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Additional XML Security Uniform Resource Identifiers (URIs)
draft-eastlake-rfc6931bis-xmlsec-uris-26

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 9231.
Author Donald E. Eastlake 3rd
Last updated 2022-02-23
RFC stream Internet Engineering Task Force (IETF)
Formats
Reviews
Stream WG state (None)
Document shepherd (None)
IESG IESG state Became RFC 9231 (Proposed Standard)
Consensus boilerplate Yes
Telechat date (None)
Needs 3 more YES or NO OBJECTION positions to pass.
Responsible AD Roman Danyliw
Send notices to (None)
IANA IANA review state Version Changed - Review Needed
IANA expert review state Expert Reviews OK
IANA expert review comments Expert has approved.
draft-eastlake-rfc6931bis-xmlsec-uris-26
INTERNET-DRAFT                                               D. Eastlake
Obsoletes: 6931                                   Futurewei Technologies
Intended Status: Proposed Standard
Expires: August 22, 2022                               February 23, 2022

      Additional XML Security Uniform Resource Identifiers (URIs)
             <draft-eastlake-rfc6931bis-xmlsec-uris-26.txt>

Abstract

   This document updates and corrects the IANA "XML Security URIs"
   registry that lists URIs intended for use with XML digital
   signatures, encryption, canonicalization, and key management.  These
   URIs identify algorithms and types of information.  This document
   also updates, corrects three errata against, and obsoletes RFC 6931.

Status of This Memo
   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Distribution of this document is unlimited. Comments should be sent
   to the author.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   https://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
   Shadow Directories can be accessed at
   https://www.ietf.org/shadow.html.

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Table of Contents

      1. Introduction............................................4
       1.1 Terminology...........................................5
       1.2 Acronyms..............................................5

      2. Algorithms..............................................7
       2.1 DigestMethod (Hash) Algorithms........................7
       2.1.1 MD5.................................................8
       2.1.2 SHA-224.............................................8
       2.1.3 SHA-384.............................................8
       2.1.4 Whirlpool...........................................9
       2.1.5 SHA3 Algorithms.....................................9
       2.2 SignatureMethod MAC Algorithms........................9
       2.2.1 HMAC-MD5...........................................10
       2.2.2 HMAC SHA Variations................................10
       2.2.3 HMAC-RIPEMD160.....................................11
       2.2.4 Poly1305...........................................11
       2.2.5 SipHash-2-4........................................11
       2.2.6 XMSS and XMSSMT....................................12
       2.3 SignatureMethod Public Key Signature Algorithms......14
       2.3.1 RSA-MD5............................................14
       2.3.2 RSA-SHA256.........................................15
       2.3.3 RSA-SHA384.........................................15
       2.3.4 RSA-SHA512.........................................15
       2.3.5 RSA-RIPEMD160......................................16
       2.3.6 ECDSA-SHA*, ECDSA-RIPEMD160, ECDSA-Whirlpool.......16
       2.3.7 ESIGN-SHA*.........................................17
       2.3.8 RSA-Whirlpool......................................17
       2.3.9 RSASSA-PSS with Parameters.........................18
       2.3.10 RSASSA-PSS without Parameters.....................19
       2.3.11 RSA-SHA224........................................20
       2.3.12 Edwards-Curve.....................................20
       2.4 Minimal Canonicalization.............................21
       2.5 Transform Algorithms.................................21
       2.5.1 XPointer...........................................21
       2.6 EncryptionMethod Algorithms..........................22
       2.6.1 ARCFOUR Encryption Algorithm.......................22
       2.6.2 Camellia Block Encryption..........................23
       2.6.3 Camellia Key Wrap..................................23
       2.6.4 PSEC-KEM, RSAES-KEM, and ECIES-KEM.................24
       2.6.5 SEED Block Encryption..............................24
       2.6.6 SEED Key Wrap......................................25
       2.6.7 ChaCha20...........................................25
       2.6.8 ChaCha20+Poly1305..................................26
       2.7 Key AgreementMethod Algorithms.......................26
       2.7.1 X25519 Key Agreement...............................26
       2.7.2 HKDF Key Derivation................................27

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Table of Contents (continued)

      3. KeyInfo................................................29
       3.1 PKCS #7 Bag of Certificates and CRLs.................29
       3.2 Additional RetrievalMethod Type Values...............29

      4. Indexes................................................30
       4.1 Index by Fragment Index..............................30
       4.2 Index by URI.........................................36

      5. Allocation Considerations..............................43
       5.1 W3C Allocation Considerations........................43
       5.2 IANA Considerations..................................43

      6. Security Considerations................................45

      Acknowledgements..........................................46

      Appendix A: Changes from [RFC6931]........................47
      Appendix B: Bad URIs......................................48

      Appendix Z: Change History................................49

      Normative References......................................51
      Informational References..................................55

      Author's Address..........................................59

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1. Introduction

   XML digital signatures, canonicalization, and encryption were
   standardized by the W3C and by the joint IETF/W3C XMLDSIG working
   group [W3C] [XMLSEC].  These are now W3C Recommendations and some are
   also RFCs.  They are available as follows:

      RFC
      Status            W3C REC      Topic
      -----------       -------      -----

      [RFC3275]         [XMLDSIG10]  XML Digital Signatures
      Draft Standard

      [RFC3076]         [CANON10]    Canonical XML
      Informational

      - - - - - -       [XMLENC10]   XML Encryption 1.0

      [RFC3741]         [XCANON]     Exclusive XML Canonicalization 1.0
      Informational

   These documents and recommendations use URIs [RFC3986] to identify
   algorithms and keying information types.  The W3C has subsequently
   produced updated XML Signature 1.1 [XMLDSIG11], Canonical XML 1.1
   [CANON11], and XML Encryption 1.1 [XMLENC11] versions, as well as a
   new XML Signature Properties specification [XMLDSIG-PROP].

   In addition, the XML Encryption recommendation has been augmented by
   [GENERIC] which defines algorithms, XML types, and elements necessary
   to use generic hybrid ciphers in XML Security applications. [GENERIC]
   also provides for a key encapsulation algorithm and a data
   encapsulation algorithm, with the combination of the two forming the
   generic hybrid cipher.

   All camel-case element names (names with both interior upper and
   lower case letters) herein, such as DigestValue, are from these
   documents.

   This document is an updated convenient reference list of URIs and
   corresponding algorithms in which there is expressed interest.  This
   document fixes Errata [Err3597], [Err3965], [Err4004] against and
   obsoletes [RFC6931].

   All of the URIs for algorithms and data types herein are listed in
   the indexes in Section 4.  Of these URIs, those that were added by
   earlier RFCs or by this document have a subsection in Section 2 or 3.
   A few URIs defined elsewhere also have a subsection in Section 2 or 3
   but most such URIs do not. For example, use of SHA-256 as defined in
   [XMLENC11] has no subsection here but is included in the indexes in

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   Section 4.

   Specification in this document of the URI representing an algorithm
   does not imply endorsement of the algorithm for any particular
   purpose.  A protocol specification, which this is not, generally
   gives algorithm and implementation requirements for the protocol.
   Security considerations for algorithms are constantly evolving, as
   documented elsewhere.  This specification simply provides some URIs
   and relevant formatting when those URIs are used.

   This document is not intended to change the algorithm implementation
   requirements of any IETF or W3C document. Use of [RFC2119]/[RFC8174]
   terminology is intended to be only such as is already stated or
   implied by other authoritative documents.

   Progressing XML Digital Signature [RFC3275] along the Standards Track
   required removal of any algorithms from the original version
   [RFC3075] for which there was not demonstrated interoperability.
   This required removal of the Minimal Canonicalization algorithm, in
   which there was continued interest.  The URI for Minimal
   Canonicalization was included in [RFC6931] and is included here.

1.1 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   "camel-case" refers to terms that are mostly lower case but have
   internal capital letters.

1.2 Acronyms

   The following acronyms are used in this document:

      AAD - Additional Authenticated Data

      AEAD - Authenticated Encryption with Additional Data

      HMAC - Hashed Message Authentication Code [RFC2104] [RFC5869]

      IETF - Internet Engineering Task Force <https://www.ietf.org>

      MAC - Message Authentication Code

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      MD - Message Digest

      NIST - United States National Institute of Standards and
            Technology <https://www.nist.gov>

      RSA - Rivest, Shamir, and Adleman

      SHA - Secure Hash Algorithm

      URI - Uniform Resource Identifier [RFC3986]

      W3C - World Wide Web Consortium <https://www.w3.org>

      XML - eXtensible Markup Language

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2. Algorithms

   The URI [RFC3986] that was dropped from the XML Digital Signature
   standard due to the transition from Proposed Standard to Draft
   Standard [RFC3275] is included in Section 2.4 below with its original

        http://www.w3.org/2000/09/xmldsig#

   prefix so as to avoid changing the XMLDSIG standard's namespace.

   Additional algorithms in RFC 4051 were given URIs that start with

        http://www.w3.org/2001/04/xmldsig-more#

   further algorithms added in [RFC6931] were given URIs that start with

        http://www.w3.org/2007/05/xmldsig-more#

   and algorithms added in this document are given URIs that start with

        http://www.w3.org/2021/04/xmldsig-more#

   In addition, for ease of reference, this document includes in the
   indexes in Section 4 many cryptographic algorithm URIs from XML
   security documents using the namespaces with which they are defined
   in those documents as follows:

        http://www.w3.org/2000/09/xmldsig#

   for some URIs specified in [RFC3275],

        http://www.w3.org/2001/04/xmlenc#

   for some URIs specified in [XMLENC10], and

        http://www.w3/org/xmlsec-ghc#

   for some URIs specified in [GENERIC].

   See also [XMLSECXREF].

2.1 DigestMethod (Hash) Algorithms

   These algorithms are usable wherever a DigestMethod element occurs.

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2.1.1 MD5

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#md5

   The MD5 algorithm [RFC1321] takes no explicit parameters. An example
   of an MD5 DigestAlgorithm element is:

   <DigestAlgorithm
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#md5"/>

   An MD5 digest is a 128-bit string. The content of the DigestValue
   element SHALL be the base64 [RFC4648] encoding of this bit string
   viewed as a 16-octet stream. See [RFC6151] for MD5 security
   considerations.

2.1.2 SHA-224

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#sha224

   The SHA-224 algorithm [FIPS180-4] [RFC6234] takes no explicit
   parameters.  An example of a SHA-224 DigestAlgorithm element is:

   <DigestAlgorithm
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#sha224" />

   A SHA-224 digest is a 224-bit string. The content of the DigestValue
   element SHALL be the base64 [RFC4648] encoding of this string viewed
   as a 28-octet stream.

2.1.3 SHA-384

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#sha384

   The SHA-384 algorithm [FIPS180-4] takes no explicit parameters.  An
   example of a SHA-384 DigestAlgorithm element is:

   <DigestAlgorithm
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#sha384" />

   A SHA-384 digest is a 384-bit string. The content of the DigestValue
   element SHALL be the base64 [RFC4648] encoding of this string viewed
   as a 48-octet stream.

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2.1.4 Whirlpool

   Identifier:
        http://www.w3.org/2007/05/xmldsig-more#whirlpool

   The Whirlpool algorithm [10118-3] takes no explicit parameters. An
   example of a Whirlpool DigestAlgorithm element is:

   <DigestAlgorithm
      Algorithm="http://www.w3.org/2007/05/xmldsig-more#whirlpool" />

   A Whirlpool digest is a 512-bit string.  The content of the
   DigestValue element SHALL be the base64 [RFC4648] encoding of this
   string viewed as a 64-octet stream.

2.1.5 SHA3 Algorithms

   Identifiers:
        http://www.w3.org/2007/05/xmldsig-more#sha3-224
        http://www.w3.org/2007/05/xmldsig-more#sha3-256
        http://www.w3.org/2007/05/xmldsig-more#sha3-384
        http://www.w3.org/2007/05/xmldsig-more#sha3-512

   NIST conducted a hash function competition for an alternative to the
   SHA family.  The Keccak-f[1600] algorithm was selected [Keccak].
   This hash function is commonly referred to as "SHA-3" [FIPS202].

   A SHA-3 224, 256, 384, and 512 digest is a 224-, 256-, 384-, and
   512-bit string, respectively.  The content of the DigestValue element
   SHALL be the base64 [RFC4648] encoding of this string viewed as a
   28-, 32-, 48-, and 64-octet stream, respectively. An example of a
   SHA3-224 DigestAlgorithm element is:

   <DigestAlgorithm
      Algorithm="http://www.w3.org/2007/05/xmldsig-more#sha3-224" />

2.2 SignatureMethod MAC Algorithms

   This section covers SignatureMethod MAC (Message Authentication Code)
   Algorithms.

   Note: Some text in this section is duplicated from [RFC3275] for the
   convenience of the reader. [RFC3275] is normative in case of
   conflict.

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2.2.1 HMAC-MD5

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#hmac-md5

   The HMAC algorithm [RFC2104] takes the truncation length in bits as a
   parameter; if the parameter is not specified, then all the bits of
   the hash are output. An example of an HMAC-MD5 SignatureMethod
   element is as follows:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#hmac-md5">
      <HMACOutputLength>112</HMACOutputLength>
   </SignatureMethod>

   The output of the HMAC algorithm is the output (possibly truncated)
   of the chosen digest algorithm. This value SHALL be base64 [RFC4648]
   encoded in the same straightforward fashion as the output of the
   digest algorithms. Example: the SignatureValue element for the HMAC-
   MD5 digest

        9294727A 3638BB1C 13F48EF8 158BFC9D

   from the test vectors in [RFC2104] would be

        kpRyejY4uxwT9I74FYv8nQ==

   Schema Definition:

        <simpleType name="HMACOutputLength">
           <restriction base="integer"/>
        </simpleType>

   DTD:

        <!ELEMENT HMACOutputLength (#PCDATA) >

   The Schema Definition and DTD immediately above are copied from
   [RFC3275].

   See [RFC6151] for HMAC-MD5 security considerations.

2.2.2 HMAC SHA Variations

   Identifiers:
        http://www.w3.org/2001/04/xmldsig-more#hmac-sha224
        http://www.w3.org/2001/04/xmldsig-more#hmac-sha256
        http://www.w3.org/2001/04/xmldsig-more#hmac-sha384

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        http://www.w3.org/2001/04/xmldsig-more#hmac-sha512

   SHA-224, SHA-256, SHA-384, and SHA-512 [FIPS180-4] [RFC6234] can also
   be used in HMAC as described in Section 2.2.1 above for HMAC-MD5.

2.2.3 HMAC-RIPEMD160

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#hmac-ripemd160

   RIPEMD-160 [10118-3] is a 160-bit hash that is used here in HMAC. The
   output can be optionally truncated. An example is as follows:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#hmac-ripemd160">
      <HMACOutputLength>144</HMACOutputLength>
   </SignatureMethod>

2.2.4 Poly1305

   Identifier:
        http://www.w3.org/2021/04/xmldsig-more#poly1305

   Poly1305 [RFC8439] [Poly1305] is a high-speed message authentication
   code algorithm. It takes a 32-octet one-time key and a message and
   produces a 16-octet tag which is used to authenticate the message. An
   example of a Poly1305 SignatureMethod element is as follows:

   <SignatureMethod
      Algorithm="http://www.w3.org/2021/04/xmldsig-more#poly1305"/>

2.2.5 SipHash-2-4

   Identifier:
        http://www.w3.org/2021/04/xmldsig-more#siphash-2-4

   SipHash [SipHash1] [SipHash2] computes a 64-bit MAC from a 128-bit
   secret key and a variable length message. An example of a SipHash-2-4
   SignatureMethod element is as follows:

   <SignatureMethod
      Algorithm="http://www.w3.org/2021/04/xmldsig-more#siphash-2-4"/>

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2.2.6 XMSS and XMSSMT

   XMSS (eXtended Merkle Signature Scheme) [RFC8391] and XMSSMT (XMSS
   Multi-Tree) are stateful hash-based signature schemes [NIST800-208].
   According to NIST, it is believed that the security of these schemes
   depends only on the security of the underlying hash functions -- in
   particular the infeasibility of finding a preimage or a second
   preimage -- and it is believed that the security of these hash
   functions will not be broken by the development of large-scale
   quantum computers.

   IANA maintains a registry most of whose entries correspond to the
   XMSS and XMSSMT Identifiers below (see [XMSS]).

   Identifiers for XMSS:
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-10-192
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-10-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-10-512
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake-10-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake-10-512
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-16-192
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-16-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-16-512
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake-16-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake-16-512
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-20-192
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-20-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-20-512
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake-20-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake-20-512
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake256-10-192
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake256-10-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake256-16-192
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake256-16-256
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake256-20-192
        http://www.w3.org/2021/04/xmldsig-more#xmss-shake256-20-256

   Identifiers for XMSSMT:
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-20-2-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-20-2-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-20-4-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-20-4-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-40-2-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-40-2-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-40-4-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-40-4-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-40-8-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-40-8-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-60-3-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-60-3-256

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        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-60-6-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-60-6-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-60-12-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-60-12-256

        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-20-2-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-20-2-512
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-20-4-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-20-4-512
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-40-2-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-40-2-512
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-40-4-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-40-4-512
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-40-8-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-40-8-512
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-60-3-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-60-3-512
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-60-6-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-60-6-512
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-60-12-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake-60-12-512

        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-20-2-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-20-2-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-20-4-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-20-4-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-40-2-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-40-2-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-40-4-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-40-4-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-40-8-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-40-8-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-60-3-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-60-3-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-60-6-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-60-6-256
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-60-12-192
        http://www.w3.org/2021/04/xmldsig-more#xmssmt-shake256-60-12-256

   The hash function used in these signature schemes is SHA2 [RFC6234]
   or the SHAKE extensible output function [FIPS202] as indicated by the
   second token of the URI extension. The tree height for XMSS is 10,
   16, or 20 and for XMSSMT is 20, 40, or 60 as indicated by the third
   token of the URI extension. For XMSSMT, the number of layers is
   indicated by a fourth token. The SHA2 or SHAKE output size is 192,
   256, or 512 bits as indicated by the final token of the URI
   extension.

   For further information on the intended usage of these signature
   schemes and the careful state management required to maintain their

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   strength, see [NIST800-208].

   An example of an XMSS SignatureAlgorithm element is:

   <SignatureAlgorithm
     Algorithm="http://www.w3.org/2021/04/xmldsig-more#xmss-sha2-10-192"
     />

2.3 SignatureMethod Public Key Signature Algorithms

   These algorithms are distinguished from those in Section 2.2 above in
   that they use public key methods. That is to say, the signing key is
   different from and not feasibly derivable from the verification key.

2.3.1 RSA-MD5

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#rsa-md5

   This implies the PKCS#1 v1.5 padding algorithm described in
   [RFC8017]. An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-md5" />

   The SignatureValue content for an RSA-MD5 signature is the base64
   [RFC4648] encoding of the octet string computed as per [RFC8017],
   Section 8.2.1, signature generation for the RSASSA-PKCS1-v1_5
   signature scheme. As specified in the EMSA-PKCS1-V1_5-ENCODE function
   in [RFC8017], Section 9.2, the value input to the signature function
   MUST contain a prepended algorithm object identifier for the hash
   function, but the availability of an ASN.1 parser and recognition of
   OIDs is not required of a signature verifier. The PKCS#1 v1.5
   representation appears as:

        CRYPT (PAD (ASN.1 (OID, DIGEST (data))))

   The padded ASN.1 will be of the following form:

        01 | FF* | 00 | prefix | hash

   Vertical bar ("|") represents concatenation. "01", "FF", and "00" are
   fixed octets of the corresponding hexadecimal value, and the asterisk
   ("*") after "FF" indicates repetition. "hash" is the MD5 digest of
   the data. "prefix" is the ASN.1 BER MD5 algorithm designator prefix

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   required in PKCS #1 [RFC8017], that is,

        hex 30 20 30 0c 06 08 2a 86 48 86 f7 0d 02 05 05 00 04 10

   This prefix is included to make it easier to use standard
   cryptographic libraries. The FF octet MUST be repeated enough times
   that the value of the quantity being CRYPTed is exactly one octet
   shorter than the RSA modulus.

   See [RFC6151] for MD5 security considerations.

2.3.2 RSA-SHA256

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#rsa-sha256

   This implies the PKCS#1 v1.5 padding algorithm [RFC8017] as described
   in Section 2.3.1, but with the ASN.1 BER SHA-256 algorithm designator
   prefix.  An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256" />

2.3.3 RSA-SHA384

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#rsa-sha384

   This implies the PKCS#1 v1.5 padding algorithm [RFC8017] as described
   in Section 2.3.1, but with the ASN.1 BER SHA-384 algorithm designator
   prefix.  An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha384" />

   Because it takes about the same effort to calculate a SHA-384 message
   digest as it does a SHA-512 message digest, it is suggested that RSA-
   SHA512 be used in preference to RSA-SHA384 where possible.

2.3.4 RSA-SHA512

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#rsa-sha512

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   This implies the PKCS#1 v1.5 padding algorithm [RFC8017] as described
   in Section 2.3.1, but with the ASN.1 BER SHA-512 algorithm designator
   prefix.  An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha512" />

2.3.5 RSA-RIPEMD160

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#rsa-ripemd160

   This implies the PKCS#1 v1.5 padding algorithm [RFC8017] as described
   in Section 2.3.1, but with the ASN.1 BER RIPEMD160 algorithm
   designator prefix.  An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-ripemd160"
   />

2.3.6 ECDSA-SHA*, ECDSA-RIPEMD160, ECDSA-Whirlpool

   Identifiers:
        http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha1
        http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha224
        http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256
        http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384
        http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512
        http://www.w3.org/2021/04/xmldsig-more#ecdsa-sha3-224
        http://www.w3.org/2021/04/xmldsig-more#ecdsa-sha3-256
        http://www.w3.org/2021/04/xmldsig-more#ecdsa-sha3-384
        http://www.w3.org/2021/04/xmldsig-more#ecdsa-sha3-512
        http://www.w3.org/2007/05/xmldsig-more#ecdsa-ripemd160
        http://www.w3.org/2007/05/xmldsig-more#ecdsa-whirlpool

   The Elliptic Curve Digital Signature Algorithm (ECDSA) [FIPS186-4] is
   the elliptic curve analogue of the Digital Signature Algorithm (DSA)
   signature method, i.e., the Digital Signature Standard (DSS). It
   takes no explicit parameters. For some detailed specifications of how
   to use it with SHA hash functions and XML Digital Signature, please
   see [X9.62] and [RFC4050].  The #sha3-*, #ecdsa-ripemd160, and
   #ecdsa-whirlpool fragments identify signature methods processed in
   the same way as specified by the #ecdsa-sha1 fragment, with the
   exception that a SHA3 function (see Section 2.1.5), RIPEMD160, or
   Whirlpool (see Section 2.1.4) is used instead of SHA-1.

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   The output of the ECDSA algorithm consists of a pair of integers
   usually referred to as the pair (r, s).  The signature value consists
   of the base64 encoding of the concatenation of two octet streams that
   respectively result from the octet encoding of the values r and s in
   that order.  Conversion from integer to octet-stream must be done
   according to the I2OSP operation defined in the [RFC8017]
   specification with the l parameter equal to the size of the base
   point order of the curve in octets (e.g., 32 for the P-256 curve and
   66 for the P-521 curve [FIPS186-4]).

   For an introduction to elliptic curve cryptographic algorithms, see
   [RFC6090] and note the errata (Errata IDs 2773-2777).

2.3.7 ESIGN-SHA*

   Identifiers:
        http://www.w3.org/2001/04/xmldsig-more#esign-sha1
        http://www.w3.org/2001/04/xmldsig-more#esign-sha224
        http://www.w3.org/2001/04/xmldsig-more#esign-sha256
        http://www.w3.org/2001/04/xmldsig-more#esign-sha384
        http://www.w3.org/2001/04/xmldsig-more#esign-sha512

   The ESIGN algorithm specified in [IEEEP1363a] is a signature scheme
   based on the integer factorization problem.

   An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#esign-sha1"
   />

2.3.8 RSA-Whirlpool

   Identifier:
        http://www.w3.org/2007/05/xmldsig-more#rsa-whirlpool

   As in the definition of the RSA-SHA1 algorithm in [XMLDSIG11], the
   designator "RSA" means the RSASSA-PKCS1-v1_5 algorithm as defined in
   [RFC8017].  When identified through the #rsa-whirlpool fragment
   identifier, Whirlpool is used as the hash algorithm instead.  Use of
   the ASN.1 BER Whirlpool algorithm designator is implied. That
   designator is:

        hex 30 4e 30 0a 06 06 28 cf 06 03 00 37 05 00 04 40

   as an explicit octet sequence. This corresponds to OID

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   1.0.10118.3.0.55 defined in [10118-3].

   An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2007/05/xmldsig-more#rsa-whirlpool"
   />

2.3.9 RSASSA-PSS with Parameters

   Identifiers:
        http://www.w3.org/2007/05/xmldsig-more#rsa-pss
        http://www.w3.org/2007/05/xmldsig-more#MGF1

   These identifiers use the PKCS#1 EMSA-PSS encoding algorithm
   [RFC8017].  The RSASSA-PSS algorithm takes the digest method (hash
   function), a mask generation function, the salt length in octets
   (SaltLength), and the trailer field as explicit parameters.

   Algorithm identifiers for hash functions specified in XML encryption
   [XMLENC11] [XMLDSIG11] and in Section 2.1 are considered to be valid
   algorithm identifiers for hash functions.  According to [RFC8017],
   the default value for the digest function is SHA-1, but due to the
   discovered weakness of SHA-1 [RFC6194], it is recommended that
   SHA-256 or a stronger hash function be used. Notwithstanding
   [RFC8017], SHA-256 is the default to be used with these
   SignatureMethod identifiers if no hash function has been specified.

   The default salt length for these SignatureMethod identifiers, if the
   SaltLength is not specified, SHALL be the number of octets in the
   hash value of the digest method, as recommended in [RFC4055]. In a
   parameterized RSASSA-PSS signature the ds:DigestMethod and the
   SaltLength parameters usually appear. If they do not, the defaults
   make this equivalent to http://www.w3.org/2007/05/xmldsig-
   more#sha256-rsa-MGF1 (see Section 2.3.10). The TrailerField defaults
   to 1 (0xBC) when omitted.

   Schema Definition (target namespace
   http://www.w3.org/2007/05/xmldsig-more#):

      <xs:element name="RSAPSSParams" type="pss:RSAPSSParamsType">
          <xs:annotation>
              <xs:documentation>
      Top level element that can be used in xs:any namespace="#other"
      wildcard of ds:SignatureMethod content.
              </xs:documentation>
          </xs:annotation>
      </xs:element>

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      <xs:complexType name="RSAPSSParamsType">
          <xs:sequence>
              <xs:element ref="ds:DigestMethod" minOccurs="0"/>
              <xs:element name="MaskGenerationFunction"
                 type="pss:MaskGenerationFunctionType" minOccurs="0"/>
              <xs:element name="SaltLength" type="xs:int"
                 minOccurs="0"/>
              <xs:element name="TrailerField" type="xs:int"
                 minOccurs="0"/>
          </xs:sequence>
      </xs:complexType>
      <xs:complexType name="MaskGenerationFunctionType">
          <xs:sequence>
              <xs:element ref="ds:DigestMethod" minOccurs="0"/>
          </xs:sequence>
          <xs:attribute name="Algorithm" type="xs:anyURI"
             default="http://www.w3.org/2007/05/xmldsig-more#MGF1"/>
      </xs:complexType>

2.3.10 RSASSA-PSS without Parameters

   [RFC8017] currently specifies only one mask generation function MGF1
   based on a hash function.  Although [RFC8017] allows for
   parameterization, the default is to use the same hash function as the
   digest method function.  Only this default approach is supported by
   this section; therefore, the definition of a mask generation function
   type is not needed yet.  The same applies to the trailer field. There
   is only one value (0xBC) specified in [RFC8017].  Hence, this default
   parameter must be used for signature generation. The default salt
   length is the length of the hash function.

   Identifiers:
        http://www.w3.org/2007/05/xmldsig-more#sha3-224-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha3-256-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha3-384-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha3-512-rsa-MGF1

        http://www.w3.org/2007/05/xmldsig-more#md2-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#md5-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha1-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha224-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha256-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha384-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#sha512-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#ripemd128-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#ripemd160-rsa-MGF1
        http://www.w3.org/2007/05/xmldsig-more#whirlpool-rsa-MGF1

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   An example of use is:

   <SignatureMethod
      Algorithm=
      "http://www.w3.org/2007/05/xmldsig-more#SHA3-256-rsa-MGF1"
   />

2.3.11 RSA-SHA224

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#rsa-sha224

   This implies the PKCS#1 v1.5 padding algorithm [RFC8017] as described
   in Section 2.3.1 but with the ASN.1 BER SHA-224 algorithm designator
   prefix.  An example of use is:

   <SignatureMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha224" />

   Because it takes about the same effort to calculate a SHA-224 message
   digest as it does a SHA-256 message digest, it is suggested that RSA-
   SHA256 be used in preference to RSA-SHA224 where possible.

   See also Appendix B concerning an erroneous version of this URI that
   appeared in [RFC6931].

2.3.12 Edwards-Curve

   The Edwards-curve Digital Signature Algorithm (EdDSA) is a variant of
   Schnorr's signature system with Edwards curves. A specification is
   provided and some advantages listed in [RFC8032]. The general EdDSA
   takes 11 parameters that must be carefully chosen for secure and
   efficient operation. Identifiers for two variants, Ed25519 and Ed448,
   are given below.

   Ed25519 uses 32-octet public keys and produces 64-octet signatures.
   It provides about 128 bits of security and uses SHA-512 [RFC6234]
   internally as part of signature generation.

   Ed448 uses 57-octet public keys and produces 114-octet signatures. It
   provides about 224 bits of security and uses "SHAKE256" [FIPS202]
   internally as part of signature generation.  (SHAKE256 is specified
   by NIST as an "Extensible Output Function" and not specified or
   approved by NIST as a secure hash function.)

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   For further information on the variants of EdDSA identified below,
   see [RFC8032].

   Identifiers:
        http://www.w3.org/2021/04/xmldsig-more#eddsa-ed25519ph
        http://www.w3.org/2021/04/xmldsig-more#eddsa-ed25519ctx
        http://www.w3.org/2021/04/xmldsig-more#eddsa-ed25519

        http://www.w3.org/2021/04/xmldsig-more#eddsa-ed448
        http://www.w3.org/2021/04/xmldsig-more#eddsa-ed448ph

   An example of use is:

   <SignatureMethod Algorithm=
      "http://www.w3.org/2021/04/xmldsig-more#eddsa-ed448" />

2.4 Minimal Canonicalization

   Thus far, two independent interoperable implementations of Minimal
   Canonicalization have not been announced.  Therefore, when XML
   Digital Signature was advanced along the Standards Track from
   [RFC3075] to [RFC3275], Minimal Canonicalization was dropped.
   However, there was still interest.  For its definition, see Section
   6.5.1 of [RFC3075].

   For reference, its identifier remains:
        http://www.w3.org/2000/09/xmldsig#minimal

2.5 Transform Algorithms

   The XPointer Transform algorithm syntax is described below. All
   CanonicalizationMethod algorithms can also be used as Transform
   algorithms.

2.5.1 XPointer

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#xptr

   This transform algorithm takes an [XPointer] as an explicit
   parameter.  An example of use is:

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   <Transform
      Algorithm="http://www.w3.org/2001/04/xmldsig-more/xptr">
      <XPointer
         xmlns="http://www.w3.org/2001/04/xmldsig-more/xptr">
            xpointer(id("foo")) xmlns(bar=http://foobar.example)
            xpointer(//bar:Zab[@Id="foo"])
      </XPointer>
   </Transform>

   Schema Definition:

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

   DTD:

        <!ELEMENT XPointer (#PCDATA) >

   Input to this transform is an octet stream (which is then parsed into
   XML).

   Output from this transform is a node set; the results of the XPointer
   are processed as defined in the XMLDSIG specification [RFC3275] for a
   same-document XPointer.

2.6 EncryptionMethod Algorithms

   This subsection gives identifiers and information for several
   EncryptionMethod Algorithms.

2.6.1 ARCFOUR Encryption Algorithm

   Identifier:
        http://www.w3.org/2001/04/xmldsig-more#arcfour

   ARCFOUR is a fast, simple stream encryption algorithm that is
   compatible with RSA Security's RC4 algorithm [RC4] (Rivest Cipher 4);
   however, RC4 has been found to have a number of weaknesses and its
   use is prohibited in several IETF protols, for example TLS [RFC7465].
   An example EncryptionMethod element using ARCFOUR is:

   <EncryptionMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#arcfour">
      <KeySize>40</KeySize>
   </EncryptionMethod>

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   Arcfour makes use of the generic KeySize parameter specified and
   defined in [XMLENC11].

2.6.2 Camellia Block Encryption

   Identifiers:
        http://www.w3.org/2001/04/xmldsig-more#camellia128-cbc
        http://www.w3.org/2001/04/xmldsig-more#camellia192-cbc
        http://www.w3.org/2001/04/xmldsig-more#camellia256-cbc

   Camellia is a block cipher with the same interface as the AES
   [Camellia] [RFC3713]; it has a 128-bit block size and 128-, 192-, and
   256-bit key sizes. In XML Encryption Camellia is used in the same way
   as the AES: It is used in the Cipher Block Chaining (CBC) mode with a
   128-bit initialization vector (IV). The resulting cipher text is
   prefixed by the IV. If included in XML output, it is then base64
   encoded. An example Camellia EncryptionMethod is as follows:

   <EncryptionMethod
      Algorithm=
      "http://www.w3.org/2001/04/xmldsig-more#camellia128-cbc"
   />

2.6.3 Camellia Key Wrap

   Identifiers:
        http://www.w3.org/2001/04/xmldsig-more#kw-camellia128
        http://www.w3.org/2001/04/xmldsig-more#kw-camellia192
        http://www.w3.org/2001/04/xmldsig-more#kw-camellia256

   Camellia [Camellia] [RFC3713] key wrap is identical to the AES key
   wrap algorithm [RFC3394] specified in the XML Encryption standard
   with "AES" replaced by "Camellia". As with AES key wrap, the check
   value is 0xA6A6A6A6A6A6A6A6.

   The algorithm is the same whatever the size of the Camellia key used
   in wrapping, called the "key encrypting key" or "KEK". If Camellia is
   supported, it is particularly suggested that wrapping 128-bit keys
   with a 128-bit KEK and wrapping 256-bit keys with a 256-bit KEK be
   supported.

   An example of use is:

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   <EncryptionMethod
      Algorithm=
      "http://www.w3.org/2001/04/xmldsig-more#kw-camellia128"
   />

2.6.4 PSEC-KEM, RSAES-KEM, and ECIES-KEM

   Identifiers:
        http://www.w3.org/2001/04/xmldsig-more#psec-kem
        http://www.w3.org/2010/xmlsec-ghc#rsaes-kem
        http://www.w3.org/2010/xmlsec-ghc#ecies-kem

   These algorithms, specified in [18033-2], are key encapsulation
   mechanisms using elliptic curve or RSA encryption. RSAEA-KEM and
   ECIES-KEM are also specified in [GENERIC].

   An example of use of PSEC-KEM is:

   <EncryptionMethod
      Algorithm="http://www.w3.org/2001/04/xmldsig-more#psec-kem">
      <ECParameters>
         <Version>version</Version>
         <FieldID>id</FieldID>
         <Curve>curve</Curve>
         <Base>base</Base>
         <Order>order</Order>
         <Cofactor>cofactor</Cofactor>
      </ECParameters>
   </EncryptionMethod>

   See [18033-2] for information on the parameters above.

2.6.5 SEED Block Encryption

   Identifier:
        http://www.w3.org/2007/05/xmldsig-more#seed128-cbc

   SEED [RFC4269] is a block cipher with a 128-bit block size and
   128-bit key size. In XML Encryption, SEED can be used in the Cipher
   Block Chaining (CBC) mode with a 128-bit initialization vector (IV).
   The resulting cipher text is prefixed by the IV. If included in XML
   output, it is then base64 encoded.

   An example SEED EncryptionMethod is as follows:

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   <EncryptionMethod
      Algorithm="http://www.w3.org/2007/05/xmldsig-more#seed128-cbc" />

2.6.6 SEED Key Wrap

   Identifier:
        http://www.w3.org/2007/05/xmldsig-more#kw-seed128

   Key wrapping with SEED is identical to Section 2.2.1 of [RFC3394]
   with "AES" replaced by "SEED". The algorithm is specified in
   [RFC4010].  The implementation of SEED is optional. The default
   initial value is 0xA6A6A6A6A6A6A6A6.

   An example of use is:

   <EncryptionMethod
      Algorithm=
      "http://www.w3.org/2007/05/xmldsig-more#kw-seed128"
   />

2.6.7 ChaCha20

   Identifier:
        http://www.w3.org/2021/04/xmldsig-more#chacha20

   ChaCha20 [RFC8439], a stream cipher, is a variant of Salsa20
   [ChaCha]. It is considerably faster than AES in software-only
   implementations. In addition to a 256-bit key and the plain text to
   be encrypted, ChaCha20 takes a 96-bit Nonce and an initial 32-bit
   Counter. The Nonce and Counter are represented as hex in nested
   elements as shown below.

   An example of use is:

   <EncryptionMethod
      Algorithm=
      "http://www.w3.org/2021/04/xmldsig-more#chacha20">
      <Nonce>0123456789abcdef01234567</Nonce>
      <Counter>fedcba09</Counter>
   </EncryptionMethod>

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2.6.8 ChaCha20+Poly1305

   Identifier:
        http://www.w3.org/2021/04/xmldsig-more#chacha20poly1305

   ChaCha20+Poly1305 is an Authenticated Encryption with Additional Data
   (AEAD) algorithm. In addition to a 256-bit key and plain text to be
   encrypted and authenticated, ChaCha20+Poly1305 takes a 96-bit Nonce
   and variable length Additional Authenticated Data (AAD). The Nonce is
   represented as a child element of the EncryptionMethod element with a
   hex value. The AAD is a string which may be null. The AAD element may
   be absent in which case the AAD is null. The CipherData, either
   present in the CipherValue or by reference, is the concatenation of
   the encrypted ChaCha20 output and the Poly1305 128-bit tag.

   An example of use is:

   <EncryptionMethod
      Algorithm=
      "http://www.w3.org/2021/04/xmldsig-more#chacha20poly1305">
      <Nonce>0123456789abcdef01234567</Nonce>
      <AAD>The quick brown fox jumps over the lazy dog.</AAD>
   </EncryptionMethod>

2.7 Key AgreementMethod Algorithms

   This subsection gives identifiers and information
     - for an additional key AgreementMethod Algorithm [XMLENC11] and
     - for a key derivation function HKDF since such an algorithm fits
       most naturally as an "AgreementMethod".

2.7.1 X25519 Key Agreement

   Identifier:
        http://www.w3.org/2021/04/xmldsig-more#x25519
        http://www.w3.org/2021/04/smldsig-more#x448

   The X25519 and X448 key agreement algorithms are specified in
   [RFC7748].

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2.7.2 HKDF Key Derivation

   This section covers the HMAC-based Extract-and-Expand Key Derivation
   Function (HKDF [RFC5869]).

   Identifier:
        http://www.w3.org/2021/04/xmldsig-more#hkdf

   Although perhaps not exactly the sort of key agreement algorithm for
   which the AgreementMethod element was originally specified to go
   under the KeyInfo element, this is the most natural way to classify
   key derivation algorithms in XML security.

   HKDF takes as inputs a hash function, an optional non-secret "salt",
   initial keying material (IKM), optional context and application
   specific "info", and the required output keying size. Note that these
   strictly determine the output so, for example, invoking HKDF at
   different times but with the same salt, info, initial keying
   material, and output key size will produce identical output keying
   material.

   The inputs can be supplied to HKDF as follows:

     hash function: The algorithm attribute of a child DigestMethod
       element.

     salt: The content of a Salt child element of AgreementMethod in
       hex. If not provided, a string of zero octets as long as the hash
       function output is used as specified in [RFC5869].

     IKM: The content of an OriginatorKeyInfo child element of
       AgreementMethod in hex. May be absent in some applications where
       this is known through some other method.

     info: The content of the KA-Nonce child element of AgreementMethod
       in hex.

     size: The content of a KeySize child element of AgreementMethod as
       a decimal number.

   Here is the test case from Section A.1 in Appendix A to [RFC5869] as
   an example:

   <AgreementMethod
     algorithm="http://www.w3.org/2021/04/xmldsig-more#hkdf">
     <DigestMethod
       algorithm="http://www.w3.org/2001/04/xmldsig-more#hmac-sha256"/>
     <Salt>000102030405060708090a0b0c</Salt>
     <OriginatorKeyInfo>0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b
     </OriginatorKeyInfo>

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     <KA-Nonce>f0f1f2f3f4f5f6f7f8f9</KA-Nonce>
     <KeySize>42</KeySize>
   </AgreementMethod>

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3. KeyInfo

   In Section 3.1 below, a KeyInfo element child is specified, while in
   Section 3.2, additional KeyInfo Type values for use in
   RetrievalMethod are specified.

3.1 PKCS #7 Bag of Certificates and CRLs

   A PKCS #7 [RFC2315] "signedData" can also be used as a bag of
   certificates and/or certificate revocation lists (CRLs).  The
   PKCS7signedData element is defined to accommodate such structures
   within KeyInfo.  The binary PKCS #7 structure is base64 [RFC4648]
   encoded.  Any signer information present is ignored.  The following
   is an example [RFC3092], eliding the base64 data:

   <foo:PKCS7signedData
      xmlns:foo="http://www.w3.org/2001/04/xmldsig-more">
      ...
   </foo:PKCS7signedData>

3.2 Additional RetrievalMethod Type Values

   The Type attribute of RetrievalMethod is an optional identifier for
   the type of data to be retrieved. The result of dereferencing a
   RetrievalMethod reference for all KeyInfo types with an XML structure
   is an XML element or document with that element as the root. The
   various "raw" key information types return a binary value. Thus, they
   require a Type attribute because they are not unambiguously parsable.

   Identifiers:
        http://www.w3.org/2001/04/xmldsig-more#KeyName
        http://www.w3.org/2001/04/xmldsig-more#KeyValue
        http://www.w3.org/2001/04/xmldsig-more#PKCS7signedData
        http://www.w3.org/2001/04/xmldsig-more#rawPGPKeyPacket
        http://www.w3.org/2001/04/xmldsig-more#rawPKCS7signedData
        http://www.w3.org/2001/04/xmldsig-more#rawSPKISexp
        http://www.w3.org/2001/04/xmldsig-more#rawX509CRL
        http://www.w3.org/2001/04/xmldsig-more#RetrievalMethod

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4. Indexes

   The following subsections provide an index by URI and by fragment
   identifier (the portion of the URI after "#") of the algorithm and
   KeyInfo URIs defined in this document and in the standards plus the
   one KeyInfo child element name defined in this document. The
   "Sec/Doc" column has the section of this document or, if not
   specified in this document, the standards document where the item is
   specified. See also [XMLSECXREF].

4.1 Index by Fragment Index

   The initial "http://www.w3.org/" part of the URI is not included
   below. The first six entries have a null fragment identifier or no
   fragment identifier. "{Bad}" indicates a Bad value that was
   accidentally included in [RFC6931]. Implementations SHOULD only
   generate the correct URI but SHOULD understand both the correct and
   erroneous URI. See also Appendix B.

   Fragment            URI                                  Sec/Doc
   ---------           ----                                --------
                       2002/06/xmldsig-filter2               [XPATH]
                       2006/12/xmlc12n11#   {Bad}          [CANON11]
                       2006/12/xmlc14n11#                  [CANON11]
                       TR/1999/REC-xslt-19991116              [XSLT]
                       TR/1999/REC-xpath-19991116            [XPATH]
                       TR/2001/06/xml-exc-c14n#             [XCANON]
                       TR/2001/REC-xml-c14n-20010315       [CANON10]
                       TR/2001/REC-xmlschema-1-20010502     [Schema]

   aes128-cbc          2001/04/xmlenc#aes128-cbc          [XMLENC11]
   aes128-gcm          2009/xmlenc11#aes128-gcm           [XMLENC11]
   aes192-cbc          2001/04/xmlenc#aes192-cbc          [XMLENC11]
   aes192-gcm          2009/xmlenc11#aes192-gcm           [XMLENC11]
   aes256-cbc          2001/04/xmlenc#aes256-cbc          [XMLENC11]
   aes256-gcm          2009/xmlenc11#aes256-gcm           [XMLENC11]
   arcfour             2001/04/xmldsig-more#arcfour           2.6.1

   base64              2000/09/xmldsig#base64              [RFC3275]

   camellia128-cbc     2001/04/xmldsig-more#camellia128-cbc   2.6.2
   camellia192-cbc     2001/04/xmldsig-more#camellia192-cbc   2.6.2
   camellia256-cbc     2001/04/xmldsig-more#camellia256-cbc   2.6.2
   chacha20            2021/04/xmldsig-more#chacha20          2.6.7
   chacha20poly1305    2021/04/xmldsig-more#chacha20poly1305  2.6.8
   ConcatKDF           2009/xmlenc11#ConcatKDF            [XMLENC11]

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   decrypt#XML         2002/07/decrypt#XML                 [DECRYPT]
   decrypt#Binary      2002/07/decrypt#Binary              [DECRYPT]
   DEREncodedKeyValue  2009/xmldsig11#DEREncodedKeyValue [XMLDSIG11]
   dh                  2001/04/xmlenc#dh                  [XMLENC11]
   dh-es               2009/xmlenc11#dh-es                [XMLENC11]
   dsa-sha1            2000/09/xmldsig#dsa-sha1            [RFC3275]
   dsa-sha256          2009/xmldsig11#dsa-sha256         [XMLDSIG11]
   DSAKeyValue         2000/09/xmldsig#DSAKeyValue       [XMLDSIG11]

   ECDH-ES             2009/xmlenc11#ECDH-ES              [XMLENC11]
   ecdsa-ripemd160     2007/05/xmldsig-more#ecdsa-ripemd160   2.3.6
   ecdsa-sha1          2001/04/xmldsig-more#ecdsa-sha1        2.3.6
   ecdsa-sha224        2001/04/xmldsig-more#ecdsa-sha224      2.3.6
   ecdsa-sha256        2001/04/xmldsig-more#ecdsa-sha256      2.3.6
   ecdsa-sha384        2001/04/xmldsig-more#ecdsa-sha384      2.3.6
   ecdsa-sha512        2001/04/xmldsig-more#ecdsa-sha512      2.3.6
   ecdsa-sha3-224      2021/04/xmldsig-more#ecdsa-sha3-224    2.3.6
   ecdsa-sha3-256      2021/04/xmldsig-more#ecdsa-sha3-256    2.3.6
   ecdsa-sha3-384      2021/04/xmldsig-more#ecdsa-sha3-384    2.3.6
   ecdsa-sha3-512      2021/04/xmldsig-more#ecdsa-sha3-512    2.3.6
   ecdsa-whirlpool     2007/05/xmldsig-more#ecdsa-whirlpool   2.3.5
   ecies-kem           2010/xmlsec-ghc#ecies-kem           [GENERIC]
   ECKeyValue          2009/xmldsig11#ECKeyValue         [XMLDSIG11]
   eddsa-ed25519       2021/04/xmldsig-more#eddsa-ed25519    2.3.12
   eddsa-ed25519ctx    2021/04/xmldsig-more#eddsa-ed25519ctx 2.3.12
   eddsa-ed25519ph     2021/04/xmldsig-more#eddsa-ed25519ph  2.3.12
   eddsa-ed448         2021/04/xmldsig-more#eddsa-ed448      2.3.12
   eddsa-ed448ph       2021/04/xmldsig-more#eddsa-ed448ph    2.3.12
   enveloped-signature 2000/09/xmldsig#enveloped-signature [RFC3275]
   esign-sha1          2001/04/xmldsig-more#esign-sha1        2.3.7
   esign-sha224        2001/04/xmldsig-more#esign-sha224      2.3.7
   esign-sha256        2001/04/xmldsig-more#esign-sha256      2.3.7
   esign-sha384        2001/04/xmldsig-more#esign-sha384      2.3.7
   esign-sha512        2001/04/xmldsig-more#esign-sha512      2.3.7

   generic-hybrid      2010/xmlsec-ghc#generic-hybrid      [GENERIC]

   hkdf                2021/04/xmldsig-more#hkdf              2.7.2
   hmac-md5            2001/04/xmldsig-more#hmac-md5          2.2.1
   hmac-ripemd160      2001/04/xmldsig-more#hmac-ripemd160    2.2.3
   hmac-sha1           2000/09/xmldsig#hmac-sha1           [RFC3275]
   hmac-sha224         2001/04/xmldsig-more#hmac-sha224       2.2.2
   hmac-sha256         2001/04/xmldsig-more#hmac-sha256       2.2.2
   hmac-sha384         2001/04/xmldsig-more#hmac-sha384       2.2.2
   hmac-sha512         2001/04/xmldsig-more#hmac-sha512       2.2.2

   KeyName             2001/04/xmldsig-more#KeyName           3.2
   KeyValue            2001/04/xmldsig-more#KeyValue          3.2
   kw-aes128           2001/04/xmlenc#kw-aes128           [XMLENC11]
   kw-aes128-pad       2009/xmlenc11#kw-aes-128-pad       [XMLENC11]

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   kw-aes192           2001/04/xmlenc#kw-aes192           [XMLENC11]
   kw-aes192-pad       2009/xmlenc11#kw-aes-192-pad       [XMLENC11]
   kw-aes256           2001/04/xmlenc#kw-aes256           [XMLENC11]
   kw-aes256-pad       2009/xmlenc11#kw-aes-256-pad       [XMLENC11]
   kw-camellia128      2001/04/xmldsig-more#kw-camellia128    2.6.3
   kw-camellia192      2001/04/xmldsig-more#kw-camellia192    2.6.3
   kw-camellia256      2001/04/xmldsig-more#kw-camellia256    2.6.3
   kw-seed128          2007/05/xmldsig-more#kw-seed128        2.6.6

   md2-rsa-MGF1        2007/05/xmldsig-more#md2-rsa-MGF1      2.3.10
   md5                 2001/04/xmldsig-more#md5               2.1.1
   md5-rsa-MGF1        2007/05/xmldsig-more#md5-rsa-MGF1      2.3.10
   MGF1                2007/05/xmldsig-more#MGF1              2.3.9
   mgf1sha1            2009/xmlenc11#mgf1sha1             [XMLENC11]
   mgf1sha224          2009/xmlenc11#mgf1sha224           [XMLENC11]
   mgf1sha256          2009/xmlenc11#mgf1sha256           [XMLENC11]
   mgf1sha384          2009/xmlenc11#mgf1sha384           [XMLENC11]
   mgf1sha512          2009/xmlenc11#mgf1sha512           [XMLENC11]
   MgmtData            2000/09/xmldsig#MgmtData          [XMLDSIG11]
   minimal             2000/09/xmldsig#minimal                2.4

   pbkdf2              2009/xmlenc11#pbkdf2               [XMLENC11]
   PGPData             2000/09/xmldsig#PGPData           [XMLDSIG11]
   PKCS7signedData     2001/04/xmldsig-more#PKCS7signedData   3.1
   PKCS7signedData     2001/04/xmldsig-more#PKCS7signedData   3.2
   poly1305            2021/04/xmldsig-more#poly1305          2.2.4
   psec-kem            2001/04/xmldsig-more#psec-kem          2.6.4

   rawPGPKeyPacket     2001/04/xmldsig-more#rawPGPKeyPacket   3.2
   rawPKCS7signedData  2001/04/xmldsig-more#rawPKCS7signedData 3.2
   rawSPKISexp         2001/04/xmldsig-more#rawSPKISexp       3.2
   rawX509Certificate  2000/09/xmldsig#rawX509Certificate  [RFC3275]
   rawX509CRL          2001/04/xmldsig-more#rawX509CRL        3.2
   RetrievalMethod     2001/04/xmldsig-more#RetrievalMethod   3.2
   ripemd128-rsa-MGF1  2007/05/xmldsig-more#ripemd128-rsa-MGF1
                                                              2.3.10
   ripemd160           2001/04/xmlenc#ripemd160           [XMLENC11]
   ripemd160-rsa-MGF1  2007/05/xmldsig-more#ripemd160-rsa-MGF1
                                                              2.3.10
   rsa-1_5             2001/04/xmlenc#rsa-1_5             [XMLENC11]
   rsa-md5             2001/04/xmldsig-more#rsa-md5           2.3.1
   rsa-oaep            2009/xmlenc11#rsa-oaep             [XMLENC11]
   rsa-oaep-mgf1p      2001/04/xmlenc#rsa-oaep-mgf1p      [XMLENC11]
   rsa-pss             2007/05/xmldsig-more#rsa-pss           2.3.9
   rsa-ripemd160       2001/04/xmldsig-more#rsa-ripemd160     2.3.5
   rsa-sha1            2000/09/xmldsig#rsa-sha1            [RFC3275]
   rsa-sha224          2007/05/xmldsig-more#rsa-sha224 {Bad}  2.3.11
   rsa-sha224          2001/04/xmldsig-more#rsa-sha224        2.3.11
   rsa-sha256          2001/04/xmldsig-more#rsa-sha256        2.3.2
   rsa-sha384          2001/04/xmldsig-more#rsa-sha384        2.3.3

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   rsa-sha512          2001/04/xmldsig-more#rsa-sha512        2.3.4
   rsa-whirlpool       2007/05/xmldsig-more#rsa-whirlpool     2.3.5
   rsaes-kem           2010/xmlsec-ghc#rsaes-kem           [GENERIC]
   RSAKeyValue         2000/09/xmldsig#RSAKeyValue       [XMLDSIG11]

   seed128-cbc         2007/05/xmldsig-more#seed128-cbc       2.6.5
   sha1                2000/09/xmldsig#sha1                [RFC3275]
   sha1-rsa-MGF1       2007/05/xmldsig-more#sha1-rsa-MGF1     2.3.10
   sha224              2001/04/xmldsig-more#sha224            2.1.2
   sha224-rsa-MGF1     2007/05/xmldsig-more#sha224-rsa-MGF1   2.3.10
   sha256              2001/04/xmlenc#sha256              [XMLENC11]
   sha256-rsa-MGF1     2007/05/xmldsig-more#sha256-rsa-MGF1   2.3.10
   sha3-224            2007/05/xmldsig-more#sha3-224          2.1.5
   sha3-224-rsa-MGF1   2007/05/xmldsig-more#sha3-224-rsa-MGF1 2.3.10
   sha3-256            2007/05/xmldsig-more#sha3-256          2.1.5
   sha3-256-rsa-MGF1   2007/05/xmldsig-more#sha3-256-rsa-MGF1 2.3.10
   sha3-384            2007/05/xmldsig-more#sha3-384          2.1.5
   sha3-384-rsa-MGF1   2007/05/xmldsig-more#sha3-384-rsa-MGF1 2.3.10
   sha3-512            2007/05/xmldsig-more#sha3-512          2.1.5
   sha3-512-rsa-MGF1   2007/05/xmldsig-more#sha3-512-rsa-MGF1 2.3.10
   sha384              2001/04/xmldsig-more#sha384            2.1.3
   sha384-rsa-MGF1     2007/05/xmldsig-more#sha384-rsa-MGF1   2.3.10
   sha512              2001/04/xmlenc#sha512              [XMLENC11]
   sha512-rsa-MGF1     2007/05/xmldsig-more#sha512-rsa-MGF1   2.3.10
   siphash-2-4         2021/04/xmldsig-more#siphash-2-4       2.2.5
   SPKIData            2000/09/xmldsig#SPKIData          [XMLDSIG11]

   tripledes-cbc       2001/04/xmlenc#tripledes-cbc       [XMLENC11]

   whirlpool           2007/05/xmldsig-more#whirlpool         2.1.4
   whirlpool-rsa-MGF1  2007/05/xmldsig-more#whirlpool-rsa-MGF1
                                                              2.3.10
   WithComments        2006/12/xmlc14n11#WithComments      [CANON11]
   WithComments        TR/2001/06/xml-exc-c14n#WithComments
                                                            [XCANON]
   WithComments        TR/2001/REC-xml-c14n-20010315#WithComments
                                                           [CANON10]

   x25519              2021/04/xmldsig-more#x25519            2.7.1
   x448                2021/04/xmldsig-more#x448              2.7.1
   X509Data            2000/09/xmldsig#X509Data          [XMLDSIG11]

   xmss-sha2-10-192    2021/04/xmldsig-more#xmss-sha2-10-192  2.2.6
   xmss-sha2-10-256    2021/04/xmldsig-more#xmss-sha2-10-256  2.2.6
   xmss-sha2-10-512    2021/04/xmldsig-more#xmss-sha2-10-512  2.2.6
   xmss-sha2-16-192    2021/04/xmldsig-more#xmss-sha2-16-192  2.2.6
   xmss-sha2-16-256    2021/04/xmldsig-more#xmss-sha2-16-256  2.2.6
   xmss-sha2-16-512    2021/04/xmldsig-more#xmss-sha2-16-512  2.2.6
   xmss-sha2-20-192    2021/04/xmldsig-more#xmss-sha2-20-192  2.2.6
   xmss-sha2-20-256    2021/04/xmldsig-more#xmss-sha2-20-256  2.2.6

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   xmss-sha2-20-512    2021/04/xmldsig-more#xmss-sha2-20-512  2.2.6
   xmss-shake-10-256   2021/04/xmldsig-more#xmss-shake-10-256 2.2.6
   xmss-shake-10-512   2021/04/xmldsig-more#xmss-shake-10-512 2.2.6
   xmss-shake-16-256   2021/04/xmldsig-more#xmss-shake-16-256 2.2.6
   xmss-shake-16-512   2021/04/xmldsig-more#xmss-shake-16-512 2.2.6
   xmss-shake-20-256   2021/04/xmldsig-more#xmss-shake-20-256 2.2.6
   xmss-shake-20-512   2021/04/xmldsig-more#xmss-shake-20-512 2.2.6
   xmss-shake256-10-192 2021/04/xmldsig-more#xmss-shake256-10-192
                                                              2.2.6
   xmss-shake256-10-256 2021/04/xmldsig-more#xmss-shake256-10-256
                                                              2.2.6
   xmss-shake256-16-192 2021/04/xmldsig-more#xmss-shake256-16-192
                                                              2.2.6
   xmss-shake256-16-256 2021/04/xmldsig-more#xmss-shake256-16-256
                                                              2.2.6
   xmss-shake256-20-192 2021/04/xmldsig-more#xmss-shake256-20-192
                                                              2.2.6
   xmss-shake256-20-256 2021/04/xmldsig-more#xmss-shake256-20-256
                                                              2.2.6

   xmssmt-sha2-20-2-192 2021/04/xmldsig-more#xmssmt-sha2-20-2-192
                                                              2.2.6
   xmssmt-sha2-20-2-256 2021/04/xmldsig-more#xmssmt-sha2-20-2-256
                                                              2.2.6
   xmssmt-sha2-20-4-192 2021/04/xmldsig-more#xmssmt-sha2-20-4-192
                                                              2.2.6
   xmssmt-sha2-20-4-256 2021/04/xmldsig-more#xmssmt-sha2-20-4-256
                                                              2.2.6
   xmssmt-sha2-20-2-192 2021/04/xmldsig-more#xmssmt-sha2-20-2-192
                                                              2.2.6
   xmssmt-sha2-20-2-256 2021/04/xmldsig-more#xmssmt-sha2-20-2-256
                                                              2.2.6
   xmssmt-sha2-40-2-192 2021/04/xmldsig-more#xmssmt-sha2-40-2-192
                                                              2.2.6
   xmssmt-sha2-40-2-256 2021/04/xmldsig-more#xmssmt-sha2-40-2-256
                                                              2.2.6
   xmssmt-sha2-40-4-192 2021/04/xmldsig-more#xmssmt-sha2-40-4-192
                                                              2.2.6
   xmssmt-sha2-40-4-256 2021/04/xmldsig-more#xmssmt-sha2-40-4-256
                                                              2.2.6
   xmssmt-sha2-40-8-192 2021/04/xmldsig-more#xmssmt-sha2-40-8-192
                                                              2.2.6
   xmssmt-sha2-40-8-256 2021/04/xmldsig-more#xmssmt-sha2-40-8-256
                                                              2.2.6
   xmssmt-sha2-60-3-192 2021/04/xmldsig-more#xmssmt-sha2-60-3-192
                                                              2.2.6
   xmssmt-sha2-60-3-256 2021/04/xmldsig-more#xmssmt-sha2-60-3-256
                                                              2.2.6

D. Eastlake 3rd            Expires August 2022                 [Page 34]
INTERNET-DRAFT        Additional XML Security URIs         February 2022

   xmssmt-sha2-60-6-192 2021/04/xmldsig-more#xmssmt-sha2-60-6-192
                                                              2.2.6
   xmssmt-sha2-60-6-256 2021/04/xmldsig-more#xmssmt-sha2-60-6-256
                                                              2.2.6
   xmssmt-sha2-60-12-192 2021/04/xmldsig-more#xmssmt-sha2-20-12-192
                                                              2.2.6
   xmssmt-sha2-60-12-256 2021/04/xmldsig-more#xmssmt-sha2-20-12-256
                                                              2.2.6

   xmssmt-shake-20-2-256 2021/04/xmldsig-more#xmssmt-shake-20-2-256
                                                              2.2.6
   xmssmt-shake-20-2-512 2021/04/xmldsig-more#xmssmt-shake-20-2-512
                                                              2.2.6
   xmssmt-shake-20-4-256 2021/04/xmldsig-more#xmssmt-shake-20-4-256
                                                              2.2.6
   xmssmt-shake-20-4-512 2021/04/xmldsig-more#xmssmt-shake-20-4-512
                                                              2.2.6
   xmssmt-shake-20-2-256 2021/04/xmldsig-more#xmssmt-shake-20-2-256
                                                              2.2.6
   xmssmt-shake-20-2-512 2021/04/xmldsig-more#xmssmt-shake-20-2-512
                                                              2.2.6
   xmssmt-shake-40-2-256 2021/04/xmldsig-more#xmssmt-shake-40-2-256
                                                              2.2.6
   xmssmt-shake-40-2-512 2021/04/xmldsig-more#xmssmt-shake-40-2-512
                                                              2.2.6
   xmssmt-shake-40-4-256 2021/04/xmldsig-more#xmssmt-shake-40-4-256
                                                              2.2.6
   xmssmt-shake-40-4-512 2021/04/xmldsig-more#xmssmt-shake-40-4-512
                                                              2.2.6
   xmssmt-shake-40-8-256 2021/04/xmldsig-more#xmssmt-shake-40-8-256
                                                              2.2.6
   xmssmt-shake-40-8-512 2021/04/xmldsig-more#xmssmt-shake-40-8-512
                                                              2.2.6
   xmssmt-shake-60-3-256 2021/04/xmldsig-more#xmssmt-shake-60-3-256
                                                              2.2.6
   xmssmt-shake-60-3-512 2021/04/xmldsig-more#xmssmt-shake-60-3-512
                                                              2.2.6
   xmssmt-shake-60-6-256 2021/04/xmldsig-more#xmssmt-shake-60-6-256
                                                              2.2.6
   xmssmt-shake-60-6-512 2021/04/xmldsig-more#xmssmt-shake-60-6-512
                                                              2.2.6
   xmssmt-shake-60-12-256 2021/04/xmldsig-more#xmssmt-shake-20-12-256
                                                              2.2.6
   xmssmt-shake-60-12-512 2021/04/xmldsig-more#xmssmt-shake-20-12-512
                                                              2.2.6

   xmssmt-shake256-20-2-192
                2021/04/xmldsig-more#xmssmt-shake256-20-2-192 2.2.6
   xmssmt-shake256-20-2-256
                2021/04/xmldsig-more#xmssmt-shake256-20-2-256 2.2.6

D. Eastlake 3rd            Expires August 2022                 [Page 35]
INTERNET-DRAFT        Additional XML Security URIs         February 2022

   xmssmt-shake256-20-4-192
                2021/04/xmldsig-more#xmssmt-shake256-20-4-192 2.2.6
   xmssmt-shake256-20-4-256
                2021/04/xmldsig-more#xmssmt-shake256-20-4-256 2.2.6
   xmssmt-shake256-40-2-192
                2021/04/xmldsig-more#xmssmt-shake256-40-2-192 2.2.6
   xmssmt-shake256-40-2-256
                2021/04/xmldsig-more#xmssmt-shake256-40-2-256 2.2.6
   xmssmt-shake256-40-4-192
                2021/04/xmldsig-more#xmssmt-shake256-40-4-192 2.2.6
   xmssmt-shake256-40-4-256
                2021/04/xmldsig-more#xmssmt-shake256-40-4-256 2.2.6
   xmssmt-shake256-40-8-192
                2021/04/xmldsig-more#xmssmt-shake256-40-8-192 2.2.6
   xmssmt-shake256-40-8-256
                2021/04/xmldsig-more#xmssmt-shake256-40-8-256 2.2.6
   xmssmt-shake256-60-3-192
                2021/04/xmldsig-more#xmssmt-shake256-60-3-192 2.2.6
   xmssmt-shake256-60-3-256
                2021/04/xmldsig-more#xmssmt-shake256-60-3-256 2.2.6
   xmssmt-shake256-60-6-192
                2021/04/xmldsig-more#xmssmt-shake256-60-6-192 2.2.6
   xmssmt-shake256-60-6-256
                2021/04/xmldsig-more#xmssmt-shake256-60-6-256 2.2.6
   xmssmt-shake256-60-12-192
               2021/04/xmldsig-more#xmssmt-shake256-60-12-192 2.2.6
   xmssmt-shake256-60-12-256
               2021/04/xmldsig-more#xmssmt-shake256-60-12-256 2.2.6

   xptr                2001/04/xmldsig-more#xptr              2.5.1
   ---------           ----                                --------
    Fragment            URI                                  Sec/Doc

   The initial "http://www.w3.org/" part of the URI is not included
   above.

4.2 Index by URI

   The initial "http://www.w3.org/" part of the URI is not included
   below. "{Bad}" indicates a Bad value that was accidentally included
   in [RFC6931]. Implementations SHOULD only generate the correct URI
   but SHOULD understand both the correct and erroneous URI. See also
   Appendix B.

D. Eastlake 3rd            Expires August 2022                 [Page 36]
INTERNET-DRAFT        Additional XML Security URIs         February 2022

   URI                                 Sec/Doc       Type
   ----                                --------     ------
   2000/09/xmldsig#base64              [RFC3275]    Transform
   2000/09/xmldsig#DSAKeyValue         [RFC3275]    Retrieval type
   2000/09/xmldsig#dsa-sha1            [RFC3275]    SignatureMethod
   2000/09/xmldsig#enveloped-signature [RFC3275]    Transform
   2000/09/xmldsig#hmac-sha1           [RFC3275]    SignatureMethod
   2000/09/xmldsig#MgmtData            [RFC3275]    Retrieval type
   2000/09/xmldsig#minimal                2.4       Canonicalization
   2000/09/xmldsig#PGPData             [RFC3275]    Retrieval type
   2000/09/xmldsig#rawX509Certificate  [RFC3275]    Retrieval type
   2000/09/xmldsig#rsa-sha1            [RFC3275]    SignatureMethod
   2000/09/xmldsig#RSAKeyValue         [RFC3275]    Retrieval type
   2000/09/xmldsig#sha1                [RFC3275]    DigestAlgorithm
   2000/09/xmldsig#SPKIData            [RFC3275]    Retrieval type
   2000/09/xmldsig#X509Data            [RFC3275]    Retrieval type

   2001/04/xmldsig-more#arcfour           2.6.1     EncryptionMethod
   2001/04/xmldsig-more#camellia128-cbc   2.6.2     EncryptionMethod
   2001/04/xmldsig-more#camellia192-cbc   2.6.2     EncryptionMethod
   2001/04/xmldsig-more#camellia256-cbc   2.6.2     EncryptionMethod
   2001/04/xmldsig-more#ecdsa-sha1        2.3.6     SignatureMethod
   2001/04/xmldsig-more#ecdsa-sha224      2.3.6     SignatureMethod
   2001/04/xmldsig-more#ecdsa-sha256      2.3.6     SignatureMethod
   2001/04/xmldsig-more#ecdsa-sha384      2.3.6     SignatureMethod
   2001/04/xmldsig-more#ecdsa-sha512      2.3.6     SignatureMethod
   2001/04/xmldsig-more#esign-sha1        2.3.7     SignatureMethod
   2001/04/xmldsig-more#esign-sha224      2.3.7     SignatureMethod
   2001/04/xmldsig-more#esign-sha256      2.3.7     SignatureMethod
   2001/04/xmldsig-more#esign-sha384      2.3.7     SignatureMethod
   2001/04/xmldsig-more#esign-sha512      2.3.7     SignatureMethod
   2001/04/xmldsig-more#hmac-md5          2.2.1     SignatureMethod
   2001/04/xmldsig-more#hmac-ripemd160    2.2.3     SignatureMethod
   2001/04/xmldsig-more#hmac-sha224       2.2.2     SignatureMethod
   2001/04/xmldsig-more#hmac-sha256       2.2.2     SignatureMethod
   2001/04/xmldsig-more#hmac-sha384       2.2.2     SignatureMethod
   2001/04/xmldsig-more#hmac-sha512       2.2.2     SignatureMethod
   2001/04/xmldsig-more#KeyName           3.2       Retrieval type
   2001/04/xmldsig-more#KeyValue          3.2       Retrieval type
   2001/04/xmldsig-more#kw-camellia128    2.6.3     EncryptionMethod
   2001/04/xmldsig-more#kw-camellia192    2.6.3     EncryptionMethod
   2001/04/xmldsig-more#kw-camellia256    2.6.3     EncryptionMethod
   2001/04/xmldsig-more#md5               2.1.1     DigestAlgorithm
   2001/04/xmldsig-more#PKCS7signedData   3.2       Retrieval type
   2001/04/xmldsig-more#psec-kem          2.6.4     EncryptionMethod
   2001/04/xmldsig-more#rawPGPKeyPacket   3.2       Retrieval type
   2001/04/xmldsig-more#rawPKCS7signedData 3.2      Retrieval type
   2001/04/xmldsig-more#rawSPKISexp       3.2       Retrieval type
   2001/04/xmldsig-more#rawX509CRL        3.2       Retrieval type
   2001/04/xmldsig-more#RetrievalMethod   3.2       Retrieval type

D. Eastlake 3rd            Expires August 2022                 [Page 37]
INTERNET-DRAFT        Additional XML Security URIs         February 2022

   2001/04/xmldsig-more#rsa-md5           2.3.1     SignatureMethod
   2001/04/xmldsig-more#rsa-sha224        2.3.11    SignatureMethod
   2001/04/xmldsig-more#rsa-sha256        2.3.2     SignatureMethod
   2001/04/xmldsig-more#rsa-sha384        2.3.3     SignatureMethod
   2001/04/xmldsig-more#rsa-sha512        2.3.4     SignatureMethod
   2001/04/xmldsig-more#rsa-ripemd160     2.3.5     SignatureMethod
   2001/04/xmldsig-more#sha224            2.1.2     DigestAlgorithm
   2001/04/xmldsig-more#sha384            2.1.3     DigestAlgorithm
   2001/04/xmldsig-more#xptr              2.5.1     Transform
   2001/04/xmldsig-more#PKCS7signedData   3.1       KeyInfo child

   2001/04/xmlenc#aes128-cbc          [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#aes192-cbc          [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#aes256-cbc          [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#dh                  [XMLENC11]    AgreementMethod
   2001/04/xmlenc#kw-aes128           [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#kw-aes192           [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#kw-aes256           [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#ripemd160           [XMLENC11]    DigestAlgorithm
   2001/04/xmlenc#rsa-1_5             [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#rsa-oaep-mgf1p      [XMLENC11]    EncryptionMethod
   2001/04/xmlenc#sha256              [XMLENC11]    DigestAlgorithm
   2001/04/xmlenc#sha512              [XMLENC11]    DigestAlgorithm
   2001/04/xmlenc#tripledes-cbc       [XMLENC11]    EncryptionMethod

   2002/06/xmldsig-filter2               [XPATH]    Transform

   2002/07/decrypt#XML                 [DECRYPT]    Transform
   2002/07/decrypt#Binary              [DECRYPT]    Transform

   2006/12/xmlc12n11#   {Bad}          [CANON11]    Canonicalization
   2006/12/xmlc14n11#                  [CANON11]    Canonicalization
   2006/12/xmlc14n11#WithComments      [CANON11]    Canonicalization

   2007/05/xmldsig-more#ecdsa-ripemd160   2.3.6     SignatureMethod
   2007/05/xmldsig-more#ecdsa-whirlpool   2.3.5     SignatureMethod
   2007/05/xmldsig-more#kw-seed128        2.6.6     EncryptionMethod
   2007/05/xmldsig-more#md2-rsa-MGF1      2.3.10    SignatureMethod
   2007/05/xmldsig-more#md5-rsa-MGF1      2.3.10    SignatureMethod
   2007/05/xmldsig-more#MGF1              2.3.9     SignatureMethod
   2007/05/xmldsig-more#ripemd128-rsa-MGF1 2.3.10   SignatureMethod
   2007/05/xmldsig-more#ripemd160-rsa-MGF1 2.3.10   SignatureMethod
   2007/05/xmldsig-more#rsa-pss           2.3.9     SignatureMethod
   2007/05/xmldsig-more#rsa-sha224 {Bad}  2.3.11    SignatureMethod
   2007/05/xmldsig-more#rsa-whirlpool     2.3.5     SignatureMethod
   2007/05/xmldsig-more#seed128-cbc       2.6.5     EncryptionMethod
   2007/05/xmldsig-more#sha1-rsa-MGF1     2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha224-rsa-MGF1   2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha256-rsa-MGF1   2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha3-224          2.1.5     DigestAlgorithm

D. Eastlake 3rd            Expires August 2022                 [Page 38]
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   2007/05/xmldsig-more#sha3-224-rsa-MGF1 2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha3-256          2.1.5     DigestAlgorithm
   2007/05/xmldsig-more#sha3-256-rsa-MGF1 2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha3-384          2.1.5     DigestAlgorithm
   2007/05/xmldsig-more#sha3-384-rsa-MGF1 2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha3-512          2.1.5     DigestAlgorithm
   2007/05/xmldsig-more#sha3-512-rsa-MGF1 2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha384-rsa-MGF1   2.3.10    SignatureMethod
   2007/05/xmldsig-more#sha512-rsa-MGF1   2.3.10    SignatureMethod
   2007/05/xmldsig-more#whirlpool         2.1.4     DigestAlgorithm
   2007/05/xmldsig-more#whirlpool-rsa-MGF1 2.3.10   SignatureMethod
   2009/xmlenc11#kw-aes-128-pad       [XMLENC11]    EncryptionMethod
   2009/xmlenc11#kw-aes-192-pad       [XMLENC11]    EncryptionMethod
   2009/xmlenc11#kw-aes-256-pad       [XMLENC11]    EncryptionMethod

   2009/xmldsig11#dsa-sha256         [XMLDSIG11]    SignatureMethod
   2009/xmldsig11#ECKeyValue         [XMLDSIG11]    Retrieval type
   2009/xmldsig11#DEREncodedKeyValue [XMLDSIG11]    Retrieval type

   2009/xmlenc11#aes128-gcm           [XMLENC11]    EncryptionMethod
   2009/xmlenc11#aes192-gcm           [XMLENC11]    EncryptionMethod
   2009/xmlenc11#aes256-gcm           [XMLENC11]    EncryptionMethod
   2009/xmlenc11#ConcatKDF            [XMLENC11]    EncryptionMethod
   2009/xmlenc11#mgf1sha1             [XMLENC11]    SignatureMethod
   2009/xmlenc11#mgf1sha224           [XMLENC11]    SignatureMethod
   2009/xmlenc11#mgf1sha256           [XMLENC11]    SignatureMethod
   2009/xmlenc11#mgf1sha384           [XMLENC11]    SignatureMethod
   2009/xmlenc11#mgf1sha512           [XMLENC11]    SignatureMethod
   2009/xmlenc11#pbkdf2               [XMLENC11]    EncryptionMethod
   2009/xmlenc11#rsa-oaep             [XMLENC11]    EncryptionMethod
   2009/xmlenc11#ECDH-ES              [XMLENC11]    EncryptionMethod
   2009/xmlenc11#dh-es                [XMLENC11]    EncryptionMethod

   2010/xmlsec-ghc#generic-hybrid      [GENERIC]    Generic Hybrid
   2010/xmlsec-ghc#rsaes-kem           [GENERIC]    Generic Hybrid
   2010/xmlsec-ghc#ecies-kem           [GENERIC]    Generic Hybrid

   2021/04/xmldsig-more#chacha20           2.6.7    EncryptionMethod
   2021/04/xmldsig-more#chacha20poly1305   2.6.8    EncryptionMethod
   2021/04/xmldsig-more#ecdsa-sha3-224     2.3.6    SignatureMethod
   2021/04/xmldsig-more#ecdsa-sha3-256     2.3.6    SignatureMethod
   2021/04/xmldsig-more#ecdsa-sha3-384     2.3.6    SignatureMethod
   2021/04/xmldsig-more#ecdsa-sha3-512     2.3.6    SignatureMethod
   2021/04/xmldsig-more#eddsa-ed25519ph   2.3.12    SignatureMethod
   2021/04/xmldsig-more#eddsa-ed25519ctx  2.3.12    SignatureMethod
   2021/04/xmldsig-more#eddsa-ed25519     2.3.12    SignatureMethod
   2021/04/xmldsig-more#eddsa-ed448       2.3.12    SignatureMethod
   2021/04/xmldsig-more#eddsa-ed448ph     2.3.12    SignatureMethod
   2021/04/xmldsig-more#hkdf               2.7.2    AgreementMethod
   2021/04/xmldsig-more#po1y305            2.2.4    SignatureMethod

D. Eastlake 3rd            Expires August 2022                 [Page 39]
INTERNET-DRAFT        Additional XML Security URIs         February 2022

   2021/04/xmldsig-more#siphash-2-4        2.2.5    SignatureMethod
   2021/04/xmldsig-more#x25519             2.7.1    AgreementMethod
   2021/04/xmldsig-more#x448               2.7.1    AgreementMethod

   2021/04/xmldsig-more#xmss-sha2-10-192   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-10-256   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-10-512   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-16-192   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-16-256   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-16-512   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-20-192   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-20-256   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-sha2-20-512   2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-shake-10-256  2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-shake-10-512  2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-shake-16-256  2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-shake-16-512  2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-shake-20-256  2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-shake-20-512  2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmss-shake256-10-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmss-shake256-10-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmss-shake256-16-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmss-shake256-16-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmss-shake256-20-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmss-shake256-20-256 2.2.6  SignatureMethod

   2021/04/xmldsig-more#xmssmt-sha2-20-2-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-20-2-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-20-4-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-20-4-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-40-2-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-40-2-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-40-4-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-40-4-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-40-8-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-40-8-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-60-3-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-60-3-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-60-6-192 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-60-6-256 2.2.6  SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-60-12-192 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-sha2-60-12-256 2.2.6 SignatureMethod

   2021/04/xmldsig-more#xmssmt-shake-20-2-256 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-20-2-512 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-20-4-256 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-20-4-512 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-40-2-256 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-40-2-512 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-40-4-256 2.2.6 SignatureMethod

D. Eastlake 3rd            Expires August 2022                 [Page 40]
INTERNET-DRAFT        Additional XML Security URIs         February 2022

   2021/04/xmldsig-more#xmssmt-shake-40-4-512 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-40-8-256 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-40-8-512 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-60-3-256 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-60-3-512 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-60-6-256 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-60-6-512 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-60-12-256 2.2.6 SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake-60-12-512 2.2.6 SignatureMethod

   2021/04/xmldsig-more#xmssmt-shake256-20-2-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-20-2-256
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-20-4-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-20-4-256
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-40-2-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-40-2-256
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-40-4-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-40-4-256
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-40-8-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-40-8-256
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-60-3-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-60-3-256
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-60-6-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-60-6-256
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-60-12-192
                                           2.2.6    SignatureMethod
   2021/04/xmldsig-more#xmssmt-shake256-60-12-256
                                           2.2.6    SignatureMethod

   TR/1999/REC-xpath-19991116            [XPATH]    Transform
   TR/1999/REC-xslt-19991116              [XSLT]    Transform
   TR/2001/06/xml-exc-c14n#             [XCANON]    Canonicalization
   TR/2001/06/xml-exc-c14n#WithComments [XCANON]    Canonicalization
   TR/2001/REC-xml-c14n-20010315       [CANON10]    Canonicalization

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   TR/2001/REC-xml-c14n-20010315#WithComments
                                       [CANON10]    Canonicalization
   TR/2001/REC-xmlschema-1-20010502     [Schema]    Transform
   ----                                --------     ------
    URI                                 Sec/Doc      Type

   The initial "http://www.w3.org/" part of the URI is not included
   above. "{Bad}" indicates a Bad value that was accidentally included
   in [RFC6931]. Implementations SHOULD only generate the correct URI
   but SHOULD understand both the correct and erroneous URI. See also
   Appendix B.

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5. Allocation Considerations

   W3C and IANA allocation considerations are given below.

5.1 W3C Allocation Considerations

   As it is easy for people to construct their own unique URIs [RFC3986]
   and, if appropriate, to obtain a URI from the W3C, additional URI
   specification under the following XMLSEC URI prefixes is prohibited
   as shown:

       URI                                      Status
      ---------------------------------------  ----------------------
      http://www.w3.org/2000/09/xmldsig#       Frozen by W3C.
      http://www.w3.org/2001/04/smldsig-more#  Frozen with RFC 4051.
      http://www.w3.org/2007/05/xmldsig-more#  Frozen with [RFC6931].

   The W3C has assigned "http://www.w3.org/2021/04/xmldsig-more#" for
   additional new URIs specified in this document.

   There are also occurrences in this document of
   "http://www.w3.org/2010/xmlsec-ghc#" due to the inclusion of some
   algorithms from [GENERIC] for convenience.

   An "xmldsig-more" URI does not imply any official W3C or IETF status
   for these algorithms or identifiers nor does it imply that they are
   only useful in digital signatures.  Currently, dereferencing such
   URIs may or may not produce a temporary placeholder document.
   Permission to use these URI prefixes has been given by the W3C.

5.2 IANA Considerations

   IANA has established a registry entitled "XML Security URIs".  The
   contents will be updated to correspond to Section 4.2 of this
   document with each section number in the "Sec/Doc" column augmented
   with a reference to this RFC (for example, "2.6.4" means "[this
   document], Section 2.6.4"). All references to [RFC6931] in that
   registry should be updated to [this document].

   New entries, including new Types, will be added based on
   Specification Required [RFC8126].  Criteria for the designated expert
   for inclusion are (1) documentation sufficient for interoperability
   of the algorithm or data type and the XML syntax for its
   representation and use and (2) sufficient importance as normally
   indicated by inclusion in (2a) an approved W3C Note, Proposed
   Recommendation, or Recommendation or (2b) an approved IETF RFC.

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   Typically, the registry will reference a W3C or IETF document
   specifying such XML syntax; that document will either contain a more
   detailed description of the algorithm or data type or reference
   another document with a more detailed description.

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6. Security Considerations

   This RFC is concerned with documenting the URIs that designate
   algorithms and some data types used in connection with XML security.
   The security considerations vary widely with the particular
   algorithms, and the general security considerations for XML security
   are outside of the scope of this document but appear in [XMLDSIG11],
   [XMLENC11], [CANON10], [CANON11], and [GENERIC].

   [RFC6151] should be consulted before considering the use of MD5 as a
   DigestMethod or the use of HMAC-MD5 or RSA-MD5 as a SignatureMethod.

   See [RFC6194] for SHA-1 security considerations.

   Additional security considerations are given in connection with the
   description of some algorithms in the body of this document.

   Implementers should be aware that cryptographic algorithms become
   weaker with time.  As new cryptoanalysis techniques are developed and
   computing performance improves, the work factor to break a particular
   cryptographic algorithm will decrease.  Therefore, cryptographic
   implementations should be modular, allowing new algorithms to be
   readily inserted.  That is, implementers should be prepared for the
   set of mandatory-to-implement algorithms for any particular use to
   change over time. This is sometimes referred to as "algorithm
   agility" [RFC7696].

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Acknowledgements

   The contributions of the following, listed in alphabetic order, by
   reporting errata against [RFC6931] or contributing to this document,
   are gratefully acknowledged:

      Roman Danyliw, Pim van der Eijk, Frederick Hirsch, Benjamin Kaduk,
      Alexey Melnikov, Gayle Noble, Axel Puhlmann, Peter Yee, and Annie
      Yousar.

   The contributions of the following, listed in alphabetic order, to
   [RFC6931], on which this document is based, are gratefully
   acknowledged:

      Benoit Claise, Adrian Farrel, Stephen Farrell, Ernst Giessmann,
      Frederick Hirsch, Bjoern Hoehrmann, Russ Housley, Satoru Kanno,
      Charlie Kaufman, Konrad Lanz, HwanJin Lee, Barry Leiba, Peter
      Lipp, Subramanian Moonesamy, Thomas Roessler, Hanseong Ryu, Peter
      Saint-Andre, and Sean Turner.

   The following contributors to RFC 4051 are gratefully acknowledged:

      Glenn Adams, Merlin Hughs, Gregor Karlinger, Brian LaMachia, Shiho
      Moriai, Joseph Reagle, Russ Housley, and Joel Halpern.

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Appendix A: Changes from [RFC6931]

   The following changes have been made in [RFC6931] to produce this
   document.

    1. Delete Appendix on Changes from RFC 4051, since they were already
       included in [RFC6931], and remove reference to RFC 4051 and to
       the one Errata against RFC 4051.

    2. Fix three errata as follows: [Err3597], [Err3965], and [Err4004].
       In cases where [RFC6931] had an erroneous URI, it is still
       included in the indices and it is stated that implementations
       SHOULD only generate the correct URI but SHOULD understand both
       the correct and erroneous URI.

    3. Added the following algorithms:

          Section   Algorithm(s)
          -------   ------------
           2.2.4    Poly1305
           2.2.5    SipHash-2-4
           2.2.6    XMSS and XMSSMT
           2.3.6    ECDSA with SHA3
           2.3.12   Edwards-Curve Signatures
           2.6.7    ChaCha20
           2.6.8    ChaCha20+Poly1305
           2.7.1    X25519
           2.7.2    HKDF

    4. Listed ECIES-KEM and RSAES-KEM in Section 2.6.4 so they are
       easier to find even though the URI for them is specified in
       [GENERIC].

    5. Updated references for [GENERIC] and FIPS 186, added appropriate
       references.

    6. Addition of some XML examples.

    7. Minor typo fixes and editorial changes.

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Appendix B: Bad URIs

   [RFC6931] included two bad URIs as shown below. "{Bad}" in the
   indexes (Sections 4.1 and 4.2) indicates such a bad value.
   Implementations SHOULD only generate the correct URI but SHOULD
   understand both the correct and erroneous URI.

   2006/12/xmlc12n11#
       Appears in the indices (Section 4.1 and 4.2] of [RFC6931] when it
       should be "2006/12/xmlc14n11#" (i.e., the "12" inside "xmlc12n11"
       should have been "14"). This is [Err3965] and is corrected in
       this document.

   2007/05/xmldsig-more#rsa-sha224
       Appears in the indices (Section 4.1 and 4.2] of [RFC6931] when it
       should be "2001/04/xmldsig-more#rsa-sha224". This is [Err4004]
       and is corrected in this document.

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Appendix Z: Change History

   RFC Editor Note: Please delete this Appendix before publication.

-00 to -01 to -02 to -03 to -04 to -05 to -06 to -07 to -08

   Bump up version and date to keep draft alive as a place where new
   URIs can be accumulated. At some point in here, author address was
   updated.

-08 to -09 to -10

   Update author affiliation and references.

-10 to -11

   Update author address.

-11 to -12

   Bump up version and date to keep draft alive.

-12 to -13

   Numerous editorial/typo fixes thanks to Gayle Noble who is added to
   the acknowledgements section.

-13 to -14

   Numerous additional algorithms almost all as requested by Pim van der
   Eijk who is added to the acknowledgements section. Update and add
   references.

-14 to -15

   Add URLs for ECDSA with SHA3, SipHash-2-4, X25519, XMSS and XMSSMT.
   Add RFC reference 5869 for HKDF but not yet added elsewhere in the
   document.

-15 to -16

   Fix text for ChaCha20 to include the required Nonce and Counter
   inputs. Add ChaCha20+Poly1305 AEAD algorithm. Add HKDF key derivation
   function.

-16 to -17

   Mostly editorial fixes.

-17 to -18

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   Resolve AD review comments. Globally replace "byte" with "octet".
   Update reference to "US National Institute of Standards and
   Technology, "SHA-3 WINNER", February 2013" to reference [FIPS202].

-18 to -19

   Resolve GENART review comments.

-19 to -20 to -21

   Minor Editorial improvements.

-21 to -22

   Fix typos.

-22 to -23

   Resolve IESG Discuss and Comments.

-23 to -24

   Minor fixes to 2.2.6 re XMSS & XMSSMT.

-24 to -25

   Add the X448 key agreement algorithm so 2.7.1 as approved by IESG and
   sponsoring AD.

-25 to -26

   Fix typos in URL for X448.

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Normative References

   [10118-3] - ISO, "Information technology -- Security techniques --
         Hash-functions -- Part 3: Dedicated hash-functions", ISO/IEC
         10118-3:2004, 2004.

   [18033-2] - ISO, "Information technology -- Security techniques --
         Encryption algorithms -- Part 3: Asymmetric ciphers", ISO/IEC
         18033-2:2010, 2010.

   [FIPS180-4] - US National Institute of Standards and Technology,
         "Secure Hash Standard (SHS)", FIPS 180-4, March 2012,
         <https://csrc.nist.gov/publications/fips/fips180-4/
         fips-180-4.pdf>.

   [FIPS186-4] - US National Institute of Standards and Technology,
         "Digital Signature Standard (DSS)", FIPS 186-4, July 2013,
         <https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf>.

   [FIPS202] - US National Institute of Standards and Technology, "SHA-3
         Standard: Permutation-Based Hash and Extendable-Output
         Functions", FIPS 202, August 2015,
         <https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf>.

   [IEEEP1363a] - IEEE, "Standard Specifications for Public Key
         Cryptography- Amendment 1: Additional Techniques", IEEE
         1363a-2004, 2004.

   [NIST800-208] - US National Institute of Standards and Technology,
         "Recommendation for Stateful Hash-Based Signature Schemes",
         NIST 800-208, Otober 202,
         <https://csrc.nist.gov/publications/detail/sp/800-208/final>.

   [RC4] - Schneier, B., "Applied Cryptography: Protocols, Algorithms,
         and Source Code in C", Second Edition, John Wiley and Sons, New
         York, NY, 1996.

   [RFC1321] - Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
         DOI 10.17487/RFC1321, April 1992, <https://www.rfc-
         editor.org/info/rfc1321>.

   [RFC2104] - Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
         Hashing for Message Authentication", RFC 2104, DOI
         10.17487/RFC2104, February 1997, <https://www.rfc-
         editor.org/info/rfc2104>.

   [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate
         Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119,
         March 1997, <https://www.rfc-editor.org/info/rfc2119>.

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   [RFC2315] - Kaliski, B., "PKCS #7: Cryptographic Message Syntax
         Version 1.5", RFC 2315, DOI 10.17487/RFC2315, March 1998,
         <https://www.rfc-editor.org/info/rfc2315>.

   [RFC3275] - Eastlake 3rd, D., Reagle, J., and D. Solo, "(Extensible
         Markup Language) XML-Signature Syntax and Processing", RFC
         3275, DOI 10.17487/RFC3275, March 2002, <https://www.rfc-
         editor.org/info/rfc3275>.

   [RFC3394] - Schaad, J. and R. Housley, "Advanced Encryption Standard
         (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
         September 2002, <https://www.rfc-editor.org/info/rfc3394>.

   [RFC3713] - Matsui, M., Nakajima, J., and S. Moriai, "A Description
         of the Camellia Encryption Algorithm", RFC 3713, DOI
         10.17487/RFC3713, April 2004, <https://www.rfc-
         editor.org/info/rfc3713>.

   [RFC3986] - Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
         Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
         DOI 10.17487/RFC3986, January 2005, <https://www.rfc-
         editor.org/info/rfc3986>.

   [RFC4050] - Blake-Wilson, S., Karlinger, G., Kobayashi, T., and Y.
         Wang, "Using the Elliptic Curve Signature Algorithm (ECDSA) for
         XML Digital Signatures", RFC 4050, DOI 10.17487/RFC4050, April
         2005, <https://www.rfc-editor.org/info/rfc4050>.

   [RFC4055] - Schaad, J., Kaliski, B., and R. Housley, "Additional
         Algorithms and Identifiers for RSA Cryptography for use in the
         Internet X.509 Public Key Infrastructure Certificate and
         Certificate Revocation List (CRL) Profile", RFC 4055, DOI
         10.17487/RFC4055, June 2005, <https://www.rfc-
         editor.org/info/rfc4055>.

   [RFC4269] - Lee, H., Lee, S., Yoon, J., Cheon, D., and J. Lee, "The
         SEED Encryption Algorithm", RFC 4269, DOI 10.17487/RFC4269,
         December 2005, <https://www.rfc-editor.org/info/rfc4269>.

   [RFC4648] - Josefsson, S., "The Base16, Base32, and Base64 Data
         Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
         <https://www.rfc-editor.org/info/rfc4648>.

   [RFC5869] - Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-
         Expand Key Derivation Function (HKDF)", RFC 5869, DOI
         10.17487/RFC5869, May 2010, <https://www.rfc-
         editor.org/info/rfc5869>.

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   [RFC6234] - Eastlake 3rd, D. and T. Hansen, "US Secure Hash
         Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI
         10.17487/RFC6234, May 2011, <https://www.rfc-
         editor.org/info/rfc6234>.

   [RFC7748] - Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
         for Security", RFC 7748, DOI 10.17487/RFC7748, January 2016,
         <https://www.rfc-editor.org/info/rfc7748>.

   [RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
         "PKCS #1: RSA Cryptography Specifications Version 2.2", RFC
         8017, DOI 10.17487/RFC8017, November 2016, <https://www.rfc-
         editor.org/info/rfc8017>.

   [RFC8032] - Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
         Signature Algorithm (EdDSA)", RFC 8032, DOI 10.17487/RFC8032,
         January 2017, <https://www.rfc-editor.org/info/rfc8032>.

   [RFC8126] - Cotton, M., Leiba, B., and T. Narten, "Guidelines for
         Writing an IANA Considerations Section in RFCs", BCP 26, RFC
         8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-
         editor.org/info/rfc8126>.

   [RFC8174] - Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
         2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May
         2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8391] - Huelsing, A., Butin, D., Gazdag, S., Rijneveld, J., and
         A. Mohaisen, "XMSS: eXtended Merkle Signature Scheme", RFC
         8391, DOI 10.17487/RFC8391, May 2018, <https://www.rfc-
         editor.org/info/rfc8391>.

   [RFC8439] - Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
         Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018,
         <https://www.rfc-editor.org/info/rfc8439>.

   [SipHash1] - Aumasson, J. and D. Bernstein, "SipHash: A Fast Short-
         Input PRF", Progress in Cryptology - INDOCRYPT 2012, Lecture
         Notes in Computer Science, vol. 7668, December 2012,
         <https://doi.org/10.1007/978-3-642-34931-7_28>.

   [X9.62] - American National Standards Institute, Accredited Standards
         Committee X9, "Public Key Cryptography for the Financial
         Services Industry: The Elliptic Curve Digital Signature
         Algorithm (ECDSA)", ANSI X9.62:2005, 2005.

   [XMLENC10] - Reagle, J. and D. Eastlake, "XML Encryption Syntax and
         Processing", W3C Recommendation, 10 December 2002,
         <https://www.w3.org/TR/2002/REC-xmlenc-core-20021210/>.

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   [XMLENC11] - Eastlake, D., Reagle, J., Hirsch, F., and T. Roessler,
         "XML Encryption Syntax and Processing Version 1.1", W3C
         Proposed Recommendation, 11 April 2013,
         <https://www.w3.org/TR/xmlenc-core1/>.

   [XPointer] - Grosso, P., Maler, E., Marsh, J., and N. Walsh,
         "XPointer Framework", W3C Recommendation, 25 March 2003,
         <https://www.w3.org/TR/2003/ REC-xptr-framework-20030325/>.

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Informational References

   [Camellia] - Aoki, K., Ichikawa, T., Matsui, M., Moriai, S.,
         Nakajima, J., and T. Tokita, "Camellia: A 128-bit Block Cipher
         Suitable for Multiple Platforms - Design and Analysis", in
         Selected Areas in Cryptography, 7th Annual International
         Workshop, SAC 2000, August 2000, Proceedings, Lecture Notes in
         Computer Science 2012, pp. 39-56, Springer-Verlag, 2001.

   [CANON10] - Boyer, J., "Canonical XML Version 1.0", W3C
         Recommendation, 15 March 2001, <https://www.w3.org/TR/2001/REC-
         xml-c14n-20010315>.

   [CANON11] - Boyer, J., and G. Marcy, "Canonical XML Version 1.1", W3C
         Recommendation, 2 May 2008, <https://www.w3.org/TR/2008/REC-
         xml-c14n11-20080502/>.

   [ChaCha] - Bernstein, D., "ChaCha, a variant of Salsa20", January
         2008, <https://cr.yp.to/chacha/chacha-20080128.pdf>.

   [DECRYPT] - Hughes, M., Imamura, T., and H. Maruyama, "Decryption
         Transform for XML Signature", W3C Recommendation, 10 December
         2002, <https://www.w3.org/TR/2002/ REC-xmlenc-
         decrypt-20021210>.

   [Err3597] - RFC Errata, Errata ID 3597, RFC 6931, <https://www.rfc-
         editor.org>.

   [Err3965] - RFC Errata, Errata ID 3965, RFC 6931, <https://www.rfc-
         editor.org>.

   [Err4004] - RFC Errata, Errata ID 4004, RFC 6931, <https://www.rfc-
         editor.org>.

   [GENERIC] - Nystrom, M. and F. Hirsch, "XML Security Generic Hybrid
         Ciphers", W3C Working Group Note, 11 April 2013,
         <https://www.w3.org/TR/xmlsec-generic-hybrid/>.

   [Keccak] - Bertoni, G., Daeman, J., Peeters, M., and G. Van Assche,
         "The KECCAK sponge function family", January 2013,
         <http://keccak.noekeon.org>.

   [Poly1305] - Bernstein, D., "The Poly1305-AES message-authentication
         code", March 2005,
         <https://cr.yp.to/mac/poly1305-20050329.pdf>.

   [RFC3075] - Eastlake 3rd, D., Reagle, J., and D. Solo, "XML-Signature
         Syntax and Processing", RFC 3075, DOI 10.17487/RFC3075, March
         2001, <https://www.rfc-editor.org/info/rfc3075>.

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   [RFC3076] - Boyer, J., "Canonical XML Version 1.0", RFC 3076, DOI
         10.17487/RFC3076, March 2001, <https://www.rfc-
         editor.org/info/rfc3076>.

   [RFC3092] - Eastlake 3rd, D., Manros, C., and E. Raymond, "Etymology
         of "Foo"", RFC 3092, DOI 10.17487/RFC3092, April 1 2001,
         <https://www.rfc-editor.org/info/rfc3092>.

   [RFC3741] - Boyer, J., Eastlake 3rd, D., and J. Reagle, "Exclusive
         XML Canonicalization, Version 1.0", RFC 3741, DOI
         10.17487/RFC3741, March 2004, <https://www.rfc-
         editor.org/info/rfc3741>.

   [RFC4010] - Park, J., Lee, S., Kim, J., and J. Lee, "Use of the SEED
         Encryption Algorithm in Cryptographic Message Syntax (CMS)",
         RFC 4010, DOI 10.17487/RFC4010, February 2005,
         <https://www.rfc-editor.org/info/rfc4010>.

   [RFC5869] - Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-
         Expand Key Derivation Function (HKDF)", RFC 5869, DOI
         10.17487/RFC5869, May 2010, <https://www.rfc-
         editor.org/info/rfc5869>.

   [RFC6090]
         - McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
         Curve Cryptography Algorithms", RFC 6090, DOI 10.17487/RFC6090,
         February 2011, <https://www.rfc-editor.org/info/rfc6090>.
         - Note RFC Errata numbers 2773, 2774, 2775, 2776, and 2777.

   [RFC6151] - Turner, S. and L. Chen, "Updated Security Considerations
         for the MD5 Message-Digest and the HMAC-MD5 Algorithms", RFC
         6151, DOI 10.17487/RFC6151, March 2011, <https://www.rfc-
         editor.org/info/rfc6151>.

   [RFC6194] - Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
         Considerations for the SHA-0 and SHA-1 Message-Digest
         Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
         <https://www.rfc-editor.org/info/rfc6194>.

   [RFC6931] - Eastlake 3rd, D., "Additional XML Security Uniform
         Resource Identifiers (URIs)", RFC 6931, DOI 10.17487/RFC6931,
         April 2013, <https://www.rfc-editor.org/info/rfc6931>

   [RFC7465] - Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465, DOI
         10.17487/RFC7465, February 2015, <https://www.rfc-
         editor.org/info/rfc7465>.

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   [RFC7696] - Housley, R., "Guidelines for Cryptographic Algorithm
         Agility and Selecting Mandatory-to-Implement Algorithms", BCP
         201, RFC 7696, DOI 10.17487/RFC7696, November 2015,
         <https://www.rfc-editor.org/info/rfc7696>.

   [Schema] - Thompson, H., Beech, D., Maloney, M., and N.  Mendelsohn,
         "XML Schema Part 1: Structures Second Edition", W3C
         Recommendation, 28 October 2004,
         <https://www.w3.org/TR/2004/REC-xmlschema-1-20041028/>.
         - Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
         Second Edition", W3C Recommendation, 28 October 2004,
         <https://www.w3.org/TR/2004/REC-xmlschema-2-20041028/>.

   [SipHash2] - Aumasson, J. and D. Bernstein, "SipHash: A Fast Short-
         Input PRF", Department of Computer Science, Iniversity of
         Illinois at Chicago,
         <https://www.aumasson.jp/siphash/siphash.pdf>.

   [W3C] - World Wide Web Consortium, <https://www.w3.org>.

   [XCANON] - Boyer, J., Eastlake, D., and J. Reagle, "Exclusive XML
         Canonicalization Version 1.0", W3C Recommendation, 18 July
         2002, <https://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/>.

   [XMLDSIG10] - Eastlake, D., Reagle, J., Solo, D., Hirsch, F., and T.
         Roessler, "XML Signature Syntax and Processing (Second
         Edition)", W3C Recommendation, 10 June 2008,
         <https://www.w3.org/TR/2008/REC-xmldsig-core-20080610/>./

   [XMLDSIG11] - Eastlake, D., Reagle, J., Solo, D., Hirsch, F.,
         Nystrom, M., Roessler, T., and K. Yiu, "XML Signature Syntax
         and Processing Version 1.1", W3C Proposed Recommendation, 11
         April 2013, <https://www.w3.org/TR/xmldsig-core1/>.

   [XMLDSIG-PROP] - Hirsch, F., "XML Signature Properties", W3C Proposed
         Recommendation, 24 January 2013, <https://www.w3.org/TR/
         2013/PR-xmldsig-properties-20130124/>.

   [XMLSEC] - Eastlake, D., and K. Niles, "Secure XML: The New Syntax
         for Signatures and Encryption", Addison-Wesley (Pearson
         Education), 2003, ISBN 0-201-75605-6.

   [XMLSECXREF] - Hirsch, F., Roessler, T., and K. Yiu, "XML Security
         Algorithm Cross-Reference", W3C Working Group Note, 24 January
         2013, <https://www.w3.org/TR/2013/ NOTE-xmlsec-
         algorithms-20130124/>.

   [XMSS] - IANA Registry for XMSS and XMSSMT Extended Hash-Based
         Signature schemes: https://www.iana.org/assignments/xmss-
         extended-hash-based-signatures

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   [XPATH] - Boyer, J., Hughes, M., and J. Reagle, "XML-Signature XPath
         Filter 2.0", W3C Recommendation, 8 November 2002,
         <https://www.w3.org/TR/2002/ REC-xmldsig-filter2-20021108/>.
         - Berglund, A., Boag, S., Chamberlin, D., Fernandez, M., Kay,
         M., Robie, J., and J. Simeon, "XML Path Language (XPath) 2.0
         (Second Edition)", W3C Recommendation, 14 December 2010,
         <https://www.w3.org/TR/2010/REC-xpath20-20101214/>.

   [XSLT] - Saxonica, M., "XSL Transformations (XSLT) Version 2.0", W3C
         Recommendation, 23 January 2007,
         <https://www.w3.org/TR/2007/REC-xslt20-20070123/>.

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Author's Address

   Donald E. Eastlake 3rd
   Futurewei Technologies, Inc.
   2386 Panoramic Circle
   Apopka, FL 32703 USA

   Phone:    +1-508-333-2270
   EMail:    d3e3e3@gmail.com

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Copyright, Disclaimer, and Additional IPR Provisions

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

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