path: root/doc/rfc/rfc9231.txt

Internet Engineering Task Force (IETF)                   D. Eastlake 3rd
Request for Comments: 9231                  Futurewei Technologies, Inc.
Obsoletes: 6931                                                July 2022
Category: Standards Track                                               
ISSN: 2070-1721


      Additional XML Security Uniform Resource Identifiers (URIs)

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 obsoletes and corrects three errata against RFC 6931.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9231.

Copyright Notice

   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
   (https://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.

Table of Contents

   1.  Introduction
     1.1.  Terminology
     1.2.  Acronyms
   2.  Algorithms
     2.1.  DigestMethod (Hash) Algorithms
       2.1.1.  MD5
       2.1.2.  SHA-224
       2.1.3.  SHA-384
       2.1.4.  Whirlpool
       2.1.5.  SHA-3 Algorithms
     2.2.  SignatureMethod MAC Algorithms
       2.2.1.  HMAC-MD5
       2.2.2.  HMAC SHA Variations
       2.2.3.  HMAC-RIPEMD160
       2.2.4.  Poly1305
       2.2.5.  SipHash-2-4
       2.2.6.  XMSS and XMSSMT
     2.3.  SignatureMethod Public Key Signature Algorithms
       2.3.1.  RSA-MD5
       2.3.2.  RSA-SHA256
       2.3.3.  RSA-SHA384
       2.3.4.  RSA-SHA512
       2.3.5.  RSA-RIPEMD160
       2.3.6.  ECDSA-SHA*, ECDSA-RIPEMD160, ECDSA-Whirlpool
       2.3.7.  ESIGN-SHA*
       2.3.8.  RSA-Whirlpool
       2.3.9.  RSASSA-PSS with Parameters
       2.3.10. RSASSA-PSS without Parameters
       2.3.11. RSA-SHA224
       2.3.12. Edwards-Curve
     2.4.  Minimal Canonicalization
     2.5.  Transform Algorithms
       2.5.1.  XPointer
     2.6.  EncryptionMethod Algorithms
       2.6.1.  ARCFOUR Encryption Algorithm
       2.6.2.  Camellia Block Encryption
       2.6.3.  Camellia Key Wrap
       2.6.4.  PSEC-KEM, RSAES-KEM, and ECIES-KEM
       2.6.5.  SEED Block Encryption
       2.6.6.  SEED Key Wrap
       2.6.7.  ChaCha20
       2.6.8.  ChaCha20+Poly1305
     2.7.  Key AgreementMethod Algorithm
       2.7.1.  X25519 and X448 Key Agreement
     2.8.  KeyDerivationMethod Algorithm
       2.8.1.  HKDF Key Derivation
   3.  KeyInfo
     3.1.  PKCS #7 Bag of Certificates and CRLs
     3.2.  Additional RetrievalMethod Type Values
   4.  Indexes
     4.1.  Index by Fragment Index
     4.2.  Index by URI
   5.  Allocation Considerations
     5.1.  W3C Allocation Considerations
     5.2.  IANA Considerations
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Appendix A.  Changes from RFC 6931
   Appendix B.  Bad URIs
   Acknowledgements
   Author's Address

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            | W3C REC     | Topic                |
          | Status         |             |                      |
          +================+=============+======================+
          | [RFC3275]      | [XMLDSIG10] | XML Digital          |
          | Draft Standard |             | Signatures           |
          +----------------+-------------+----------------------+
          | [RFC3076]      | [CANON10]   | Canonical XML        |
          | Informational  |             |                      |
          +----------------+-------------+----------------------+
          | - - - - - -    | [XMLENC10]  | XML Encryption 1.0   |
          +----------------+-------------+----------------------+
          | [RFC3741]      | [XCANON]    | Exclusive XML        |
          | Informational  |             | Canonicalization 1.0 |
          +----------------+-------------+----------------------+

                                  Table 1

   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], and [Err4004], 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 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 terminology from
   [RFC2119] and [RFC8174] 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 Associated Data

   ASN.1 -  Abstract Syntax Notation 1

   BER -  Basic Encoding Rules [ITU-T-X.680]

   DSA -  Digital Signature Algorithm

   DSS -  Digital Signature Standard [FIPS186-4]

   ECDSA -  Elliptic Curve DSA

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

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

   MAC -  Message Authentication Code

   MD -  Message Digest

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

   OID -  Object Identifier [ITU-T-X.660]

   PKCS -  Public Key Cryptography Standard

   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

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 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.

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.

2.1.4.  Whirlpool

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

   The Whirlpool algorithm [ISO-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.  SHA-3 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 Message Authentication Code (MAC)
   Algorithms.

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

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
      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 for HMAC-MD5.

2.2.3.  HMAC-RIPEMD160

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

   RIPEMD-160 [ISO-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"/>

2.2.6.  XMSS and XMSSMT

   XMSS (eXtended Merkle Signature Scheme) and XMSSMT (XMSS Multi-Tree)
   [RFC8391] 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.

   For further information on the intended usage of these signature
   schemes and the careful state management required to maintain their
   strength, see [NIST800-208].

   IANA maintains a registry whose entries correspond to the XMSS
   Identifiers below (see [XMSS]).  The fragment part of the URIs is
   formed by replacing occurrences of underscore ("_") in the name
   appearing in the IANA registry with hyphen ("-").

   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-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-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-10-256
      http://www.w3.org/2021/04/xmldsig-more#xmss-shake-10-512
      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-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

   The hash functions used in the XMSS signature schemes above are SHA2
   [RFC6234] or one of the two SHAKE extensible output functions
   [FIPS202] as indicated by the second token of the URI extension
   (SHAKE means SHAKE128).  The tree height for XMSS is 10, 16, or 20 as
   indicated by the third token of the URI extension.  The SHA2 or SHAKE
   output size is 192, 256, or 512 bits as indicated by the final token
   of the URI extension.  SHA2 with 192 bits of output means
   SHA2-256/192, that is, the most significant 192 bits of the SHA-256
   hash as specified in [NIST800-208].

   IANA maintains a registry whose entries correspond to the XMSSMT
   Identifiers below (see [XMSS]).  The fragment part of the URIs is
   formed by replacing occurrences of underscore ("_") and slash ("/")
   in the name appearing in the IANA registry with hyphen ("-").

   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-sha2-20-2-512
      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-sha2-20-4-512
      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-sha2-40-2-512
      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-sha2-40-4-512
      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-sha2-40-8-512
      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
      http://www.w3.org/2021/04/xmldsig-more#xmssmt-sha2-60-3-512
      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-sha2-60-6-512
      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-sha2-60-12-512

      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 functions used in the XMSSMT signature schemes above are
   SHA2 [RFC6234] or one of the two the SHAKE extensible output function
   [FIPS202] as indicated by the second token of the URI extension
   (SHAKE means SHAKE128).  The tree height for XMSSMT is 20, 40, or 60
   as indicated by the third token of the URI extension.  The number of
   layers is indicated by a fourth token.  The SHA2, SHAKE, or SHAKE256
   output size is 192, 256, or 512 bits as indicated by the final token
   of the URI extension.  SHA2 with 192 bits of output means
   SHA2-256/192, that is, the most significant 192 bits of the SHA-256
   hash as specified in [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 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 Section 8.2.1
   of [RFC8017], signature generation for the RSASSA-PKCS1-v1_5
   signature scheme.  As specified in the EMSA-PKCS1-V1_5-ENCODE
   function in Section 9.2 of [RFC8017], 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

   The 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 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

   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.

   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
   1.0.10118.3.0.55 defined in [ISO-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>
      <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

   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.)

   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-
   Signature Syntax and Processing" 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:

   <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 protocols, 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>

   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 regardless of 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:

   <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 [ISO-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 [ISO-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:

   <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>

2.6.8.  ChaCha20+Poly1305

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

   ChaCha20+Poly1305 is an Authenticated Encryption with Associated 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 Algorithm

   This subsection gives identifiers and information for an additional
   key AgreementMethod Algorithm [XMLENC11].

2.7.1.  X25519 and X448 Key Agreement

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

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

2.8.  KeyDerivationMethod Algorithm

   This subsection gives identifiers and information for an additional
   KeyDerivationMethod Algorithm [XMLENC11].

2.8.1.  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

   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 Appendix A.1 of [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>
     <KA-Nonce>f0f1f2f3f4f5f6f7f8f9</KA-Nonce>
     <KeySize>42</KeySize>
   </AgreementMethod>

3.  KeyInfo

   In Section 3.1, 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

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]
   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              2.8.1
   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]
   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
   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
   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-sha2-20-2-256 2021/04/xmldsig-more#xmssmt-sha2-20-2-512
                                                              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-sha2-20-4-256 2021/04/xmldsig-more#xmssmt-sha2-20-4-512
                                                              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-sha2-40-2-256 2021/04/xmldsig-more#xmssmt-sha2-40-2-512
                                                              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-sha2-40-4-256 2021/04/xmldsig-more#xmssmt-sha2-40-4-512
                                                              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-sha2-40-8-256 2021/04/xmldsig-more#xmssmt-sha2-40-8-512
                                                              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
   xmssmt-sha2-60-3-256 2021/04/xmldsig-more#xmssmt-sha2-60-3-512
                                                              2.2.6
   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-sha2-60-6-256 2021/04/xmldsig-more#xmssmt-sha2-60-6-512
                                                              2.2.6
   xmssmt-sha2-60-12-192 2021/04/xmldsig-more#xmssmt-sha2-60-12-192
                                                              2.2.6
   xmssmt-sha2-60-12-256 2021/04/xmldsig-more#xmssmt-sha2-60-12-256
                                                              2.2.6
   xmssmt-sha2-60-12-256 2021/04/xmldsig-more#xmssmt-sha2-60-12-512
                                                              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-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-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
   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.

   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
   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
   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]    KeyDerivation
   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]    KeyDerivation
   2009/xmlenc11#rsa-oaep             [XMLENC11]    EncryptionMethod
   2009/xmlenc11#ECDH-ES              [XMLENC11]    AgreementMethod
   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               2.8.1    KeyDerivation
   2021/04/xmldsig-more#po1y305            2.2.4    SignatureMethod
   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-sha2-20-2-512 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-sha2-20-4-512 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-sha2-40-2-512 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-sha2-40-4-512 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-sha2-40-8-512 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-sha2-60-3-512 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-sha2-60-6-512 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-sha2-60-12-512 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
   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
   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.

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/xmldsig-more# | Frozen with RFC 4051.  |
   +-----------------------------------------+------------------------+
   | http://www.w3.org/2007/05/xmldsig-more# | Frozen with [RFC6931]. |
   +-----------------------------------------+------------------------+

                                 Table 2

   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 have been 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 "[RFC9231],
   Section 2.6.4").  All references to [RFC6931] in that registry have
   been updated to RFC 9231.

   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 RFC.

   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.

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].

7.  References

7.1.  Normative References

   [FIPS180-4]
              National Institute of Standards and Technology (NIST),
              "Secure Hash Standard (SHS)", DOI 10.6028/NIST.FIPS.180-4,
              FIPS 180-4, August 2015,
              <https://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.180-4.pdf>.

   [FIPS186-4]
              National Institute of Standards and Technology (NIST),
              "Digital Signature Standard (DSS)", FIPS 186-4,
              DOI 10.6028/NIST.FIPS.186-4, July 2013,
              <https://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.186-4.pdf>.

   [FIPS202]  National Institute of Standards and Technology (NIST),
              "SHA-3 Standard: Permutation-Based Hash and Extendable-
              Output Functions", FIPS 202, DOI 10.6028/NIST.FIPS.202,
              August 2015, <https://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.202.pdf>.

   [IEEEP1363a]
              Institute of Electrical and Electronics Engineers, "IEEE
              Standard Specifications for Public-Key Cryptography -
              Amendment 1: Additional Techniques", IEEE Std 1363a-2004,
              2004.

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

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

   [NIST800-208]
              National Institute of Standards and Technology (NIST),
              "Recommendation for Stateful Hash-Based Signature
              Schemes", NIST 800-208, DOI 10.6028/NIST.SP.800-208,
              October 2020,
              <https://nvlpubs.nist.gov/nistpubs/SpecialPublications/
              NIST.SP.800-208.pdf>.

   [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>.

   [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.J., Lee, S.J., Yoon, J.H., Cheon, D.H., and J.I.
              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>.

   [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 3rd, "XML Encryption Syntax and
              Processing", W3C Recommendation, December 2002,
              <https://www.w3.org/TR/2002/REC-xmlenc-core-20021210/>.

   [XMLENC11] Eastlake 3rd, D., Reagle, J., Hirsch, F., and T. Roessler,
              "XML Encryption Syntax and Processing Version 1.1",
              W3C Proposed Recommendation, April 2013,
              <https://www.w3.org/TR/xmlenc-core1/>.

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

7.2.  Informative References

   [CAMELLIA] Aoki, K., Ichikawa, T., Kanda, M., 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.

   [CANON10]  Boyer, J., "Canonical XML Version 1.0",
              W3C Recommendation, 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, 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, December
              2002,
              <https://www.w3.org/TR/2002/REC-xmlenc-decrypt-20021210>.

   [Err3597]  RFC Errata, "Erratum ID 3597", RFC 6931,
              <https://www.rfc-editor.org/errata/eid3597>.

   [Err3965]  RFC Errata, "Erratum ID 3965", RFC 6931,
              <https://www.rfc-editor.org/errata/eid3965>.

   [Err4004]  RFC Errata, "Erratum ID 4004", RFC 6931,
              <https://www.rfc-editor.org/errata/eid4004>.

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

   [ITU-T-X.660]
              ITU-T, "Information technology - Procedures for the
              operation of object identifier registration authorities:
              General procedures and top arcs of the international
              object identifier tree", ITU-T Recommendation X.660, July
              2011, <https://www.itu.int/rec/T-REC-X.660>.

   [ITU-T-X.680]
              ITU-T, "Information technology - Abstract Syntax Notation
              One (ASN.1): Specification of basic notation", ITU-T
              Recommendation X.680, February 2021,
              <https://www.itu.int/rec/T-REC-X.680>.

   [KECCAK]   Bertoni, G., Daeman, J., Peeters, M., and G. Van Assche,
              "KECCAK sponge function family", Version 2.1, June 2010,
              <https://keccak.team/obsolete/Keccak-main-2.1.pdf>.

   [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>.

   [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 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>.

   [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>.

   [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>.

   [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 REC-xmlschema-1-20041028, 28 October 2004.

              Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
              Second Edition", W3C Recommendation REC-xmlschema-
              2-20041028, 28 October 2004.

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

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

   [XCANON]   Boyer, J., Eastlake 3rd, D., and J. Reagle, "Exclusive XML
              Canonicalization Version 1.0", W3C Recommendation, July
              2002,
              <https://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/>.

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

   [XMLDSIG10]
              Bartel, M., Boyer, J., Fox, B., Simon, E., and B.
              LaMacchia, "XML Signature Syntax and Processing (Second
              Edition)", W3C Recommendation, June 2008,
              <https://www.w3.org/TR/2008/REC-xmldsig-core-20080610/>.

   [XMLDSIG11]
              Bartel, M., Boyer, J., Fox, B., Simon, E., and B.
              LaMacchia, "XML Signature Syntax and Processing Version
              1.1", W3C Proposed Recommendation, April 2013,
              <https://www.w3.org/TR/xmldsig-core1/>.

   [XMLSEC]   Eastlake 3rd, D. and K. Niles, "Secure XML: The New Syntax
              for Signatures and Encryption", Addison-Wesley (Pearson
              Education) ISBN 0-201-75605-6, 2003.

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

   [XMSS]     IANA, "XMSS: Extended Hash-Based Signatures",
              <https://www.iana.org/assignments/xmss-extended-hash-
              based-signatures>.

   [XPATH]    Boyer, J., Hughes, M., and J. Reagle, "XML-Signature XPath
              Filter 2.0", W3C Recommendation REC-xmldsig-
              filter2-20021108, 8 November 2002.

              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 REC-
              xpath20-20101214, 14 December 2010.

   [XSLT]     Kay, M., "XSL Transformations (XSLT) Version 2.0", W3C
              Recommendation, Second Edition, March 2021,
              <https://www.w3.org/TR/xslt20/>.

Appendix A.  Changes from RFC 6931

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

   *  Deleted 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.

   *  Fixed 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.

   *  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                   |
                  +---------+--------------------------+
                  | 2.8.1   | HKDF                     |
                  +---------+--------------------------+

                                 Table 3

   *  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].

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

   *  Added some XML examples.

   *  Fixed minor typos and added editorial changes.

   *  A number of acronyms were added to Section 1.2.

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 (Sections 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 (Sections 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.

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, Juraj Somorovsky,
      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, Björn Höhrmann, 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, Joel Halpern, Russ Housley, Merlin Hughs, Gregor
      Karlinger, Brian LaMachia, Shiho Moriai, and Joseph Reagle.

Author's Address

   Donald E. Eastlake 3rd
   Futurewei Technologies, Inc.
   2386 Panoramic Circle
   Apopka, FL 32703
   United States of America
   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com