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© 2008 ©
2010 The Internet Society IETF
Trust & W3C ® ® (
MIT ,
ERCIM
, Keio ), All Rights Reserved.
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, trademark
and document
use rules apply.
This document specifies XML digital signature processing rules and syntax. XML Signatures provide integrity , message authentication , and/or signer authentication services for data of any type, whether located within the XML that includes the signature or elsewhere.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
At the time of this specification was produced by publication, the IETF/W3C most recent W3C
Recommendation of XML Signature Working
Group which believes the specification 1 is sufficient for
the creation of independent interoperable
implementations; the Interoperability Report shows at least
10
implementations with at least two
interoperable implementations over every feature. This Second
Edition was produced by the W3C June
2008 XML Security Specifications
Maintenance Signature (Second Edition)
Recommendation .Please review
differences
between the previous and this Working Group Draft ,
part of and
differences
between the W3C Security Activity (
Activity Statement ). This Second Edition of previous XML Signature Syntax Recommendation
and Processing adds Canonical XML 1.1
as this Working Draft
; a required
canonicalization algorithm and recommends its use for inclusive
canonicalization. This version of Canonical XML enables use
detailed explanation of
xml:id and xml:base Recommendations with XML
Signature and changes
is also enables
other possible future attributes in the XML namespace. Additional
minor changes, including available.
Conformance-affecting changes against this
previous recommendation mainly affect the incorporation set of
known errata, are documented in Changes in
XML Signature Syntax mandatory to
implement cryptographic algorithms, including Elliptic Curve DSA
(and mark-up for corresponding key material), and Processing (Second Edition) . additional hash algorithms.
The This Last
Call Working Group conducted an
interoperability test as part Draft
includes the ECDSAwithSHA256
signature algorithm, which is ECDSA over the P-256 prime
curve specified in Section D.2.3 of its
activity. The Test Cases for C14N 1.1 and XMLDSig
Interoperability FIPS 186-3 [
TESTCASES FIPS-186-3 ] are
available (and using the SHA-256 hash
algorithm), as a companion
mandatory to implement algorithm. The
Working Group Note. may request
transition to Candidate Recommendation with this feature marked as "at risk". If issues about
deployment of this feature are raised during Candidate
Recommendation, the group may elect to make this feature
optional.
The Implementation Report
Working Group is, in parallel to this work,
developing requirements and designs for a more radically different version 2 of XML
Signature, Second Edition is also publicly
available. Signature.
Please send comments about this
This document was
developed by the XML Security
Working Group .The Working Group
expects to public-xmlsec-comments@w3.org (with public archive
). advance this Working Draft to
Recommendation Status.
This document has been reviewed by W3C
Members, by software developers, and by other W3C groups and
interested parties, and is endorsed was
published by the Director
XML
Security Working Group as an
Editor's Draft. If you wish to make comments regarding this
document, please send them to public-xmlsec@w3.org ( subscribe ,archives ). All feedback
is welcome.
Publication as a Editor's Draft does not imply endorsement by the
W3C Recommendation. It Membership. This is a stable draft document
and may be used as reference material
updated, replaced or cited from another document. W3C's role in making the
Recommendation obsoleted by other
documents at any time. It is inappropriate to draw
attention to the specification and to promote its widespread
deployment. This enhances the functionality and interoperability of
the Web. cite this document as other
than work in progress.
This document is governed by the 24
January 2002 CPP as amended was
produced by a group operating
under the 5 February 2004 W3C Patent Policy Transition Procedure . W3C maintains a
public list of any patent disclosures made in
connection with the deliverables of the group; that page also
includes instructions for disclosing a patent. An individual who
has actual knowledge of a patent which the individual believes
contains
Essential Claim(s) must disclose the information in accordance
with
section 6 of the W3C Patent Policy . Patent disclosures relevant to this specification may be
found on the IETF Page of Intellectual Property Rights Notices , in
conformance with IETF policy. The English version of this
specification is the only normative version.
ds:CryptoBinary
Simple TypeSignature
elementSignatureValue
ElementSignedInfo
Element
KeyInfo
Element
KeyName
ElementKeyValue
Element
RetrievalMethod
ElementX509Data
Element
PGPData
ElementSPKIData
ElementMgmtData
ElementEncryptedKey
and DerivedKey
ElementsDEREncodedKeyValue
ElementKeyInfoReference
ElementObject
ElementThis document specifies XML syntax and processing rules for creating and representing digital signatures. XML Signatures can be applied to any digital content (data object) , including XML. An XML Signature may be applied to the content of one or more resources. Enveloped or enveloping signatures are over data within the same XML document as the signature; detached signatures are over data external to the signature element. More specifically, this specification defines an XML signature element type and an XML signature application ; conformance requirements for each are specified by way of schema definitions and prose respectively. This specification also includes other useful types that identify methods for referencing collections of resources, algorithms, and keying and management information.
The XML Signature is a method of associating a key with referenced data (octets); it does not normatively specify how keys are associated with persons or institutions, nor the meaning of the data being referenced and signed. Consequently, while this specification is an important component of secure XML applications, it itself is not sufficient to address all application security/trust concerns, particularly with respect to using signed XML (or other data formats) as a basis of human-to-human communication and agreement. Such an application must specify additional key, algorithm, processing and rendering requirements. For further information, please see Security Considerations (section 8).
For readability, brevity, and historic reasons this document
uses the term "signature" to generally refer to digital
authentication values of all types. Obviously, the term is also
strictly used to refer to authentication values that are based on
public keys and that provide signer authentication. When
specifically discussing authentication values based on symmetric
secret key codes we use the terms authenticators or authentication
codes. (See Check the Security
Model , section 8.3.) 8.2.)
This specification provides an
a normative XML Schema [ XML-schema XMLSCHEMA-1 ] and
DTD ], [ XML XMLSCHEMA-2 ]. The full normative grammar is defined by the XSD schema and
the normative text in this specification. The standalone XSD
schema definition file is normative.
authoritative in case there is any
disagreement between it and the XSD schema portions in this
specification.
The key words "MUST", "MUST NOT",
"REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", "
must ", "
must
not ", " required
", " shall ", " shall not ", " should ", " should not
", " recommended
", " may ", and "OPTIONAL"
" optional " in this specification are to be interpreted as
described in RFC2119 [ KEYWORDS RFC2119
]: ].
"they MUST"They must only be used where it is actually required for interoperation or to limit behavior which has potential for causing harm (e.g., limiting retransmissions)"
Consequently, we use these capitalized key words to
unambiguously specify requirements over protocol and application
features and behavior that affect the interoperability and security
of implementations. These key words are not used (capitalized) to
describe XML grammar; schema definitions unambiguously describe
such requirements and we wish to reserve the prominence of these
terms for the natural language descriptions of protocols and
features. For instance, an XML attribute might be described as
being "optional." Compliance with the Namespaces in XML
specification [ XML-ns XML-NAMES ] is described as "REQUIRED." "
required ."
The design philosophy and requirements of this specification are
addressed in the original XML-Signature
Requirements document [ XML-Signature-RD XMLDSIG-REQUIREMENTS ] and the XML Security 1.1 Requirements document [
XMLSEC11-REQS ].
No provision is made for an explicit
version number in this syntax. If a future version is needed, it
will This specification makes use
a different namespace. The of XML namespace
namespaces, and uses Uniform Resource
Identifiers [ XML-ns
URI ] URI that MUST be used by implementations
to identify resources, algorithms, and
semantics.
Implementations of this (dated) specification is: must use the following
XML namespace URIs:
URI | namespace |
XML internal entity |
---|---|---|
http://www.w3.org/2000/09/xmldsig# |
default namespace
,ds: ,dsig: |
<!ENTITY dsig
"http://www.w3.org/2000/09/xmldsig#"> |
http://www.w3.org/2009/xmldsig11# |
dsig11: |
<!ENTITY dsig11
"http://www.w3.org/2009/xmldsig11#"> |
While applications MUST implementations must support XML and XML
namespaces, the and while use of internal
entities [ XML ] or our "dsig" XML the
above namespace prefix
URIs is required ,the namespace prefixes and defaulting/scoping conventions entity declarations given are OPTIONAL; we merely
editorial conventions used in this document. Their use
these facilities to provide compact and
readable examples. by implementations
is optional .
This specification uses
Uniform Resource Identifiers [ URI ] to identify resources,
algorithms, and semantics. The URI in the These namespace declaration
above is URIs are also used as
a the
prefix for URIs algorithm identifiers that are under the control of this specification. For resources
not under the control of this specification, we use the designated
Uniform Resource Names [ URN ], [
RFC3406 ] or
Uniform Resource Locators Identifiers [ URL
URI ] defined by
its the
relevant normative external specification. If an external specification has not allocated itself a
Uniform Resource Identifier we allocate an identifier under our own
namespace.
For instance:
SignatureProperties
is identified and defined by disg:
namespacehttp://www.w3.org/2000/09/xmldsig#SignatureProperties
ECKeyValue
is
identified and defined by the dsig11:
namespacehttp://www.w3.org/2009/xmldsig11#ECKeyValue
http://www.w3.org/TR/1999/REC-xslt-19991116
Finally, The http://www.w3.org/2000/09/xmldsig#
( dsig:
) namespace was
introduced in order to provide
the first edition of this specification. This
version does not coin any new elements or algorithm identifiers in
that namespace; instead, the http://www.w3.org/2009/xmldsig11#
( dsig11:
) namespace
is used.
No provision is made for terse an explicit version
number in this syntax. If a future version of this specification
requires explicit versioning of the document format, a
different namespace declarations we
sometimes use XML internal entities [ XML ] within URIs. For
instance: will be used.
The contributions of the following
members of the XML Signature Working
Group members to this the first edition
specification are gratefully acknowledged: Mark Bartel, Adobe, was
Accelio (Author) (Author); John Boyer, IBM (Author) (Author);
Mariano P. Consens, University of Waterloo Waterloo;
John Cowan, Reuters Health Health; Donald Eastlake 3rd, Motorola
(Chair, Author/Editor) Author/Editor); Barb Fox, Microsoft (Author) (Author);
Christian Geuer-Pollmann, University Siegen Siegen; Tom
Gindin, IBM IBM; Phillip Hallam-Baker, VeriSign Inc Inc; Richard
Himes, US Courts Courts; Merlin Hughes, Baltimore Baltimore;
Gregor Karlinger, IAIK TU Graz
Graz; Brian LaMacchia, Microsoft
(Author) (Author); Peter Lipp, IAIK TU Graz Graz; Joseph
Reagle, NYU, was W3C (Chair, Author/Editor) Author/Editor); Ed Simon, XMLsec (Author) (Author);
David Solo, Citigroup (Author/Editor)
(Author/Editor); Petteri Stenius,
Capslock Capslock; Raghavan Srinivas, Sun Sun; Kent Tamura,
IBM IBM;
Winchel Todd Vincent III, GSU
GSU; Carl Wallace, Corsec Security,
Inc. Inc.;
Greg Whitehead, Signio Inc.
As are the first edition Last Call comments from the following:
The following members of the XML Security Specification
Maintenance Working Group contributed to the second edition: Juan
Carlos Cruellas, Universitat Politècnica Politècnica de Catalunya Catalunya;
Pratik Datta, Oracle Corporation
Corporation; Phillip Hallam-Baker,
VeriSign, Inc. Inc.; Frederick Hirsch, Nokia, (Chair, Editor) Editor);
Konrad Lanz, A-SIT Applied Information processing and Kommunications
(IAIK); Hal Lockhart, BEA Systems, Inc. Inc.; Robert
Miller, MITRE Corporation Corporation; Sean Mullan, Sun Microsystems,
Inc. Inc.;
Bruce Rich, IBM Corporation Corporation; Thomas Roessler, W3C/ERCIM, (Staff
contact, Editor) Editor); Ed Simon, W3C Invited Expert Expert; Greg
Whitehead, HP HP.
Contributions for version 1.1 were received from the members of the XML Security Working Group: Scott Cantor, Juan Carlos Cruellas, Pratik Datta, Gerald Edgar, Ken Graf, Phillip Hallam-Baker, Brad Hill, Frederick Hirsch (Chair, Editor), Brian LaMacchia, Konrad Lanz, Hal Lockhart, Cynthia Martin, Rob Miller, Sean Mullan, Shivaram Mysore, Magnus Nyström, Bruce Rich, Thomas Roessler (Staff contact, Editor), Ed Simon, Chris Solc, John Wray, Kelvin Yiu (Editor).
The Working Group thanks Makoto Murata for assistance with the RELAX NG schemas.
This section provides an overview and examples of XML digital signature syntax. The specific processing is given in Processing Rules (section 3). The formal syntax is found in Core Signature Syntax (section 4) and Additional Signature Syntax (section 5).
In this section, an informal representation and examples are used to describe the structure of the XML signature syntax. This representation and examples may omit attributes, details and potential features that are fully explained later.
XML Signatures are applied to arbitrary digital content (data
objects) via an indirection. Data objects are digested, the
resulting value is placed in an element (with other information)
and that element is then digested and cryptographically signed. XML
digital signatures are represented by the Signature
element which has the following structure (where "?" denotes zero
or one occurrence; "+" denotes one or more occurrences; and "*"
denotes zero or more occurrences):
<Signature ID?> <SignedInfo> <CanonicalizationMethod/> <SignatureMethod/> (<Reference URI? > (<Transforms>)? <DigestMethod> <DigestValue> </Reference>)+ </SignedInfo> <SignatureValue> (<KeyInfo>)? (<Object ID?>)* </Signature>
Signatures are related to data objects via URIs [ URI ]. Within an XML
document, signatures are related to local data objects via fragment
identifiers. Such local data can be included within an enveloping signature or can enclose an enveloped signature. Detached signatures are over external network
resources or local data objects that reside within the same XML
document as sibling elements; in this case, the signature is
neither enveloping (signature is parent) nor enveloped (signature
is child). Since a Signature
element (and its
Id
attribute value/name) may co-exist or be combined
with other elements (and their IDs) within a single XML document,
care should be taken in choosing names such that there are no
subsequent collisions that violate the ID uniqueness validity
constraint [ XML XML10 ].
Signature
, SignedInfo
,
Methods
, and Reference
The following example is a detached signature of the content of the HTML4 in XML specification.
[s01] <Signature Id="MyFirstSignature" xmlns="http://www.w3.org/2000/09/xmldsig#"> [s02] <SignedInfo> [s03] <CanonicalizationMethod Algorithm="http://www.w3.org/2006/12/xml-c14n11"/>[s04] <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#dsa-sha1"/>[s04] <SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/> [s05] <Reference URI="http://www.w3.org/TR/2000/REC-xhtml1-20000126/"> [s06] <Transforms> [s07] <Transform Algorithm="http://www.w3.org/2006/12/xml-c14n11"/> [s08] </Transforms>[s09] <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/> [s10] <DigestValue>dGhpcyBpcyBub3QgYSBzaWduYXR1cmUK.../DigestValue>[s09] <DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/> [s10] <DigestValue>dGhpcyBpcyBub3QgYSBzaWduYXR1cmUK...</DigestValue> [s11] </Reference> [s12] </SignedInfo> [s13] <SignatureValue>...</SignatureValue> [s14] <KeyInfo> [s15a] <KeyValue> [s15b] <DSAKeyValue> [s15c] <P>...</P><Q>...</Q><G>...</G><Y>...</Y> [s15d] </DSAKeyValue> [s15e] </KeyValue> [s16] </KeyInfo> [s17] </Signature>
[s02-12]
The required SignedInfo
element is the information that is actually signed. Core validation of
SignedInfo
consists of two mandatory processes:
validation of
the signature over SignedInfo
and validation of each
Reference
digest within SignedInfo
.
Note that the algorithms used in calculating the
SignatureValue
are also included in the signed
information while the SignatureValue
element is
outside SignedInfo
.
[s03]
The CanonicalizationMethod
is
the algorithm that is used to canonicalize the
SignedInfo
element before it is digested as part of
the signature operation. Note that this example, and all example is
not in canonical form. (None of the examples in this
specification, specification are not
in canonical form. form.)
[s04]
The SignatureMethod
is the
algorithm that is used to convert the canonicalized
SignedInfo
into the SignatureValue
. It
is a combination of a digest algorithm and a key dependent
algorithm and possibly other algorithms such as padding, for
example RSA-SHA1. The algorithm names are signed to resist attacks
based on substituting a weaker algorithm. To promote application
interoperability we specify a set of signature algorithms that
MUST must be implemented, though
their use is at the discretion of the signature creator. We specify
additional algorithms as RECOMMENDED
recommended or OPTIONAL optional for
implementation; the design also permits arbitrary user specified
algorithms.
[s05-11]
Each Reference
element
includes the digest method and resulting digest value calculated
over the identified data object. It also may include
transformations that produced the input to the digest operation. A
data object is signed by computing its digest value and a signature
over that value. The signature is later checked via reference and signature validation .
[s14-16]
KeyInfo
indicates the key to
be used to validate the signature. Possible forms for
identification include certificates, key names, and key agreement
algorithms and information -- we define only a few.
KeyInfo
is optional for two reasons. First, the signer
may not wish to reveal key information to all document processing
parties. Second, the information may be known within the
application's context and need not be represented explicitly. Since
KeyInfo
is outside of SignedInfo
, if the
signer wishes to bind the keying information to the signature, a
Reference
can easily identify and include the
KeyInfo
as part of the signature. Use of KeyInfo
is optional,
however note that senders and receivers must agree on how it will
be used through a mechanism out of scope for this
specification.
Reference
[s05] <Reference URI="http://www.w3.org/TR/2000/REC-xhtml1-20000126/"> [s06] <Transforms> [s07] <Transform Algorithm="http://www.w3.org/2006/12/xml-c14n11"/> [s08] </Transforms>[s09] <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>[s09] <DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/> [s10] <DigestValue>dGhpcyBpcyBub3QgYSBzaWduYXR1cmUK...</DigestValue> [s11] </Reference>
[s05]
The optional URI
attribute of
Reference
identifies the data object to be signed.
This attribute may be omitted on at most one Reference
in a Signature
. (This limitation is imposed in order
to ensure that references and objects may be matched
unambiguously.)
[s05-08]
This identification, along with the
transforms, is a description provided by the signer on how they
obtained the signed data object in the form it was digested (i.e.
the digested content). The verifier may obtain the digested content
in another method so long as the digest verifies. In particular,
the verifier may obtain the content from a different location such
as a local store than that specified in the URI
.
[s06-08] Transforms
is an optional ordered list of
processing steps that were applied to the resource's content before
it was digested. Transforms can include operations such as
canonicalization, encoding/decoding (including
compression/inflation), XSLT, XPath, XML schema validation, or
XInclude. XPath transforms permit the signer to derive an XML
document that omits portions of the source document. Consequently
those excluded portions can change without affecting signature
validity. For example, if the resource being signed encloses the
signature itself, such a transform must be used to exclude the
signature value from its own computation. If no
Transforms
element is present, the resource's content
is digested directly. While the Working Group has specified
mandatory (and optional) canonicalization and decoding algorithms,
user specified transforms are permitted.
[s09-10] DigestMethod
is the algorithm applied to
the data after Transforms
is applied (if specified) to
yield the DigestValue
. The signing of the
DigestValue
is what binds a
resources the content of a resource to the signer's key.
Object
and SignatureProperty
)This specification does not address mechanisms for making
statements or assertions. Instead, this document defines what it
means for something to be signed by an XML Signature ( integrity , message
authentication , and/or signer authentication ). Applications that
wish to represent other semantics must rely upon other
technologies, such as [ XML , RDF
XML10
], [ RDF-PRIMER ]. For instance, an
application might use a foo:assuredby
attribute within
its own markup to reference a Signature
element.
Consequently, it's the application that must understand and know
how to make trust decisions given the validity of the signature and
the meaning of assuredby
syntax. We also define a
SignatureProperties
element type for the inclusion of
assertions about the signature itself (e.g., signature semantics,
the time of signing or the serial number of hardware used in
cryptographic processes). Such assertions may be signed by
including a Reference
for the
SignatureProperties
in SignedInfo
. While
the signing application should be very careful about what it signs
(it should understand what is in the SignatureProperty
) a receiving application has no obligation to understand that
semantic (though its parent trust engine may wish to). Any content
about the signature generation may be located within the
SignatureProperty
element. The mandatory
Target
attribute references the Signature
element to which the property applies.
Consider the preceding example with an additional reference to a
local Object
that includes a
SignatureProperty
element. (Such a signature would not
only be detached [p02]
but enveloping [p03]
.)
[ ] <Signature Id="MySecondSignature" ...> [p01] <SignedInfo> [ ] ... [p02] <Reference URI="http://www.w3.org/TR/xml-stylesheet/"> [ ] ... [p03] <Reference URI="#AMadeUpTimeStamp" [p04] Type="http://www.w3.org/2000/09/xmldsig#SignatureProperties"> [p05] <Transforms> [p06] <Transform Algorithm="http://www.w3.org/2006/12/xml-c14n11"/> [p07] </Transforms>[p08] <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>[p08] <DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/> [p09] <DigestValue>dGhpcyBpcyBub3QgYSBzaWduYXR1cmUK...</DigestValue> [p10] </Reference> [p11] </SignedInfo> [p12] ... [p13] <Object> [p14] <SignatureProperties> [p15] <SignatureProperty Id="AMadeUpTimeStamp" Target="#MySecondSignature"> [p16] <timestamp xmlns="http://www.ietf.org/rfcXXXX.txt"> [p17] <date>19990914</date> [p18] <time>14:34:34:34</time> [p19] </timestamp> [p20] </SignatureProperty> [p21] </SignatureProperties> [p22] </Object> [p23]</Signature>
[p04]
The optional Type
attribute of
Reference
provides information about the resource
identified by the URI
. In particular, it can indicate
that it is an Object
, SignatureProperty
, or Manifest
element. This can be used by
applications to initiate special processing of some
Reference
elements. References to an XML data element
within an Object
element SHOULD should identify the
actual element pointed to. Where the element content is not XML
(perhaps it is binary or encoded data) the reference should
identify the Object
and the Reference
Type
, if given, SHOULD
should indicate Object
. Note
that Type
is advisory and no action based on it or
checking of its correctness is required by core behavior.
[p13]
Object
is an optional element
for including data objects within the signature element or
elsewhere. The Object
can be optionally typed and/or
encoded.
[p14-21]
Signature properties, such as time of
signing, can be optionally signed by identifying them from within a
Reference
. (These properties are traditionally called
signature "attributes" although that term has no relationship to
the XML term "attribute".)
Object
and Manifest
)The Manifest
element is provided to meet additional
requirements not directly addressed by the mandatory parts of this
specification. Two requirements and the way the
Manifest
satisfies them follow.
First, applications frequently need to efficiently sign multiple
data objects even where the signature operation itself is an
expensive public key signature. This requirement can be met by
including multiple Reference
elements within
SignedInfo
since the inclusion of each digest secures
the data digested. However, some applications may not want the
core
validation behavior associated with this approach because it
requires every Reference
within
SignedInfo
to undergo reference
validation -- the DigestValue
elements are
checked. These applications may wish to reserve reference
validation decision logic to themselves. For example, an
application might receive a signature valid SignedInfo
element that includes three Reference
elements. If a
single Reference
fails (the identified data object
when digested does not yield the specified DigestValue
) the signature would fail core validation . However, the application may wish
to treat the signature over the two valid Reference
elements as valid or take different actions depending on which
fails. To accomplish this, SignedInfo
would
reference a Manifest
element that contains one or more
Reference
elements (with the same structure as those
in SignedInfo
). Then, reference validation of the
Manifest
is under application control.
Second, consider an application where many signatures (using
different keys) are applied to a large number of documents. An
inefficient solution is to have a separate signature (per key)
repeatedly applied to a large SignedInfo
element (with
many Reference
s); this is wasteful and redundant. A
more efficient solution is to include many references in a single
Manifest
that is then referenced from multiple
Signature
elements.
The example below includes a Reference
that signs a
Manifest
found within the Object
element.
[ ] ... [m01] <Reference URI="#MyFirstManifest" [m02] Type="http://www.w3.org/2000/09/xmldsig#Manifest"> [m03] <Transforms> [m04] <Transform Algorithm="http://www.w3.org/2006/12/xml-c14n11"/> [m05] </Transforms>[m06] <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>[m06] <DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/> [m07] <DigestValue>dGhpcyBpcyBub3QgYSBzaWduYXR1cmUK...=</DigestValue> [m08] </Reference> [ ] ... [m09] <Object> [m10] <Manifest Id="MyFirstManifest"> [m11] <Reference> [m12] ... [m13] </Reference> [m14] <Reference> [m15] ... [m16] </Reference> [m17] </Manifest> [m18] </Object>
The sections below describe the operations to be performed as part of signature generation and validation.
The REQUIRED required steps
include the generation of Reference
elements and the
SignatureValue
over SignedInfo
.
For each data object being signed:
Transforms
, as determined by the
application, to the data object.Reference
element, including the
(optional) identification of the data object, any (optional)
transform elements, the digest algorithm and the
DigestValue
. (Note, it is the canonical form of these
references that are signed in 3.1.2 and validated in 3.2.1 .)Transform
elements is a node-set. We RECOMMEND that, when generating
signatures, signature applications do not rely on this default
behavior, but explicitly identify the transformation that is
applied to perform this mapping. In cases in which inclusive
canonicalization is desired, we RECOMMEND that Canonical XML 1.1 [
XML-C14N11 ] be used.SignedInfo
element with
SignatureMethod
, CanonicalizationMethod
and Reference
(s).SignatureValue
over SignedInfo
based on algorithms specified in
SignedInfo
.Signature
element that includes
SignedInfo
, Object
(s) (if desired,
encoding may be different than that used for signing),
KeyInfo
(if required), and SignatureValue
.
Note, if the Signature
includes same-document
references, [ XML XML10 ] or [ XML-schema XMLSCHEMA-1 ],
[ XMLSCHEMA-2 ] validation of the
document might introduce changes that break the signature.
Consequently, applications should be careful to consistently
process the document or refrain from using external contributions
(e.g., defaults and entities).
The REQUIRED required steps of
core validation
include (1) reference validation , the verification of the
digest contained in each Reference
in
SignedInfo
, and (2) the cryptographic signature
validation of the signature calculated over
SignedInfo
.
Note, there may be valid signatures that some signature applications are unable to validate. Reasons for this include failure to implement optional parts of this specification, inability or unwillingness to execute specified algorithms, or inability or unwillingness to dereference specified URIs (some URI schemes may cause undesirable side effects), etc.
Comparison of values each value in reference and signature validation
are is over
the numeric (e.g., integer) or decoded octet sequence of the value.
Different implementations may produce different encoded digest and
signature values when processing the same resources because of
variances in their encoding, such as accidental white space. But if
one uses numeric or octet comparison (choose one) on both the
stated and computed values these problems are eliminated.
SignedInfo
element based on the
CanonicalizationMethod
in SignedInfo
.Reference
in SignedInfo
:
URI
and
execute Transforms
provided by the signer in the
Reference
element, or it may obtain the content
through other means such as a local cache.)DigestMethod
specified in its Reference
specification.DigestValue
in the SignedInfo
Reference
; if there is any mismatch, validation
fails.Note, SignedInfo
is canonicalized in step 1. The
application must ensure that the
CanonicalizationMethod
has no dangerous side
affects, effects, such as rewriting URIs, (see
CanonicalizationMethod
Note (section 4.3)) 4.4.1)) and that
it Sees What is Signed , which is the
canonical form.
Note, After a Signature
element has
been created in Signature Generation for a signature with a same
document reference, an implementation can serialize the XML content
with variations in that serialization. This means that Reference
Validation needs to canonicalize the XML document before digesting
in step 1 to avoid issues related to variations in
serialization.
KeyInfo
or from an external source.SignatureMethod
using the CanonicalizationMethod
and use
the result (and previously obtained KeyInfo
) to
confirm the SignatureValue
over the
SignedInfo
element.Note, KeyInfo
(or some transformed version thereof) may
be signed via a Reference
element. Transformation and
validation of this reference (3.2.1) is orthogonal to Signature
Validation which uses the KeyInfo
as parsed.
Additionally, the SignatureMethod
URI may have been
altered by the canonicalization of SignedInfo
(e.g.,
absolutization of relative URIs) and it is the canonical form that
MUST must be used. However, the
required canonicalization [ XML-C14N ] of this
specification does not change URIs.
The general structure of an XML signature is described in
Signature Overview (section 2). This
section provides detailed syntax of the core signature features.
Features described in this section are mandatory to implement
unless otherwise indicated. The syntax is defined via DTDs and an [
XML-Schema XMLSCHEMA-1 ][ XMLSCHEMA-2 ] with the following XML
preamble, declaration, and internal entity.
Schema Definition: <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE schema PUBLIC "-//W3C//DTD XMLSchema 200102//EN" "http://www.w3.org/2001/XMLSchema.dtd"[ <!ATTLIST schema[ <!ATTLIST schema xmlns:ds CDATA #FIXED "http://www.w3.org/2000/09/xmldsig#"><!ENTITY dsig 'http://www.w3.org/2000/09/xmldsig#'><!ENTITY dsig 'http://www.w3.org/2000/09/xmldsig#'> <!ENTITY % p ''> <!ENTITY % s ''> ]> <schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" targetNamespace="http://www.w3.org/2000/09/xmldsig#" version="0.1" elementFormDefault="qualified">
Additional markup defined in version 1.1
of this specification uses the dsig11:
namespace.
The syntax is defined in an XML schema with the following
preamble:
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE schema PUBLIC "-//W3C//DTD XMLSchema 200102//EN" "http://www.w3.org/2001/XMLSchema.dtd" [ <!ENTITY dsig 'http://www.w3.org/2000/09/xmldsig#'> <!ENTITY dsig11 'http://www.w3.org/2009/xmldsig11#'> <!ENTITY % p ''> <!ENTITY % s ''> ]><!ENTITY % Object.ANY ''> <!ENTITY % Method.ANY ''> <!ENTITY % Transform.ANY ''> <!ENTITY % SignatureProperty.ANY ''> <!ENTITY % KeyInfo.ANY ''> <!ENTITY % KeyValue.ANY ''> <!ENTITY % PGPData.ANY ''> <!ENTITY % X509Data.ANY ''> <!ENTITY % SPKIData.ANY ''><schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:dsig11="http://www.w3.org/2009/xmldsig11#" targetNamespace="http://www.w3.org/2009/xmldsig11#" version="0.1" elementFormDefault="qualified">
ds:CryptoBinary
Simple TypeThis specification defines the ds:CryptoBinary
simple type for representing arbitrary-length integers (e.g.
"bignums") in XML as octet strings. The integer value is first
converted to a "big endian" bitstring. The bitstring is then padded
with leading zero bits so that the total number of bits == 0 mod 8
(so that there are an integral number of octets). If the bitstring
contains entire leading octets that are zero, these are removed (so
the high-order octet is always non-zero). This octet string is then
base64 [ MIME RFC2045 ] encoded. (The conversion from
integer to octet string is equivalent to IEEE 1363's I2OSP [
1363 IEEE1363 ] with minimal length).
This type is used by "bignum" values such as
RSAKeyValue
and DSAKeyValue
. If a value
can be of type base64Binary
or
ds:CryptoBinary
they are defined as base64Binary
. For example, if the
signature algorithm is RSA or DSA then SignatureValue
represents a bignum and could be ds:CryptoBinary
.
However, if HMAC-SHA1 is the signature algorithm then
SignatureValue
could have leading zero octets that
must be preserved. Thus SignatureValue
is generically
defined as of type base64Binary
.
Schema Definition: <simpleType name="CryptoBinary"> <restriction base="base64Binary"> </restriction> </simpleType>
Signature
elementThe Signature
element is the root element of an XML
Signature. Implementation MUST
must generate laxly
schema valid [ XML-schema
XMLSCHEMA-1 ][ XMLSCHEMA-2 ] Signature
elements as specified by the following schema:
Schema Definition: <element name="Signature" type="ds:SignatureType"/> <complexType name="SignatureType"> <sequence> <element ref="ds:SignedInfo"/> <element ref="ds:SignatureValue"/> <element ref="ds:KeyInfo" minOccurs="0"/> <element ref="ds:Object" minOccurs="0" maxOccurs="unbounded"/> </sequence> <attribute name="Id" type="ID" use="optional"/> </complexType>
SignatureValue
ElementThe SignatureValue
element contains the actual
value of the digital signature; it is always encoded using base64 [
MIME RFC2045 ]. While
we identify two SignatureMethod algorithms, one mandatory and one
optional to implement, user specified algorithms may be used as
well.
Schema Definition: <element name="SignatureValue" type="ds:SignatureValueType"/> <complexType name="SignatureValueType"> <simpleContent> <extension base="base64Binary"> <attribute name="Id" type="ID" use="optional"/> </extension> </simpleContent> </complexType>
SignedInfo
ElementThe structure of SignedInfo
includes the
canonicalization algorithm, a signature algorithm, and one or more
references. The SignedInfo
element may contain an
optional ID attribute that will allow it to be referenced by other
signatures and objects.
SignedInfo
does not include explicit signature or
digest properties (such as calculation time, cryptographic device
serial number, etc.). If an application needs to associate
properties with the signature or digest, it may include such
information in a SignatureProperties
element within an
Object
element.
Schema Definition: <element name="SignedInfo" type="ds:SignedInfoType"/> <complexType name="SignedInfoType"> <sequence> <element ref="ds:CanonicalizationMethod"/> <element ref="ds:SignatureMethod"/> <element ref="ds:Reference" maxOccurs="unbounded"/> </sequence> <attribute name="Id" type="ID" use="optional"/> </complexType>
CanonicalizationMethod
ElementCanonicalizationMethod
is a required element that
specifies the canonicalization algorithm applied to the
SignedInfo
element prior to performing signature
calculations. This element uses the general structure for
algorithms described in Algorithm
Identifiers and Implementation Requirements (section 6.1).
Implementations MUST must
support the REQUIRED required canonicalization algorithms .
Alternatives to the REQUIRED
required canonicalization algorithms (section 6.5), such as
Canonical XML with Comments (section
6.5.1) or a minimal canonicalization (such as CRLF and charset
normalization), normalization) , may be explicitly specified but
are NOT REQUIRED. not required
. Consequently, their use may not interoperate with other
applications that do not support the specified algorithm (see
XML Canonicalization and Syntax
Constraint Considerations , section 7). Security issues may
also arise in the treatment of entity processing and comments if
non-XML aware canonicalization algorithms are not properly
constrained (see section 8.2:
8.1.2: Only What is
"Seen" Should be Signed ).
The way in which the SignedInfo
element is
presented to the canonicalization method is dependent on that
method. The following applies to algorithms which process XML as
nodes or characters:
SignedInfo
and currently indicating the
SignedInfo
, its descendants, and the attribute and
namespace nodes of SignedInfo
and its descendant
elements.SignedInfo
element,
from the first character to the last character of the XML
representation, inclusive. This includes the entire text of the
start and end tags of the SignedInfo
element as well
as all descendant markup and character data (i.e., the text ) between those tags. Use of text based
canonicalization of SignedInfo
is We recommend applications that implement a text-based instead of
XML-based canonicalization -- such as resource constrained apps --
generate canonicalized XML as their output serialization so as to
mitigate interoperability and security concerns. For instance, such
an implementation SHOULD should
(at least) generate standalone XML
instances [ XML XML10 ].
NOTE Note : The signature application must
exercise great care in accepting and executing an arbitrary
CanonicalizationMethod
. For example, the
canonicalization method could rewrite the URIs of the
Reference
s being validated. Or, the method could
massively transform SignedInfo
so that validation
would always succeed (i.e., converting it to a trivial signature
with a known key over trivial data). Since
CanonicalizationMethod
is inside
SignedInfo
, in the resulting canonical form it could
erase itself from SignedInfo
or modify the
SignedInfo
element so that it appears that a different
canonicalization function was used! Thus a Signature
which appears to authenticate the desired data with the desired
key, DigestMethod
, and SignatureMethod
,
can be meaningless if a capricious
CanonicalizationMethod
is used.
Schema Definition: <element name="CanonicalizationMethod" type="ds:CanonicalizationMethodType"/> <complexType name="CanonicalizationMethodType" mixed="true"> <sequence> <any namespace="##any" minOccurs="0" maxOccurs="unbounded"/> <!-- (0,unbounded) elements from (1,1) namespace --> </sequence> <attribute name="Algorithm" type="anyURI" use="required"/> </complexType>
SignatureMethod
ElementSignatureMethod
is a required element that
specifies the algorithm used for signature generation and
validation. This algorithm identifies all cryptographic functions
involved in the signature operation (e.g. hashing, public key
algorithms, MACs, padding, etc.). This element uses the general
structure here for algorithms described in section 6.1: Algorithm Identifiers and Implementation
Requirements . While there is a single identifier, that
identifier may specify a format containing multiple distinct
signature values.
Schema Definition: <element name="SignatureMethod" type="ds:SignatureMethodType"/> <complexType name="SignatureMethodType" mixed="true"> <sequence> <element name="HMACOutputLength" minOccurs="0" type="ds:HMACOutputLengthType"/> <any namespace="##other" minOccurs="0" maxOccurs="unbounded"/> <!-- (0,unbounded) elements from (1,1) external namespace --> </sequence> <attribute name="Algorithm" type="anyURI" use="required"/> </complexType>
The ds:HMACOutputLength
parameter is used for HMAC [ <!ELEMENT SignatureMethod (#PCDATA|HMACOutputLength
%Method.ANY;)* > <!ATTLIST SignatureMethod Algorithm CDATA
#REQUIRED > 4.3.3 HMAC
] algorithms. The parameter specifies a truncation length in bits. If this
parameter is trusted without further verification, then this can
lead to a security bypass [ CVE-2009-0217 ].
Signatures must be deemed invalid
if the truncation length is below the larger of (a) half the
underlying hash algorithm's output length, and (b) 80 bits. Note
that some implementations are known to not accept truncation
lengths that are lower than the underlying hash algorithm's output
length.
Reference
ElementReference
is an element that may occur one or more
times. It specifies a digest algorithm and digest value, and
optionally an identifier of the object being signed, the type of
the object, and/or a list of transforms to be applied prior to
digesting. The identification (URI) and transforms describe how the
digested content (i.e., the input to the digest method) was
created. The Type
attribute facilitates the processing
of referenced data. For example, while this specification makes no
requirements over external data, an application may wish to signal
that the referent is a Manifest
. An optional ID
attribute permits a Reference
to be referenced from
elsewhere.
Schema Definition: <element name="Reference" type="ds:ReferenceType"/> <complexType name="ReferenceType"> <sequence> <element ref="ds:Transforms" minOccurs="0"/> <element ref="ds:DigestMethod"/> <element ref="ds:DigestValue"/> </sequence> <attribute name="Id" type="ID" use="optional"/> <attribute name="URI" type="anyURI" use="optional"/> <attribute name="Type" type="anyURI" use="optional"/> </complexType>
URI
AttributeThe URI
attribute identifies a data object using a
URI-Reference [ URI ].
The mapping from this attribute's value to a URI reference
MUST must be performed as
specified in section 3.2.17 of [ XMLSCHEMA
Datatypes, 2nd Edition XMLSCHEMA-2 ]. Additionally: Some
existing implementations are known to verify the value of the
URI
attribute against the grammar in [ URI ]. It is
therefore safest to perform any necessary escaping while generating
the URI
attribute.
We RECOMMEND XML signature
Signature applications be able to
dereference URIs in the HTTP scheme. Dereferencing a URI in the
HTTP scheme MUST must comply with the
Status
Code Definitions of [ HTTP
HTTP11 ]
(e.g., 302, 305 and 307 redirects are followed to obtain the
entity-body of a 200 status code response). Applications should
also be cognizant of the fact that protocol parameter and state
information, (such as HTTP cookies, HTML device profiles or content
negotiation), may affect the content yielded by dereferencing a
URI.
If a resource is identified by more than one URI, the most
specific should be used (e.g.
http://www.w3.org/2000/06/interop-pressrelease.html.en instead of
http://www.w3.org/2000/06/interop-pressrelease). (See the Reference Validation section (section 3.2.1) for a further information on reference
processing.)
If the URI
attribute is omitted altogether, the
receiving application is expected to know the identity of the
object. For example, a lightweight data protocol might omit this
attribute given the identity of the object is part of the
application context. This attribute may be omitted from at most one
Reference
in any particular SignedInfo
,
or Manifest
.
The optional Type attribute contains information about the type
of object being signed after all ds:Reference
transforms have been applied. This is represented as a URI. For
example:
Type= "http://www.w3.org/2000/09/xmldsig#Object"
Type= "http://www.w3.org/2000/09/xmldsig#Manifest"
The Type
attribute applies to the item being
pointed at, not its contents. For example, a reference that results
in the digesting of an Object
element containing a
SignatureProperties
element is still of type
#Object
. The type
Type
attribute is
advisory. No validation of the type information is required by this
specification.
Note : XPath is RECOMMENDED. recommended .
Signature applications need not conform to [ XPath XPATH ]
specification in order to conform to this specification. However,
the XPath data model, definitions (e.g., node-sets )
and syntax is used within this document in order to describe
functionality for those that want to process XML-as-XML (instead of
octets) as part of signature generation. For those that want to use
these features, a conformant [ XPath
XPATH ]
implementation is one way to implement these features, but it is
not required. Such applications could use a sufficiently functional
replacement to a node-set and implement only those XPath expression
behaviors REQUIRED required by this
specification. However, for simplicity we generally will use XPath
terminology without including this qualification on every point.
Requirements over "XPath node-sets" can include a node-set
functional equivalent. Requirements over XPath processing can
include application behaviors that are equivalent to the
corresponding XPath behavior.
The data-type of the result of URI dereferencing or subsequent Transforms is either an octet stream or an XPath node-set.
The Transforms
specified in this document are
defined with respect to the input they require. The following is
the default signature application behavior:
Users may specify alternative transforms that override these
defaults in transitions between transforms that expect different
inputs. The final octet stream contains the data octets being
secured. The digest algorithm specified by
DigestMethod
is then applied to these data octets,
resulting in the DigestValue
.
Note: The Reference Generation Model (section 3.1.1) includes further restrictions on the reliance upon defined default transformations when applications generate signatures.
In this specification, a 'same-document' reference is defined as a URI-Reference that consists of a hash sign ('#') followed by a fragment or alternatively consists of an empty URI [ URI ].
Unless the URI-Reference is such a 'same-document' reference ,
the result of dereferencing the URI-Reference MUST must be an octet stream. In particular, an
XML document identified by URI is not parsed by the signature
application unless the URI is a same-document reference or unless a
transform that requires XML parsing is applied. (See Transforms (section 4.3.3.1).) 4.4.3.4).)
When a fragment is preceded by an absolute or relative URI in
the URI-Reference, the meaning of the fragment is defined by the
resource's MIME type. type [ RFC2045
]. Even for XML documents, URI
dereferencing (including the fragment processing) might be done for
the signature application by a proxy. Therefore, reference
validation might fail if fragment processing is not performed in a
standard way (as defined in the following section for same-document
references). Consequently, we RECOMMEND in this case that the
URI
attribute not include fragment identifiers
and that such processing be specified as an additional XPath Transform .
or XPath Filter 2 Transform [
XMLDSIG-XPATH-FILTER2 ].
When a fragment is not preceded by a URI in the URI-Reference,
XML Signature applications MUST
must support the null URI and shortname
XPointer [ XPointer-Framework
XPTR-FRAMEWORK ]. We RECOMMEND support
for the same-document XPointers ' #xpointer(/)
' and '
#xpointer(id('ID'))
' if the application also intends
to support any canonicalization that preserves comments. (Otherwise
URI="#foo"
will automatically remove comments before
the canonicalization can even be invoked due to the processing
defined in Same-Document
URI-References (section 4.3.3.3).)
4.4.3.3).) All other support for
XPointers is OPTIONAL, optional , especially all support for
shortname and other XPointers in external resources since the
application may not have control over how the fragment is generated
(leading to interoperability problems and validation failures).
' #xpointer(/)
' MUST
must be interpreted to identify the root node
[ XPath XPATH ] of the document that contains
the URI
attribute.
' #xpointer(id(' ID '))
' MUST must be interpreted to identify the element
node identified by ' #element( ID )
' [
XPointer-Element XPTR-ELEMENT ] when evaluated with
respect to the document that contains the URI
attribute.
The original edition of this specification [ XMLDSIG-2002 XMLDSIG-CORE ] referenced the XPointer
Candidate Recommendation [ XPTR-2001
XPTR-XPOINTER-CR2001 ] and some
implementations support it optionally. That Candidate
Recommendation has been superseded by the [ XPointer-Framework XPTR-FRAMEWORK ], [ XPointer-xmlns XPTR-XMLNS ] and [ XPointer-Element XPTR-ELEMENT ] Recommendations, and --
at the time of this edition -- the [ XPointer-xpointer XPTR-XPOINTER ] Working Draft.
Therefore, the use of the xpointer()
scheme [
XPointer-xpointer XPTR-XPOINTER ] beyond the usage
discussed in this section is discouraged.
The following examples demonstrate what the URI attribute identifies and how it is dereferenced:
URI="http://example.com/bar.xml"
URI="http://example.com/bar.xml#chapter1"
URI=""
URI="#chapter1"
Dereferencing a same-document reference MUST must result in an XPath node-set suitable for
use by Canonical XML [ XML-C14N ]. Specifically,
dereferencing a null URI ( URI=""
) MUST must result in an XPath node-set that
includes every non-comment node of the XML document containing the
URI
attribute. In a fragment URI, the characters after
the number sign ('#') character conform to the XPointer syntax [
XPointer-Framework XPTR-FRAMEWORK ]. When processing an
XPointer, the application MUST
must behave as if the XPointer was evaluated
with respect to the XML document containing the URI
attribute . The application MUST
must behave as if the result of XPointer
processing [ XPointer-Framework
XPTR-FRAMEWORK ] were a node-set
derived from the resultant subresource as follows:
The second to last replacement is necessary because XPointer typically indicates a subtree of an XML document's parse tree using just the element node at the root of the subtree, whereas Canonical XML treats a node-set as a set of nodes in which absence of descendant nodes results in absence of their representative text from the canonical form.
The last step is performed for null URIs and shortname XPointers
. It is necessary because when [ XML-C14N ] or [
XML-C14N11 ] is passed a node-set, it
processes the node-set as is: with or without comments. Only when
it is called with an octet stream does it invoke its own XPath
expressions (default or without comments). Therefore to retain the
default behavior of stripping comments when passed a node-set, they
are removed in the last step if the URI is not a scheme-based
XPointer. To retain comments while selecting an element by an
identifier ID , use the following scheme-based XPointer:
URI='#xpointer(id(' ID '))'
. To retain
comments while selecting the entire document, use the following
scheme-based XPointer: URI='#xpointer(/)'
.
The interpretation of these XPointers is defined in The Reference Processing Model
(section 4.3.3.2). 4.4.3.2).
Transforms
ElementThe optional Transforms
element contains an ordered
list of Transform
elements; these describe how the
signer obtained the data object that was digested. The output of
each Transform
serves as input to the next
Transform
. The input to the first
Transform
is the result of dereferencing the
URI
attribute of the Reference
element.
The output from the last Transform
is the input for
the DigestMethod
algorithm. When transforms are
applied the signer is not signing the native (original) document
but the resulting (transformed) document. (See Only What is Signed is Secure (section
8.1).) 8.1.1).)
Each Transform
consists of an
Algorithm
attribute and content parameters, if any,
appropriate for the given algorithm. The Algorithm
attribute value specifies the name of the algorithm to be
performed, and the Transform
content provides
additional data to govern the algorithm's processing of the
transform input. (See Algorithm Identifiers
and Implementation Requirements (section 6).) 6.1).)
As described in The Reference Processing Model (section
4.3.3.2), 4.4.3.2), some transforms take an XPath node-set
as input, while others require an octet stream. If the actual input
matches the input needs of the transform, then the transform
operates on the unaltered input. If the transform input requirement
differs from the format of the actual input, then the input must be
converted.
Some Transform
s may require explicit MIME type,
charset (IANA registered "character set"), or other such
information concerning the data they are receiving from an earlier
Transform
or the source data, although no
Transform
algorithm specified in this document needs
such explicit information. Such data characteristics are provided
as parameters to the Transform
algorithm and should be
described in the specification for the algorithm.
Examples of transforms include but are not limited to base64
decoding [ MIME RFC2045 ], canonicalization [
XML-C14N ], XPath filtering [
XPath XPATH ], and XSLT [ XSLT ]. The
generic definition of the Transform
element also
allows application-specific transform algorithms. For example, the
transform could be a decompression routine given by a Java class
appearing as a base64 encoded parameter to a Java
Transform
algorithm. However, applications should
refrain from using application-specific transforms if they wish
their signatures to be verifiable outside of their application
domain. Transform Algorithms
(section 6.6) defines the list of standard transformations.
Schema Definition: <element name="Transforms" type="ds:TransformsType"/> <complexType name="TransformsType"> <sequence> <element ref="ds:Transform" maxOccurs="unbounded"/> </sequence> </complexType> <element name="Transform" type="ds:TransformType"/> <complexType name="TransformType" mixed="true"> <choice minOccurs="0" maxOccurs="unbounded"> <any namespace="##other" processContents="lax"/> <!-- (1,1) elements from (0,unbounded) namespaces --> <element name="XPath" type="string"/> </choice> <attribute name="Algorithm" type="anyURI" use="required"/> </complexType>
DigestMethod
ElementDigestMethod
is a required element that identifies
the digest algorithm to be applied to the signed object. This
element uses the general structure here for algorithms specified in
Algorithm Identifiers and
Implementation Requirements (section 6.1).
If the result of the URI dereference and application of
Transforms is an XPath node-set (or sufficiently functional
replacement implemented by the application) then it must be
converted as described in the Reference Processing Model
(section 4.3.3.2). 4.4.3.2). If the result of URI dereference and
application of transforms is an octet stream, then no conversion
occurs (comments might be present if the Canonical XML with
Comments was specified in the Transforms). The digest algorithm is
applied to the data octets of the resulting octet stream.
Schema Definition: <element name="DigestMethod" type="ds:DigestMethodType"/> <complexType name="DigestMethodType" mixed="true"> <sequence> <any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/> </sequence> <attribute name="Algorithm" type="anyURI" use="required"/> </complexType>
DigestValue
ElementDigestValue is an element that contains the encoded value of the
digest. The digest is always encoded using base64 [ MIME RFC2045
].
Schema Definition: <element name="DigestValue" type="ds:DigestValueType"/> <simpleType name="DigestValueType"> <restriction base="base64Binary"/> </simpleType>
KeyInfo
ElementKeyInfo
is an optional element that enables the
recipient(s) to obtain the key needed to validate the
signature. KeyInfo
may contain keys, names,
certificates and other public key management information, such as
in-band key distribution or key agreement data. This specification
defines a few simple types but applications may extend those types
or all together replace them with their own key identification and
exchange semantics using the XML namespace facility. facility [
XML-ns XML-NAMES ]
]. However, questions of trust of such
key information (e.g., its authenticity or strength) are out
of scope of this specification and left to the application.
If KeyInfo
is omitted, the recipient is expected to
be able to identify the key based on application context. Multiple
declarations within KeyInfo
refer to the same key.
While applications may define and use any mechanism they choose
through inclusion of elements from a different namespace, compliant
versions MUST must implement
KeyValue
(section
4.4.2) 4.5.2) and SHOULD
should implement RetrievalMethod
(section
4.4.3). 4.5.3).
The schema/DTD specifications
schema specification of many of
KeyInfo
's children (e.g., PGPData
,
SPKIData
, X509Data
) permit their
content to be extended/complemented with elements from another
namespace. This may be done only if it is safe to ignore these
extension elements while claiming support for the types defined in
this specification. Otherwise, external elements, including
alternative structures to those defined by this
specification, MUST must be a child of
KeyInfo
. For example, should a complete XML-PGP
standard be defined, its root element MUST must be a child of KeyInfo
. (Of
course, new structures from external namespaces can incorporate
elements from the
namespace via features of
the type definition language. For instance, they can create a
&dsig;
dsig:DTD that mixes their own and dsig qualified
elements, or a schema that permits, includes, imports, or
derives new types based on
elements.)&dsig; dsig:
The following list summarizes the KeyInfo
types
that are allocated an identifier in the
namespace; these can be used within
the &dsig; dsig:RetrievalMethod
Type
attribute to
describe a remote KeyInfo
structure.
The following list summarizes the
additional KeyInfo
types that are allocated an identifier in
the dsig11:
namespace.
In addition to the types above for which we define an XML structure, we specify one additional type to indicate a binary (ASN.1 DER) X.509 Certificate .
Schema Definition: <element name="KeyInfo" type="ds:KeyInfoType"/> <complexType name="KeyInfoType" mixed="true"> <choice maxOccurs="unbounded"> <element ref="ds:KeyName"/> <element ref="ds:KeyValue"/> <element ref="ds:RetrievalMethod"/> <element ref="ds:X509Data"/> <element ref="ds:PGPData"/> <element ref="ds:SPKIData"/> <element ref="ds:MgmtData"/> <!-- <element ref="dsig11:DEREncodedKeyValue"/> --> <!-- DEREncodedKeyValue (XMLDsig 1.1) will use the any element --> <!-- <element ref="dsig11:KeyInfoReference"/> --> <!-- KeyInfoReference (XMLDsig 1.1) will use the any element --> <!-- <element ref="xenc:EncryptedKey"/> --> <!-- EncryptedKey (XMLEnc) will use the any element --> <!-- <element ref="xenc:Agreement"/> --> <!-- Agreement (XMLEnc) will use the any element --> <any processContents="lax" namespace="##other"/> <!-- (1,1) elements from (0,unbounded) namespaces --> </choice> <attribute name="Id" type="ID" use="optional"/> </complexType>
KeyName
ElementThe KeyName
element contains a string value (in
which white space is significant) which may be used by the signer
to communicate a key identifier to the recipient. Typically,
KeyName
contains an identifier related to the key pair
used to sign the message, but it may contain other protocol-related
information that indirectly identifies a key pair. (Common uses of
KeyName
include simple string names for keys, a key
index, a distinguished name (DN), an email address, etc.)
Schema Definition: <element name="KeyName" type="string"/>
KeyValue
ElementThe KeyValue
element contains a single public key
that may be useful in validating the signature. Structured formats
for defining DSA (REQUIRED) and
( required ), RSA (RECOMMENDED)
( required ) and ECDSA ( required ) public keys are defined in Signature Algorithms (section
6.4). The KeyValue
element may include externally
defined public keys values represented as PCDATA or element types
from an external namespace.
Schema Definition: <element name="KeyValue" type="ds:KeyValueType"/> <complexType name="KeyValueType" mixed="true"> <choice> <element ref="ds:DSAKeyValue"/> <element ref="ds:RSAKeyValue"/> <!-- <element ref="dsig11:ECKeyValue"/> --> <!-- ECC keys (XMLDsig 1.1) will use the any element --> <any namespace="##other" processContents="lax"/> </choice> </complexType>
DSAKeyValue
ElementType=" http://www.w3.org/2000/09/xmldsig#DSAKeyValue
"
(this can be used within a
RetrievalMethod
or Reference
element to
identify the referent's type)DSA keys and the DSA signature algorithm are specified in
[DSS]. [
FIPS-186-3
]. DSA public key values can have the
following fields:
P
Q
G
Y
J
seed
pgenCounter
Parameter J
is available for inclusion solely for
efficiency as it is calculatable from P
and
Q. Q
. Parameters seed
and
pgenCounter
are used in the DSA prime number
generation algorithm specified in [DSS]. [
FIPS-186-3
]. As such, they are optional but must
either both be present or both be absent. This prime generation
algorithm is designed to provide assurance that a weak prime is not
being used and it yields a P
and Q
value.
Parameters P, Q, P
,Q
, and G
can be public and
common to a group of users. They might be known from application
context. As such, they are optional but P
and
Q
must either both appear or both be absent. If all of
P
, Q
, seed
, and
pgenCounter
are present, implementations are not
required to check if they are consistent and are free to use either
P
and Q
or seed
and
pgenCounter
. All parameters are encoded as base64 [
MIME RFC2045 ] values.
Arbitrary-length integers (e.g. "bignums" such as RSA moduli)
are represented in XML as octet strings as defined by the ds:CryptoBinary
type .
Schema Definition:
<element name="DSAKeyValue" type="ds:DSAKeyValueType"/>
<complexType name="DSAKeyValueType">
<sequence>
<sequence minOccurs="0">
<element name="P" type="ds:CryptoBinary"/>
<element name="Q" type="ds:CryptoBinary"/>
</sequence>
<element name="G" type="ds:CryptoBinary" minOccurs="0"/>
<element name="Y" type="ds:CryptoBinary"/>
<element name="J" type="ds:CryptoBinary" minOccurs="0"/>
<sequence minOccurs="0">
<element name="Seed" type="ds:CryptoBinary"/>
<element name="PgenCounter" type="ds:CryptoBinary"/>
</sequence>
</sequence>
</complexType>
RSAKeyValue
ElementType=" http://www.w3.org/2000/09/xmldsig#RSAKeyValue
"
(this can be used within a
RetrievalMethod
or Reference
element to
identify the referent's type)RSA key values have two fields: Modulus
and
Exponent. Exponent
.
<RSAKeyValue> <Modulus>xA7SEU+e0yQH5rm9kbCDN9o3aPIo7HbP7tX6WOocLZAtNfyxSZDU16ksL6W jubafOqNEpcwR3RdFsT7bCqnXPBe5ELh5u4VEy19MzxkXRgrMvavzyBpVRgBUwUlV 5foK5hhmbktQhyNdy/6LpQRhDUDsTvK+g9Ucj47es9AQJ3U= </Modulus> <Exponent>AQAB</Exponent> </RSAKeyValue>
Arbitrary-length integers (e.g. "bignums" such as RSA moduli)
are represented in XML as octet strings as defined by the ds:CryptoBinary
type .
Schema Definition:
<element name="RSAKeyValue" type="ds:RSAKeyValueType"/>
<complexType name="RSAKeyValueType">
<sequence>
<element name="Modulus" type="ds:CryptoBinary"/>
<element name="Exponent" type="ds:CryptoBinary"/>
</sequence>
</complexType>
ECKeyValue
ElementType=" http://www.w3.org/2009/xmldsig11#ECKeyValue
"
(this can be used within a
RetrievalMethod
or
Reference
element to identify the referent's type)The ECKeyValue
element is
defined in the http://www.w3.org/2009/xmldsig11#
namespace.
EC public key values consists of two sub
components: Domain parameters and PublicKey
.
<ECKeyValue xmlns="http://www.w3.org/2009/xmldsig11#"> <NamedCurve URI="urn:oid:1.2.840.10045.3.1.7" /> <PublicKey> vWccUP6Jp3pcaMCGIcAh3YOev4gaa2ukOANC7Ufg Cf8KDO7AtTOsGJK7/TA8IC3vZoCy9I5oPjRhyTBulBnj7Y </PublicKey> </ECKeyValue>
Note - A line break has been added to
the PublicKey
content to preserve printed page
width.
Domain parameters can be encoded
explicitly using the ECParameters
element
or by reference using the NamedCurve
element. A
named curve is specified through the URI
attribute. For
named curves that are identified by OIDs, such as those defined in
[ RFC3279
][ RFC4055 ], and
[ SECG1
], the OID should be encoded according to [ URN-OID ].
Conformant applications must support the NamedCurve
element
and the 256-bit prime field curve as identified by the OID
1.2.840.10045.3.1.7
.
The PublicKey
element
contains a Base64 encoding of a binary representation of the x and
y coordinates of the point. Its value is computed as
follows:
Schema Definition:
<!-- targetNamespace="http://www.w3.org/2009/xmldsig11#" -->
<element name="ECKeyValue" type="dsig11:ECKeyValueType"/>
<complexType name="ECKeyValueType">
<sequence>
<choice>
<element name="ECParameters" type="dsig11:ECParametersType"/>
<element name="NamedCurve" type="dsig11:NamedCurveType"/>
</choice>
<element name="PublicKey" type="dsig11:ECPointType"/>
</sequence>
<attribute name="Id" type="ID" use="optional"/>
</complexType>
<complexType name="NamedCurveType">
<attribute name="URI" type="anyURI" use="required"/>
</complexType>
<simpleType name="ECPointType">
<restriction base="ds:CryptoBinary"/>
</simpleType>
The ECParameters
element
consists of the following subelements. Note these definitions are
based on the those described in [ RFC3279 ].
FieldID
element
identifies the finite field over which the elliptic curve is
defined. Additional details on the structures for defining prime
and characteristic two fields is provided below.Curve
element
specifies the coefficients a and b of the elliptic curve E. Each
coefficient is first converted from a field element to an octet
string as specified in section 2.3.5 of [ SECG1 ], then the
resultant octet string is encoded in base64.Base
element
specifies the base point P on the elliptic curve. The base point is
represented as a value of type ECPointType
.Order
element
specifies the order n of the base point and is encoded as a
positiveInteger.Cofactor
element is
an optional element that specifies the integer h = #E(Fq)/n. The
cofactor is not required to support ECDSA, except in parameter
validation. The cofactor may be
included to support parameter validation for ECDSA keys. Parameter
validation is not required by this specification. The cofactor is
required in ECDH public key parameters.ValidationData
element is an optional element that specifies the hash
algorithm used to generate the elliptic curve E and the base point
G verifiably at random. It also specifies the seed that was used to
generate the curve and the base point. When verifiably random
curves and base points are used, they shall be generated as
described in Section 3.1.3 of [ SECG1 ].
Schema Definition:
<!-- targetNamespace="http://www.w3.org/2009/xmldsig11#" -->
<complexType name="ECParametersType">
<sequence>
<element name="FieldID" type="dsig11:FieldIDType"/>
<element name="Curve" type="dsig11:CurveType"/>
<element name="Base" type="dsig11:ECPointType"/>
<element name="Order" type="ds:CryptoBinary"/>
<element name="CoFactor" type="integer" minOccurs="0"/>
<element name="ValidationData" type="dsig11:ECValidationDataType" minOccurs="0"/>
</sequence>
</complexType>
<complexType name="FieldIDType">
<choice>
<element ref="dsig11:Prime"/>
<element ref="dsig11:TnB"/>
<element ref="dsig11:PnB"/>
<element ref="dsig11:GnB"/>
<any namespace="##other" processContents="lax"/>
</choice>
</complexType>
<complexType name="CurveType">
<sequence>
<element name="A" type="ds:CryptoBinary"/>
<element name="B" type="ds:CryptoBinary"/>
</sequence>
</complexType>
<complexType name="ECValidationDataType">
<sequence>
<element name="seed" type="ds:CryptoBinary"/>
</sequence>
<attribute name="hashAlgorithm" type="anyURI" use="required"/>
</complexType>
Prime fields are described by a single
subelement P
,which represents the field size in bits. It
is encoded as a positiveInteger.
Schema Definition:
<!-- targetNamespace="http://www.w3.org/2009/xmldsig11#" -->
<element name="Prime" type="dsig11:PrimeFieldParamsType"/>
<complexType name="PrimeFieldParamsType">
<sequence>
<element name="P" type="ds:CryptoBinary"/>
</sequence>
</complexType>
Structures are defined for three types of characteristic two fields: gaussian normal basis, pentanomial basis and trinomial basis.
Schema Definition:
<!-- targetNamespace="http://www.w3.org/2009/xmldsig11#" -->
<element name="GnB" type="dsig11:CharTwoFieldParamsType"/>
<complexType name="CharTwoFieldParamsType">
<sequence>
<element name="M" type="positiveInteger"/>
</sequence>
</complexType>
<element name="TnB" type="dsig11:TnBFieldParamsType"/>
<complexType name="TnBFieldParamsType">
<complexContent>
<extension base="dsig11:CharTwoFieldParamsType">
<sequence>
<element name="K" type="positiveInteger"/>
</sequence>
</extension>
</complexContent>
</complexType>
<element name="PnB" type="dsig11:PnBFieldParamsType"/>
<complexType name="PnBFieldParamsType">
<complexContent>
<extension base="dsig11:CharTwoFieldParamsType">
<sequence>
<element name="K1" type="positiveInteger"/>
<element name="K2" type="positiveInteger"/>
<element name="K3" type="positiveInteger"/>
</sequence>
</extension>
</complexContent>
</complexType>
Implementations that need to support the [ RFC4050 ] format for ECDSA keys can avoid known interoperability problems with that specification by adhering to the following profile:
ECDSAKeyValue
element against the [ RFC4050 ] schema.
XML schema validators may not support integer types with decimal
data exceeding 18 decimal digits. [ XMLSCHEMA-1 ][ XMLSCHEMA-2 ].NamedCurve
element.urn:oid:1.2.840.10045.3.1.7
.The following is an example of a
ECDSAKeyValue
element that meets the profile described in this
section.
<ECDSAKeyValue xmlns="http://www.w3.org/2001/04/xmldsig-more#"> <DomainParameters> <NamedCurve URN="urn:oid:1.2.840.10045.3.1.7" /> </DomainParameters> <PublicKey> <X Value="5851106065380174439324917904648283332 0204931884267326155134056258624064349885"> <Y Value="1024033521368277752409102672177795083 59028642524881540878079119895764161434936"> </PublicKey> </ECDSAKeyValue>
Note - A line break has been added to
the X
and Y
Value
attribute values to preserve printed page
width.
RetrievalMethod
ElementA RetrievalMethod
element within
KeyInfo
is used to convey a reference to
KeyInfo
information that is stored at another
location. For example, several signatures in a document might use a
key verified by an X.509v3 certificate chain appearing once in the
document or remotely outside the document; each signature's
KeyInfo
can reference this chain using a single
RetrievalMethod
element instead of including the
entire chain with a sequence of X509Certificate
elements.
RetrievalMethod
uses the same syntax and
dereferencing behavior as Reference
's URI (section 4.3.3.1) 4.4.3.1) and
The Reference Processing
Model (section 4.3.3.2) 4.4.3.2) except that there is are no
DigestMethod
or DigestValue
child
elements and presence of the URI
attribute is mandatory.
Type
is an optional identifier for the type of data
retrieved after all transforms have been applied. The result of
dereferencing a RetrievalMethod
Reference
for all KeyInfo
types defined by this
specification (section 4.4)
4.5) with a corresponding XML structure
is an XML element or document with that element as the root. The
rawX509Certificate
KeyInfo
(for which
there is no XML structure) returns a binary X509 certificate.
Note that when referencing one of the
defined KeyInfo
types within the same document, or some
remote documents, at least one Transform
is required
to turn an ID-based reference to a KeyInfo
element into
a child element located inside it. This is due to the lack of an
XML ID attribute on the defined KeyInfo
types. In
such cases, use of KeyInfoReference
is
encouraged instead, see section 4.5.10.
Schema Definition <element name="RetrievalMethod" type="ds:RetrievalMethodType"/> <complexType name="RetrievalMethodType"> <sequence> <element ref="ds:Transforms" minOccurs="0"/> </sequence> <attribute name="URI" type="anyURI"/> <attribute name="Type" type="anyURI" use="optional"/> </complexType>
Note: The schema for the URI
attribute of RetrievalMethod erroneously omitted the attribute:
use="required"
. However, this error only results in a more
lax schema which permits all valid The DTD is
correct.RetrievalMethod
elements. Because the existing schema is embedded in many
applications, which may include the schema in their signatures, the
schema has not been corrected to be more restrictive.
X509Data
ElementType=" http://www.w3.org/2000/09/xmldsig#X509Data
"RetrievalMethod
or
Reference
element to identify the referent's
type)An X509Data
element within KeyInfo
contains one or more identifiers of keys or X509 certificates (or
certificates' identifiers or a revocation list). The content of
X509Data
is: At
is at least one element, from the
following set of element types; any of these may appear together or
more than once iff (if and only if) each instance describes or is
related to the same certificate:
X509IssuerSerial
element, which contains an X.509
issuer distinguished name/serial number pair. The distinguished
name X509SubjectName
element, which contains an
X.509 subject distinguished name that X509SKI
element, which contains the base64
encoded plain (i.e. non-DER-encoded) value of a X509 V.3
SubjectKeyIdentifier X509Certificate
element, which contains a
base64-encoded [ X509CRL
element, which contains a base64-encoded
certificate revocation list (CRL) [ dsig11:X509Digest
element contains a base64-encoded digest of a
certificate. The digest algorithm URI is identified with a
required Algorithm
attribute. The input to the digest
must be the raw octets
that would be base64-encoded were the same certificate to appear in
the X509Certificate element.dsig11:OCSPResponse
element contains a base64-encoded OCSP response in DER
encoding. [ OCSP ].Any X509IssuerSerial
, X509SKI
,
and X509SubjectName
,
and dsig11:X509Digest
elements that appear
MUST must refer to the
certificate or certificates containing the validation key. All such
elements that refer to a particular individual certificate
MUST must be grouped inside a
single X509Data
element and if the certificate to
which they refer appears, it MUST
must also be in that X509Data
element.
Any X509IssuerSerial
, X509SKI
,
and X509SubjectName
,
and dsig11:X509Digest
elements that relate to
the same key but different certificates MUST must be grouped within a single
KeyInfo
but MAY may occur in
multiple X509Data
elements.
Note that if X509Data
child
elements are used to identify a trusted certificate (rather than
solely as an untrusted hint supplemented by validation by policy),
the complete set of such elements that are intended to identify a
certificate should be integrity
protected, typically by signing an entire X509Data
or
KeyInfo
element.
All certificates appearing in an X509Data
element
MUST must relate to the
validation key by either containing it or being part of a
certification chain that terminates in a certificate containing the
validation key.
No ordering is implied by the above constraints. The comments in the following instance demonstrate these constraints:
<KeyInfo> <X509Data> <!-- two pointers to certificate-A --> <X509IssuerSerial><X509IssuerName><span class= "tx">CN=TAMURA Kent, OU=TRL, O=IBM,<X509IssuerName>CN=TAMURA Kent, OU=TRL, O=IBM, L=Yamato-shi, ST=Kanagawa, C=JP</X509IssuerName> <X509SerialNumber>12345678</X509SerialNumber> </X509IssuerSerial> <X509SKI>31d97bd7</X509SKI> </X509Data> <X509Data><!-- single pointer to certificate-B --> <X509SubjectName>Subject of Certificate B</X509SubjectName> </X509Data> <X509Data> <!-- certificate chain --> <!--Signer cert, issuer CN=arbolCA,OU=FVT,O=IBM,C=US, serial 4--> <X509Certificate>MIICXTCCA..</X509Certificate> <!-- Intermediate cert subject CN=arbolCA,OU=FVT,O=IBM,C=US issuer CN=tootiseCA,OU=FVT,O=Bridgepoint,C=US --> <X509Certificate>MIICPzCCA...</X509Certificate> <!-- Root cert subject CN=tootiseCA,OU=FVT,O=Bridgepoint,C=US --> <X509Certificate>MIICSTCCA...</X509Certificate> </X509Data> </KeyInfo>
Note, there is no direct provision for a PKCS#7 encoded "bag" of
certificates or CRLs. However, a set of certificates and CRLs can
occur within an X509Data
element and multiple
X509Data
elements can occur in a KeyInfo
. Whenever multiple certificates occur in an X509Data
element, at least one such certificate must contain the public key
which verifies the signature.
While in principle many certificate
encodings are possible, it is recommended
that certificates appearing in an
X509Certificate
element be limited to an encoding of BER or
its DER subset, allowing that within the certificate other content
may be present. The use of other encodings may lead to
interoperability issues. In any case, XML Signature
implementations should not
alter or re-encode certificates, as doing so
could invalidate their signatures.
The X509IssuerSerial
element has been deprecated in favor of the
newly-introduced dsig11:X509Digest
element. The XML Schema type of the serial number was
defined to be an integer, and XML Schema validators may not support
integer types with decimal data exceeding 18 decimal digits [
4.4.4.1 XMLSCHEMA-2 ].
This has proven insufficient, because many Certificate Authorities
issue certificates with large, random serial numbers that exceed
this limit. As a result, deployments that do make use of this
element should take care if schema validation is involved. New
deployments should avoid use of the
element.
To encode a distinguished name ( X509IssuerSerial
,
X509SubjectName
, and KeyName
if
appropriate), the encoding rules in section 2 of RFC 4514 [
LDAP-DN ] SHOULD should be applied, except
that the character escaping rules in section 2.4 of RFC 4514 [
LDAP-DN ] MAY
may be augmented as follows:
Since a an XML document logically consists of characters,
not octets, the resulting Unicode string is finally encoded
according to the character encoding used for producing the physical
representation of the XML document.
Schema Definition <element name="X509Data" type="ds:X509DataType"/> <complexType name="X509DataType"> <sequence maxOccurs="unbounded"> <choice> <element name="X509IssuerSerial" type="ds:X509IssuerSerialType"/> <element name="X509SKI" type="base64Binary"/> <element name="X509SubjectName" type="string"/> <element name="X509Certificate" type="base64Binary"/> <element name="X509CRL" type="base64Binary"/> <!-- <element ref="dsig11:OCSPResponse"/> --> <!-- <element ref="dsig11:X509Digest"/> --> <!-- OCSPResponse and X509Digest elements (XMLDsig 1.1) will use the any element --> <any namespace="##other" processContents="lax"/> </choice> </sequence> </complexType> <complexType name="X509IssuerSerialType"> <sequence> <element name="X509IssuerName" type="string"/> <element name="X509SerialNumber" type="integer"/> </sequence> </complexType>DTD<!ELEMENT X509Data ((X509IssuerSerial | X509SKI | X509SubjectName | X509Certificate | X509CRL)+ %X509.ANY;)> <!ELEMENT X509IssuerSerial (X509IssuerName, X509SerialNumber) > <!ELEMENT X509IssuerName (#PCDATA) > <!ELEMENT X509SubjectName (#PCDATA) > <!ELEMENT X509SerialNumber (#PCDATA) > <!ELEMENT X509SKI (#PCDATA) > <!ELEMENT X509Certificate (#PCDATA) > <!ELEMENT X509CRL (#PCDATA) > <!-- Note, this DTD and schema permit to be empty; this is precluded by the text in <a href="#sec-KeyInfo" shape= "rect"> (section 4.4) which states<!-- Note, this schema permits X509Data to be empty; this is precluded by the text in KeyInfo Element (section 4.5) which states that at least one element from the dsig namespace should be present in the PGP, SPKI, and X509 structures. This is easily expressed for the other key types, but not for X509Data because of its rich structure. -->
<!-- targetNameSpace="http://www.w3.org/2009/xmldsig11#" --> <element name="OCSPResponse" type="base64Binary" /> <element name="X509Digest" type="dsig11:X509DigestType"/> <complexType name="X509DigestType"> <simpleContent> <extension base="base64Binary"> <attribute name="Algorithm" type="anyURI" use="required"/> </extension> </simpleContent> </complexType>
PGPData
ElementType=" http://www.w3.org/2000/09/xmldsig#PGPData
"RetrievalMethod
or
Reference
element to identify the referent's
type)The PGPData
element within KeyInfo
is
used to convey information related to PGP public key pairs and
signatures on such keys. The PGPKeyID
's value is a
base64Binary sequence containing a standard PGP public key
identifier as defined in [ PGP , ] section
11.2]. The PGPKeyPacket
contains a base64-encoded Key
Material Packet as defined in [ PGP , ] section
5.5]. These children element types can be complemented/extended by
siblings from an external namespace within PGPData
,
or PGPData
can be replaced all together with an
alternative PGP XML structure as a child of KeyInfo
.
PGPData
must contain one PGPKeyID
and/or
one PGPKeyPacket
and 0 or more elements from an
external namespace.
Schema Definition: <element name="PGPData" type="ds:PGPDataType"/> <complexType name="PGPDataType"> <choice> <sequence> <element name="PGPKeyID" type="base64Binary"/> <element name="PGPKeyPacket" type="base64Binary" minOccurs="0"/> <any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/> </sequence> <sequence> <element name="PGPKeyPacket" type="base64Binary"/> <any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/> </sequence> </choice> </complexType>
SPKIData
ElementType=" http://www.w3.org/2000/09/xmldsig#SPKIData
"RetrievalMethod
or
Reference
element to identify the referent's
type)The SPKIData
element within KeyInfo
is
used to convey information related to SPKI public key pairs,
certificates and other SPKI data. SPKISexp
is the
base64 encoding of a SPKI canonical S-expression.
SPKIData
must have at least one SPKISexp
; SPKISexp
can be complemented/extended by siblings
from an external namespace within SPKIData
, or
SPKIData
can be entirely replaced with an alternative
SPKI XML structure as a child of KeyInfo
.
Schema Definition: <element name="SPKIData" type="ds:SPKIDataType"/> <complexType name="SPKIDataType"> <sequence maxOccurs="unbounded"> <element name="SPKISexp" type="base64Binary"/> <any namespace="##other" processContents="lax" minOccurs="0"/> </sequence> </complexType>
MgmtData
ElementType=" http://www.w3.org/2000/09/xmldsig#MgmtData
"RetrievalMethod
or
Reference
element to identify the referent's
type)MgmtData
element within KeyInfo
is a
string value used to convey in-band key distribution or agreement
data. KeyInfo
types for
conveying key Schema Definition: <element name="MgmtData" type="string"/>
EncryptedKey
and DerivedKey
Elements<xenc:EncryptedKey>
and <xenc:DerivedKey>
elements defined in [ XMLENC-CORE1 ] as
children of ds:KeyInfo
can be
used to convey in-band encrypted or xenc:DerivedKey
>
element may be present when the key used in calculating a Message
Authentication Code is derived from a shared secret.DEREncodedKeyValue
ElementType=" http://www.w3.org/2009/xmldsig11#DEREncodedKeyValue
"
(this can be KeyInfo RetrievalMethod
or Reference
element to
identify the referent's type)The public key algorithm and value are DER-encoded in accordance with the value that would be used in the Subject Public Key Info field of an X.509 certificate, per section 4.1.2.7 of [ RFC5280 ]. The DER-encoded value is then base64-encoded.
For the key value types supported in this
specification, refer to the following for normative references on the transmission format of
encrypted keys Subject Public Key Info and the relevant OID values that identify the key/algorithm
type:
Specifications that define additional key
types should provide such a normative reference for
their own key agreement types where
possible.
Schema Definition: <!-- targetNamespace="http://www.w3.org/2009/xmldsig11#" --> <element name="DEREncodedKeyValue" type="dsig11:DEREncodedKeyValueType"/> <complexType name="DEREncodedKeyValueType"> <simpleContent> <extension base="base64Binary"> <attribute name="Id" type="ID" use="optional"/> </extension> </simpleContent> </complexType>
Historical note: The
DEREncodedKeyValue
element was added to XML Signature 1.1 in
order to support certain interoperability scenarios where at least
one of signer and/or verifier are being
specified by not able to serialize keys
in the W3C XML Encryption Working Group and they should
formats described in Section 4.5.2 above.
The KeyValue
element is to be used instead for "bare" XML key
representations (not XML wrappings around other binary encodings
like ASN.1 DER); for this reason the DEREncodedKeyValue
element is not a child of
. The
MgmtData KeyValueDEREncodedKeyValue
element is also not a child of the
X509Data
element, as the keys represented by
DEREncodedKeyValue
may not have X.509 certificates associated
with them (a requirement for X509Data
).
KeyInfoReference
ElementA KeyInfoReference
element within KeyInfo
is used to
convey a reference to a KeyInfo
element at
another location in the same or different document. For example,
several signatures in a document might use a key verified by an
X.509v3 certificate chain appearing once in the document or
remotely outside the document; each signature's
KeyInfo
can reference this chain using a single
KeyInfoReference
element instead of including the entire chain
with a sequence of X509Certificate
elements repeated in multiple places.
KeyInfoReference
uses the same syntax and dereferencing
behavior as Reference
's
URI
(section 4.4.3.1) and the Reference Processing Model
(section 4.4.3.2) except that there are no child elements and the
presence of the URI
attribute is mandatory.
The result of dereferencing a
KeyInfoReference
must be a
KeyInfo
element, or an XML document with a
KeyInfo
element as the root.
Note: The KeyInfoReference
element is a desirable alternative to the use of
RetrievalMethod
when the data being referred to is a
KeyInfo
element and the use of RetrievalMethod
would
require one or more Transform
child
elements, which introduce security risk and implementation
challenges.
Schema Definition<!ELEMENT MgmtData (#PCDATA)><!-- targetNamespace="http://www.w3.org/2009/xmldsig11#" --> <element name="KeyInfoReference" type="dsig11:KeyInfoReferenceType"/> <complexType name="KeyInfoReferenceType"> <attribute name="URI" type="anyURI" use="required"/> <attribute name="Id" type="ID" use="optional"/> </complexType>
Object
ElementType= "http://www.w3.org/2000/09/xmldsig#Object"
(this can be used within a Reference
element to identify the referent's type)Object
is an optional element that may occur one or
more times. When present, this element may contain any data. The
Object
element may include optional MIME type, ID, and
encoding attributes.
The Object
's Encoding
attributed may
be used to provide a URI that identifies the method by which the
object is encoded (e.g., a binary file).
The MimeType
attribute is an optional attribute
which describes the data within the Object
(independent of its encoding). This is a string with values defined
by [ MIME RFC2045 ]. For example, if the
Object
contains base64 encoded PNG , the
Encoding
may be specified as
'http://www.w3.org/2000/09/xmldsig#base64' and the
MimeType
as 'image/png'. This attribute is purely
advisory; no validation of the MimeType
information is
required by this specification. Applications which require
normative type and encoding information for signature validation
should specify Transforms
with well defined resulting types
and/or encodings.
The Object
's Id
is commonly
referenced from a Reference
in SignedInfo
, or Manifest
. This element is typically used for
enveloping
signatures where the object being signed is to be included in
the signature element. The digest is calculated over the entire
Object
element including start and end tags.
Note, if the application wishes to exclude the
<Object>
tags from the digest calculation the
Reference
must identify the actual data object (easy
for XML documents) or a transform must be used to remove the
Object
tags (likely where the data object is non-XML).
Exclusion of the object tags may be desired for cases where one
wants the signature to remain valid if the data object is moved
from inside a signature to outside the signature (or vice versa),
or where the content of the Object
is an encoding of
an original binary document and it is desired to extract and decode
so as to sign the original bitwise representation.
Schema Definition: <element name="Object" type="ds:ObjectType"/> <complexType name="ObjectType" mixed="true"> <sequence minOccurs="0" maxOccurs="unbounded"> <any namespace="##any" processContents="lax"/> </sequence> <attribute name="Id" type="ID" use="optional"/> <attribute name="MimeType" type="string" use="optional"/> <attribute name="Encoding" type="anyURI" use="optional"/> </complexType>
This section describes the optional to implement
Manifest
and SignatureProperties
elements
and describes the handling of XML processing instructions and
comments. With respect to the elements Manifest
and
SignatureProperties
this section specifies syntax and
little behavior -- it is left to the application. These elements
can appear anywhere the parent's content model permits; the
Signature
content model only permits them within
Object
.
Manifest
ElementType= "http://www.w3.org/2000/09/xmldsig#Manifest"
(this can be used within a Reference
element to
identify the referent's type)The Manifest
element provides a list of
Reference
s. The difference from the list in
SignedInfo
is that it is application defined which, if
any, of the digests are actually checked against the objects
referenced and what to do if the object is inaccessible or the
digest compare fails. If a Manifest
is pointed to from
SignedInfo
, the digest over the Manifest
itself will be checked by the core signature validation behavior.
The digests within such a Manifest
are checked at the
application's discretion. If a Manifest
is referenced
from another Manifest
, even the overall digest of
this two level deep Manifest
might not be checked.
Schema Definition: <element name="Manifest" type="ds:ManifestType"/> <complexType name="ManifestType"> <sequence> <element ref="ds:Reference" maxOccurs="unbounded"/> </sequence> <attribute name="Id" type="ID" use="optional"/> </complexType>
SignatureProperties
ElementType=" http://www.w3.org/2000/09/xmldsig#SignatureProperties
"
(this can be used within a Reference
element to identify the referent's type)Additional information items concerning the generation of the
signature(s) can be placed in a SignatureProperty
element (i.e., date/time stamp or the serial number of
cryptographic hardware used in signature generation).
Schema Definition: <element name="SignatureProperties" type="ds:SignaturePropertiesType"/> <complexType name="SignaturePropertiesType"> <sequence> <element ref="ds:SignatureProperty" maxOccurs="unbounded"/> </sequence> <attribute name="Id" type="ID" use="optional"/> </complexType> <element name="SignatureProperty" type="ds:SignaturePropertyType"/> <complexType name="SignaturePropertyType" mixed="true"> <choice maxOccurs="unbounded"> <any namespace="##other" processContents="lax"/> <!-- (1,1) elements from (1,unbounded) namespaces --> </choice> <attribute name="Target" type="anyURI" use="required"/> <attribute name="Id" type="ID" use="optional"/> </complexType>
No XML processing instructions (PIs) are used by this specification.
Note that PIs placed inside SignedInfo
by an
application will be signed unless the
CanonicalizationMethod
algorithm discards them. (This
is true for any signed XML content.) All of the
CanonicalizationMethod
s identified within this
specification retain PIs. When a PI is part of content that is
signed (e.g., within SignedInfo
or referenced XML
documents) any change to the PI will obviously result in a
signature failure.
XML comments are not used by this specification.
Note that unless CanonicalizationMethod
removes
comments within SignedInfo
or any other referenced XML
(which [ XML-C14N ] does), they will be signed.
Consequently, if they are retained, a change to the comment will
cause a signature failure. Similarly, the XML signature over any
XML data will be sensitive to comment changes unless a
comment-ignoring canonicalization/transform method, such as the
Canonical XML [ XML-C14N ], is specified.
This section identifies algorithms used with the XML digital
signature specification. Entries contain the identifier to be used
in Signature
elements, a reference to the formal
specification, and definitions, where applicable, for the
representation of keys and the results of cryptographic
operations.
ECDSAwithSHA256
marked as "at risk". If issues about deployment of this
feature are raised during Candidate Recommendation, the group may
elect to make this feature optional.Algorithms are identified by URIs that appear as an attribute to
the element that identifies the algorithms' role (
DigestMethod
, Transform
,
SignatureMethod
, or
CanonicalizationMethod
). All algorithms used herein
take parameters but in many cases the parameters are implicit. For
example, a SignatureMethod
is implicitly given two
parameters: the keying info and the output of
CanonicalizationMethod
. Explicit additional
parameters to an algorithm appear as content elements within the
algorithm role element. Such parameter elements have a descriptive
element name, which is frequently algorithm specific, and
MUST must be in the XML
Signature namespace or an algorithm specific namespace.
This specification defines a set of algorithms, their URIs, and requirements for implementation. Requirements are specified over implementation, not over requirements for signature use. Furthermore, the mechanism is extensible; alternative algorithms may be used by signature applications.
* The Enveloped Signature transform removes the
Signature
element from the calculation of the
signature when the signature is within the content that it is being
signed. This MAY may be implemented via
the RECOMMENDED XPath specification
specified in 6.6.4: Enveloped
Signature Transform ; it MUST
must have the same effect as that specified
by the XPath Transform . Transform.
When using transforms, we RECOMMEND selecting the least expressive choice that still accomplishes the needs of the use case at hand: Use of XPath filter 2.0 is recommended over use of XPath filter. Use of XPath filter is recommended over use of XSLT.
Note: Implementation requirements for the XPath transform may be downgraded to optional in a future version of this specification.
Only one digest algorithm is defined
herein. However, it is expected that one or more additional
strong This specification defines
several possible digest algorithms will
be developed in connection with for the US Advanced
Encryption Standard effort. DigestMethod element, including required algorithm
SHA-256. Use of MD5 [ MD5 ]
SHA-256 is NOT
RECOMMENDED strongly recommended over
SHA-1 because recent advances in cryptanalysis (see e.g. [ SHA-1-Analysis ]) have cast doubt on its
strength. the long-term collision
resistance of SHA-1. Therefore, SHA-1 support is required in this
specification only for backwards-compatibility reasons.
Digest algorithms that are known not to be collision resistant should not be used in DigestMethod elements. For example, the MD5 message digest algorithm should not be used as specific collisions have been demonstrated for that algorithm.
Note: Use of SHA-256 is strongly recommended over SHA-1 because recent advances in cryptanalysis (see e.g. [ SHA-1-Analysis ], [ SHA-1-Collisions ] ) have cast doubt on the long-term collision resistance of SHA-1.
The
SHA-1 algorithm [ SHA-1
FIPS-186-3
] takes no explicit parameters. An example of an SHA-1 DigestAlg
element is:
<DigestMethod Algorithm="
http://www.w3.org/2000/09/xmldsig#sha1"/>
A SHA-1 digest is a 160-bit string. The content of the DigestValue element shall be the base64 encoding of this bit string viewed as a 20-octet octet stream. For example, the DigestValue element for the message digest:
A9993E36 4706816A BA3E2571 7850C26C 9CD0D89D
from Appendix A of the SHA-1 standard would be:
<DigestValue>qZk+NkcGgWq6PiVxeFDCbJzQ2J0=</DigestValue>
The SHA-256 algorithm [ FIPS-180-3 ] takes no explicit parameters. A SHA-256 digest is a 256-bit string. The content of the DigestValue element shall be the base64 encoding of this bit string viewed as a 32-octet octet stream.
The SHA-384 algorithm [ FIPS-180-3 ] takes no explicit parameters. A SHA-384 digest is a 384-bit string. The content of the DigestValue element shall be the base64 encoding of this bit string viewed as a 48-octet octet stream.
The SHA-512 algorithm [ FIPS-180-3 ] takes no explicit parameters. A SHA-512 digest is a 512-bit string. The content of the DigestValue element shall be the base64 encoding of this bit string viewed as a 64-octet octet stream.
MAC algorithms take two implicit parameters, their keying
material determined from KeyInfo
and the octet stream
output by CanonicalizationMethod
. MACs and signature
algorithms are syntactically identical but a MAC implies a shared
secret key.
The HMAC
algorithm (RFC2104 [ HMAC ]) takes the truncation output
(truncation) length in bits as a parameter; if this specification
REQUIRES that the truncation length be a multiple of 8 (i.e. fall
on a byte boundary) because Base64 encoding operates on full
bytes. If the truncation
parameter is not specified then all the bits of the hash are
output. Any signature with a truncation
length that is less than half the output length of the underlying
hash algorithm must be deemed
invalid. An example of an HMAC SignatureMethod
element:
<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1"> <HMACOutputLength>128</HMACOutputLength> </SignatureMethod>
The output of the HMAC algorithm is ultimately the output
(possibly truncated) of the chosen digest algorithm. This value
shall be base64 encoded in the same straightforward fashion as the
output of the digest algorithms. Example: the
SignatureValue
element for the HMAC-SHA1 digest
9294727A 3638BB1C 13F48EF8 158BFC9D
from the test vectors in [ HMAC ] would be
<SignatureValue>kpRyejY4uxwT9I74FYv8nQ==</SignatureValue>
Schema Definition: <simpleType name="HMACOutputLengthType"> <restriction base="integer"/> </simpleType>
Signature algorithms take two implicit parameters, their keying
material determined from KeyInfo
and the octet stream
output by CanonicalizationMethod
. Signature and MAC
algorithms are syntactically identical but a signature implies
public key cryptography.
The DSA algorithm family of algorithms is defined in FIPS 186-3 [
DSS FIPS-186-3 ] ]. FIPS 186-3
defines DSA in terms of two security parameters L and N where L =
|p|, N = |q|, p is the prime modulus, q is a prime divisor of
(p-1). FIPS 186-3 defines four valid pairs of (L, N); they
are: (1024, 160), (2048, 224), (2048, 256) and (3072, 256).
The pair (1024, 160) corresponds to the algorithm DSAwithSHA1,
which is identified in this specification by the URI http://www.w3.org/2000/09/xmldsig#dsa-sha1
. The pairs (2048, 256) and (3072, 256)
correspond to the algorithm DSAwithSHA256, which is identified in
this specification by the URI http://www.w3.org/2009/xmldsig11#dsa-sha256
. This specification does not use the
(2048, 224) instance of DSA (which corresponds to
DSAwithSHA224).
DSA takes no explicit
parameters. An parameters; an example of a DSA
SignatureMethod
element is:
<SignatureMethod Algorithm="http://www.w3.org/2009/xmldsig11#dsa-sha256"/>
The output of the DSA algorithm consists of a pair of integers
usually referred by 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. Integer to octet-stream conversion must be
done according to the I2OSP operation defined in the RFC 2437 3447 [
PKCS1 ] specification with a l
parameter equal to 20. For example, the SignatureValue
element for a DSA signature ( r
, s
)
with values specified in hexadecimal:
r = 8BAC1AB6 6410435C B7181F95 B16AB97C 92B341C0
s = 41E2345F 1F56DF24 58F426D1 55B4BA2D B6DCD8C8
from the example in Appendix 5 of the DSS standard would be
<SignatureValue>
i6watmQQQ1y3GB+VsWq5fJKzQcBB4jRfH1bfJFj0JtFVtLotttzYyA==</SignatureValue>
Per FIPS 186-3 [ FIPS-186-3 ], the DSA security parameter L is defined to be 1024, 2048 or 3072 bits and the corresponding DSA q value is defined to be 160, 224/256 and 256 bits respectively. Special Publication SP 800-57 Part 1 [ SP800-57 ], NIST recommends using at least at 2048-bit public keys for securing information beyond 2010 (and 3072-bit keys for securing information beyond 2030).
Since XML Signature 1.0 requires implementations to support DSA-based digital signatures, this XML Signature 1.1 revision REQUIRES signature verifiers to implement DSA only for keys of 1024 bits in order to guarantee interoperability with XML Signature 1.0 generators. XML Signature 1.1 implementations may but are not required to support DSA-based signature generation, and given the short key size and the SP800-57 guidelines, DSA with 1024-bit prime moduli should not be used for signatures that will be verified beyond 2010.
The expression "RSA algorithm" as used in this specification
refers to the RSASSA-PKCS1-v1_5 algorithm described in RFC 2437 3447 [
PKCS1 ]. The RSA algorithm takes no
explicit parameters. An example of an RSA SignatureMethod element
is:
<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
The SignatureValue
content for an RSA signature is
the base64 [ MIME RFC2045 ] encoding of the octet string
computed as per RFC
2437 3447 [ PKCS1 , ],
section 8.1.1: 8.2.1: Signature generation for the
RSASSA-PKCS1-v1_5 signature scheme]. As
specified in the EMSA-PKCS1-V1_5-ENCODE function RFC 2437 [ PKCS1 ,
section 9.2.1], the value input to Computation of the signature function MUST contain a pre-pended algorithm object
identifier for will require
concatenation of the hash function, but
the availability value and a constant
string determined by RFC 3447. Signature computation and
verification does not require implementation of an ASN.1
parser and recognition of OIDs
parser.
The resulting base64 [
RFC2045
] string is not
required the value of a signature verifier. The PKCS#1 v1.5 representation
appears as: the child text node of the
SignatureValue element, e.g.
<SignatureValue> IWijxQjUrcXBYoCei4QxjWo9Kg8D3p9tlWoT4t0/gyTE96639In0FZFY2/rvP+/bMJ01EArmKZsR5VW3rwoPxw= </SignatureValue>
Note In
Special Publication SP 800-57 Part 1 [ SP800-57 ], NIST
recommends using at least 2048-bit public keys for securing
information beyond 2010 (and 3072-bit keys for securing information
beyond 2030). All conforming implementations of XML Signature
1.1 must support RSA
signature generation and verification with public keys at least
2048 bits in length. RSA public keys of 1024 bits or less
should
not be used for signatures
that the padded ASN.1 will be
verified beyond 2010. XML Signature 1.1
implementations should use at least 2048-bit keys for all signatures, and
should use at least
3072-bit keys for signatures that will be verified beyond
2030.
The ECDSA algorithm [
FIPS-186-3
] takes no explicit parameters. An
example of the following form:
a ECDSA SignatureMethod
element is:
<SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256"/>
where "|" is concatenation, "01", "FF",
and "00" are fixed octets The
output of the corresponding hexadecimal
value, "hash" is ECDSA algorithm
consists of a pair of integers usually referred by the
SHA1 digest pair
(r, s). The signature value consists of the data, and "prefix" is base64
encoding of the ASN.1 BER SHA1
algorithm designator prefix required concatenation of two octet-streams that respectively
result from the octet-encoding of the values r and s in
PKCS1 [RFC 2437], that is, hex 30 21 30 09 06 05 2B 0E 03 02 1A 05 00 04 14
This prefix is included to make it easier order. Integer to use
standard cryptographic libraries. The FF octet MUST
octet-stream conversion must be
repeated done
according to the maximum number
I2OSP operation defined in the RFC
3447 [ PKCS1 ]
specification with the l
parameter equal to
the size of times such that the
value base point
order of the quantity being CRYPTed is
one octet shorter than curve in bytes
(e.g. 32 for the RSA modulus.
P-256 curve and 66 for the P-521
curve).
The resulting base64 This specification REQUIRES implementations to support
the ECDSAwithSHA256 signature algorithm, which is ECDSA over the
P-256 prime curve specified in Section D.2.3 of FIPS 186-3 [
MIME FIPS-186-3 ] string is (and using
the value of SHA-256 hash algorithm). It is further recommended that
implementations also support ECDSA over the child text node P-384 and
P-521 prime curves; these curves are defined in Sections D.2.4 and
D.2.5 of the SignatureValue element,
e.g. FIPS 186-3,
respectively.
If canonicalization is performed over octets, the
canonicalization algorithms take two implicit parameters: the
content and its charset. The charset is derived according to the
rules of the transport protocols and media types (e.g, RFC2376 [ XML-MT
XML-MEDIA-TYPES ] defines the media
types for XML). This information is necessary to correctly sign and
verify documents and often requires careful server side
configuration.
Various canonicalization algorithms require conversion to [
UTF-8 ].The
]. The algorithms below understand at
least [ UTF-8 ] and [ UTF-16 ] as input
encodings. We RECOMMEND that externally specified algorithms do the
same. Knowledge of other encodings is OPTIONAL. optional .
Various canonicalization algorithms transcode from a non-Unicode
encoding to Unicode. The output of these algorithms will be in NFC
[ NFC
, NFC-Corrigendum ]. This is
because the XML processor used to prepare the XPath data model
input is required (by the Data Model) to use Normalization Form C
when converting an XML document to the UCS character domain from
any encoding that is not UCS-based.
We RECOMMEND that externally specified canonicalization
algorithms do the same. (Note, there can be ambiguities in
converting existing charsets to Unicode, for an example see the XML
Japanese Profile Note [ XML-Japanese ]
Note.) ].)
This specification REQUIRES implementation of both Canonical XML 1.0 [ XML-C14N ] and ],
Canonical XML 1.1 [ XML-C14N11 ]]
and Exclusive XML Canonicalization [ XML-EXC-C14N ]. We RECOMMEND that
applications that generate signatures choose Canonical XML 1.1 [
XML-C14N11 ] when inclusive
canonicalization is desired.
Note : Canonical XML 1.0 [ XML-C14N ] and
Canonical XML 1.1 [ XML-C14N11 ] specify a standard
serialization of XML that, when applied to a subdocument, includes
the subdocument's ancestor context including all of the namespace
declarations and some attributes in the 'xml:' namespace. However,
some applications require a method which, to the extent practical,
excludes unused ancestor context from a canonicalized subdocument.
The Exclusive XML Canonicalization Recommendation [ XML-exc-C14N XML-EXC-C14N ] may be used to address
requirements resulting from scenarios where a subdocument is moved
between contexts.
An example of an XML canonicalization element is:
<CanonicalizationMethod Algorithm="
http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
The normative specification of Canonical XML1.0 is [ XML-C14N ]. The algorithm is capable of taking as input either an octet stream or an XPath node-set (or sufficiently functional alternative). The algorithm produces an octet stream as output. Canonical XML is easily parameterized (via an additional URI) to omit or retain comments.
The normative specification of Canonical XML 1.1 is [ XML-C14N11 ]. The algorithm is capable of taking as input either an octet stream or an XPath node-set (or sufficiently functional alternative). The algorithm produces an octet stream as output. Canonical XML 1.1 is easily parameterized (via an additional URI) to omit or retain comments.
The normative specification of Exclusive XML Canonicalization 1.0 is [XML-EXC-C14N]].
Transform
AlgorithmsA Transform
algorithm has a single implicit
parameter: an octet stream from the Reference
or the
output of an earlier Transform
.
For implementation requirements, please
see Algorithm
Identifiers and Implementation Requirements . Application
developers are strongly encouraged to support all transforms
that are listed in this section as RECOMMENDED recommended unless
the application environment has resource constraints that would
make such support impractical. Compliance with this recommendation
will maximize application interoperability and libraries should be
available to enable support of these transforms in applications
without extensive development.
Any canonicalization algorithm that can be used for
CanonicalizationMethod
(such as those in
Canonicalization Algorithms (section
6.5)) can be used as a Transform
.
The normative specification for base64 decoding transforms is [
MIME RFC2045 ]. The base64
Transform
element has no content. The input is decoded
by the algorithms. This transform is useful if an application needs
to sign the raw data associated with the encoded content of an
element.
This transform requires accepts either an octet
stream for octet-stream or a node-set
as input. If an octet-string is given
as input, then this octet-stream is processed directly. If an
XPath node-set (or sufficiently functional alternative) is given as
input, then it is converted to an octet stream by performing
operations logically equivalent to 1) applying an XPath transform
with expression self::text()
, then 2) taking the
string-value of the node-set. Thus, if an XML element is identified
by a shortname XPointer in the Reference
URI, and its
content consists solely of base64 encoded character data, then this
transform automatically strips away the start and end tags of the
identified element and any of its descendant elements as well as
any descendant comments and processing instructions. The output of
this transform is an octet stream.
The normative specification for XPath expression evaluation is [
XPath XPATH ]. The XPath expression to be
evaluated appears as the character content of a transform parameter
child element named XPath
.
The input required by this transform is an XPath node-set. node-set or an
octet-stream. Note that if the actual input is an XPath
node-set resulting from a null URI or shortname XPointer
dereference, then comment nodes will have been omitted. If the
actual input is an octet stream, then the application MUST must convert the octet stream to an XPath
node-set suitable for use by Canonical XML with Comments. (A
subsequent application of the REQUIRED
required Canonical XML algorithm would strip
away these comments.) In other words, the input node-set should be
equivalent to the one that would be created by the following
process:
(//. | //@* |
//namespace::*)
The evaluation of this expression includes all of the document's nodes (including comments) in the node-set representing the octet stream.
The transform output is also
always an XPath node-set. The XPath
expression appearing in the XPath
parameter is
evaluated once for each node in the input node-set. The result is
converted to a boolean. If the boolean is true, then the node is
included in the output node-set. If the boolean is false, then the
node is omitted from the output node-set.
Note: Even if the input node-set has had
comments removed, the comment nodes still exist in the underlying
parse tree and can separate text nodes. For example, the markup
<e>Hello, <!-- comment -->world!</e>
contains two text nodes. Therefore, the expression
self::text()[string()="Hello, world!"]
would fail.
Should this problem arise in the application, it can be solved by
either canonicalizing the document before the XPath transform to
physically remove the comments or by matching the node based on the
parent element's string value (e.g. by using the expression
self::text()[string(parent::e)="Hello, world!"]
).
The primary purpose of this transform is to ensure that only specifically defined changes to the input XML document are permitted after the signature is affixed. This is done by omitting precisely those nodes that are allowed to change once the signature is affixed, and including all other input nodes in the output. It is the responsibility of the XPath expression author to include all nodes whose change could affect the interpretation of the transform output in the application context.
Note that the XML-Signature XPath Filter 2.0 Recommendation [
XPath-Filter-2 XMLDSIG-XPATH-FILTER2 ] may be used for
this purpose. This That recommendation defines an XPath transform
that permits the easy specification of subtree selection and
omission that can be efficiently implemented.
An important scenario would be a document requiring two enveloped signatures. Each signature must omit itself from its own digest calculations, but it is also necessary to exclude the second signature element from the digest calculations of the first signature so that adding the second signature does not break the first signature.
The XPath transform establishes the following evaluation context for each node of the input node-set:
As a result of the context node setting, the XPath expressions
appearing in this transform will be quite similar to those used in
used in [ XSLT ], except that the size and position
are always 1 to reflect the fact that the transform is
automatically visiting every node (in XSLT, one recursively calls
the command apply-templates
to visit the nodes of the
input tree).
The function here()
is defined as
follows:
The here function returns a node-set containing the attribute or processing instruction node or the parent element of the text node that directly bears the XPath expression. This expression results in an error if the containing XPath expression does not appear in the same XML document against which the XPath expression is being evaluated.
As an example, consider creating an enveloped signature (a
Signature
element that is a descendant of an element
being signed). Although the signed content should not be changed
after signing, the elements within the Signature
element are changing (e.g. the digest value must be put inside the
DigestValue
and the SignatureValue
must
be subsequently calculated). One way to prevent these changes from
invalidating the digest value in DigestValue
is to add
an XPath Transform
that omits all
Signature
elements and their descendants. For
example,
<Document> ... <Signature xmlns="http://www.w3.org/2000/09/xmldsig#"> <SignedInfo> ... <Reference URI=""> <Transforms> <Transform Algorithm="http://www.w3.org/TR/1999/REC-xpath-19991116"> <XPath xmlns:dsig="&dsig;"> not(ancestor-or-self::dsig:Signature) </XPath> </Transform> </Transforms> <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/> <DigestValue></DigestValue> </Reference> </SignedInfo> <SignatureValue></SignatureValue> </Signature> ... </Document>
Due to the null Reference
URI in this example, the
XPath transform input node-set contains all nodes in the entire
parse tree starting at the root node (except the comment nodes).
For each node in this node-set, the node is included in the output
node-set except if the node or one of its ancestors has a tag of
Signature
that is in the namespace given by the
replacement text for the entity &dsig;
.
A more elegant solution uses the here function to omit only the
Signature
containing the XPath Transform, thus
allowing enveloped signatures to sign other signatures. In the
example above, use the XPath
element:
<XPath xmlns:dsig="&dsig;"> count(ancestor-or-self::dsig:Signature | here()/ancestor::dsig:Signature[1]) > count(ancestor-or-self::dsig:Signature)</XPath>
Since the XPath equality operator converts node sets to string
values before comparison, we must instead use the XPath union
operator (|). For each node of the document, the predicate
expression is true if and only if the node-set containing the node
and its Signature
element ancestors does not include
the enveloped Signature
element containing the XPath
expression (the union does not produce a larger set if the
enveloped Signature
element is in the node-set given
by ancestor-or-self::Signature
).
An enveloped signature transform T
removes the whole Signature
element containing
T from the digest calculation of the
Reference
element containing
T . The entire string of characters used
by an XML processor to match the Signature
with the
XML production element
is removed. The output of the
transform is equivalent to the output that would result from
replacing T with an XPath transform
containing the following XPath
parameter element:
<XPath xmlns:dsig="&dsig;"> count(ancestor-or-self::dsig:Signature | here()/ancestor::dsig:Signature[1]) > count(ancestor-or-self::dsig:Signature)</XPath>
The input and output requirements of this transform are
identical to those of the XPath transform, but may only be applied
to a node-set from its parent XML document. Note that it is not
necessary to use an XPath expression evaluator to create this
transform. However, this transform MUST
must produce output in exactly the same
manner as the XPath transform parameterized by the XPath expression
above.
The normative specification for XSL Transformations is [
XSLT ]. Specification of a
namespace-qualified stylesheet element, which MUST must be the sole child of the
Transform
element, indicates that the specified style
sheet should be used. Whether this instantiates in-line processing
of local XSLT declarations within the resource is determined by the
XSLT processing model; the ordered application of multiple
stylesheet may require multiple Transforms
. No
special provision is made for the identification of a remote
stylesheet at a given URI because it can be communicated via an
xsl:include
or
xsl:import
within the stylesheet
child of the Transform
.
This transform requires an octet stream as input. If the actual input is an XPath node-set, then the
signature application should attempt to convert it to octets (apply
Canonical XML ]) as described in the Reference Processing Model
(section 4.3.3.2).
The output of this transform is an octet stream. The processing rules for the XSL style sheet [ XSL10 ] or transform element are stated in the XSLT specification [ XSLT ].
We RECOMMEND that XSLT transform authors use an output method of
xml
for XML and HTML. As XSLT implementations do not
produce consistent serializations of their output, we further
RECOMMEND inserting a transform after the XSLT transform to
canonicalize the output. These steps will help to ensure
interoperability of the resulting signatures among applications
that support the XSLT transform. Note that if the output is
actually HTML, then the result of these steps is logically
equivalent [ XHTML XHTML10 ].
Digital signatures only work if the verification calculations are performed on exactly the same bits as the signing calculations. If the surface representation of the signed data can change between signing and verification, then some way to standardize the changeable aspect must be used before signing and verification. For example, even for simple ASCII text there are at least three widely used line ending sequences. If it is possible for signed text to be modified from one line ending convention to another between the time of signing and signature verification, then the line endings need to be canonicalized to a standard form before signing and verification or the signatures will break.
XML is subject to surface representation changes and to processing which discards some surface information. For this reason, XML digital signatures have a provision for indicating canonicalization methods in the signature so that a verifier can use the same canonicalization as the signer.
Throughout this specification we distinguish between the
canonicalization of a Signature
element and other
signed XML data objects. It is possible for an isolated XML
document to be treated as if it were binary data so that no changes
can occur. In that case, the digest of the document will not change
and it need not be canonicalized if it is signed and verified as
such. However, XML that is read and processed using standard XML
parsing and processing techniques is frequently changed such that
some of its surface representation information is lost or modified.
In particular, this will occur in many cases for the
Signature
and enclosed SignedInfo
elements since they, and possibly an encompassing XML document,
will be processed as XML.
Similarly, these considerations apply to Manifest
,
Object
, and SignatureProperties
elements
if those elements have been digested, their
DigestValue
is to be checked, and they are being
processed as XML.
The kinds of changes in XML that may need to be canonicalized
can be divided into four categories. There are those related to the
basic [ XML XML10 ], as described in 7.1 below.
There are those related to [ DOM
DOM-LEVEL-1 ], [ SAX ], or
similar processing as described in 7.2 below. Third, there is the
possibility of coded character set conversion, such as between
UTF-8 and UTF-16, both of which all [ XML XML10 ]
compliant processors are required to support, which is described in
the paragraph immediately below. And, fourth, there are changes
that related to namespace declaration and XML namespace attribute
context as described in 7.3 below.
Any canonicalization algorithm should yield output in a specific
fixed coded character set. All canonicalization algorithms identified in this document use UTF-8
(without a byte order mark (BOM)) and do not provide character
normalization. We RECOMMEND that signature applications create XML
content ( Signature
elements and their descendents/content) descendants/content) in Normalization Form C [
NFC
, NFC-Corrigendum ] and
check that any XML being consumed is in that form as well; (if not,
signatures may consequently fail to validate). Additionally, none
of these algorithms provide data type normalization. Applications
that normalize data types in varying formats (e.g., (true, false)
or (1,0)) may not be able to validate each other's signatures.
XML 1.0 [ XML XML10 ]
]] defines an interface where a
conformant application reading XML is given certain information
from that XML and not other information. In particular,
Note that items (2), (4), and (5.3) depend on the presence of a
schema, DTD or similar declarations. The Signature
element type is laxly
schema valid [ XML-schema
XMLSCHEMA-1 ][ XMLSCHEMA-2 ], consequently external
XML or even XML within the same document as the signature may be
(only) well-formed or from another namespace (where permitted by
the signature schema); the noted items may not be present. Thus, a
signature with such content will only be verifiable by other
signature applications if the following syntax constraints are
observed when generating any signed material including the
SignedInfo
element:
In addition to the canonicalization and syntax constraints
discussed above, many XML applications use the Document Object
Model [ DOM DOM-LEVEL-1 ] or the Simple API for
XML [ SAX ]. DOM maps XML into a tree structure of
nodes and typically assumes it will be used on an entire document
with subsequent processing being done on this tree. SAX converts
XML into a series of events such as a start tag, content, etc. In
either case, many surface characteristics such as the ordering of
attributes and insignificant white space within start/end tags is
lost. In addition, namespace declarations are mapped over the nodes
to which they apply, losing the namespace prefixes in the source
text and, in most cases, losing where namespace declarations
appeared in the original instance.
If an XML Signature is to be produced or verified on a system
using the DOM or SAX processing, a canonical method is needed to
serialize the relevant part of a DOM tree or sequence of SAX
events. XML canonicalization specifications, such as [
XML-C14N ], are based only on
information which is preserved by DOM and SAX. For an XML Signature
to be verifiable by an implementation using DOM or SAX, not only
must the XML 1.0 syntax constraints given in
the previous section be followed but an appropriate XML
canonicalization MUST must be
specified so that the verifier can re-serialize DOM/SAX mediated
input into the same octet stream that was signed.
In [ XPath XPATH ] and consequently the Canonical
XML data model an element has namespace nodes that correspond to
those declarations within the element and its ancestors:
" Note: An element E has namespace nodes that represent its namespace declarations as well as any namespace declarations made by its ancestors that have not been overridden in E 's declarations, the default namespace if it is non-empty, and the declaration of the prefix
xml
." [ XML-C14N ]
When serializing a Signature
element or signed XML
data that's the child of other elements using these data models,
that Signature
element and its children, may contain
namespace declarations from its ancestor context. In addition, the
Canonical XML and Canonical XML with Comments algorithms import all
xml XML
namespace attributes (such as xml:lang
) from the
nearest ancestor in which they are declared to the apex node of
canonicalized XML unless they are already declared at that node.
This may frustrate the intent of the signer to create a signature
in one context which remains valid in another. For example, given a
signature which is a child of B
and a grandchild of
A
:
<A xmlns:n1="&foo;"> <B xmlns:n2="&bar;"> <Signature xmlns="&dsig;"> ... <Reference URI="#signme"/> ... </Signature> <C ID="signme" xmlns="&baz;"/> </B> </A>
when either the element B
or the signed element
C
is moved into a [ SOAP
SOAP12-PART1 ] envelope for
transport:
<SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/"> ... <SOAP:Body> <B xmlns:n2="&bar;"> <Signature xmlns="&dsig;"> ... </Signature> <C ID="signme" xmlns="&baz;"/> </B> </SOAP:Body> </SOAP:Envelope>
The canonical form of the signature in this context will contain
new namespace declarations from the SOAP:Envelope
context, invalidating the signature. Also, the canonical form will
lack namespace declarations it may have originally had from element
A
's context, also invalidating the signature. To
avoid these problems, the application may:
The XML Signature specification provides a very flexible digital
signature mechanism. Implementors
Implementers must give consideration to
their application threat models and to the following factors.
For additional security considerations in
implementation and deployment of this specification, see [
XMLDSIG-BESTPRACTICES ].
A requirement of this specification is to permit signatures to
"apply to a part or totality of a XML document." (See [
XML-Signature-RD , XMLDSIG-REQUIREMENTS ], section 3.1.3].) The Transforms
mechanism meets this requirement by permitting one to sign data
derived from processing the content of the identified resource. For
instance, applications that wish to sign a form, but permit users
to enter limited field data without invalidating a previous
signature on the form might use [ XPath
XPATH ] to
exclude those portions the user needs to change.
Transforms
may be arbitrarily specified and may
include encoding transforms, canonicalization instructions or even
XSLT transformations. Three cautions are raised with respect to
this feature in the following sections.
Note, core validation behavior does not confirm that the signed data was obtained by applying each step of the indicated transforms. (Though it does check that the digest of the resulting content matches that specified in the signature.) For example, some applications may be satisfied with verifying an XML signature over a cached copy of already transformed data. Other applications might require that content be freshly dereferenced and transformed.
First, obviously, signatures over a transformed document do not secure any information discarded by transforms: only what is signed is secure.
Note that the use of Canonical XML [ XML-C14N
] ensures that all internal entities and XML namespaces are
expanded within the content being signed. All entities are replaced
with their definitions and the canonical form explicitly represents
the namespace that an element would otherwise inherit. Applications
that do not canonicalize XML content (especially the
SignedInfo
element) SHOULD
NOT should not use internal entities and
SHOULD should represent the
namespace explicitly within the content being signed since they can
not rely upon canonicalization to do this for them. Also, users
concerned with the integrity of the element type definitions
associated with the XML instance being signed may wish to sign
those definitions as well (i.e., the schema, DTD, or natural
language description associated with the namespace/identifier).
Second, an envelope containing signed information is not secured by the signature. For instance, when an encrypted envelope contains a signature, the signature does not protect the authenticity or integrity of unsigned envelope headers nor its ciphertext form, it only secures the plaintext actually signed.
Additionally, the signature secures any information introduced by the transform: only what is "seen" (that which is represented to the user via visual, auditory or other media) should be signed. If signing is intended to convey the judgment or consent of a user (an automated mechanism or person), then it is normally necessary to secure as exactly as practical the information that was presented to that user. Note that this can be accomplished by literally signing what was presented, such as the screen images shown a user. However, this may result in data which is difficult for subsequent software to manipulate. Instead, one can sign the data along with whatever filters, style sheets, client profile or other information that affects its presentation.
Just as a user should only sign what he or she "sees," persons
and automated mechanism that trust the validity of a transformed
document on the basis of a valid signature should operate over the
data that was transformed (including canonicalization) and signed,
not the original pre-transformed data. This recommendation applies
to transforms specified within the signature as well as those
included as part of the document itself. For instance, if an XML
document includes an
embedded style sheet [ XSLT ] it is the
transformed document that should be represented to the user and
signed. To meet this recommendation where a document references an
external style sheet, the content of that external resource should
also be signed as via a signature Reference
otherwise
the content of that external content might change which alters the
resulting document without invalidating the signature.
Some applications might operate over the original or intermediary data but should be extremely careful about potential weaknesses introduced between the original and transformed data. This is a trust decision about the character and meaning of the transforms that an application needs to make with caution. Consider a canonicalization algorithm that normalizes character case (lower to upper) or character composition ('e and accent' to 'accented-e'). An adversary could introduce changes that are normalized and consequently inconsequential to signature validity but material to a DOM processor. For instance, by changing the case of a character one might influence the result of an XPath selection. A serious risk is introduced if that change is normalized for signature validation but the processor operates over the original data and returns a different result than intended.
As a result:
This specification uses public key signatures and keyed hash authentication codes. These have substantially different security models. Furthermore, it permits user specified algorithms which may have other models.
With public key signatures, any number of parties can hold the public key and verify signatures while only the parties with the private key can create signatures. The number of holders of the private key should be minimized and preferably be one. Confidence by verifiers in the public key they are using and its binding to the entity or capabilities represented by the corresponding private key is an important issue, usually addressed by certificate or online authority systems.
Keyed hash authentication codes, based on secret keys, are typically much more efficient in terms of the computational effort required but have the characteristic that all verifiers need to have possession of the same key as the signer. Thus any verifier can forge signatures.
This specification permits user provided signature algorithms and keying information designators. Such user provided algorithms may have different security models. For example, methods involving biometrics usually depend on a physical characteristic of the authorized user that can not be changed the way public or secret keys can be and may have other security model differences.
The strength of a particular signature depends on all links in the security chain. This includes the signature and digest algorithms used, the strength of the key generation [ RANDOM ] and the size of the key, the security of key and certificate authentication and distribution mechanisms, certificate chain validation policy, protection of cryptographic processing from hostile observation and tampering, etc.
Care must be exercised by applications in executing the various algorithms that may be specified in an XML signature and in the processing of any "executable content" that might be provided to such algorithms as parameters, such as XSLT transforms. The algorithms specified in this document will usually be implemented via a trusted library but even there perverse parameters might cause unacceptable processing or memory demand. Even more care may be warranted with application defined algorithms.
The security of an overall system will also depend on the security and integrity of its operating procedures, its personnel, and on the administrative enforcement of those procedures. All the factors listed in this section are important to the overall security of a system; however, most are beyond the scope of this specification.
This section is non-normative.
Non-normative RELAX NG schema [ RELAXNG-SCHEMAObject
designates a specific XML element. Occasionally
we refer to a data object as a document or as a
resource 's
content . The term element content is used to
describe the data between XML start and end tags [ Object
element is merely one type of digital data (or
document) that can be signed via a Reference
.Signature
element type and its children (including
SignatureValue
) and the specified algorithms.Signature
element, and can be identified via a
URI
or transform. Consequently, the signature is
"detached" from the content it signs. This definition typically
applies to separate data objects, but it also includes the instance
where the Signature
and data object reside within the
same XML document but are sibling elements.Object
element of the signature itself. The
Object
(or its content) is identified via a
Reference
(via a URI
fragment identifier
or transform).SignatureValue
.SignedInfo
reference
validation .Reference
, matches its specified
DigestValue
.SignatureValue
matches the result of
processing SignedInfo
with
CanonicalizationMethod
and
SignatureMethod
as specified in Core Validation (section 3.2).Dated references below are to the latest known or appropriate edition of the referenced work. The referenced works may be subject to revision, and conformant implementations may follow, and are encouraged to investigate the appropriateness of following, some or all more recent editions or replacements of the works cited. It is in each case implementation-defined which editions are supported.