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</style><link href="http://www.w3.org/StyleSheets/TR/W3C-WD" rel="stylesheet" type="text/css" charset="utf-8"></head><body style="display: inherit; "><div class="head"><p><a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C"></a></p><h1 class="title" id="title">XML Security 1.1 Requirements and Design Considerations</h1><h2 id="w3c-working-draft-03-march-2011">W3C Working Draft 03 March 2011</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2011/WD-xmlsec-reqs-20110303/">http://www.w3.org/TR/2011/WD-xmlsec-reqs-20110303/</a></dd><dt>Latest published version:</dt><dd><a href="http://www.w3.org/TR/xmlsec-reqs/">http://www.w3.org/TR/xmlsec-reqs/</a></dd><dt>Latest editor's draft:</dt><dd><a href="http://www.w3.org/2008/xmlsec/Drafts/xmlsec-reqs/">http://www.w3.org/2008/xmlsec/Drafts/xmlsec-reqs/</a></dd><dt>Previous version:</dt><dd><a href="http://www.w3.org/TR/2010/WD-xmlsec-reqs-20100204/">http://www.w3.org/TR/2010/WD-xmlsec-reqs-20100204/</a></dd><dt>Editors:</dt><dd><span>Frederick Hirsch</span>, Nokia</dd>
<dd><span>Thomas Roessler</span>, W3C</dd>
</dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2011 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.eu/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.</p><hr></div>
            <div id="abstract" class="introductory section"><h2>Abstract</h2>
              This Note summarizes scenarios, design decisions, and
              requirements for 
              the XML Signature and Canonical XML specifications, to
              guide ongoing W3C 
              work to revise these specifications.
              
            </div><div id="sotd" class="introductory section"><h2>Status of This Document</h2><p><em>This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at http://www.w3.org/TR/.</em></p>
              <p>Changes since the previous publication include
                addition of a new section to record 
                requirements to correct known issues and formatting
                changes due to conversion to use ReSpec source. Please review 
                <a href="Overview_diff.html">differences between this
                  and the previous  Working Draft</a>.
              </p>
            <p>This document was published by the <a href="http://www.w3.org/2008/xmlsec/">XML Security Working Group</a> as a Working Draft. If you wish to make comments regarding this document, please send them to <a href="mailto:public-xmlsec@w3.org">public-xmlsec@w3.org</a> (<a href="mailto:public-xmlsec-request@w3.org?subject=subscribe">subscribe</a>, <a href="http://lists.w3.org/Archives/Public/public-xmlsec/">archives</a>). All feedback is welcome.</p><p>Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.</p><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>. The group does not expect this document to become a W3C Recommendation. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/42458/status" rel="disclosure">public list of any patent disclosures</a> made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>.</p></div><div id="toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#Introduction" class="tocxref"><span class="secno">1. </span>Introduction</a></li><li class="tocline"><a href="#principles" class="tocxref"><span class="secno">2. </span>Principles</a></li><li class="tocline"><a href="#scenarios" class="tocxref"><span class="secno">3. </span>Requirements and Design Options</a><ul class="toc"><li class="tocline"><a href="#widget-security" class="tocxref"><span class="secno">3.1 </span>Widget Security</a><ul class="toc"><li class="tocline"><a href="#use-cases" class="tocxref"><span class="secno">3.1.1 </span>Use Cases</a></li><li class="tocline"><a href="#requirements" class="tocxref"><span class="secno">3.1.2 </span>Requirements</a></li><li class="tocline"><a href="#design" class="tocxref"><span class="secno">3.1.3 </span>Design</a></li></ul></li><li class="tocline"><a href="#derived-keys" class="tocxref"><span class="secno">3.2 </span>Derived Keys</a><ul class="toc"><li class="tocline"><a href="#use-cases-and-background" class="tocxref"><span class="secno">3.2.1 </span>Use Cases and Background</a></li><li class="tocline"><a href="#use-of-derived-keys-in-existing-ws---specifications" class="tocxref"><span class="secno">3.2.2 </span>Use Of Derived Keys in Existing WS-* Specifications</a><ul class="toc"><li class="tocline"><a href="#ws-trust-version-1.3" class="tocxref"><span class="secno">3.2.2.1 </span>WS-Trust Version 1.3:</a></li><li class="tocline"><a href="#ws-securitypolicy-1.2" class="tocxref"><span class="secno">3.2.2.2 </span>WS-SecurityPolicy 1.2:</a></li><li class="tocline"><a href="#ws-secureconversation-1.3" class="tocxref"><span class="secno">3.2.2.3 </span>WS-SecureConversation 1.3:</a></li></ul></li><li class="tocline"><a href="#solution-requirements" class="tocxref"><span class="secno">3.2.3 </span>Solution Requirements</a><ul class="toc"><li class="tocline"><a href="#use-in-existing-specifications--r1" class="tocxref"><span class="secno">3.2.3.1 </span>Use in existing specifications (R1)</a></li><li class="tocline"><a href="#no-external-dependencies--r2" class="tocxref"><span class="secno">3.2.3.2 </span>No external dependencies (R2)</a></li><li class="tocline"><a href="#continued-use-of-existing-derivation-methods--r3" class="tocxref"><span class="secno">3.2.3.3 </span>Continued use of existing derivation methods (R3)</a></li><li class="tocline"><a href="#future-proof-with-regards-to-key-lengths--r4" class="tocxref"><span class="secno">3.2.3.4 </span>Future-proof with regards to key lengths (R4)</a></li><li class="tocline"><a href="#referential-flexibility--r5" class="tocxref"><span class="secno">3.2.3.5 </span>Referential flexibility (R5)</a></li></ul></li><li class="tocline"><a href="#existing-specifications-vs.-requirements" class="tocxref"><span class="secno">3.2.4 </span>Existing Specifications vs. Requirements</a></li><li class="tocline"><a href="#design-options" class="tocxref"><span class="secno">3.2.5 </span> Design Options</a><ul class="toc"><li class="tocline"><a href="#create-a-ds-derivedkeytype-type-modeled-after-the---------------------xenc-encryptedkeytype." class="tocxref"><span class="secno">3.2.5.1 </span>Create a ds:DerivedKeyType type modeled after the
                    xenc:EncryptedKeyType.
                    </a></li></ul></li></ul></li><li class="tocline"><a href="#algorithms" class="tocxref"><span class="secno">3.3 </span>Algorithm security and interoperability</a><ul class="toc"><li class="tocline"><a href="#algorithm-fundamentals" class="tocxref"><span class="secno">3.3.1 </span>Fundamentals</a></li><li class="tocline"><a href="#algorithm-requirements" class="tocxref"><span class="secno">3.3.2 </span>Requirements</a><ul class="toc"><li class="tocline"><a href="#algorithm-sha" class="tocxref"><span class="secno">3.3.2.1 </span>Address SHA security concerns, recognize RSA de-facto use.</a></li><li class="tocline"><a href="#algorithm-dsawithsha1-guidance" class="tocxref"><span class="secno">3.3.2.2 </span>Revise guidance for DSAwithSHA1</a></li><li class="tocline"><a href="#algorithm-suiteb" class="tocxref"><span class="secno">3.3.2.3 </span>Add Suite B algorithm support</a></li></ul></li><li class="tocline"><a href="#algorithm-eckeyvalue-design" class="tocxref"><span class="secno">3.3.3 </span>Suite B Elliptic Curve Key Value Design (ECKeyValue)</a><ul class="toc"><li class="tocline"><a href="#algorithm-eckeyvalue-issues" class="tocxref"><span class="secno">3.3.3.1 </span>RFC 4050 issues in XML Signature context</a></li><li class="tocline"><a href="#algorithm-eckeyvalue-proposal" class="tocxref"><span class="secno">3.3.3.2 </span>Proposed Solution to RFC 4050 issues in XML Signature context</a></li></ul></li></ul></li><li class="tocline"><a href="#correct-issues" class="tocxref"><span class="secno">3.4 </span>Correct known issues</a><ul class="toc"><li class="tocline"><a href="#issueserial" class="tocxref"><span class="secno">3.4.1 </span>Limitations associated with <code>X509IssueSerial</code></a></li><li class="tocline"><a href="#RetrievalMethod" class="tocxref"><span class="secno">3.4.2 </span>Simplify access to <code>ds:KeyInfo</code></a></li><li class="tocline"><a href="#DEREncodedKeyValue" class="tocxref"><span class="secno">3.4.3 </span>XML <code>KeyValue</code> type interoperability</a></li><li class="tocline"><a href="#OCSPResponse" class="tocxref"><span class="secno">3.4.4 </span>Support OCSP use case</a></li></ul></li></ul></li><li class="tocline"><a href="#thanks" class="tocxref"><span class="secno">4. </span>Acknowledgments</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">A. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">A.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">A.2 </span>Informative references</a></li></ul></li></ul></div>
            
            
            <div id="Introduction" class="section">
              
              <!--OddPage--><h2><span class="secno">1. </span>Introduction</h2>
              
              <p>
                This use case and requirements document is intended to
                summarize use   
                cases and requirements driving revisions to XML Signature
                2nd Edition [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-CORE">XMLDSIG-CORE</a></cite>],  XML Encryption [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLENC-CORE">XMLENC-CORE</a></cite>],  
                and Canonical XML 1.1 [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-C14N11">XML-C14N11</a></cite>]. It is not intended
                to define all   
                possible use cases for these Recommendations, but rather
                to provide   
                rationale for decisions leading to XML Signature 1.1, XML
                Encryption   
                1.1, XML Signature Properties and XML Security Generic
                Hybrid Ciphers. 
              </p>
              <p>
                This document outlines general principles and use cases
                leading to 
                requirements and offers some design options. It
                elaborates on principles and updates requirements  
                expressed for the original XML Security work including
                original requirements documents (e.g. [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-CANONICAL-REQ">XML-CANONICAL-REQ</a></cite>], and
                [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-REQUIREMENTS">XMLDSIG-REQUIREMENTS</a></cite>]).
                This document also reflects material from a  W3C workshop on
                next steps for XML 
                Security [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSEC-NEXTSTEPS-2007">XMLSEC-NEXTSTEPS-2007</a></cite>] and position papers
                associated with the workshop, including
                [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-COMPLEXITY">XMLDSIG-COMPLEXITY</a></cite>], [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-SEMANTICS">XMLDSIG-SEMANTICS</a></cite>], and
                [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-THOMPSON">XMLDSIG-THOMPSON</a></cite>].
                </p><p>
                Design options were documented early on to provide a
                starting point with the expectation that specifications
                developed to meet the requirements could subsequently differ
                in design choices.Thus the design choices in this document
                should be viewed as historical information.
              </p> 
            </div>
            
            <div id="principles" class="section">
              <!--OddPage--><h2><span class="secno">2. </span>Principles</h2>
              <p>
                The following design principles will be used to guide further
                development of XML Security, including XML Signature, XML Encryption
                and Canonical XML. These principles are intended to encourage
                consistent design decisions, to provide insight
                into design rationale and to anchor discussions on requirements and
                design. This list includes items from the original requirements for
                XML Signature 
                [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-REQUIREMENTS">XMLDSIG-REQUIREMENTS</a></cite>]
                as well as general principles from EXI
                [<cite><a class="bibref" rel="biblioentry" href="#bib-EXI">EXI</a></cite>]. Listed in alphabetical order:
                </p><dl>
                  <dt>
                    Backward compatible:
                  </dt>
                  
                  <dd>
                    <p>Backward compatibility should not be
                    broken unnecessarily. Versioning should be clearly
                    considered. Consideration must be given, for example, for
                    interoperability with the First and Second Editions of XML
                    Signature 
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-CORE">XMLDSIG-CORE</a></cite>].
                    </p>
                  </dd>
                  <dt>
                    Consistent with the Web Architecture:
                  </dt>
                  <dd>
                    <p>XML Security must be consistent with the Web
                    Architecture [<cite><a class="bibref" rel="biblioentry" href="#bib-WEBARCH">WEBARCH</a></cite>].
                    </p> 
                  </dd>
                  <dt>
                    Efficient:
                  </dt>
                  <dd>
                    <p>XML Security should enable efficient implementations, in
                    order to remove barriers to adoption and use. 
                    </p>
                  </dd>
                  <dt>
                    Meet common requirements, enable extensibility:
                  </dt>
                  <dd>
                    <p>One of primary objectives of XML Signature is to support a
                    wide variety of use cases requiring digital signatures,
                    including situations requiring multiple signatures,
                    counter-signatures, and signatures including multiple items
                    to be included in a signature. 
                    Extensibility should be possible, but by default
                    options should be constrained when the flexibility is not
                    needed. 
                    </p>
                  </dd>
                  <dt>
                    Minimal: 
                  </dt>
                  <dd>
                    <p>To reach the broadest set of applications, reduce the
                    security threat footprint and improve efficiency, simple,
                    elegant approaches are preferred to large, analytical or
                    complex ones. 
                    </p>
                  </dd>
                  <dt>
                    Pragmatic:
                  </dt>
                  <dd>
                    <p>Recognize pragmatic issues, including recognizing that
                    software might be implemented in layers, with a security
                    layer independent of an application layer.
                    </p>
                  </dd>
                  <dt>
                    Reuse Existing Open Standards
                  </dt>
                  <dd>
                    <p>Existing open standards should be reused where possible,
                    as long as other principles can be met. 
                    </p>
                  </dd>
                  <dt>
                    Secure:
                  </dt>
                  <dd>
                    <p> XML Security should  adhere to security best practices,
                    and minimize the opportunities for threats based on XML
                    Security mechanisms. 
                    </p>
                  </dd>
                  <dt>
                    XML Interoperable:
                  </dt>
                  <dd>
                    <p> XML Security must integrate well with existing XML
                    technologies,  be compatible with the XML Information Set
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-INFOSET">XML-INFOSET</a></cite>],  in order to maintain
                    interoperability with 
                    existing and prospective XML specifications.  
                    </p>
                  </dd>
                  <dt>
                    XML Signatures are First Class Objects:
                  </dt>
                  
                  <dd>
                    
                    <p>XML Signatures should themselves be self-describing first
                    class XML objects 
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-REQUIREMENTS">XMLDSIG-REQUIREMENTS</a></cite>]
                    . This means that XML
                    Signatures can be referenced via URI and used in   
                    other operations. For example, an XML Signature may be signed or  
                    encrypted, or referred to in a statement  (such as an RDF statement). 
                    
                    </p>
                    
                  </dd>
                  
                  
                </dl>
                
              <p></p> 
              
            </div>
            
            <div id="scenarios" class="section">
              
              <!--OddPage--><h2><span class="secno">3. </span>Requirements and Design Options</h2>
              
              <p> 
                This section outlines the motivation, requirements and design  
                considerations for  XML Security  1.1.
                
              </p>
              
              <div id="widget-security" class="section">
                
                <h3><span class="secno">3.1 </span>Widget Security</h3>
                
                <div id="use-cases" class="section">
                  
                  <h4><span class="secno">3.1.1 </span>Use Cases</h4>
                  
                  <p>
                    Widgets may require signing for integrity protection and source  
                    authentication. This signing of a Widget package may be provided  
                    using  XML Signature.
                    
                  </p>
                  
                </div>
                
                <div id="requirements" class="section">
                  
                  <h4><span class="secno">3.1.2 </span>Requirements</h4>
                  
                  <p>
                    Provide the ability to sign and verify a widget package using XML   
                    Signature. Enable the use of SHA-256 to  support sufficient security.
                    Support the use of properties in a XML Signature, including  Profile,   
                    Role, and Identifier properties to enable interoperable  
                    interpretation  of signatures. See the Widget Signature specification  
                    for a summary of  requirements 
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-WIDGETS-DIGSIG">WIDGETS-DIGSIG</a></cite>]
                    .   
                    
                  </p>
                  
                </div>
                
                <div id="design" class="section">
                  
                  <h4><span class="secno">3.1.3 </span>Design</h4>
                  
                  <p>
                    Define generic widget properties. See XML Signature Properties  
                    
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLDSIG-PROPERTIES">XMLDSIG-PROPERTIES</a></cite>]
                    .
                    
                  </p>
                  
                </div>
                
              </div>
              
              
              <div id="derived-keys" class="section">
                
                <h3><span class="secno">3.2 </span>Derived Keys</h3>
                
                <div id="use-cases-and-background" class="section">
                  
                  <h4><span class="secno">3.2.1 </span>Use Cases and Background</h4>
                  
                  <p>
                    Several open specifications make use of derived keys, e.g. RSA
                    Laboratories' PKCS #5 v2.0 
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-PKCS5">PKCS5</a></cite>]
                    and OASIS'
                    WS-SecureConversation 
                    Version 1.3 
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-WS-SECURECONVERSATION13">WS-SECURECONVERSATION13</a></cite>]
                    . These derived keys are used
                    for a variety of purposes 
                    including encryption and message authentication, and the purpose of
                    key derivation itself is typically a combination of a desire to expand
                    a given, but limited, set of key material and prudent security
                    practices of limiting use (exposure) of such key material.
                    
                  </p>
                  
                  <p>
                    Contrary to the situation in the ASN.1-based world (e.g. S/MIME
                    
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-SMIME">SMIME</a></cite>]
                    ), there is currently a lack of general
                    support in the core XML 
                    Security specifications, XML Signature and XML Encryption, for derived
                    keys. Amendment 1 of the aforementioned PKCS #5 v2.0 Amendment 1
                    
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-PKCS5">PKCS5</a></cite>]
                    
                    adds support for derived keys only in the context of
                    password-based cryptography. Other XML-based open specifications have
                    similar limitations (see below). This means that an originator of an
                    XML document or message cannot generally make use of key derivation
                    in a standardized manner when performing cryptographic operations on
                    that document.
                    
                  </p>
                  
                </div>
                
                <div id="use-of-derived-keys-in-existing-ws---specifications" class="section">
                  
                  <h4><span class="secno">3.2.2 </span>Use Of Derived Keys in Existing WS-* Specifications</h4>
                  
                  <div class="section">
                    <p>This section outlines the use of derived keys with Web Services
                    specifications related to Web Services Security [<cite><a class="bibref" rel="biblioentry" href="#bib-WS-SECURITY11">WS-SECURITY11</a></cite>].
                    </p>
                    
                    <h4 id="web-services-security--usernametoken-profile-version-1.1">Web Services Security: UsernameToken Profile Version 1.1</h4>
                    
                    <p>
                      This specification 
                      [<cite><a class="bibref" rel="biblioentry" href="#bib-WSS-USERNAME11">WSS-USERNAME11</a></cite>]
                      describes a key
                      derivation technique for 
                      passwords using salt and iteration count (PKCS #5 PBKDF1). It does not
                      allow use of PBKDF2, which is the recommended method to derive keys
                      from passwords in PKCS #5 v2.0. Initial key material cannot be
                      referenced other than with wsu:Id. The key length will always be 160
                      bits.
                      
                    </p>
                    
                  </div>
                  <div id="ws-trust-version-1.3" class="section">
                    
                    <h5><span class="secno">3.2.2.1 </span>WS-Trust Version 1.3:</h5>
                    
                    <p>
                      Ws-Trust Version 1.3 
                      [<cite><a class="bibref" rel="biblioentry" href="#bib-WS-TRUST13">WS-TRUST13</a></cite>]
                      describes key
                      derivation through a 
                      combination of entropies from both parties. The key is never sent on
                      the wire. The key is never referenced directly (but further key
                      material is derived from it). WS-Trust provides one specific method to
                      derive keys which builds on the P_hash (P_SHA-1) function from TLS.
                      
                    </p>
                    
                  </div>
                  <div id="ws-securitypolicy-1.2" class="section">
                    
                    <h5><span class="secno">3.2.2.2 </span>WS-SecurityPolicy 1.2:</h5>
                    
                    <p>
                      WS-SecurityPolicy Version 1.2 
                      [<cite><a class="bibref" rel="biblioentry" href="#bib-WS-SECURITYPOLICY12">WS-SECURITYPOLICY12</a></cite>]
                      really only specifies whether
                      derived keys shall be used or not but may also specify the algorithm
                      to derive keys. The specification also identifies when derived key
                      tokens shall appear in message headers (header
                      layout). WS-SecurityPolicy relies on WS-SecureConversation for the
                      definition of derived keys, key derivation methods and derived key
                      token format.
                      
                    </p>
                    
                  </div>
                  <div id="ws-secureconversation-1.3" class="section">
                    
                    <h5><span class="secno">3.2.2.3 </span>WS-SecureConversation 1.3:</h5>
                    
                    <p>
                      This specification 
                      [<cite><a class="bibref" rel="biblioentry" href="#bib-WS-SECURECONVERSATION13">WS-SECURECONVERSATION13</a></cite>]
                      defines the wsc:DerivedKeyTokenType token
                      type. The derived key token can be used to derive keys from any other
                      token that contains keys. The key derivation algorithm specified
                      builds on the P_hash (P_SHA-1) function from TLS, just as the
                      algorithm in the Web Service Security UsernameToken Profile
                      document. Citing from the specification: "The <code>&lt;wsc:DerivedKeyToken&gt;</code>
                      element is used to indicate that the key for a specific reference is
                      generated from the function. This is so that explicit security tokens,
                      secrets, or key material need not be exchanged as often." (This latter
                      seems dubious since the DerivedKeyToken still needs to be exchanged.)
                      Further: "Basically, a signature or encryption references a
                      <code>&lt;wsc:DerivedKeyToken&gt;</code> in the <code>&lt;wsse:Security&gt;</code> header that, in turn,
                      references the <code>&lt;wsc:SecurityContextToken&gt;</code>." The derived key token does
                      not support references using key identifiers or key names. All
                      references <em class="rfc2119" title="must">must</em> use an ID (to a wsu:Id attribute) or a URI reference
                      to the <code>&lt;wsc:Identifier&gt;</code> element in the Security Context Token.
                      
                    </p>
                    
                  </div>
                  
                </div>
                
                <div id="solution-requirements" class="section">
                  
                  <h4><span class="secno">3.2.3 </span>Solution Requirements</h4>
                  
                  <div id="use-in-existing-specifications--r1" class="section">
                    
                    <h5><span class="secno">3.2.3.1 </span>Use in existing specifications (R1)</h5>
                    
                    <p>
                      A derived key type shall be possible to use in those
                      situations where existing specifications make use of ad-hoc
                      derived keys or needs a derived key type
                      
                    </p>
                    
                    <p>
                      The motivation for this requirement is that any XML Security
                      definition shall be generic enough that there shall be no need to
                      continue with "point" solutions for derived keys; i.e. it shall cover
                      existing and foreseeable uses.
                      
                    </p>
                    
                  </div>
                  <div id="no-external-dependencies--r2" class="section">
                    
                    <h5><span class="secno">3.2.3.2 </span>No external dependencies (R2)</h5>
                    
                    <p>
                      A derived key type shall enable the simple use of derived keys with
                      XML Signature or XML Encryption -using applications, and shall not
                      require import of non-W3C developed specifications with complex
                      security tokens.
                      
                    </p>
                    
                    <p>
                      The motivation for this is that basic use of XML Signature or XML
                      Encryption should not require use of externally defined security
                      tokens or other security specification elements.
                      
                    </p>
                    
                  </div>
                  <div id="continued-use-of-existing-derivation-methods--r3" class="section">
                    
                    <h5><span class="secno">3.2.3.3 </span>Continued use of existing derivation methods (R3)</h5>
                    
                    <p>
                      An XML Security derived key type shall allow for existing methods to
                      derive keys; i.e. it shall be possible to use already specified key
                      derivation methods with the new derived key type.
                      
                    </p>
                    
                    <p>
                      This requirement is based on the assumptions that implementations may
                      want to continue with already chosen key derivation schemes.
                      
                    </p>
                    
                  </div>
                  <div id="future-proof-with-regards-to-key-lengths--r4" class="section">
                    
                    <h5><span class="secno">3.2.3.4 </span>Future-proof with regards to key lengths (R4)</h5>
                    
                    <p>
                      A derived key type shall allow for arbitrary derived key lengths.
                      
                    </p>
                    
                  </div>
                  <div id="referential-flexibility--r5" class="section">
                    
                    <h5><span class="secno">3.2.3.5 </span>Referential flexibility (R5)</h5>
                    
                    <p>
                      A derived key type shall allow for referencing using any referencing
                      method in use today for other key types used in XMLDsig or XMLEnc.
                      
                    </p>
                    
                    <p>
                      A derived key type shall allow for forward
                      referencing with reference 
                      lists as recommended by WS-I BSP 
                      [<cite><a class="bibref" rel="biblioentry" href="#bib-WSI-BSP10">WSI-BSP10</a></cite>]
                      .
                      
                    </p>
                    
                  </div>
                </div>
                <div id="existing-specifications-vs.-requirements" class="section">
                  
                  <h4><span class="secno">3.2.4 </span>Existing Specifications vs. Requirements</h4>
                  
                  <p>
                    Evaluating the existing specifications against the requirements gives
                    the following result:
                    
                  </p>
                  
                  <p>
                    UsernameToken Profile:
                    
                    </p><ul>
                      
                      <li>
                        <p>R1: Not met (method specified in UsernameToken profile is ad-hoc for
                        UsernameToken specifically) 
                        </p>
                      </li>
                      
                      <li>
                        <p>R2: Not met (method requires use of UsernameToken profile)</p>
                      </li>
                      
                      <li>
                        <p>R3: Not met (UsernameToken profile mandates use of specified
                        mechanism)
                        </p>
                      </li>
                      
                      <li>
                        <p>R4: Not met (Only accept length of 160 bits)</p>
                      </li>
                      
                      <li>
                        <p>R5: Not met (No referencing with KeyName or KeyIdentifier and no
                        <code>&lt;referenceList&gt;</code> element)
                        </p>
                      </li>
                      
                    </ul>
                    
                  <p></p>
                  
                  <p>
                    WS-Trust:
                    
                    </p><ul>
                      
                      <li>
                        <p>R1: N/A (WS-Trust does not define a derived key type per se; only a
                        method to derive keys)
                        </p>
                      </li>
                      
                      <li>
                        <p>R2: N/A</p>
                      </li>
                      
                      <li>
                        <p>R3: Meets (Through use of URI to identify method and extensibility)</p>
                      </li>
                      
                      <li>
                        <p>R4: Meets</p>
                      </li>
                      
                      <li>
                        <p>R5: Meets (Choice of STS on how to identify key)</p>
                      </li>
                      
                    </ul>
                    
                  <p></p>
                  
                  <p>
                    WS-SecurityPolicy:
                    
                    </p><ul>
                      
                      <li>
                        <p>R1: N/A (WS-SecurityPolicy does not define a derived key type)</p>
                      </li>
                      
                      <li>
                        <p>R2: N/A</p>
                      </li>
                      
                      <li>
                        <p>R3: Meets (Through the use of URIs to identify key derivation
                        methods and schema extensibility)
                        </p>
                      </li>
                      
                      <li>
                        <p>R4: Meets</p>
                      </li>
                      
                      <li>
                        <p>R5: N/A</p>
                      </li>
                      
                    </ul>
                    
                  <p></p>
                  
                  <p>
                    WS-SecureConversation:
                    
                    </p><ul>
                      
                      <li>
                        <p>R1: Meets</p>
                      </li>
                      
                      <li>
                        <p>R2: Does not meet.</p>
                      </li>
                      
                      <li>
                        <p>R3: Meets (may use the <code>&lt;Properties&gt;</code> element to carry parameters for
                        other key derivation methods.
                        </p>
                      </li>
                      
                      <li>
                        <p>R4: Meets</p>
                      </li>
                      
                      <li>
                        <p>R5: Does not meet as referencing can only be done to a
                        <code>&lt;wsse:SecurityTokenReference&gt;</code></p>
                      </li>
                      
                    </ul>
                    
                  <p></p>
                  
                </div>
                <div id="design-options" class="section">
                  
                  <h4><span class="secno">3.2.5 </span> Design Options</h4>
                  
                  <div id="create-a-ds-derivedkeytype-type-modeled-after-the---------------------xenc-encryptedkeytype." class="section">
                    
                    <h5><span class="secno">3.2.5.1 </span>Create a ds:DerivedKeyType type modeled after the
                    xenc:EncryptedKeyType.
                    </h5>
                    
                    <p>
                      In this design option, the new DerivedKeyType is modeled after the
                      xenc:EncryptedKeyType. A *possible* outline of such a type could be:
                      
                    </p>
                    <pre class="example sh_html sh_sourceCode">Outline of possible DerivedKeyType schema definition

<span class="sh_keyword">&lt;element</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"DerivedKey"</span> <span class="sh_type">type</span><span class="sh_symbol">=</span><span class="sh_string">"xmlsec:DerivedKeyType"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;complexType</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"DerivedKeyType"</span><span class="sh_keyword">&gt;</span>
<span class="sh_keyword">&lt;sequence&gt;</span>
<span class="sh_keyword">&lt;element</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"KeyDerivationMethod"</span> 
<span class="sh_type">type</span><span class="sh_symbol">=</span><span class="sh_string">"xmlsec:KeyDerivationMethodType"</span> <span class="sh_type">minOccurs</span><span class="sh_symbol">=</span><span class="sh_string">"0"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;element</span> <span class="sh_type">ref</span><span class="sh_symbol">=</span><span class="sh_string">"xenc:ReferenceList"</span> <span class="sh_type">minOccurs</span><span class="sh_symbol">=</span><span class="sh_string">"0"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;element</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"CarriedKeyName"</span> <span class="sh_type">type</span><span class="sh_symbol">=</span><span class="sh_string">"string"</span> <span class="sh_type">minOccurs</span><span class="sh_symbol">=</span><span class="sh_string">"0"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;/sequence&gt;</span>
<span class="sh_keyword">&lt;attribute</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"Id"</span> <span class="sh_type">type</span><span class="sh_symbol">=</span><span class="sh_string">"ID"</span> <span class="sh_type">use</span><span class="sh_symbol">=</span><span class="sh_string">"optional"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;attribute</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"Type"</span> <span class="sh_type">type</span><span class="sh_symbol">=</span><span class="sh_string">"anyURI"</span> <span class="sh_type">use</span><span class="sh_symbol">=</span><span class="sh_string">"optional"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;/complexType&gt;</span>

<span class="sh_keyword">&lt;complexType</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"KeyDerivationMethodType"</span><span class="sh_keyword">&gt;</span>
<span class="sh_keyword">&lt;sequence&gt;</span>
<span class="sh_keyword">&lt;any</span> <span class="sh_type">namespace</span><span class="sh_symbol">=</span><span class="sh_string">"##other"</span> <span class="sh_type">minOccurs</span><span class="sh_symbol">=</span><span class="sh_string">"0"</span> <span class="sh_type">maxOccurs</span><span class="sh_symbol">=</span><span class="sh_string">"unbounded"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;/sequence&gt;</span>
<span class="sh_keyword">&lt;attribute</span> <span class="sh_type">name</span><span class="sh_symbol">=</span><span class="sh_string">"Algorithm"</span> <span class="sh_type">type</span><span class="sh_symbol">=</span><span class="sh_string">"anyURI"</span> <span class="sh_type">use</span><span class="sh_symbol">=</span><span class="sh_string">"required"</span><span class="sh_keyword">/&gt;</span>
<span class="sh_keyword">&lt;/complexType&gt;</span></pre>                  
                    <p>
                      The proposal immediately meets requirements R2, R3 (any key derivation
                      method may be used, including the ones specified, e.g., in
                      WS-SecureConversation), R4 and R5. For R1 we have:
                      
                    </p>
                    
                    <p>
                      Username Token Profile: As the UsernameToken Profile requires use of an
                      existing procedure to derive keys, the proposal
                      cannot formally meet 
                      requirement R1. However, since the UsernameTokenType is extensible,
                      syntactically the requirement can be met since a <code>&lt;ds:DerivedKey&gt;</code>
                      element could be placed in lieu of the current <code>&lt;salt&gt;</code> and <code>&lt;iteration&gt;</code>
                      elements.
                      
                    </p>
                    
                    <p>
                      WS-Trust: Use of derived keys in WS-Trust is _implicit_, since the
                      derived key is never sent. The derived keys may be referenced by any
                      available means in issued tokens and the requester is only required to
                      identify particular key derivation methods. Since URIs are used for
                      this (the <code>&lt;wst:ComputedKey&gt;</code> element), any other key derivation method
                      with a well-known URI may be used. Specifically, one can also envision
                      an STS returning a proof token containing a <code>&lt;DerivedKey&gt;</code> element when
                      there already is a shared key between the STS and a token
                      requester. And so, R1 is met.
                      
                    </p>
                    
                    <p>
                      WS-SecurityPolicy: Not affected by a new key type. R1 is met.
                      
                    </p>
                    
                    <p>
                      WS-SecureConversation: Use of derived keys in WS-SecureConversation is
                      typically based on the establishment of a session context, from which
                      specific keys are derived. The proposed <code>&lt;xmlsec:DerivedKeyType&gt;</code> type may be
                      used in a similar fashion, although the interactive nature of
                      WS-SecureConversation (exchange of Nonces, Labels) may still favor use
                      of the existing DerivedKeyToken in this context. But as a counterexample, a
                      party that wishes to send data authenticated with a key derived from a
                      key established in the session, may do so using the
                      <code>&lt;xmlsec:DerivedKey&gt;</code> element in the <code>&lt;ds:KeyInfo&gt;</code> element, and the
                      element may refer to a SecurityContextToken that identifies the base
                      key. This would, it seems, eliminate an absolute need for a
                      <code>&lt;wsc:DerivedKeyToken&gt;</code> (and should be similar in nature as the "Implied
                      Derived Key" option in WS-SecureConversation). Also, the
                      <code>&lt;wsc:DerivedKeyToken&gt;</code> implies use of a particular key derivation
                      algorithm (the <code>&lt;Label&gt;</code> and <code>&lt;Nonce&gt;</code> elements) although it does not
                      require them.
                      
                    </p>
                    
                    <p>
                      In summary, WS-Trust and WS-SecurityPolicy are not directly affected
                      by this proposal. UsernameToken profile could use the proposal if the
                      (artificial) requirement to only use the key derivation method
                      specified in the UsernameToken Profile document was
                      relaxed. WS-SecureConversation comes close in establishing an
                      alternative but the specification defines a token primarily for use in
                      interactive sessions based on a security context and which is designed
                      for a particular key derivation method. It also seems strange to
                      require use of such a token in more basic XMLDsig or XMLEnc
                      situations. Finally, the proposal seems to be able to replace the
                      DerivedKeyToken currently used in WS-SecureConversation.
                      
                    </p>
                    
                  </div>
                  
                </div>
                
              </div>
              
              <div id="algorithms" class="section">
                
                <h3><span class="secno">3.3 </span>Algorithm security and interoperability</h3>
                
                <div id="algorithm-fundamentals" class="section">
                  
                  <h4><span class="secno">3.3.1 </span>Fundamentals</h4>
                  
                  <p>
                    XML Signature specifies algorithm identifiers and implementation
                    requirements for algorithms related to various aspects of signature
                    processing, including digest and signature algorithms. The algorithms
                    listed in XML Signature, Second Edition date from the original XML
                    Signature Recommendation, published in 2002. Since that time there have
                    been new algorithms introduced to address security risks associated with
                    earlier algorithms (e.g. SHA-256 versus SHA-1), changes in patent status
                    related to algorithms (e.g. RSA signing no longer has licensing
                    requirements), and additional algorithms introduced to meet additional
                    requirements (Suite B algorithms 
                    [<cite><a class="bibref" rel="biblioentry" href="#bib-SUITEB">SUITEB</a></cite>], [<cite><a class="bibref" rel="biblioentry" href="#bib-ECC-ALGS">ECC-ALGS</a></cite>]
                    ).
                    
                  </p>
                  <p>
                    In order to meet the principle of "Secure" and "Pragmatic", new
                    algorithm requirements should be met. 
                  </p>
                  
                </div>
                
                <div id="algorithm-requirements" class="section">
                  
                  <h4><span class="secno">3.3.2 </span>Requirements</h4>
                  
                  <div id="algorithm-sha" class="section">
                    
                    <h5><span class="secno">3.3.2.1 </span>Address SHA security concerns, recognize RSA de-facto use.</h5>
                    
                    <p>
                      In order to address concerns related to potential
                      risks associated with 
                      SHA-1 
                      [<cite><a class="bibref" rel="biblioentry" href="#bib-SHA-1-Collisions">SHA-1-Collisions</a></cite>], the following algorithm
                      requirements that update the SHA algorithm should
                      be met in XML Signature 1.1 and XML 
                      Encryption 1.1:
                      
                    </p>
                    
                    <ul>
                      
                      <li>
                        <p>Digest:</p>
                        <p>SHA256 be required.</p>
                        <p>SHA384 and SHA512 optional.
                        
                        </p>
                      </li>
                      
                      <li>
                        <p>Mac:</p>
                        <p>HMAC-SHA256 recommended.</p>
                        <p>HMAC-SHA384 and
                        HMAC-SHA512 optional.
                        (Note these are Recommended in XML Signature 1.1.)
                        
                        </p>
                      </li>
                      
                      <li>
                        <p>Signature:</p>
                        <p>RSAwithSHA256 required.</p>
                        <p>RSAwithSHA384, RSAwithSHA512
                        optional.
                        
                        </p>
                      </li>
                      
                    </ul>
                    
                  </div>
                  
                  <div id="algorithm-dsawithsha1-guidance" class="section">
                    
                    <h5><span class="secno">3.3.2.2 </span>Revise guidance for DSAwithSHA1</h5>
                    
                    <p>
                      In order to discourage the use of DSAwithSHA1 but to continue to
                      enable interoperability, the following algorithm changes are
                      requirements;
                      
                    </p>
                    
                    <ul>
                      
                      <li>
                        <p>Signature:</p>
                        <p>Continue to require DSAwithSHA1 for
                        signature verification, 
                        but change DSAwithSHA1 to optional (from required) for signature
                        generation.
                        
                        </p>
                      </li>
                      
                    </ul>
                    
                  </div>
                  
                  <div id="algorithm-suiteb" class="section">
                    
                    <h5><span class="secno">3.3.2.3 </span>Add Suite B algorithm support</h5>
                    
                    <p>
                      In order to:
                      
                      </p><ol>
                        
                        <li>
                          <p>
                            enable long term security for digital signatures (including in commercial contexts),
                            
                          </p>
                        </li>
                        
                        <li>
                          <p>
                            ensure that the XML Signature standard is cryptographically secure and makes use of the best current practices for digital
                            signature algorithms, and
                            
                          </p>
                        </li>
                        
                        <li>
                          <p>
                            enable use of XML Signature technology in a wide variety of commercial and government applications, including those that require
                            Suite B
                            
                          </p>
                        </li>
                        
                      </ol>
                      elliptic curve algorithms are to be added to XML Signature. 
                      
                    <p></p>
                    <p>
                      The additional algorithm requirements are as follows:
                      
                    </p>
                    
                    <ul>
                      
                      <li>
                        <p>Signature:</p>
                        <p>Require ECDSAwithSHA256.</p>
                        <p>ECDSAwithSHA1,
                        ECDSAwithSHA384, ECDSAwithSHA512 optional.
                        (Note ECDSAwithSHA1 is Discouraged in XML Signature 1.1 due to
                        concerns with SHA-1.)
                        
                        </p>
                      </li>
                      
                      <li>
                        <p>Define ECKeyValue element to enable interoperable exchange of EC
                        public key values in XML Signature context.
                        
                        </p>
                      </li>
                      
                      <li>
                        <p>Provide profile guidance for use of RFC 4050 
                        
                        [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4050">RFC4050</a></cite>]
                        
                        when it
                        continues to be used in XML Signature context but indicate preference
                        for mechanism defined in XML Signature. 
                        
                        </p>
                      </li>
                      
                    </ul>
                    
                    <p>
                      The last two requirements are discussed in more detail in the
                      following design section.
                      
                    </p>
                    
                  </div>
                  
                </div>
                
                <div id="algorithm-eckeyvalue-design" class="section">
                  
                  <h4><span class="secno">3.3.3 </span>Suite B Elliptic Curve Key Value Design (ECKeyValue)</h4>
                  
                  <div id="algorithm-eckeyvalue-issues" class="section">
                    
                    <h5><span class="secno">3.3.3.1 </span>RFC 4050 issues in XML Signature context</h5>
                    
                    <p>
                      RFC 4050 is an informational RFC that defines a method of representing
                      ECDSA public keys and ECC curve parameters for use with XML Signature,
                      but it has some issues related to XML Signature:
                    </p>
                    
                    <ul>
                      
                      <li>
                        <p>The RFC 4050 definition of an ECDSAKeyValue is larger than
                        necessary.
                        </p>
                        <p>
                          An ECDSAKeyValue is defined by the type ECPointType, which has
                          subelements X and Y. X and Y are defined as FieldParamsType which is an
                          abstract type. Separate derived types are defined for prime fields,
                          trinomial base fields, pentanomial base fields, and odd characteristic
                          extension fields.  In order to validate against the 4050 schema, one
                          must include the type attribute from the XML schema instance
                          namespace. This is not a significant problem but it does make the
                          public key larger than necessary.
                          
                        </p>
                      </li>
                      
                      <li>
                        <p>ECPointType definition is inconsistent with ANSI X9.62 and
                        RFC 3279.
                        </p>
                        <p> 
                          ECPointType is reused in the definition of the ExplicitParamsType to
                          describe the base point of a curve. The field parameters are already
                          included in the FieldParams element. The use of the FieldParamsType in
                          the ECPointType definition appears to be a mistake in 4050. If you
                          look at the ASN.1 definition for ECC public keys in RFC 3279 
                          [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3279">RFC3279</a></cite>]
                          , ECPoint
                          simply references the Point to Octet String conversion function in
                          ANSI X9.62 (section A.5.6 in the 2005 version, section 4.3.6 in the
                          1998 version). The conversion functions in X9.62 are not ASN.1
                          specific and it appears they would be implemented as part of any ECC
                          crypto library. It appears that RFC 4050 tried to avoid using any of
                          the conversion functions in X9.62 but somehow mixed up the definitions
                          between a field type and a field element. 
                          
                        </p>
                      </li>
                      
                      <li>
                        <p>Limitation of the decimal type in XSD</p>
                        <p>
                          RFC 4050 defines X and Y (at least for prime and odd characteristic
                          extension fields) as xs:nonNegativeInteger which derives from the
                          xs:decimal primitive type. However, XSD requires implementations to
                          support only a maximum of 18 digits (see <a href="http://www.w3.org/TR/xmlschema-2/#decimal">section 3.2.3</a>
                          in 
                          [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA11-2">XMLSCHEMA11-2</a></cite>]
                          ).
                          It is possible to create an example requiring  77 and 78 digits for X
                          and Y respectively. 
                          This means that there is no guarantee that an RFC 4050 compliant
                          ECDSAKeyValue element will actually validate against the RFC 4050 schema.
                          
                        </p>
                      </li>
                      
                      <li>
                        <p>
                          Collision between the RFC 4050 DTD and the XMLDSIG DTD
                        </p>
                        <p>
                          Merging the  RFC 4050 DTD into the XMLDSIG DTD is a problem due to
                          conflicting DTD definitions. In ECDSAKeyValue, Y is defined as follows:
                        </p>                           
                        <pre class="example sh_html sh_sourceCode">Definition of Y in ECDSAKeyValue

&lt;!ELEMENT Y EMPTY&gt;
&lt;!ATTLIST Y Value CDATA #<em class="rfc2119" title="required">required</em>&gt;</pre>
                        
                        <p>However, DSAKeyValue defines Y as follows:</p>
                        
                        <pre class="example sh_html sh_sourceCode">Definition of Y in DSAKeyValue

&lt;!ELEMENT Y (#PCDATA) &gt;</pre>
                        
                        <p>ECDSAKeyValue also contains identical definition for elements SEED and
                        P as DSAKeyValue.
                        
                        </p>
                        
                        <p>It does not seem possible to scope the definition of Y
                        under a specific element in DTD.
                        
                        </p>
                      </li>
                      
                    </ul>
                    
                  </div>
                  
                  <div id="algorithm-eckeyvalue-proposal" class="section">
                    
                    <h5><span class="secno">3.3.3.2 </span>Proposed Solution to RFC 4050 issues in XML Signature context</h5>
                    
                    <p>
                      Because of these issues, a possible proposed solution is
                      for XML Signature 
                      1.1 to define a new ECPublicKey element in the ds namespace rather
                      than attempt to reuse the RFC 4050 ECDSAPublicKey elements. This new
                      element will be based on the ASN.1
                      definition ANSI X9.62 and RFC 3279. Changing the name of the element
                      to ECPublicKey means it can be also used in XML Encryption to
                      support ECDH.  (Note, XML Signature 1.1 defined
                      ECKeyValue instead).
                      
                    </p>
                    <p>
                      To maximize interoperability with existing RFC 4050 implementations,
                      we should also put a note in 1.1 to recommend implementations to
                      support a profile of RFC 4050. The profile will support only named prime
                      curves.
                      
                    </p>
                    
                  </div>

                </div>
              </div>
              <div id="correct-issues" class="section">
                <h3><span class="secno">3.4 </span>Correct known issues</h3>
                <p>This section summarizes the motivation for new features
                designed to 
                address known issues. (This section of the requirements
                document was written after the 
                XML Signature 1.1 specification was updated in order to
                record the rationale for the changes.)</p>            

                <div id="issueserial" class="section">
                  <h4><span class="secno">3.4.1 </span>Limitations associated with <code>X509IssueSerial</code></h4>
                  <p>
                    The <code>X509IssuerSerialNumber</code> child element of
                    the <code>X509IssuerSerialType</code>
                    XML Schema type
                    was defined to be an integer 
                    holding an X.509 certificate serial number.
                    XML 
                    Schema validators may not support integer types with decimal
                    data exceeding 18 decimal digits [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-2">XMLSCHEMA-2</a></cite>]
                    and this
                    maximum length has proven
                    insufficient as many Certificate Authorities issue
                    certificates with large random serial numbers that
                    exceed this 
                    limit. A
                    new element is defined in XML Signature 1.1 with a
                    different type definition, 
                    the <code>sig11:X509Digest</code> element, and a warning
                    that 
                    deployments that make use of
                    the <code>X509IssuerSerial</code> element 
                    should take care if schema validation is involved.
                  </p>
                </div>
                <div id="RetrievalMethod" class="section">
                  <h4><span class="secno">3.4.2 </span>Simplify access to <code>ds:KeyInfo</code></h4>
                  <p>
                    The <code>RetrievalMethod</code> is ambiguous about whether the result
                    is an element within <code>KeyInfo</code> or the  <code>KeyInfo</code>
                    element itself. It also supports the use of <code>ds:Transform</code>
                    adding complexity. The new <code>KeyInfoReference</code> element
                    removes the ambiguity by always referencing the  <code>KeyInfo</code>
                    element itself. It also is simpler in that it does not allow
                    any <code>ds:Transform</code> children.
                  </p>
                </div>

                <div id="DEREncodedKeyValue" class="section">
                  <h4><span class="secno">3.4.3 </span>XML <code>KeyValue</code> type interoperability</h4> 
                  <p>
                    XML Signature 1.1 defines XML formats to
                    convey key information in the <code>KeyValue</code> 
                    element. There are scenarios
                    where at least one of signer and/or verifier are not able to
                    serialize keys in those XML formats.
                    The <code>DEREncodedKeyValue</code> element has been
                    added to XML Signature 1.1 to support use
                    of other binary encodings. 
                  </p>
                </div>
                <div id="OCSPResponse" class="section">
                  <h4><span class="secno">3.4.4 </span>Support OCSP use case</h4>
                  <p>
                    It is sometimes useful to provide an OCSP
                    response along 
                    with an X.509 certificate. The <code>OCSPResponse</code>
                    element was 
                    added to <code>X509Data</code> to support this use case.
                  </p>

                </div>
              </div>
            </div>

            <div id="thanks" class="section">
              
              <!--OddPage--><h2><span class="secno">4. </span>Acknowledgments</h2>
              
              <p> Contributions received from the members of the XML Security Working
              Group: Scott Cantor, Juan Carlos Cruellas, Pratik Datta, Gerald Edgar,
              Ken Graf, Phillip Hallam-Baker, Brad Hill, Frederick Hirsch, Brian LaMacchia, Konrad Lanz, Hal Lockhart, Cynthia Martin, Rob
              Miller, Sean Mullan, Shivaram Mysore, Magnus Nyström, Bruce Rich, Thomas
              Roessler, Ed Simon, Chris Solc, John Wray,
              Kelvin Yiu. 
              </p>
            </div>
            
          
          
        
<div id="references" class="appendix section"><!--OddPage--><h2><span class="secno">A. </span>References</h2><p>Dated references below are to the latest known or appropriate edition of the referenced work.  The referenced works may be subject to revision, and conformant implementations may follow, and are encouraged to investigate the appropriateness of following, some or all more recent editions or replacements of the works cited. It is in each case implementation-defined which  editions are supported.</p><div id="normative-references" class="section"><h3><span class="secno">A.1 </span>Normative references</h3><p>No normative references.</p></div><div id="informative-references" class="section"><h3><span class="secno">A.2 </span>Informative references</h3><dl class="bibliography"><dt id="bib-ECC-ALGS">[ECC-ALGS]</dt><dd>D. McGrew, K. Igoe, M. Salter. <a href="http://www.rfc-editor.org/rfc/rfc6090.txt"><cite>RFC 6090: Fundamental Elliptic Curve Cryptography Algorithms</cite></a>, IETF Informational RFC,  February 2011, URL: <a href="http://www.rfc-editor.org/rfc/rfc6090.txt">http://www.rfc-editor.org/rfc/rfc6090.txt</a>
</dd><dt id="bib-EXI">[EXI]</dt><dd>Takuki Kamiya; John Schneider. <a href="http://www.w3.org/TR/2009/CR-exi-20091208/"><cite>Efficient XML Interchange (EXI) Format 1.0.</cite></a> 8 December 2009. W3C Candidate Recommendation. (Work in progress.) URL: <a href="http://www.w3.org/TR/2009/CR-exi-20091208/">http://www.w3.org/TR/2009/CR-exi-20091208/</a> 
</dd><dt id="bib-PKCS5">[PKCS5]</dt><dd>B. Kaliski. <a href="http://www.ietf.org/rfc/rfc2898.txt"><cite>PKCS #5 v2.0: Password-Based Cryptography Standard</cite></a> IETF RFC 2898. September 2000. URL: <a href="http://www.ietf.org/rfc/rfc2898.txt">http://www.ietf.org/rfc/rfc2898.txt</a>
</dd><dt id="bib-RFC3279">[RFC3279]</dt><dd>W. Polk, R. Housley, L. Bassham. <a href="http://www.ietf.org/rfc/rfc3279.txt"><cite>Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile</cite></a>. April 2002. Internet RFC 3279. URL: <a href="http://www.ietf.org/rfc/rfc3279.txt">http://www.ietf.org/rfc/rfc3279.txt</a>
</dd><dt id="bib-RFC4050">[RFC4050]</dt><dd>S. Blake-Wilson, G. Karlinger, T. Kobayashi, Y. Wang.     <a href="http://www.ietf.org/rfc/rfc4050.txt"><cite>Using the Elliptic Curve Signature Algorithm (ECDSA) for XML Digital Signatures.</cite></a> IETF RFC 4050. April 2005. URL: <a href="http://www.ietf.org/rfc/rfc4050.txt">http://www.ietf.org/rfc/rfc4050.txt</a>
</dd><dt id="bib-SHA-1-Collisions">[SHA-1-Collisions]</dt><dd>X. Wang, Y.L. Yin, H. Yu. <a href="http://people.csail.mit.edu/yiqun/SHA1AttackProceedingVersion.pdf"><cite>Finding Collisions in the Full SHA-1</cite></a>. In Shoup, V., editor, Advances in Cryptology - CRYPTO 2005, 25th Annual International Cryptology Conference, Santa Barbara, California, USA, August 14-18, 2005, Proceedings, volume 3621 of LNCS, pages 17–36. Springer, 2005. URL: <a href="http://people.csail.mit.edu/yiqun/SHA1AttackProceedingVersion.pdf">http://people.csail.mit.edu/yiqun/SHA1AttackProceedingVersion.pdf</a> (also published in <a href="http://www.springerlink.com/content/26vljj3xhc28ux5m/">http://www.springerlink.com/content/26vljj3xhc28ux5m/</a>)
</dd><dt id="bib-SMIME">[SMIME]</dt><dd>B. Ramsdell. <a href="http://www.ietf.org/rfc/rfc2633.txt"><cite>S/MIME Version 3 Message Specification.</cite></a> June 1999. Internet RFC 2633. URL: <a href="http://www.ietf.org/rfc/rfc2633.txt">http://www.ietf.org/rfc/rfc2633.txt</a> 
</dd><dt id="bib-SUITEB">[SUITEB]</dt><dd><a href="http://www.nsa.gov/ia/programs/suiteb_cryptography/"><cite>NSA Suite B Cryptography</cite></a>, <a href="http://www.nsa.gov/ia/programs/suiteb_cryptography/">http://www.nsa.gov/ia/programs/suiteb_cryptography/</a> 
</dd><dt id="bib-WEBARCH">[WEBARCH]</dt><dd>Norman Walsh; Ian Jacobs. <a href="http://www.w3.org/TR/2004/REC-webarch-20041215"><cite>Architecture of the World Wide Web, Volume One.</cite></a> 15 December 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-webarch-20041215">http://www.w3.org/TR/2004/REC-webarch-20041215</a> 
</dd><dt id="bib-WIDGETS-DIGSIG">[WIDGETS-DIGSIG]</dt><dd>M. Caceres,F Hirsch, M Priestley <a href="http://www.w3.org/TR/2010/CR-widgets-digsig-20100624"><cite>Digital Signatures for Widgets.</cite></a> 24 June 2010. W3C Candidate Recommendation. (Work in progress.) URL: <a href="http://www.w3.org/TR/2010/CR-widgets-digsig-20100624">http://www.w3.org/TR/2010/CR-widgets-digsig-20100624</a> 
</dd><dt id="bib-WS-SECURECONVERSATION13">[WS-SECURECONVERSATION13]</dt><dd>A. Nadalin, M. Goodner, M. Gudgin, A. Barbir, H. Granqvist. <a href="http://www.oasis-open.org/specs/index.php#wssecconv1.3"><cite>WS-SecureConversation 1.3</cite></a>,OASIS Standard, 1 March 2007. URL: <a href="http://www.oasis-open.org/specs/index.php#wssecconv1.3">http://www.oasis-open.org/specs/index.php#wssecconv1.3</a> 
</dd><dt id="bib-WS-SECURITY11">[WS-SECURITY11]</dt><dd>A. Nadalin, C. Kaler, R. Monzillo, P. Hallam-Baker. <a href="http://www.oasis-open.org/specs/index.php#wssv1.1"><cite>Web Services Security: SOAP Message Security 1.1 (WS-Security 2004)</cite></a>,, OASIS Standard, 1 February 2006. URL: <a href="http://www.oasis-open.org/specs/index.php#wssv1.1">http://www.oasis-open.org/specs/index.php#wssv1.1</a> 
</dd><dt id="bib-WS-SECURITYPOLICY12">[WS-SECURITYPOLICY12]</dt><dd>A. Nadalin, M. Goodner, M. Gudgin, A. Barbir, H. Granqvist. <a href="http://www.oasis-open.org/specs/index.php#wssecpolv1.2"><cite>WS-SecurityPolicy 1.2, OASIS Standard</cite></a>,, 1 July 2007. URL: <a href="http://www.oasis-open.org/specs/index.php#wssecpolv1.2">http://www.oasis-open.org/specs/index.php#wssecpolv1.2</a> 
</dd><dt id="bib-WS-TRUST13">[WS-TRUST13]</dt><dd>A. Nadalin, M. Goodner, M. Gudgin, A. Barbir, H. Granqvist.  <a href="http://www.oasis-open.org/specs/index.php#wstrustv1.3"><cite>WS-Trust 1.3</cite></a>,,OASIS Standard, 19 March 2007. URL: <a href="http://www.oasis-open.org/specs/index.php#wstrustv1.3">http://www.oasis-open.org/specs/index.php#wstrustv1.3</a> 
</dd><dt id="bib-WSI-BSP10">[WSI-BSP10]</dt><dd>M. McIntosh, M. Gudgin, K. S. Morrison, A. Barbir. <a href="http://www.ws-i.org/Profiles/BasicSecurityProfile-1.0.html"><cite>Basic Security Profile Version 1.0</cite></a>, WS-I Final Material, 30 March 2007. URL: <a href="http://www.ws-i.org/Profiles/BasicSecurityProfile-1.0.html">http://www.ws-i.org/Profiles/BasicSecurityProfile-1.0.html</a> 
</dd><dt id="bib-WSS-USERNAME11">[WSS-USERNAME11]</dt><dd>A. Nadalin, C. Kaler, R. Monzillo, P. Hallam-Baker. <a href="http://www.oasis-open.org/committees/download.php/16782/wss-v1.1-spec-os-UsernameTokenProfile.pdf"><cite>Web Services Security UsernameToken Profile 1.1</cite></a>, OASIS Standard Specification, 1 February 2006. URL: <a href="http://www.oasis-open.org/committees/download.php/16782/wss-v1.1-spec-os-UsernameTokenProfile.pdf">http://www.oasis-open.org/committees/download.php/16782/wss-v1.1-spec-os-UsernameTokenProfile.pdf</a> 
</dd><dt id="bib-XML-C14N11">[XML-C14N11]</dt><dd>John Boyer, Glenn Marcy. <a href="http://www.w3.org/TR/2008/REC-xml-c14n11-20080502/"><cite>Canonical XML Version 1.1.</cite></a> 2 May 2008. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2008/REC-xml-c14n11-20080502/">http://www.w3.org/TR/2008/REC-xml-c14n11-20080502/</a> 
</dd><dt id="bib-XML-CANONICAL-REQ">[XML-CANONICAL-REQ]</dt><dd>James Tauber; Joel Nava. <a href="http://www.w3.org/TR/1999/NOTE-xml-canonical-req-19990605"><cite>XML Canonicalization Requirements.</cite></a> 5 June 1999. W3C Note. URL: <a href="http://www.w3.org/TR/1999/NOTE-xml-canonical-req-19990605">http://www.w3.org/TR/1999/NOTE-xml-canonical-req-19990605</a> 
</dd><dt id="bib-XML-INFOSET">[XML-INFOSET]</dt><dd>John Cowan; Richard Tobin. <a href="http://www.w3.org/TR/2004/REC-xml-infoset-20040204/"><cite>XML Information Set (Second Edition).</cite></a> 4 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-xml-infoset-20040204/">http://www.w3.org/TR/2004/REC-xml-infoset-20040204/</a> 
</dd><dt id="bib-XMLDSIG-COMPLEXITY">[XMLDSIG-COMPLEXITY]</dt><dd>Brad Hill. <a href="http://www.w3.org/2007/xmlsec/ws/papers/04-hill-isecpartners/"><cite>Complexity as the Enemy of Security: Position Paper for W3C Workshop on Next Steps for XML Signature and XML Encryption.</cite></a>. 25-26 September 2007. W3C Workshop. URL: <a href="http://www.w3.org/2007/xmlsec/ws/papers/04-hill-isecpartners/">http://www.w3.org/2007/xmlsec/ws/papers/04-hill-isecpartners/</a> 
</dd><dt id="bib-XMLDSIG-CORE">[XMLDSIG-CORE]</dt><dd>Joseph Reagle; et al. <a href="http://www.w3.org/TR/2008/REC-xmldsig-core-20080610/"><cite>XML Signature Syntax and Processing (Second Edition).</cite></a> 10 June 2008. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2008/REC-xmldsig-core-20080610/">http://www.w3.org/TR/2008/REC-xmldsig-core-20080610</a> 
</dd><dt id="bib-XMLDSIG-PROPERTIES">[XMLDSIG-PROPERTIES]</dt><dd>Frederick Hirsch. <a href="http://www.w3.org/TR/2011/CR-xmldsig-properties-20110303/"><cite>XML Signature Properties.</cite></a> 3 March 2011. W3C Candidate Recommendation. (Work in progress.) URL: <a href="http://www.w3.org/TR/2011/CR-xmldsig-properties-20110303/">http://www.w3.org/TR/2011/CR-xmldsig-properties-20110303/</a> 
</dd><dt id="bib-XMLDSIG-REQUIREMENTS">[XMLDSIG-REQUIREMENTS]</dt><dd>Joseph Reagle Jr. <a href="http://www.w3.org/TR/1999/WD-xmldsig-requirements-19991014"><cite>XML-Signature Requirements.</cite></a> 14 October 1999. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/1999/WD-xmldsig-requirements-19991014">http://www.w3.org/TR/1999/WD-xmldsig-requirements-19991014</a> 
</dd><dt id="bib-XMLDSIG-SEMANTICS">[XMLDSIG-SEMANTICS]</dt><dd>Sebastian Gajek, Lijun Liao, and Jörg Schwenk. <a href="http://www.w3.org/2007/xmlsec/ws/papers/07-gajek-rub/"><cite> Towards a Semantic of XML Signature: Position Paper for W3C Workshop on Next Steps for XML Signature and XML Encryption </cite></a> 25-26 September 2007. W3C Workshop. URL: <a href="http://www.w3.org/2007/xmlsec/ws/papers/07-gajek-rub/">http://www.w3.org/2007/xmlsec/ws/papers/07-gajek-rub/</a> 
</dd><dt id="bib-XMLDSIG-THOMPSON">[XMLDSIG-THOMPSON]</dt><dd>Henry Thompson. <a href="http://www.w3.org/2007/xmlsec/ws/papers/20-thompson/"><cite>Radical proposal for Vnext of XML Signature: Position Paper for W3C Workshop on Next Steps for XML Signature and XML Encryption</cite></a> 26 September 2007. W3C Workshop. URL: <a href="http://www.w3.org/2007/xmlsec/ws/papers/20-thompson/"> http://www.w3.org/2007/xmlsec/ws/papers/20-thompson/</a> 
</dd><dt id="bib-XMLENC-CORE">[XMLENC-CORE]</dt><dd>Donald Eastlake; Joseph Reagle. <a href="http://www.w3.org/TR/2002/REC-xmlenc-core-20021210/"><cite>XML Encryption Syntax and Processing.</cite></a> 10 December 2002. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2002/REC-xmlenc-core-20021210/">http://www.w3.org/TR/2002/REC-xmlenc-core-20021210/</a> 
</dd><dt id="bib-XMLSCHEMA-2">[XMLSCHEMA-2]</dt><dd>Paul V. Biron; Ashok Malhotra. <a href="http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/"><cite>XML Schema Part 2: Datatypes Second Edition.</cite></a> 28 October 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/">http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/</a> 
</dd><dt id="bib-XMLSCHEMA11-2">[XMLSCHEMA11-2]</dt><dd>Henry S. Thompson; et al. <a href="http://www.w3.org/TR/2009/WD-xmlschema11-2-20090130"><cite>W3C XML Schema Definition Language (XSD) 1.1 Part 2: Datatypes.</cite></a> 30 January 2009. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2009/WD-xmlschema11-2-20090130">http://www.w3.org/TR/2009/WD-xmlschema11-2-20090130</a> 
</dd><dt id="bib-XMLSEC-NEXTSTEPS-2007">[XMLSEC-NEXTSTEPS-2007]</dt><dd><a href="http://www.w3.org/2007/xmlsec/ws/report.html"><cite>Workshop Report W3C Workshop on Next Steps for XML Signature and XML Encryption</cite></a> 25-26 September 2007. W3C Workshop Report. URL: <a href="http://www.w3.org/2007/xmlsec/ws/report.html">http://www.w3.org/2007/xmlsec/ws/report.html</a>
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