNamespace="http://www.w3.org/2002/03/xkms#" 
      xmlns="http://www.w3.org/2001/XMLSchema" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xkms="http://www.w3.org/2002/03/xkms#" elementFormDefault="qualified" 
      attributeFormDefault="unqualified">
   <import namespace="http://www.w3.org/2000/09/xmldsig#" 
         schemaLocation="xmldsig-core-schema.xsd"/>
   <import namespace="http://www.w3.org/2001/04/xmlenc#" 
         schemaLocation="xenc-schema.xsd"/>
   <annotation>
      <documentation xml:lang="en">
              XML Schema for XKMS 2.0 draft 8  1st April 2002
      </documentation>
   </annotation>
   <!-- /Namespace -->

   ...

   <!-- End Schema -->
</schema>

1.4 Key Information Service Specification Overview (Non-Normative)

[22] X-KISS allows a client to delegate part or all of the tasks required to process XML Signature <ds:KeyInfo> elements to a Trust service. A key objective of the protocol design is to minimize the complexity of applications using XML Signature. By becoming a client of the trust service, the application is relieved of the complexity and syntax of the underlying PKI used to establish trust relationships, which may be based upon a different specification such as X.509/PKIX, SPKI or PGP.

[23] By design, the XML Signature Specification does not mandate use of a particular trust policy. The signer of a document is not required to include any key information but may include a <ds:KeyInfo> element that specifies the key itself, a key name, X.509 certificate, a PGP Key Identifier etc. Alternatively, a link may be provided to a location where the full <ds:KeyInfo> information may be found.

[24] The information provided by the signer may therefore be insufficient by itself to perform cryptographic verification and decide whether to trust the signing key, or the information may not be in a format the client can use. For example:

• The Key may be specified by a name only.
• The local trust policy of the client may require additional information in order to trust the key.
• The Key may be encoded in an X.509 certificate that the client cannot parse.

[25] In the case of an encryption operation:

• The client may not know the public key of the recipient.

1.5 Key Registration Service Specification Overview (Non-Normative)

[26] X-KRSS describes a protocol for registration of public key information. A client of a conforming service may request that the Registration Service bind information to a public key. The information bound may include a name, an identifier or extended attributes defined by the implementation.

[27] The key pair to which the information is bound may be generated in advance by the client or, to support key recovery, may be generated on request by the service. The Registration protocol may also be used for subsequent recovery of a private key.

[28] The protocol provides for authentication of the applicant and, in the case that the key pair is generated by the client, Proof of Possession (POP) of the private key. A means of communicating the private key to the client is provided in the case that the private key is generated by the Registration Service.

[29] This document specifies means of registering RSA and DSA keys and a framework for extending the protocol to support other cryptographic algorithms such as Diffie-Helleman and Elliptic Curve variants.

1.6 Structure of this document

[30] The remainder of this document describes the XML Key Information Service Specification and XML Key Registration Service Specification.

Section 2: Message Format

Features of the XKMS that are common to the XKMS services are described

Section 3: Key Information Service Specification Overview.

The functional behavior of the X-KISS service is described.

Section 4: Key Information Service Specification Message Set.

The semantics of the X-KISS protocol messages are defined.

Section 5: Key Registration Service Specification Overview.

The functional behavior of the X-KRSS service is described.

Section 6: Key Registration Service Specification Message Set.

The semantics of the X-KRSS protocol messages is defined.

Section 7: Cryptographic Algorithm Specific Parameters

Parameters and data formats specific to the use of particular cryptographic algorithms are defined.

Section 8: Security Considerations

Security considerations for implementation and deployment of XKMS are described

2 Message Format

[31] XKMS protocol exchanges consist of a sequence of either one or two request response pairs.

[32] XKMS protocol messages share a common format that is carried in the body of a SOAP message. Implementations MAY support other encapsulation formats at their option.

[33] Part II of this specification describes the XKMS Protocol bindings.

2.1 Synchronous and Asynchronous Processing

[34] XKMS services MUST support synchronous processing. In synchronous processing the service returns the final response to the requestor using the same communication channel used to issue the request.

[35] A client MAY offer to accept asynchronous processing of a request. XKMS services MAY at their option support asynchronous processing. XKMS services MUST NOT return notification of an asynchronous response unless requested by the client.

[36] Asynchronous processing is used in cases where a service cannot complete the request immediately and it is undesirable to keep the communication channel used for the request open while the request is being completed.

[37] Asynchronous processing MAY be used to allow administrator intervention during the processing of a request. For example an administrator might be required to verify and approve all XKRSS Registration requests before they are processed.

[38] The Synchronous and Asynchronous processing of requests is described in Part II.

2.2 Security Binding

[39] The security concerns that an XKMS service is required to address are dependent on the specific service deployment. For example a free XKMS Location service may not require controls for Request Authentication or to prevent Request Replay attacks while a paid Validate service might. The application of security enhancements is addressed  in Part II which describes the application of the following security enhancements:

• Confidentiality
• Request Authentication
• Response Authentication
• Transitive Authentication
• Response Replay
• Request Substitution
• Request Replay
• Denial of Service

[40] The use of security enhancements is further discussed in the section Security Considerations below.

2.3 Syntax

2.3.1 Type MessageAbstractType

[41] The MessageAbstractType abstract type is the type from which all XKMS message element types are derived. The MessageAbstractType abstract type contains the following element and attributes

<ds:Signature>  [Optional]

An XML Signature in enveloped mode. The scope of the signature is the element derived from the MessageAbstractType abstract type.

<OpaqueClientData> [Optional]

Data specified by the client that is opaque to the service. An XKMS service SHOULD return the value of the <OpaqueClientData> element unmodified in a request in a response with status code Success.

Id  [Required]

A unique identifier generated by the requestor.

Service  [Required]

The URI of the Web Service port to which the request is addressed

Nonce  [Optional]

Cryptographically random data used to defend against replay attack.

[42] The following schema defines the MessageAbstractType abstract type:

   <!-- MessageAbstractType -->
   <complexType name="MessageAbstractType" abstract="true">
      <sequence>
         <element ref="ds:Signature" minOccurs="0"/>
         <element ref="xkms:OpaqueClientData" minOccurs="0"/>
      </sequence>
      <attribute name="Id" type="ID" use="required"/>
      <attribute name="Service" type="anyURI" use="required"/>
      <attribute name="Nonce" type="ds:CryptoBinary" use="optional"/>
   </complexType>
   <!-- /MessageAbstractType -->

2.3.2 Element <ds:Signature>

[43] An XML Signature in enveloped mode. The scope of the signature is specified using the Id attribute specified in the MessageAbstractType abstract type.

[44] The <ds:Signature> element is specified in the XML Signature specification [XML-SIG].

2.3.3 Element <OpaqueClientData>

[45] The <OpaqueClientData> contains data specified by the client that is opaque to the service. An XKMS service SHOULD return the value of an <OpaqueClientData> element specified in a request unmodified in a response with status code Success.

[46] The following schema defines the OpaqueClientData element:

   <!-- OpaqueClientData -->
   <element name="OpaqueClientData" type="xkms:OpaqueClientDataType"/>
   <complexType name="OpaqueClientDataType">
      <sequence minOccurs="0" maxOccurs="unbounded">
         <any namespace="##other"/>
      </sequence>
   </complexType>
   <!-- /OpaqueClientData -->

2.3.4 Type RequestAbstractType

[47] The RequestAbstractType abstract type is the type from which all XKMS request element types are derived. The RequestAbstractType abstract type inherits the element and attributes of the MessageAbstractType abstract type and in addition contains the following attributes

<RespondWith>  [Any Number]

Specifies the types of data the recipient requests to be sent in the response.

<PendingNotification>  [Optional]

Specifies a means by which the service may notify the requestor of the completion of a pending response. If the <PendingNotification> element is present the value Pending MUST be specified as a <RespondWith> value.

OriginalRequestID  [Optional]

Specifies the identifier of the original request in the case of a represented or pending request

ResponseLimit  [Optional]

Specifies the maximum number of data items the requestor can accept in the case that the schema specifies an unbounded number of elements.

[48] The following schema defines the RequestAbstractType abstract type:

   <!-- RequestAbstractType -->
   <complexType name="RequestAbstractType" abstract="true">
      <complexContent>
         <extension base="xkms:MessageAbstractType">
            <sequence>
               <element ref="xkms:RespondWith" minOccurs="0" maxOccurs="unbounded"/>
               <element ref="xkms:PendingNotification" minOccurs="0"/>
            </sequence>
            <attribute name="OriginalRequestId" type="anyURI" use="optional"/>
            <attribute name="ResponseLimit" type="integer" use="optional"/>
         </extension>
      </complexContent>
   </complexType>
   <!-- /RequestAbstractType -->

2.3.5 Element <RespondWith>

[49] The <RespondWith> element in the request specifies one or more strings included in the request that specify data elements to be provided in the <ds:Keyinfo> element of the response. Each string is a single identifier corresponding to a sub-element of the XML Signature Specification <ds:Keyinfo> element [XML-SIG] or the private key information defined in  the section Cryptographic Algorithm Specific Parameters below.. The XML Signature elements are described here for convenience. The normative reference is the specification [XML-SIG].

[50] The Service SHOULD return a requested data element if it is available. The Service MAY return additional data elements that were not requested. In particular, the service MAY return data elements specified in the request with the response.

[51] The following identifiers are defined:

[52] For example, a client that has no X.509 processing capability might perform a Locate operation to obtain the public key parameters and name information from a <ds:Keyinfo> element that specifies only a certificate. The Respond element values in this case would be "KeyName" and "KeyValue".

[53] The following schema defines the <RespondWith> element::

   <!-- RespondWith -->
   <element name="RespondWith" type="QName"/>
   <!-- /RespondWith -->

2.3.6 Element <PendingNotification>

[54] The <PendingNotification> element is used to specify a mechanism by means of which the service can inform a requestor that a pending request has completed asynchronously.

[55] The <PendingNotification> element contains the following attributes

Mechanism  [Required]

A URI that specifies the protocol by which the notification is made

Identifier  [Required]

A URI that specified the address to which the notification is made

[56] The following mechanisms are defined:

[57] The following schema defines the <PendingNotification> element and PendingNotificationType type:

   <!-- PendingNotification -->
   <element name="PendingNotification" type="xkms:PendingNotificationType"/>
   <complexType name="PendingNotificationType">
      <attribute name="Mechanism" type="anyURI" use="required"/>
      <attribute name="Identifier" type="anyURI" use="required"/>
   </complexType>
   <!-- /PendingNotification -->

2.3.7 Element <PendingRequest>

[58] The PendingRequest element is used to request the result of a previously presented request for which the MajorResult code Pending was returned. The PendingRequest element inherits the element and attributes of AbstractRequestType and the following attribute:

ResponseID  [Optional]

The value of the ResponseID attribute sent in the original pending response.

[59] The following schema defines the PendingRequest element and PendingRequestType type:

   <!-- PendingRequest -->
   <element name="PendingRequest" type="xkms:PendingRequestType"/>
   <complexType name="PendingRequestType">
      <complexContent>
         <extension base="xkms:RequestAbstractType">
            <attribute name="ResponseId" type="anyURI" use="optional"/>
         </extension>
      </complexContent>
   </complexType>
   <!-- /PendingRequest -->

2.3.8 Element <ResultAbstractType>

[60] The ResultAbstractType abstract type is the type from which all XKMS response element types are derived. The ResultAbstractType abstract type inherits the element and attributes of the MessageAbstractType abstract type and in addition contains the following attributes

ResultMajor  [Required]

The most significant component of the result code

ResultMinor  [Optional]

The least significant component of the result code

RequestID  [Required]

The unique identifier Id specified in the request

[61] If the MajorResult value has the value Represent the nonce attribute MUST be present and MUST NOT be the empty string.

[62] The following schema defines the ResultAbstractType abstract type:

   <!-- ResultAbstractType -->
   <complexType name="ResultAbstractType" abstract="true">
      <complexContent>
         <extension base="xkms:MessageAbstractType">
            <attribute name="ResultMajor" type="QName" use="required"/>
            <attribute name="ResultMinor" type="QName" use="optional"/>
            <attribute name="RequestId" type="anyURI" use="required"/>
         </extension>
      </complexContent>
   </complexType>
   <!-- /ResultAbstractType -->

2.3.8.1 Result Codes

[63] Result codes consist of a major code and a minor code. This specification uses the notation ResultMajor.ResultMinor to specify a result code. For example the result code Sender.NoMatch indicates a ResultMajor code of Sender and a ResultMinor code of NoMatch.

[64] The following ResultMajor codes are defined:

[65] The ResultMajor codes Success, VersionMismatch, Sender and Receiver are Final, that is the protocol has completed when the code is returned. The ResultMajor codes Queued, Represent and Pending are Not Final and indicate that further processing is necessary to receive the result.

[66] The following ResultMinor codes are defined:

3 Key Information Service Overview

[67] In the XML Signature Specification, a signer may optionally include information about his public signing key ("<ds:KeyInfo>") within the signature block. This key information is designed to allow the signer to communicate "hints" to a verifier about which public key to select.

[68] Another important property of <ds:KeyInfo> is that it may or may not be cryptographically bound to the signature itself.  This allows the <ds:KeyInfo> to be substituted or supplemented without "breaking" the digital signature.

[69] For example Alice signs a document and sends it to Bob with a <ds:KeyInfo> element that specifies only the signing Key Data. On receiving the message Bob retrieves additional information required to validate the signature and adds this information into the <ds:KeyInfo> element when he passes the document on to Carol (see Figure 1 below).

[70]

[71] Figure 1: Substitution of the <ds:KeyInfo> element as a message is passed amongst processors

3.1 XKISS Locate Service

[72] The XKISS Locate service resolves a <ds:Keyinfo> element but does NOT REQUIRE the service to make an assertion concerning the validity of the binding between the data in the <ds:Keyinfo> element.

[73] The Trust service MAY resolve the <ds:Keyinfo> element using local data or MAY relay request to other servers. For example the Trust service might resolve a <ds:RetrievalMethod> element (Figure 2) or act as a gateway to an underlying PKI based on a non-XML syntax.

[74]

[75] Figure 2: Locate Service Provides Name Resolution

[76] Both the request and/or the response MAY be signed, to both authenticate the sender and protect the integrity of the data being transmitted, using an XML Signature.

3.1.1 Example: Data Encryption

[77] Alice wants to send an encrypted email to Bob but does not know his encryption key. Alice can use both the S/MIME and PGP secure email formats. Alice's client uses DNS to locate the XKMS service that provides a Locate service for keys bound to the domain bobcorp.test then sends an XKMS Locate request to the discovered XKMS service for a key bound to bob@bobcorp.test and the S/MIME or PGP rotocol.

[78] Request:

<?xml version="1.0" encoding="utf-8"?>
<LocateRequest xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="I94d1048aa24259465d7271cb4433dbb4" Service="http://test.xmltrustcenter.org/XKMS"
      xmlns="http://www.w3.org/2002/03/xkms#">
  <RespondWith>KeyName</RespondWith>
  <RespondWith>KeyValue</RespondWith>
  <RespondWith>X509Cert</RespondWith>
  <RespondWith>X509Chain</RespondWith>
  <RespondWith>PGPWeb</RespondWith>
  <RespondWith>PGP</RespondWith>
  <RespondWith>Multiple</RespondWith>
  <QueryKeyBinding>
    <KeyUsage>Encryption</KeyUsage>
    <UseKeyWith Application="urn:ietf:rfc:2440" Identifier="bob@bobcorp.test" />
    <UseKeyWith Application="urn:ietf:rfc:2633" Identifier="bob@bobcorp.test" />
  </QueryKeyBinding>
</LocateRequest>

[79] Response:

<?xml version="1.0" encoding="utf-8"?>
<LocateResult xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="I075365c6e4d9feec5abf1d8a4504e4e8" Service="http://test.xmltrustcenter.org/XKMS"
      ResultMajor="Success" RequestId="#I94d1048aa24259465d7271cb4433dbb4" 
      xmlns="http://www.w3.org/2002/03/xkms#">
  <KeyBinding Id="I9b2502783d8587288b55263b1332c83d">
    <KeyInfo>
      <ds:KeyValue>
        <ds:RSAKeyValue>
          <ds:Modulus>4i0BEhQ8Jc4tjwZYbvtMyYfBrIGOMx34K4Cdo2pAzoGnV679FLmGHWnQy2cSj39hf5D1m
                IaPyD3j
/33TdfglTaaKqp7IPf6ei754fOuI/r1HpX7uqsw+j9LC4Z7GnG3yoY/eBJOZ8TRwMnx+MkwmopXP
VLvhMWRyiUOcO3SEkTE=</ds:Modulus>
          <ds:Exponent>AQAB</ds:Exponent>
        </ds:RSAKeyValue>
      </ds:KeyValue>
      <ds:X509Data>
        <ds:X509Certificate>MIIB+zCCAWigAwIBAgIQhzf6GHdFobRCYrjlFTCekjAJBgUrDgMCHQUAMBIxEDA
              OBgNVBAMTB1Rl
c3QgQ0EwHhcNMDIwNjEzMjEzMzQyWhcNMzkxMjMxMjM1OTU5WjAlMSMwIQYDVQQGExpVUyBPPUJv
YiBDb3JwIENOPUJvYiBCYWtlcjCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEAtw2qGqYbO0aK
eZFb0Z3verx3Cp+KS94LiHG09D1DdgTd48FZaB5eXa4U3mLax2/Fsg/cxGZkXJur0YylS8QvRuX+
9STQgiFTO277sHFfRMvtFsuQ56ovrQWH/KoGQZssMUIqO2aN2cbMQJST3a2HZuxqPQ1rwXxHrEoA
XHZv3ysCAwEAAaNHMEUwQwYDVR0BBDwwOoAQRWvWDxzHMSR0xfgYCUPpNqEUMBIxEDAOBgNVBAMT
B1Rlc3QgQ0GCEHKxUcSI0WKITaXFa+Ylh5IwCQYFKw4DAh0FAAOBgQCieDKjvNCo7MPsgUwHydki
d4KnulcuBbZet87lcIA7ReH1qEK4s0p49po2UM69eWG7hfv8LW2Ga8HiEexTwLDFBvH2g7f09xI/
vYgPw4qhJfWoZuY/HWHUzZIRSoggipndVfdvUkmsFSx1rR4FMu0mYBjq79OkYsmwISQlaXejUg==</ds:X509Certif
      icate>
        <ds:X509Certificate>MIIB9zCCAWSgAwIBAgIQcrFRxIjRYohNpcVr5iWHkjAJBgUrDgMCHQUAMBIxEDA
              OBgNVBAMTB1Rl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</ds:X509Certificate>
      </ds:X509Data>
    </KeyInfo>
    <KeyUsage>Signature</KeyUsage>
    <KeyUsage>Encryption</KeyUsage>
    <KeyUsage>Exchange</KeyUsage>
    <UseKeyWith Application="urn:ietf:rfc:2633" Identifier="bob@bobcorp.test" />
    <Status StatusValue="Valid">
      <Reason>Signature</Reason>
      <Reason>ValidityInterval</Reason>
    </Status>
  </KeyBinding>
</LocateResult>

3.1.2 Example: Document Signature

[80] Bob recieves the signed document from Alice which specifies Alice's X.509v3 certificate but not the key value. Bob's email client is not capable of processing X.509v3 certificates but can obtain the key parameters from the XKMS trust service by means of the Locate service. Bob's email client sends the <ds:Keyinfo> element to the location service requesting that the <KeyName> and <KeyValue> elements be returned.

[81] Request:

<?xml version="1.0" encoding="utf-8"?>
<LocateRequest xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="I9f382e970f38be00bf4e40c5c3c54a09" Service="http://test.xmltrustcenter.org/XKMS"
      xmlns="http://www.w3.org/2002/03/xkms#">
  <RespondWith>KeyValue</RespondWith>
  <QueryKeyBinding>
    <KeyInfo>
      <ds:X509Data>
        <ds:X509Certificate>MIICAjCCAW+gAwIBAgIQlzQovIEbLLhMa8K5MR/juzAJBgUrDgMCHQUAMBIxEDA
              OBgNVBAMTB1Rl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</ds:X509Certificate>
      </ds:X509Data>
    </KeyInfo>
    <KeyUsage>Signature</KeyUsage>
  </QueryKeyBinding>
</LocateRequest>

[82] The location service extracts the X.509v3 certificate from the <ds:Keyinfo> element and returns the key values. The location service DOES NOT report the revocation status or the trustworthiness of the certificate..

[83] Response:

<?xml version="1.0" encoding="utf-8"?>
<LocateResult xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="Ie199fc61796e0c684a50e136beb009d3" Service="http://test.xmltrustcenter.org/XKMS"
      ResultMajor="Success" RequestId="#I9f382e970f38be00bf4e40c5c3c54a09" 
      xmlns="http://www.w3.org/2002/03/xkms#">
  <KeyBinding Id="If2b74b47b7cf406b140d0aacfbcaad62">
    <KeyInfo>
      <ds:KeyValue>
        <ds:RSAKeyValue>
          <ds:Modulus>zvbTdKsTprGAKJdgi7ulDR0eQBptLv/SJNIh3uVmPBObZFsLbqPwo5nyLOkzWlEHNbShP
                MRp1qFr
AfF13LMmeohNYfCXTHLqH1MaMOm+BhXABHB9rUKaGoOBjQPHCBtHbfMGQYjznGTpfCdTrUgq8VNl
qM2Ph9XWMcc7qbjNHw8=</ds:Modulus>
          <ds:Exponent>AQAB</ds:Exponent>
        </ds:RSAKeyValue>
      </ds:KeyValue>
    </KeyInfo>
    <KeyUsage>Signature</KeyUsage>
    <KeyUsage>Encryption</KeyUsage>
    <KeyUsage>Exchange</KeyUsage>
    <UseKeyWith Application="urn:ietf:rfc:2633" Identifier="alice@alicecorp.test" />
  </KeyBinding>
</LocateResult>

3.2 XKISS: Validate Service

[84] The XKISS Validate Service allows all that the Locate Service does, and in addition, the client may obtain an assertion specifying the status of the binding between the public key and other data, for example a name or a set of extended attributes. Furthermore the service represents that the status of each of the data elements returned is valid and that all are bound to the same public key. The client sends to the trust service a prototype containing some or all of the elements for which the status of the trust binding is required. If the information in the prototype is incomplete, the trust service MAY obtain additional data required from an underlying PKI Service. Once the validity of the Key Binding has been determined the Trust service returns the status result to the client (Figure 3).

[85]

[86] Figure 3: Validate Service Provides Key Validation

3.2.1 Example: Document Signature

[87] Bob has received Alice's message and his email client has verified the signature on the document against the public key in the certificate supplied by Alice. It is not yet known whether the certificate is considered trustworthy however. To determine this, Bob's email client sends the certificate chain to an XKMS Validate service. The service reports back that it has successfully determined that the key binding has a trusted issuer, has a valid validity interval and has not been revoked.

[88] Request:

<?xml version="1.0" encoding="utf-8"?>
<ValidateRequest xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="Ia3358c93f917948052898be7ca83a0bb" Service="http://test.xmltrustcenter.org/XKMS"
      xmlns="http://www.w3.org/2002/03/xkms#">
  <RespondWith>KeyName</RespondWith>
  <RespondWith>KeyValue</RespondWith>
  <RespondWith>Multiple</RespondWith>
  <QueryKeyBinding>
    <KeyInfo>
      <ds:X509Data>
        <ds:X509Certificate>MIICAjCCAW+gAwIBAgIQlzQovIEbLLhMa8K5MR/juzAJBgUrDgMCHQUAMBIxEDA
              OBgNVBAMTB1Rl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</ds:X509Certificate>
        <ds:X509Certificate>MIIB9zCCAWSgAwIBAgIQcrFRxIjRYohNpcVr5iWHkjAJBgUrDgMCHQUAMBIxEDA
              OBgNVBAMTB1Rl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</ds:X509Certificate>
      </ds:X509Data>
    </KeyInfo>
    <KeyUsage>Signature</KeyUsage>
    <UseKeyWith Application="urn:ietf:rfc:2633" Identifier="alice@alicecorp.test" />
  </QueryKeyBinding>
</ValidateRequest>

[89] Response:

<?xml version="1.0" encoding="utf-8"?>
<ValidateResult xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="I28bf26b122bccce7aa28bef014efd33a" Service="http://test.xmltrustcenter.org/XKMS"
      ResultMajor="Success" RequestId="#Ia3358c93f917948052898be7ca83a0bb" 
      xmlns="http://www.w3.org/2002/03/xkms#">
  <KeyBinding Id="Ie43b3b454bb7a41a6920acf454e14c52">
    <KeyInfo>
      <ds:KeyValue>
        <ds:RSAKeyValue>
          <ds:Modulus>zvbTdKsTprGAKJdgi7ulDR0eQBptLv/SJNIh3uVmPBObZFsLbqPwo5nyLOkzWlEHNbShP
                MRp1qFr
AfF13LMmeohNYfCXTHLqH1MaMOm+BhXABHB9rUKaGoOBjQPHCBtHbfMGQYjznGTpfCdTrUgq8VNl
qM2Ph9XWMcc7qbjNHw8=</ds:Modulus>
          <ds:Exponent>AQAB</ds:Exponent>
        </ds:RSAKeyValue>
      </ds:KeyValue>
    </KeyInfo>
    <KeyUsage>Signature</KeyUsage>
    <KeyUsage>Encryption</KeyUsage>
    <KeyUsage>Exchange</KeyUsage>
    <UseKeyWith Application="urn:ietf:rfc:2633" Identifier="alice@alicecorp.test" />
    <Status StatusValue="Valid">
      <Reason>Signature</Reason>
      <Reason>IssuerTrust</Reason>
      <Reason>RevocationStatus</Reason>
      <Reason>ValidityInterval</Reason>
    </Status>
  </KeyBinding>
</ValidateResult>

3.3 Using Locate and Validate

[90] The Locate and Validate operations are both used to obtain information about a public key from a Trust Service. Locate and Validate services are both expected to attempt to provide correct information to the requestor. The Locate and Validate services differ in the extent to which the Trust Service verifies the information returned. A Location service SHOULD attempt to provide only information which is trustworthy to the best of its knowledge. A Validation service undertakes to only return information which has been positively validated by the Trust Service as meeting its validation criteria.

[91] For example a Locate Service MAY act as an aggregator of public key related information obtained from a variety of sources without performing any checks to determine whether specific information is current or establishing any formal trust policy. Such a service would correspond to the role of a directory in a traditional PKI. A Validate service MAY provide a service that validates key information presented to it but does not provide aggregation services. An email client might use a pair of such services in combination to obtain a valid public key for the intended recipient of an encrypted email by first querying the un-trusted Locate service and then forward the information received to a Validate service to establish its trustworthiness (Figure 4).

[92]

[93] Figure 4: Combined use of Locate and Validate service

3.3.1 DNS Integration

[94] In many cases the key information which a client requires is bound to some form of address specified by an Internet protocol part of which consists of a DNS address. For example an email client may require a trustworthy key to send an encrypted email to bob@cryptographer.test. Unless an XKMS service which provides key information about keys bound to email addresses in the domain cryptographer.test is known a priori some means of locating the correct XKMS service is required.

[95] Figure 5 shows an example of using the DNS SRV record to perform discovery of XKMS services. The email client requests a key for bob@cryptographer.test from a trusted Validate service. The Validate service then queries the DNS to locate an XKMS service providing information on keys bound to addresses in the zone cryptographer.test. The Validate service does not have an established trust relationship with the cryptographer.test XKMS service and so a Locate request is made to determine if any key information bound to bob@cryptographer.test can be located. The Validate service then validates the information received by such means as are appropriate (e.g. by verifying that a certification chain may be constructed from a root of trust) and the response returned to the email client.

[96]

[97] Figure 5: Combined use of Locate and Validate service

[98] Appendix B provides further information on the use of the DNS SRV record.

4 Key Information Service Message Set

[99] The protocol consists of pairs of messages, with an application sending a request message to a trust service and the service responding with another message. 

4.1 Key Binding Specification

[100] A Key Binding asserts a binding between data elements that relate to a public key including the <ds:KeyName>, <ds:KeyID>, <ds:KeyValue> and <ds:X509Data> components contained in a <KeyInfo> element. Furthermore, the Service represents to the client accessing the service and to that client alone that the binding between the data elements is valid under whatever trust policy the service offers to that client.

[101] XKMS specifies three elements that specify key bindings, all of which are derived from the KeyBindingAbstractType. These elements are:

KeyBinding

Specifies the parameters of a particular instance of a key binding

QueryKeyBinding

A template used to specify one or more key bindings using query by example.

PrototypeKeyBinding

A template used to specify the key binding parameters requested in a registration request.

4.1.1 Abstract Type KeyBindingAbstractType

[102] The KeyBindingAbstractType is the abstract type from which all XKMS Key Binding element specifiers are derived. It contains the following elements and attribute:

Id  [Optional]

Identifier of the key binding.

<KeyInfo>   [Optional]

The public key information to which the key binding information is bound

<KeyUsage>  [0 to 3]

The cryptographic key uses for which the key may be used

<UseKeyWith>  [Any Number]

The applications with which the key may be used together with the application specific subject identifier of the key holder for that application

[103] The following schema defines the KeyBindingAbstractType type:

4.1.2 Element <KeyInfo>

[104] The following schema defines the <KeyInfo> element of the ds:KeyInfoType type imported from the XML Signature Specification:

   <!-- KeyInfo -->
   <element name="KeyInfo" type="ds:KeyInfoType"/>
   <!-- /KeyInfo -->

4.1.3 Element <KeyUsage>

[105] The <KeyUsage> element specifies one or more intended uses of the key. If no <KeyUsage> is specified all uses are permitted.

xkms:Encryption

The key pair may be used for encryption and decryption

xkms:Signature

The key pair may be used for signature and verification

xkms:Exchange

The key pair may be used for key exchange

[106] If a key usage is specified that the algorithm does not support (e.g. use of a DSA key for encryption) the element MUST be ignored.

[107] The following schema defines the <KeyUsage> element:

   <!-- KeyUsage -->
   <element name="KeyUsage" type="xkms:KeyUsageType"/>
   <simpleType name="KeyUsageType">
      <restriction base="QName">
         <enumeration value="xkms:Encryption"/>
         <enumeration value="xkms:Signature"/>
         <enumeration value="xkms:Exchange"/>
      </restriction>
   </simpleType>
   <!-- /KeyUsage -->

4.1.4 Element <UseKeyWith>

[108] The <UseKeyWith> element specifies a subject and application protocol for which the keys specified in the enclosing key binding may be used.

Application     [Required]

A URI that specifies the application protocol with which the key may be used

Identifier     [Required]

Specifies the subject to which the key corresponds within the specified application protocol.

[109] The following table lists application URIs for common protocols and the corresponding format for the identifier information:

[110] The following table describes the formatting for the specified types of identifier:

[111] The following schema defines the <UseKeyWith> element:

   <!-- UseKeyWith -->
   <element name="UseKeyWith" type="xkms:UseKeyWithType"/>
   <complexType name="UseKeyWithType">
      <attribute name="Application" type="anyURI"/>
      <attribute name="Identifier" type="string"/>
   </complexType>
   <!-- /UseKeyWith -->

4.1.5 Element <KeyBinding>

[112] The <KeyBinding> element specifies a particular instance of a key binding and is derived from the KeyBindingAbstractType.

[113] The <KeyBinding> element extends the KeyBindingAbstractType with the following additional elements:

<ValidityInterval>  [Optional]

The time interval in which the key binding relationship is asserted

<Status>  [Optional]

The status of the Key Binding instance.

any [Any Number]

Optional extension elements

[114] The following schema defines the <KeyBinding> element and KeyBindingType:

   <!-- KeyBinding -->
   <element name="KeyBinding" type="xkms:KeyBindingType"/>
   <complexType name="KeyBindingType">
      <complexContent>
         <extension base="xkms:KeyBindingAbstractType">
            <sequence>
               <element ref="xkms:Status" minOccurs="0"/>
               <element ref="xkms:ValidityInterval" minOccurs="0"/>
               <any namespace="##other" processContents="lax" minOccurs="0" 
                     maxOccurs="unbounded"/>
            </sequence>
         </extension>
      </complexContent>
   </complexType>
   <!-- /KeyBinding -->

4.1.6 Element <ValidityInterval>

[115] The <ValidityInterval> element specifies limits on the validity of the assertion.

NotBefore     [Optional]

Time instant at which the validity interval begins

NotOnOrAfter     [Optional]

Time instant at which the validity interval has ended

[116] All dateTime values MUST fully specify the date.

[117] The NotBefore and NotOnOrAfter attributes are optional. If the NotBefore attribute is omitted the assertion is valid on any date up to but excluding the date specified in the NotOnOrAfter attribute . If the NotOnOrAfter attribute is omitted the assertion is valid from the NotBefore attribute with no expiry. If both elements are omitted the assertion is valid at any time.

[118] In accordance with the XML Schema Specifications, all time instances are interpreted in Universal Coordinated Time unless they explicitly indicate a time zone.

[119] Implementations MUST NOT generate time instances that specify leap seconds.

[120] For purposes of comparison, the time interval NotBefore to NotOnOrAfter begins at the earliest time instant compatible with the specification of NotBefore and has ended at the earliest time instant compatible with the specification of NotOnOrAfter

[121] For example if the time interval specified is dayT12:03:02 to dayT12:05:12 the times 12:03:02.00 and 12:05:11.9999 are within the time interval. The time 12:05:12.0000 is outside the time interval.

[122] The following schema defines the <ValidityInterval> element:

   <!-- ValidityInterval -->
   <element name="ValidityInterval" type="xkms:ValidityIntervalType"/>
   <complexType name="ValidityIntervalType">
      <attribute name="NotBefore" type="dateTime"/>
      <attribute name="NotOnOrAfter" type="dateTime"/>
   </complexType>
   <!-- /ValidityInterval -->

4.1.7 Element <Status>

[123] The <status> element specifies the status of a KeyBinding instance.

[124] The status value MAY be supplemented with codes that state the aspects of the key binding status that were validated and resulted in the status value being reported.

[125] The <Status> element contains the following element and attribute:

<Reason>  [Any Number]

A code that specifies a reason for the assignment of the status indicated.

StatusValue [Optional]

The assertion status

[126] The enumerated type AssertionStatus is used to indicate the assertion status. The following values are defined:

xkms:Valid

The key binding is definitively valid.

xkms:Invalid

The key binding is definitively invalid.

xkms:Indeterminate

The status of the assertion cannot be determined.

[127] The following schema defines the <Status> element and StatusType and AssertionType types:

   <!-- Status -->
   <element name="Status" type="xkms:StatusType"/>
   <complexType name="StatusType">
      <sequence minOccurs="0" maxOccurs="unbounded">
         <element ref="xkms:Reason" minOccurs="0" maxOccurs="unbounded"/>
      </sequence>
      <attribute name="StatusValue" type="xkms:AssertionStatus"/>
   </complexType>
   <simpleType name="AssertionStatus">
      <restriction base="QName">
         <enumeration value="xkms:Valid"/>
         <enumeration value="xkms:Invalid"/>
         <enumeration value="xkms:Indeterminate"/>
      </restriction>
   </simpleType>
   <!-- /Status -->

4.1.8 Element <Reason>

[128] The <Reason> element is used to specify a string that specifies a reason for a particular assertion status.

[129] The <Reason> elements reported depend upon the value of the Key Binding Status value as follows:

Status="Valid"

The <Reason> elements list the status aspects that have been affirmatively verified to be Valid.

Status="Invalid"

The <Reason> elements list the aspects of status that have been determined to be either Invalid or Indeterminate.

Status="Indeterminate"

The <Reason> elements list the aspects of status that have been determined to be Indeterminate.

[130] For example if the key binding IssuerTrust status aspect is Valid but the ValidityInterval status aspect  is Invalid, the <Status> element would report the status code Invalid with the <Reason> code ValidityInterval.

[131] The status aspects are defined in the table below. For convenience the equivalent X509 processing steps are given:

[147] The following schema defines the <Reason> element and the ReasonCodeType type:

   <!-- Reason -->
   <element name="Reason" type="QName"/>
   <!-- /Reason -->

4.1.9 Element <QueryKeyBinding>

[148] The <QueryKeyBinding> element is derived from the KeyBindingAbstractType.

[149] The <QueryKeyBinding> element extends the KeyBindingAbstractType with the following additional elements:

<TimeInstant> [Optional]

The Time Instant for which the query is made. If no time instant is specified the default is the time the request was made.

any [Any Number]

Optional extension elements

[150] The following schema defines the <QueryKeyBinding> element and KeyBindingType:

   <!-- QueryKeyBinding -->
   <element name="QueryKeyBinding" type="xkms:QueryKeyBindingType"/>
   <complexType name="QueryKeyBindingType">
      <complexContent>
         <extension base="xkms:KeyBindingAbstractType">
            <sequence>
               <element ref="xkms:TimeInstant" minOccurs="0"/>
               <any namespace="##other" processContents="lax" minOccurs="0" 
                     maxOccurs="unbounded"/>
            </sequence>
         </extension>
      </complexContent>
   </complexType>
   <!-- /QueryKeyBinding -->

4.1.10 Element <TimeInstant>

[151] The <TimeInstant> element specifies a specific instant in time for which a key binding query is made. The <TimeInstant> element contains the following attribute:

Time     [Required]

Time instant at which the validity interval begins

[152] All dateTime values MUST fully specify the date.

[153] The following schema defines the <TimeInstant> element:

   <!-- TimeInstant -->
   <element name="TimeInstant" type="xkms:TimeInstantType"/>
   <complexType name="TimeInstantType">
      <attribute name="Time" type="dateTime"/>
   </complexType>
   <!-- /TimeInstant -->

4.1.11 Element <PrototypeKeyBinding>

[154] The <PrototypeKeyBinding> element is derived from the KeyBindingAbstractType.

[155] The <PrototypeKeyBinding> element extends the KeyBindingAbstractType with the following additional elements:

<RevocationCodeIdentifier> [Optional]

Specifies a value to be used to validate a RevocationCode value in a subsequent Revocation request

any [Any Number]

Optional extension elements

[156] The following schema defines the <PrototypeKeyBinding> element and PrototypeKeyBindingType:

   <!-- PrototypeKeyBinding -->
   <element name="PrototypeKeyBinding" type="xkms:PrototypeKeyBindingType"/>
   <complexType name="PrototypeKeyBindingType">
      <complexContent>
         <extension base="xkms:KeyBindingAbstractType">
            <sequence>
               <element ref="xkms:RevocationCodeIdentifier" minOccurs="0"/>
               <any namespace="##other" processContents="lax" minOccurs="0" 
                     maxOccurs="unbounded"/>
            </sequence>
         </extension>
      </complexContent>
   </complexType>
   <!-- /PrototypeKeyBinding -->

4.1.12 Element <RevocationCodeIdentifier>

[157] The <RevocationCodeIdentifier> element contains a MAC output value encoded as a base64 string.

[158] On initial registration the <RevocationCodeIdentifier> value is obtained by first performing the MAC calculation on the pass phrase value, then performing a second MAC calculation on the result.

[159] To prove knowledge of the pass phrase in a subsequent revocation request the <RevocationCode> value is obtained by performing the MAC calculation on the pass phrase value.

[160] Details of the MAC output value calculation are provided in the section Cryptographic Algorithm Specific Parameters below.

[161] The following schema defines the <RevocationCodeIdentifier> element and the RevocationCodeIdentifierTypetype:

   <!-- RevocationCodeIdentifier -->
   <element name="RevocationCodeIdentifier" type="xkms:RevocationCodeIdentifierType"/>
   <simpleType name="RevocationCodeIdentifierType">
      <restriction base="base64Binary"/>
   </simpleType>
   <!-- /RevocationCodeIdentifier -->

4.2 Locate Service

[162] The Locate service accepts as input a <ds:Keyinfo> element that specifies a public key and returns one or more <ds:Keyinfo> elements that relate to the same public key. The <ds:Keyinfo> elements returned are specified by the Respond element in the request.

4.2.1 Locate Request Element <LocateRequest>

[163] The request message contains a <LocateRequest> element that contains the following element.

KeyInfoQuery  [Required]

A single complex structure containing a <ds:Keyinfo> element that specifies the public key for which additional data is requested.

[164]  The following schema defines the <LocateRequest> element:

   <!-- LocateRequest -->
   <element name="LocateRequest" type="xkms:LocateRequestType"/>
   <complexType name="LocateRequestType">
      <complexContent>
         <extension base="xkms:RequestAbstractType">
            <sequence>
               <element ref="xkms:QueryKeyBinding"/>
            </sequence>
         </extension>
      </complexContent>
   </complexType>
   <!-- /LocateRequest -->

4.2.2 Locate Response Element<LocateResult>

[165] The request message contains a <LocateResult> element

<ds:KeyInfo>  [Any Number]

A <ds:Keyinfo>element that matches the criteria specified in the corresponding request.

[166]  The following schema defines the <LocateResult> element:

   <!-- LocateResult -->
   <element name="LocateResult" type="xkms:LocateResultType"/>
   <complexType name="LocateResultType">
      <complexContent>
         <extension base="xkms:ResultAbstractType">
            <sequence>
               <element ref="xkms:KeyBinding" minOccurs="0" maxOccurs="unbounded"/>
            </sequence>
         </extension>
      </complexContent>
   </complexType>
   <!-- /LocateResult -->

4.3 Validate Service

[167] The Validate service allows the client to query the binding between a <ds:Keyinfo> element and other data such as an identifier. The client supplies a prototype for the <KeyBinding> assertion requested. The prototype may specify either a <KeyId> or a <ds:Keyinfo> element or both. The server returns one or more <KeyBinding> assertions that meet the criteria specified in the request.

4.3.1 Validate Request Element <ValidateRequest>

[168] The validate request message contains a <ValidateRequest> element:

<KeyBindingQuery>     [Required]

A single KeyBinding structure that is to be completed and validated.

[169] The following schema defines the <ValidateRequest> element:

   <!-- ValidateRequest -->
   <element name="ValidateRequest" type="xkms:ValidateRequestType"/>
   <complexType name="ValidateRequestType">
      <complexContent>
         <extension base="xkms:RequestAbstractType">
            <sequence>
               <element ref="xkms:QueryKeyBinding"/>
            </sequence>
         </extension>
      </complexContent>
   </complexType>
   <!-- /ValidateRequest -->

4.3.2 Validate Response Element <ValidateResult>

[170] The validate response message contains a <ValidateResult> element:

<Keybinding>     [Any Number]

A sequence of <KeyBinding> structures that contain the results of the validation. If no results are found the sequence is empty and the <ResultCode>NoMatch returned. In some circumstances a Locate operation MAY return multiple matching results.

[171] The following schema defines the <ValidateResult> element and the ValidateResultType type.

   <!-- ValidateResult -->
   <element name="ValidateResult" type="xkms:ValidateResultType"/>
   <complexType name="ValidateResultType">
      <complexContent>
         <extension base="xkms:ResultAbstractType">
            <sequence>
               <element ref="xkms:KeyBinding" minOccurs="0" maxOccurs="unbounded"/>
            </sequence>
         </extension>
      </complexContent>
   </complexType>
   <!-- /ValidateResult -->

5 Key Registration Service Overview

[172] The XML Key Registration Service Specification permits management of information that is bound to a public key pair. The XKRSS service specification supports the following operations:

Register

Information is bound to a public key pair through a key binding

Reissue

A previously registered key binding is reissued.

Revoke

A previously registered key binding is revoked.

Recover

The private key associated with a key binding is recovered.

[173] The Register operation does not in itself place any requirement on the Registration Service to communicate that information to any other party. In most applications, however, a Registration Service will provide key information to other trust services such as those described in the XKMS specification or a separate underlying PKI such as PKIX.

5.1 Registration

[174] The Register request is used to assert a binding of information to a public key pair. Generation of the public key pair MAY be performed by either the client or the Registration service.

[175] The Registration request message contains a prototype of the requested assertion. The Registration Service MAY require the client to provide additional information to authenticate the request. If the public key pair is generated by the client, the service MAY require the client to provide Proof of Possession of the private key.

[176] The Registration service MAY accept the name specified in the prototype or MAY substitute its own name.

[177] On receipt of a registration request, the registration service verifies the authentication and POP information provided (if any). If the registration service accepts the request an assertion is registered. This assertion MAY include some, all or none of the information provided by the prototype assertion and MAY include additional information.

[178] The Registration Service MAY return part or all of the registered assertion to the client.

[179]

[180] Figure 5: Registration of a KeyBinding

5.1.1 Example: Registration of Client-Generated Key Pair

[181] Alice requests registration of an RSA key pair for her email address Alice@cryptographer.test. Alice has previously received from the trust service the code "024837" with which to authenticate her request. Alice selects the pass phrase "Help I have revealed my key" to authenticate herself should it be necessary to revoke the registration at a later date.

[182] The X-KRSS request message contains the following <RegisterRequest> element: Because the registration request is for a client generated key the Authentication element contains both a <ProofOfPossession> element which demonstrates that the request is authorized by the holder of the private key and a <KeyBindingAuthentication> element which demonstrates that the request was made by a person who knows the authentication code "024837".

<?xml version="1.0" encoding="utf-8"?>
<RegisterRequest xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="I51c84832f9019a0cddfb4388930f7eb8" Service="http://test.xmltrustcenter.org/XKMS"
      xmlns="http://www.w3.org/2002/03/xkms#">
  <RespondWith>X509Cert</RespondWith>
  <RespondWith>X509Chain</RespondWith>
  <RespondWith>Multiple</RespondWith>
  <PrototypeKeyBinding Id="Ibb3bc708c22e69bfc8d8ac1056a5f04c">
    <KeyInfo>
      <ds:KeyValue>
        <ds:RSAKeyValue>
          <ds:Modulus>zvbTdKsTprGAKJdgi7ulDR0eQBptLv/SJNIh3uVmPBObZFsLbqPwo5nyLOkzWlEHNbShP
                MRp1qFr
AfF13LMmeohNYfCXTHLqH1MaMOm+BhXABHB9rUKaGoOBjQPHCBtHbfMGQYjznGTpfCdTrUgq8VNl
qM2Ph9XWMcc7qbjNHw8=</ds:Modulus>
          <ds:Exponent>AQAB</ds:Exponent>
        </ds:RSAKeyValue>
      </ds:KeyValue>
    </KeyInfo>
    <KeyUsage>Signature</KeyUsage>
    <KeyUsage>Encryption</KeyUsage>
    <KeyUsage>Exchange</KeyUsage>
    <UseKeyWith Application="urn:ietf:rfc:2459" Identifier="C=&quot;US&quot; O=&quot;Alice
          Corp&quot; CN=&quot;Alice Aardvark&quot;" />
    <UseKeyWith Application="urn:ietf:rfc:2633" Identifier="alice@alicecorp.test" />
  </PrototypeKeyBinding>
  <Authentication>
    <KeyBindingAuthentication>
      <ds:Signature>
        <ds:SignedInfo>
          <ds:CanonicalizationMethod 
                Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" />
          <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1" />
          <ds:Reference URI="#Ibb3bc708c22e69bfc8d8ac1056a5f04c">
            <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
            <ds:DigestValue>q3KSdY+GO/Vi0kn/ao9zm3ijt/Y=</ds:DigestValue>
          </ds:Reference>
        </ds:SignedInfo>
        <ds:SignatureValue>jo1aTOJFi23UVIpdC2+ai3KQKaA=</ds:SignatureValue>
      </ds:Signature>
    </KeyBindingAuthentication>
  </Authentication>
  <ProofOfPossession>
    <ds:Signature>
      <ds:SignedInfo>
        <ds:CanonicalizationMethod 
              Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" />
        <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
        <ds:Reference URI="#Ibb3bc708c22e69bfc8d8ac1056a5f04c">
          <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
          <ds:DigestValue>q3KSdY+GO/Vi0kn/ao9zm3ijt/Y=</ds:DigestValue>
        </ds:Reference>
      </ds:SignedInfo>
      <ds:SignatureValue>zLpScNR7EOt+YAH8hOdhN9g/guotip2OKrQzCFS1gUGtzVmWSy44FI6ilg/sGGPy7+
            aY18Dr+YZD
uBifdYL3gkS2BVqDleMtYajBqtYus9IxNS8OSKZnRycgIFACsZx1lm5ivQJODBvEHTgTXRQk4YmF
b6ZbUR75Q0ziq1sLaQs=</ds:SignatureValue>
    </ds:Signature>
  </ProofOfPossession>
</RegisterRequest>

[184] The service accepts the registration and returns the following response:

<?xml version="1.0" encoding="utf-8"?>
<RegisterResult xmlns:ds="http://www.w3.org/2000/09/xmldsig#" 
      xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" 
      Id="Id64a06d06791b5209c5e132f9408f433" Service="http://test.xmltrustcenter.org/XKMS"
      ResultMajor="Success" RequestId="#I51c84832f9019a0cddfb4388930f7eb8" 
      xmlns="http://www.w3.org/2002/03/xkms#">
  <KeyBinding Id="Ie6ddfc94f1982b2146f9afa7568c8642">
    <KeyInfo>
      <ds:X509Data>
        <ds:X509Certificate>MIICAjCCAW+gAwIBAgIQlzQovIEbLLhMa8K5MR/juzAJBgUrDgMCHQUAMBIxEDA
              OBgNVBAMTB1Rl
c3QgQ0EwHhcNMDIwNjEzMjEzMzQxWhcNMzkxMjMxMjM1OTU5WjAsMSowKAYDVQQGEyFVUyBPPUFs
aWNlIENvcnAgQ049QWxpY2UgQWFyZHZhcmswgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBAMoy
4c9+NoNJvJUnV8pqPByGb4FOJcU0VktbGJpO2imiQx+EJsCt27z/pVUDrexTyctCWbeqR5a40JCQ
mvNmRUfg2d81HXyA+iYPl4L6nUlHbkLjrhPPtMDSd5YHjyvnCN454+Hr0paA1MJXKuw8ZMkjGYsr
4fSYpPELOH5PDJEBAgMBAAGjRzBFMEMGA1UdAQQ8MDqAEEVr1g8cxzEkdMX4GAlD6TahFDASMRAw
DgYDVQQDEwdUZXN0IENBghBysVHEiNFiiE2lxWvmJYeSMAkGBSsOAwIdBQADgYEAKp+RKhDMIV