One document matched: draft-ietf-xmldsig-core-04.txt
Differences from draft-ietf-xmldsig-core-03.txt
XML Digital Signatures Working Group D. Eastlake,
INTERNET-DRAFT IBM
draft-ietf-xmldsig-core-04.txt J. Reagle,
Expires August 08, 2000 W3C/MIT
D. Solo,
Citigroup
XML-Signature Syntax
Copyright Notice
Copyright (c) 2000 The Internet Society & W3C (MIT, INRIA, Keio), All
Rights Reserved.
IETF Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
W3C Status of this document
This document is a production of the joint IETF/W3C XML Signature
Working Group.
http://www.w3.org/Signature
The comparable html draft of this version may be found at
http://www.w3.org/TR/2000/WD-xmldsig-core-20000208/
The latest version of this draft series may be found at:
http://www.w3.org/TR/xmldsig-core/
This is a public Working Draft of the IETF/W3C XML Signature Working
Group . This version follows from the January face-to-face meeting. We
hope to issue an institutional (IETF/W3C) Last Call within four weeks.
This version includes and XML Schema definition and a DTD; both of
which are fairly mature but may contain bugs.
Eastlke, Reagle, Solo [Page 1]
Internet Draft XML-Signature Syntax February 2000
Please send comments to the editors and cc: the list
<w3c-ietf-xmldsig@w3.org>. Publication as a Working Draft does not
imply endorsement by the W3C membership or IESG. This is a draft
document and may be updated, replaced or obsoleted by other documents
at any time. It is inappropriate to cite W3C Drafts as other than
"work in progress." A list of current W3C working drafts can be found
at http://www.w3.org/TR
Patent disclosures relevant to this specification may be found on the
WG's patent disclosure page.
Abstract
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.
Table of Contents
1. Introduction
1. Editorial Conventions
2. Design Philosophy
3. Namespaces and Identifiers
4. Acknowledgements
2. Signature Overview
1. The Signature Element
2. The SignedInfo Element
3. The Reference Element
4. The Manifest Element
5. The SignatureProperties Element
3. Processing Rules
1. Signature Generation
2. Signature Validation
4. Core Signature Syntax
1. The Signature element
2. The SignatureValue Element
3. The SignedInfo Element
4. The KeyInfo Element
5. The Object Element
5. Additional Signature Syntax
1. The Manifest Element
2. The SignatureProperties Element
3. Other Useful Types
4. Processing Instructions
5. Comments in dsig Elements
6. Algorithms
1. Algorithm Identifiers and Implementation Requirements
2. Message Digests
3. Message Authentication Codes
4. Signature Algorithms
5. Canonicalization Algorithms
6. Transform Algorithms
Eastlke, Reagle, Solo [Page 2]
Internet Draft XML-Signature Syntax February 2000
7. XML Canonicalization and Syntax Constraint Considerations
1. XML 1.0, Syntax Constraints, and Canonicalization
2. DOM/SAX Processing and Canonicalization
8. Security Considerations
1. Only What is Signed is Secure
2. Only What is "Seen" Should be Signed
3. Check the Security Model
4. Algorithms, Key Lengths, Etc.
9. Schema, DTD, and Data Model
10. Example Syntax
11. Definitions
12. References
_________________________________________________________________
1.0 Introduction
This 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 document.
This specification also defines other useful types including methods
of referencing collections of resources, and key management and
algorithm definitions.
1.1 Editorial Conventions
For readability we use the term "signature" to refer generically to
public key signatures and secret key authenticators. We use the term
"authenticator" and "authentication" specifically when reffering to
keyed hash message authentication.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
specification are to be interpreted as described in RFC2119
[KEYWORDS]:
"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 keywords to unambiguously
specify requirements over protocol and application features and
behavior that affect the interoperability and security of
implementations. These key words are not used (capitalized) to
describe XML grammar; schema definitions formally and unambiguously
describe such requirements and we wish to reserve the prominence of
these terms for the natural language descriptions of protocols and
features. For instance, an XML attribute might be described as being
"optional." Compliance with the XML-namespace specification is
Eastlke, Reagle, Solo [Page 3]
Internet Draft XML-Signature Syntax February 2000
described as "REQUIRED."
1.2 Design Philosophy
The design philosophy and requirements of this specification are
addressed in the XML-Signature Requirements document
[XML-Signature-RD].
1.3 Versions, Namespaces and Identifiers
No provision is made for an explicit version number in this syntax. If
a future version is needed, it will use a different namespace The XML
namespace [XML-ns] URI that MUST be used by experimental
implementations of this dated specification is:
xmlns="http://www.w3.org/2000/01/xmldsig#"
This namespace is also used as the prefix for algorithm identifiers
used by this specification. While applications MUST support XML and
XML-namespaces, the use of internal entities [XML] or our "dsig" XML
namespace prefix and defaulting/scoping conventions are OPTIONAL; we
use these facilities so as to provide compact and readable examples.
This specification uses Uniform Resource Identifiers [URI] to
identify resources, algorithms, and semantics. The URI in the
namespace declaration above is also used as a prefix for URIs under
the control of this specification. For resources not under the control
of this specification, we use the designated Uniform Resource Names
[URN] or Uniform Resource Locators [URL] defined by its 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 this specification's
namespace
http://www.w3.org/2000/01/xmldsig#SignatureProperties
XSLT is identified and defined by an external namespace
http://www.w3.org/TR/1999/PR-xslt-19991008
SHA1 is identified via this specification's namespace and defined via
a normative reference
http://www.w3.org/2000/01/xmldsig#sha1
FIPS PUB 180-1. Secure Hash Standard. U.S. Department of
Commerce/National Institute of Standards and Technology.
This specification uses both XML Schemas [XML-schema] and DTDs [XML].
(Readers unfamiliar with DTD syntax may wish to refer to Ron Bourret's
"Declaring Elements and Attributes in an XML DTD" [Bourret].)
Finally, in order to provide for terse namespace declarations we
sometimes use XML internal entities [XML] as macros within URIs. For
instance:
Eastlke, Reagle, Solo [Page 4]
Internet Draft XML-Signature Syntax February 2000
<?xml version='1.0'?>
<!DOCTYPE Signature SYSTEM "xmldsig-core-schema.dtd" [
<!ENTITY dsig "http://www.w3.org/2000/01/xmldsig#">
]>
<Signature xmlns="&dsig;">
<SignedInfo Id="mypage">
...
1.4 Acknowledgements
* Milton Anderson, FSTC
* Mark Bartel, JetForm Corporation (Author)
* John Boyer, UWI.com (Author)
* Richard Brown, Globeset
* Donald Eastlake 3rd, Motorola (Chair, Editor)
* Barb Fox, Microsoft (Author)
* Phillip Hallam-Baker, VeriSign Inc
* Richard Himes, US Courts
* Joseph Reagle, W3C (Chair, Editor)
* Ed Simon , Entrust Technologies Inc. (Author)
* Chris Smithies, PenOp
* David Solo, Citigroup (Editor)
* Winchel Todd Vincent III, GSU
* Greg Whitehead, Signio Inc.
* Gregor Karlinger, IAIK
2.0 Signature Overview
This section provides an overview of XML digital signature syntax. An
overview of processing appears in section 3:Processing Rules. The
formal syntax is found in section 4: Core Signature Syntax and section
5: Additional Signature Syntax.
In this section, an informal representation is used to describe the
structure of the XML signature syntax. This representation omits many
attributes and details. The following suffix symbols are used to
represent the number of times elements may occur: "?" denotes zero or
one occurrence; "+" denotes one or more occurrences; and "*" denotes
zero or more occurrences.
2.1 The Signature Element
XML Signatures are very flexible and can sign arbitrary digital
content (data objects). An XML Signature is applied 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. While the data object(s) are
not directly operated on by a cryptographic signature algorithm, we
still refer to the signature as being over the data object(s).
Somtimes content is obtained by dereferencing an identified resource.
Within an XML document, signatures are related to data objects via
IDREFs [XML] and the data can be included within an enveloping
Eastlke, Reagle, Solo [Page 5]
Internet Draft XML-Signature Syntax February 2000
signature or can enclose an enveloped signature. Signatures are
related to external data objects via URIs [URI] and the signature and
data object are said to be detached.
XML digital signatures are represented by the Signature element which
has the following structure:
<Signature>
(SignedInfo)
(SignatureValue)
(KeyInfo)?
(Object)*
</Signature>
The required SignedInfo element is the information which is actually
signed. SignedInfo includes a list of References to data objects and
their calculated digest value. The core validation consists of two
mandatory processes: validation of the signature over SignedInfo and
validation of each Reference digest within SignedInfo. The algorithms
used in calculating the SignatureValue are also included in the signed
information while the SignatureValue element is outside SignedInfo.
KeyInfo indicates what key is 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, KeyInfo might contain
information the signer does not wish to reveal to all signature
verifiers. 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.
Object is an optional element for including data objects within the
signature document. The Object can be optionally typed and/or encoded.
Signature properties, such as time of signing, can be optionally
included in a SignatureProperties within Object. (These properties are
traditionally called signature "attributes" although that term in that
context has no relationship to the XML term "attribute".)
SignatureProperties can be included within an Object and signed at the
signer's discretion.
2.2 The SignedInfo Element
The SignedInfo element has the structure indicated below.
<Signature>
<SignedInfo>
(CanonicalizationMethod)?
(SignatureMethod)
(Reference)+
</SignedInfo>
Eastlke, Reagle, Solo [Page 6]
Internet Draft XML-Signature Syntax February 2000
(SignatureValue)
(KeyInfo)?
(Object)*
</Signature>
The CanonicalizationMethod is the algorithm which is used to
canonicalize the SignedInfo element before it is digested as part of
the signature operation. In the absence of a CanonicalizationMethod
element, no canonicalization is done.
The SignatureMethod is the algorithm 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 or HMAC-SHA1. The algorithm
names are signed to resist attacks based on substituting a weaker
algorithm.
To promote application interoperability we specify mandatory to
implement canonicalization, digest, and signature algorithms. We
specify additional algorithms as recommended or optional and the
signature design permits arbitrary signer algorithm specification.
Each Reference element includes the digest method and resulting digest
value calculated over the identified data object. It also may include
transformations that produce 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.
2.3 The Reference Element
The Reference element has the structure indicated below.
...
<SignedInfo>
(CanonicalizationMethod)?
(SignatureMethod)
(<Reference (URI=|IDREF=)? Type=?>
(Transforms)?
(DigestMethod)
(DigestValue)
</Reference>)+
</SignedInfo>
...
The optional URI/IDREF 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.)
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
Eastlke, Reagle, Solo [Page 7]
Internet Draft XML-Signature Syntax February 2000
(i.e., relying party) 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/IDREF.
The optional Type attribute provides information about the resource
identified by the URI/IDREF. In particular, it can indicate that it is
an Object, SignatureProperties, 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 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 indicate Object. Note, that Type is advisory and no action
based on it or checking of its correctness is required by core
behaviour.
Transforms is an optional ordered list of processing steps that were
applied to the resource's content before it is digested. Transforms
can include operations such as canonicalization, encoding/decoding
(including compression/inflation), XSLT and XPath. 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 (this is how the Working Group
satisfied the requirement of signing portions of a document.) 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.
Arbitrary user specified transforms are permitted. To promote
interoperability, we specify mandatory to implement canonicalization
and decoding transformation algorithms. Additional canonicalization,
coding, XSLT, and XPath based transform algorithms are specified as
recommended or optional.
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 bind's a resources content to the signer's key.
2.4 The Manifest Element
The Manifest element is provided to meet additional requirements not
directly addressed by this mandatory part of this specification. The
level of indirection provided by these elements readily meets these
requirements. Two examples 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 achieved by including
multiple References 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
Eastlke, Reagle, Solo [Page 8]
Internet Draft XML-Signature Syntax February 2000
because it requires References within SignedInfo to undergo reference
validation -- the DigestValue elements are checked. Some 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 References. 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
References as valid.
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 References); this is wasteful
and redundant.
To address these requirements, the Manifest element type has been
defined which may be referenced by SignedInfo Reference elements.
First, the Manifest element may contain a collection of References,
but leaves reference validation up to the application. Thus the first
case above can be solved by simply putting one reference inside
SignedInfo to a Manifest which references the three data objects.
Second, multiple signatures over a large number of References need
only point to a single Manifest with the many references.
The structure of Manifest, which reuses the Reference element
described above, is as follows:
<Manifest>
(Reference)*
</Manifest>
Manifest may appear as the content of an Object. Note that an
application could decide whether to verify a DigestValue in a Manifest
based on the Type given in the enclosing Reference.
2.5 The SignatureProperties Element
This specification does not address mechanisms for making statements
or assertions. Instead, this whole document simply defines what it
means for something to be signed by an XML Signature (message
authentication, integrity, and/or signer authentication). Applications
that wish to represent other semantics must rely upon other
technologies, such as [XML, XML-schema, RDF]. However, we do define a
SignatureProperties element type for the inclusion of assertions about
the signature itself (e.g., 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.
<SignatureProperties>
(SignatureProperty Target= )*
</SignatureProperties>
Eastlke, Reagle, Solo [Page 9]
Internet Draft XML-Signature Syntax February 2000
The structure of SignatureProperties is shown above. Any content about
the signature generation may be located within the SignatureProperty
element. The mandatory Target attribute references the element to
which the property applies. In particular, target may include a
reference to a SignedInfo or Reference element.
3.0 Processing Rules
The sections below describe the operations to be performed as part of
signature generation and validation.
3.1 Generation
The REQUIRED steps include the generation of References and the
SignatureValue over SignedInfo.
3.1.1 Reference Generation
For each data object being signed:
1. Apply the Transforms, as determined by the application, to the
data object.
2. Calculate the digest value over the resulting data object.
3. Create a Reference element, including the (optional)
identification of the data object, any (optional) transform
elements, the digest algorithm and the DigestValue.
3.1.2 Signature Generation
1. Create SignedInfo element with SignatureMethod,
CanonicalizationMethod if required, and Reference(s).
2. Canonicalize and then calculate the SignatureValue over SignedInfo
based on algorithms specified in SignedInfo.
3. Construct the Signature element that includes SignedInfo, Object
(s) (if desired, encoding may be different than that used for
signing), KeyInfo (if required), and SignatureValue.
3.2 Validation
The 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.
3.2.1 Reference Validation
For each Reference in SignedInfo:
1. Obtain the data object to be digested. (The signature application
may rely upon the identification (URI/IDREF) and Transforms
provided by the signer in the Reference element, or it may obtain
the content through other means such as a local cache.)
2. Digest the resulting data object using the DigestMethod specified
in its Reference specification.
Eastlke, Reagle, Solo [Page 10]
Internet Draft XML-Signature Syntax February 2000
3. Compare the generated digest value against DigestValue in
SignedInfo; if there is any mismatch, validation fails.
3.2.2 Signature Validation
1. Canonicalize the SignedInfo element based on the
CanonicalizationMethod, if any, in SignedInfo.
2. Obtain the keying information from KeyInfo or from an external
source.
3. Use the specified SignatureMethod to validate the SignatureValue
over the (optionally canonicalized) SignedInfo element.
4.0 Core Signature Syntax
The general structure of an XML signature is described in section 2:
Signature Overview. This section provides detailed syntax of the core
signature features and actual examples. Features described in this
section are mandatory to implement unless otherwise indicated. The
syntax is defined via [XML-Schema] with the following XML preamble,
declaration, and internal entity:
Schema Definition:
<?xml version='1.0'?>
<!DOCTYPE schema
SYSTEM 'http://www.w3.org/TR/1999/WD-xmlschema-1-19991217/structures.dtd'
[
<!ENTITY dsig 'http://www.w3.org/2000/01/xmldsig#'>
]>
<schema targetNamespace='&dsig;'
version='0.1'
xmlns='http://www.w3.org/1999/XMLSchema'
xmlns:ds='&dsig;'>
4.1 The Signature element
The Signature element is the root element of a XML Signature. A simple
example of a complete signature follows:
Dummy Example:
<!DOCTYPE Signature [
<!ENTITY dsig 'http://www.w3.org/2000/01/xmldsig#'>]>
<Signature xmlns="http://www.w3.org/2000/01/xmldsig#">
<SignedInfo>
<CanonicalizationMethod
Algorithm="http://www.w3.org/1999/07/WD-xml-c14n-19990729/" />
<SignatureMethod Algorithm="&dsig;dsaWithSHA-1"/>
<Reference Location="http://www.mypage.com">
<DigestMethod Algorithm="&dsig;sha1"/>
<DigestValue>a23bcd43</DigestValue>
</Reference>
</SignedInfo>
Eastlke, Reagle, Solo [Page 11]
Internet Draft XML-Signature Syntax February 2000
<SignatureValue>C0CFFrVLtRlk</SignatureValue>
<KeyInfo>
<KeyValue>MIIBtzCCASwGByqGSM44BAE</KeyValue>
</KeyInfo>
</Signature>
Schema Definition:
<element name='Signature'>
<type content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<element ref='ds:SignedInfo' minOccurs='1' maxOccurs='1'/>
<element ref='ds:SignatureValue' minOccurs='1' maxOccurs='1'/>
<element ref='ds:KeyInfo' minOccurs='0' maxOccurs='1'/>
<element ref='ds:Object' minOccurs='0' maxOccurs='*'/>
</group>
<attribute name='Id' type='ID' minOccurs='0' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT Signature (SignedInfo, SignatureValue, KeyInfo?, Object*) >
<!ATTLIST Signature
xmlns CDATA #FIXED 'http://www.w3.org/2000/01/xmldsig#'
Id ID #IMPLIED >
4.2 The SignatureValue Element
The SignatureValue element contains the actual value of the digital
signature. The encoding of this value is determined by
SignatureMethod. Base64 [MIME] is the encoding method for all
SignatureMethods specified within this specification. The ability to
define a SignatureMethod and SignatureValue pair which includes
multiple distinct signatures is explicitly permitted (e.g.
"rsawithsha-1 and ecdsawithsha-1").
Schema Definition:
<element name='SignatureValue' type='string'/>
DTD:
<!ELEMENT SignatureValue (#PCDATA) >
4.3 The SignedInfo Element
The structure of SignedInfo includes the canonicalization algorithm
(if any), 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.
Schema Definition:
<element name='SignedInfo'>
<type content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<element ref='ds:CanonicalizationMethod' minOccurs='0' maxOccurs='1'/
Eastlke, Reagle, Solo [Page 12]
Internet Draft XML-Signature Syntax February 2000
>
<element ref='ds:SignatureMethod' minOccurs='1' maxOccurs='1'/>
<element ref='ds:Reference' minOccurs='1' maxOccurs='*'/>
</group>
<attribute name='Id' type='ID' minOccurs='0' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT SignedInfo (CanonicalizationMethod?,
SignatureMethod, Reference+) >
<!ATTLIST SignedInfo
Id ID #IMPLIED >
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 found within an Object element.
4.3.1 The CanonicalizationMethod Element
CanonicalizationMethod is an optional element which specifies the
canonicalization algorithm applied to the SignedInfo element prior to
performing signature calculations. This element uses the general
structure here for algorithms described in section 5.1: Algorithm
Identifiers. Possible options may include a minimal algorithm (CRLF
and charset normalization), or more extensive operations such as
[XML-C14N]. If the CanonicalizationMethod is omitted, no change is
made to SignedInfo before digesting. (Note this may lead to
interoperability failures as other applications may not serialize it
as the creators application did by default.)
Schema Definition:
<element name='CanonicalizationMethod'>
<type content='elementOnly'>
<attribute name='Algorithm' type='uri' minOccurs='1' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT CanonicalizationMethod ANY >
<!ATTLIST CanonicalizationMethod
Algorithm CDATA #REQUIRED >
4.3.2 The SignatureMethod Element
SignatureMethod is a required element which 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 5.1. While there is a single identifier, that identifier
Eastlke, Reagle, Solo [Page 13]
Internet Draft XML-Signature Syntax February 2000
may specify a format containing multiple distinct signature values.
Schema Definition:
<element name='SignatureMethod'>
<type content='elementOnly'>
<attribute name='Algorithm' type='uri' minOccurs='1' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT SignatureMethod ANY >
<!ATTLIST SignatureMethod
Algorithm CDATA #REQUIRED >
4.3.3 The Reference Element
Reference is an element that may occur one or more times. It specifies
a digest algorithm and digest value, and optionally the object being
signed, the type of the object, and/or a list of transforms to be
applied prior to digesting. The identification, and transforms are
information provided to inform the verifier how the digested content
(i.e., the input to the digest method) may be 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 content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<element ref='ds:Transforms' minOccurs='0' maxOccurs='1'/>
<element ref='ds:DigestMethod' minOccurs='1' maxOccurs='1'/>
<element ref='ds:DigestValue' minOccurs='1' maxOccurs='1'/>
</group>
<attribute name='Id' type='ID' minOccurs='0' maxOccurs='1'/>
<attribute name='URI' type='uri' minOccurs='0' maxOccurs='1'/>
<attribute name='IDREF' type='IDREF' minOccurs='0' maxOccurs='1'/>
<attribute name='Type' type='uri' minOccurs='0' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT Reference (Transforms?, DigestMethod, DigestValue) >
<!ATTLIST Reference
Id ID #IMPLIED
URI CDATA #IMPLIED
IDREF IDREF #IMPLIED
Type CDATA #IMPLIED>
The URI/IDREF attribute identifies a data object using a URI [URI] or
IDREF [XML]. We distinguish between URIs and IDREFs so as to provide
Eastlke, Reagle, Solo [Page 14]
Internet Draft XML-Signature Syntax February 2000
expositional clarity and ease signature processing. Note there is some
popular confusion about URIs and fragment identifiers. As specified by
RFC2396 [URI], URIs can be used in conjunction with a fragment
identifier by use of a separating pound symbol '#', but the URI proper
does not include the fragment identifier. (The meaning of the fragment
is defined by the resource's MIME type). URI/IDREF only permits a
'clean' URI or IDREF; fragment identification is specified under
Transforms. This choice permits References to identify a fragment of a
document that is encoded: the Reference identifies the resource, the
first Transform could specify decoding, and the second Transform could
specify the fragment.
Note that a null URI (URI="") is permitted and identifies the document
the reference is in (the root element).
If the URI/IDREF attribute is omitted all-together, 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 digest algorithm is applied to the data octets being secured.
Typically that is done by locating (possibly using the URI/IDREF if
provided) the data and transforming it. If the data is an XML
document, the document is assumed to be unparsed prior to the
application of Transforms. If there are no Transforms, then the data
is passed to the digest algorithm unmodified.
The optional Type attribute contains information about the type of
object being signed. This is represented as a URI. For example:
Type="http://www.w3.org/2000/01/xmldsig#Object"
Type="http://www.w3.org/2000/01/xmldsig#Manifest"
Type="http://www.w3.org/2000/01/xmldsig#SignatureProperty"
The Type attribute applies to the item being pointed at, not its
contents. For example, a reference that identifies an Object element
containing a SignatureProperties element is still of type #Object. The
type attribute is advisory. No validation of the type information is
required by this specification.
4.3.3.1 The Transforms Element
The 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 (octets) serve as input to
the next Transform. The input to the first Transform is the source
data. 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 [section 7.2: Only What is "Seen" Should be Signed].
Eastlke, Reagle, Solo [Page 15]
Internet Draft XML-Signature Syntax February 2000
Each Transform consists of an Algorithm attribute, optional MimeType
and Charset attributes, 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
input resource.
The optional MimeType and Charset (IANA registered character set)
attributes are made available to algorithms which need and are
otherwise unable to deduce that information about the data they are
processing.
Schema Definition:
<element name='Transforms' >
<type content='elementOnly'>
<element ref='ds:Transform' minOccurs='1' maxOccurs='*'/>
</type>
</element>
<element name='Transform'>
<type content='elementOnly'>
<attribute name='Algorithm' type='string' minOccurs='1' maxOccurs='1'/>
<attribute name='MimeType' type='string' minOccurs='0' maxOccurs='1'/>
<attribute name='Charset' type='string' minOccurs='0' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT Transforms (Transform+)>
<!ELEMENT Transform ANY>
<!ATTLIST Transform
Algorithm CDATA #REQUIRED
MimeType CDATA #IMPLIED
Charset CDATA #IMPLIED >
Examples of transforms include but are not limited to base-64 decoding
[MIME], canonicalization [XML-c14n], XPath filtering [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
base-64 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. Section 5-6: Transform Algorithms defines the list
of standard transformations.
4.3.3.2 The DigestMethod Element
DigestMethod is a required element which identifies the digest
algorithm to be applied to the signed object. This element uses the
general structure here for algorithms specified in section 5.1:
Algorithm Identifiers.
Eastlke, Reagle, Solo [Page 16]
Internet Draft XML-Signature Syntax February 2000
Schema Definition:
<element name='DigestMethod'>
<type content='elementOnly'>
<attribute name='Algorithm' type='uri' minOccurs='1' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT DigestMethod ANY >
<!ATTLIST DigestMethod
Algorithm CDATA #REQUIRED >
4.3.3.3 The DigestValue Element
DigestValue is an element which contains the encoded value of the
digest. The digest is always encoded using Base 64 [MIME].
Schema Definition:
<element name='DigestValue' type='ds:encoded'/>
DTD:
<!ELEMENT DigestValue (#PCDATA) >
<!-- base64 encoded signature value -->
4.4 The KeyInfo Element
KeyInfo may contain keys, names, certificates and other public key
management information (such as in-band key distribution or agreement
data or data supporting any other method.) This specification defines
a few simple types but applications may place their own key
identification and exchange semantics within this element through the
XML-namespace facility. [XML-namespace]
Schema Definition:
<element name='KeyInfo'>
<type content='elementOnly'>
<group order='choice' minOccurs='1' maxOccurs='*'>
<element name='KeyName' type='string'/>
<element name='KeyValue' type='string'/>
<element name='RetrievalMethod' type='uri'/>
<element ref='ds:X509Data'/>
<element ref='ds:PGPData'/>
<element name='MgmtData' type='string' minOccurs='0' maxOccurs='1'/>
<any/>
</group>
<attribute name='Id' type='ID' minOccurs='0' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT KeyInfo ((KeyName | KeyValue | RetrievalMethod |
X509Data | PGPData | MgmtData)*) >
Eastlke, Reagle, Solo [Page 17]
Internet Draft XML-Signature Syntax February 2000
<!ATTLIST KeyInfo
Id ID #IMPLIED>
<!ELEMENT KeyName (#PCDATA) >
<!ELEMENT KeyValue (#PCDATA) >
<!ELEMENT RetrievalMethod (#PCDATA) >
KeyInfo is an optional element which enables the recipient(s) to
obtain the key(s) needed to validate the signature. If omitted, the
recipient is expected to be able to identify the key based on
application context information. Multiple declarations within KeyInfo
refer to the same key. Applications may define and use any mechanism
they choose through inclusion of elements from a different namespace.
Compliant versions implementing KeyInfo MUST implement KeyValue, and
SHOULD implement RetrievalMethod.
* KeyName contains an identifier for the key which may be useful to
the recipient. This may be a simple string name, index, encoded
DN, email address, etc.
* KeyValue contains the actual key(s) used to validate the
signature. If the key is sent in protected form, the MgmtData
element should be used. Specific types must be defined for each
algorithm type (see algorithms).
* RetrievalMethod is a URI which may be used to obtain key and/or
certificate information. The URI should contain the complete
string for retrieving the key needed for this message (rather than
a generic URI).
* X509Data contains an identifier of the key/cert used for
validation (either an IssuerSerial value, a subject name, or a
subjectkeyID) and an optional collection of certificates and
revocation/status information which may be used by the recipient.
IssuerSerial contains the encoded issuer name (RFC 2253) along
with the serial number.
* PGPData data associated with a PGP key.
* MgmtData contains in-band key distribution or agreement data.
Examples may include DH key exchange, RSA key encryption etc.
Schema Definition
<element name='X509Data'>
<type content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<group order='choice' minOccurs='1' maxOccurs='1'>
<element ref='ds:X509IssuerSerial'/>
<element name='X509SKI' type='string'/>
<element name='X509SubjectName' type='string'/>
</group>
<element name='X509Certificate' type='string' minOccurs='0' maxOccurs='
*'/>
<element name='X509CRL' type='string' minOccurs='0' maxOccurs='*'/>
</group>
</type>
</element>
Eastlke, Reagle, Solo [Page 18]
Internet Draft XML-Signature Syntax February 2000
<element name='X509IssuerSerial'>
<type content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<element name='X509IssuerName' type='string' minOccurs='1' maxOccurs='
1'/>
<element name='X509SerialNumber' type='string' minOccurs='1' maxOccurs
='1'/>
</group>
</type>
</element>
<element name='PGPData'>
<type content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<element name='PGPKeyID' type='string' minOccurs='1' maxOccurs='1'/>
<element name='PGPKeyPacket' type='string' minOccurs='1' maxOccurs='1'
/>
</group>
</type>
</element>
DTD:
<!ELEMENT X509Data ((X509IssuerSerial | X509SKI | X509SubjectName),
X509Certificate*, X509CRL*)>
<!ELEMENT X509IssuerSerial (X509IssuerName, X509SerialNumber) >
<!ELEMENT X509IssuerName (#PCDATA) >
<!ELEMENT X509SubjectName (#PCDATA) >
<!ELEMENT X509SerialNumber (#PCDATA) >
<!ELEMENT X509SKI (#PCDATA) >
<!ELEMENT X509Certificate (#PCDATA) >
<!ELEMENT X509CRL (#PCDATA) >
<!ELEMENT PGPData (PGPKeyID, PGPKeyPacket?) >
<!ELEMENT PGPKeyPacket (#PCDATA) >
<!ELEMENT PGPKeyID (#PCDATA) >
<!ELEMENT MgmtData (#PCDATA)>
4.5 The Object Element
Object is an optional element which 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 MimeType attribute is an optional attribute which describes the
data within the Object. This is a string with values defined by
[MIME]. For example, if the Object contains XML, the MimeType would be
text/xml. This attribute is purely advisory, no validation of the
MimeType informatin is required by this specification.
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
document. The digest is calculated over the entire Object element
including start and end tags.
Eastlke, Reagle, Solo [Page 19]
Internet Draft XML-Signature Syntax February 2000
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 content='mixed'>
<any namespace='##targetNamespace'/>
<attribute name='Id' type='ID' minOccurs='0' maxOccurs='1'/>
<attribute name='MimeType' type='string' minOccurs='0' maxOccurs='1'/>
<attribute name='Encoding' type='uri' minOccurs='0' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT Object (#PCDATA) >
<!ATTLIST Object
Id ID #IMPLIED
MimeType CDATA #IMPLIED
Encoding CDATA #IMPLIED >
5.0 Additional Signature Syntax
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.
5.1 The Manifest Element
The Manifest element provides a list of References. 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
application 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:
Eastlke, Reagle, Solo [Page 20]
Internet Draft XML-Signature Syntax February 2000
<element name='Manifest'>
<type content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<element ref='ds:Reference' minOccurs='1' maxOccurs='*'/>
<element ref='ds:Object' minOccurs='0' maxOccurs='*'/>
</group>
<attribute name='Id' type='ID' minOccurs='0' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT Manifest ((Reference | Object)+) >
<!ATTLIST Manifest
Id ID #IMPLIED >
5.2 The SignatureProperties Element
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 content='elementOnly'>
<element ref='ds:SignatureProperty' minOccurs='1' maxOccurs='*'/>
<attribute name='Id' type='ID' minOccurs='0' maxOccurs='1'/>
</type>
</element>
<element name='SignatureProperty'>
<type content='mixed'>
<any namespace='##other'/>
<attribute name='Target' type='IDREF' minOccurs='1' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT SignatureProperties (SignatureProperty*) >
<!ATTLIST SignatureProperties
Id ID #IMPLIED >
<!ELEMENT SignatureProperty (#PCDATA) >
<!ATTLIST SignatureProperty
Target IDREF #REQUIRED >
5.3 Other Useful Types
We define the following URIs for use in identifying XML resources that
include non-core but signature related semantics.
http://www.w3.org/2000/01/xmldsig#Object
designates that the referenced resource is a Signature Object
element type.
Eastlke, Reagle, Solo [Page 21]
Internet Draft XML-Signature Syntax February 2000
http://www.w3.org/2000/01/xmldsig#SignatureProperties
designates that the referenced resource is a statement about
the referring signature.
http://www.w3.org/2000/01/xmldsig#Manifest
designates that the referenced resource is a collection of
other resources.
5.5 Processing Instructions in Signature Elements
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
CanonicalizationMethods specified 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.
5.5 Comments in Signature Elements
XML comments are not used by this specification.
Note that unless CanonicalizationMethod removes comments within
SignedInfo or any other referenced XML, they will be signed.
Consequently, 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-canonicalization], is
specified.
6.0 Algorithms
This section identifies algorithms used with the XML digital signature
standard. 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.
6.1 Algorithm Identifiers and Implementation Requirements
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 (or SignedInfo
directly if there is no 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 be in
Eastlke, Reagle, Solo [Page 22]
Internet Draft XML-Signature Syntax February 2000
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.
Algorithm Type Algorithm Requirements Algorithm URI
Digest
SHA1 REQUIRED http://www.w3.org/2000/01/xmldsig#sha1
Encoding
Base64 REQUIRED http://www.w3.org/2000/01/xmldsig#base64
QuotedPrintable RECOMMENDED http://www.w3.org/2000/01/xmldsig#qp
MAC
HMAC-SHA1 REQUIRED http://www.w3.org/2000/01/xmldsig#hmac-sha1
Signature
DSAwithSHA1 (DSS) REQUIRED http://www.w3.org/2000/01/xmldsig#dsa
RSAwithSHA1 RECOMMENDED http://www.w3.org/2000/01/xmldsig#rsa-sha1
[[DELETE]] ECDSAwithSHA1 OPTIONAL
http://www.w3.org/2000/01/xmldsig#ecdsa
Canonicalization
minimal REQUIRED http://www.w3.org/2000/01/xmldsig#minimal
XML-Canonicalization RECOMMENDED
http://www.w3.org/TR/1999/WD-xml-c14n-19991115
Transform
XSLT RECOMMENDED http://www.w3.org/TR/1999/REC-xslt-19991116
XPath RECOMMENDED http://www.w3.org/TR/1999/REC-xpath-19991116
XPointer RECOMMENDED http://www.w3.org/TR/1999/WD-xptr-19991206
Note that the normative identifier is the complete URIs in the table
though they are frequently abbreviated in XML syntax as "&dsig;base64"
or the like.
6.2 Message Digests
Only one digest algorithm is defined herein. However, it is expected
that one or more additional strong digest algorithms will be developed
in connection with the US Advanced Encryption Standard effort. Use of
MD5 [MD5] is NOT RECOMMENDED because recent advances in cryptography
have cast doubt on its strength.
6.2.1 SHA-1
Identifier:
http://www.w3.org/2000/01/xmldsig#sha1
The SHA-1 algorithm [SHA-1] takes no explicit parameters. An example
of an SHA-1 DigestAlg element is:
<DigestMethod Algorithm="&dsig;sha1"/>
A SHA-1 digest is a 160-bit string. The content of the DigestValue
Eastlke, Reagle, Solo [Page 23]
Internet Draft XML-Signature Syntax February 2000
element shall be the base64 encoding of this bit string viewed as a
20-octet octet stream. 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>
6.3 Message Authentication Codes
MAC algorithms take two implicit parameters, their keying material
determined from KeyInfo and the byte stream output by
CanonicalizationMethod or SignedInfo directly if there is no
CanonicalizationMethod. MACs and signature algorithms are
syntactically identical but a MAC implies a shared secret key.
6.3.1 HMAC
Identifier:
http://www.w3.org/2000/01/xmldsig#hmac-sha1
The HMAC algorithm [RFC2104:HMAC] takes the truncation length in bits
as a parameter. An example of an HMAC SignatureMethod element:
<SignatureMethod Algorithm="&dsig;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:
<element name='HMACOutputLength' type='integer' minOccurs='0' maxOccurs='1'/>
DTD:
<!ELEMENT HMACOutputLength (#PCDATA)>
6.4 Signature Algorithms
Signature algorithms take two implicit parameters, their keying
material determined from KeyInfo and the byte stream output by
CanonicalizationMethod or SignedInfo directly if there is no
Eastlke, Reagle, Solo [Page 24]
Internet Draft XML-Signature Syntax February 2000
CanonicalizationMethod. Signature and MAC algorithms are syntactically
identical but a signature implies public key cryptography.
Note: the schema and DTD declarations within this section are not yet
part of section 9: schemas.
6.4.1 DSA
Identifier:
http://www.w3.org/2000/01/xmldsig#dsa
The DSA algorithm [DSS] takes no explicit parameters. An example of a
DSA SignatureMethod element is:
<SignatureMethod Algorithm="&dsig;dsa"/>
The output of the DSA algorithm consists of a pair of integers usually
referred by the pair (r, s). The signature value shall consist of the
base64 encoding of the concatenation of two octet-streams that
respectively result from the octet-encoding of the values r and s.
Integer to octet-stream conversion shall be done according to the
I2OSP operation defined in the RFC 2437 [RSA] specification with a k
parameter equal to 20. 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==</SignatureVa
lue>
DSA key values have the following set of fields: P, Q, G and Y are
mandatory when appearing as a key value, J, seed and pgenCounter are
optional but SHOULD be present. (The seed and pgenCounter fields MUST
both either appear or be absent). All parameters are encoded as base64
values.
Schema:
<element name='DSAKeyValue'>
<type content='elementOnly'>
<group order='seq' minOccurs='1' maxOccurs='1'>
<element name='ds:P' type='string' minOccurs='1' maxOccurs='1'/>
<element name='ds:Q' type='string' minOccurs='1' maxOccurs='1'/>
<element name='ds:G' type='string' minOccurs='1' maxOccurs='1'/>
<element name='ds:Y' type='string' minOccurs='1' maxOccurs='1'/>
<element name='ds:J' type='string' minOccurs='0' maxOccurs='1'/>
</group>
<group order='seq' minOccurs='0' maxOccurs='1'>
<element name='ds:Seed' type='string' minOccurs='1' maxOccurs='1'/>
<element name='ds:PgenCounterQ' type='string' minOccurs='1' maxOccurs='
Eastlke, Reagle, Solo [Page 25]
Internet Draft XML-Signature Syntax February 2000
1'/>
</group>
</type>
</element>
DTD:
<!ELEMENT DSAKeyValue (P, Q, G, Y, J?, (Seed, PgenCounter)?) >
<!ELEMENT P (#PCDATA) >
<!ELEMENT Q (#PCDATA) >
<!ELEMENT G (#PCDATA) >
<!ELEMENT Y (#PCDATA) >
<!ELEMENT J (#PCDATA) >
<!ELEMENT Seed (#PCDATA) >
<!ELEMENT PgenCounter (#PCDATA) >
<!-- Each of these fields consists a PCDATA
where the data is base64 encoded -->
6.4.2 RSA
Identifier:
http://www.w3.org/2000/01/xmldsig#rsa-sha1
The expression "RSA algorithm" as used in this specification refers to
the RSASSA-PKCS1-v1_5 algorithm described in RFC 2437 [RSA]. The RSA
algorithm takes no parameters. An example of an RSA SignatureMethod
element is:
<SignatureMethod Algorithm="&dsig;rsa-sha1"/>
The output of the RSA algorithm is an octet string. The SignatureValue
content for an RSA signature shall be the base64 encoding of this
octet string. Example: TBD
RSA key values have two fields: Modulus and Exponent.
Schema:
<element name='RSAKeyValue'>
<type content='elementOnly'>
<element name='ds:Modulus' type='string' minOccurs='1' maxOccurs='1'/>
<element name='ds:Exponent' type='string' minOccurs='1' maxOccurs='1'/>
</type>
</element>
DTD:
<!ELEMENT RSAKeyValue (Modulus, Exponent) >
<!ELEMENT Modulus (#PCDATA) >
<!ELEMENT Exponent (#PCDATA) >
<!-- Each field contains a CDATA which is the
value for that item base64 encoded -->
6.5 Canonicalization Algorithms
6.5.1 Minimal Canonicalization
Eastlke, Reagle, Solo [Page 26]
Internet Draft XML-Signature Syntax February 2000
Identifier:
http://www.w3.org/2000/01/xmldsig#minimal
The algorithm identifier for the minimal canonicalization is
&dsig;minimal. An example of a minimal canonicalization element is:
<CanonicalizationMethod Algorithm="&dsig;minimal"/>
The minimal canonicalization algorithm:
* converts the character encoding to UTF-8, removing the encoding
pseudo-attribute
* normalizes line endings as provided by [XML]. (See section 7: XML
and Canonicalization and Syntactical Considerations.)
6.5.1 Canonical XML
Identifier:
http://www.w3.org/TR/1999/WD-xml-c14n-19991115
An example of an XML canonicalization element is:
<CanonicalizationMethod
Algorithm="http://www.w3.org/TR/1999/WD-xml-c14n-19991115"/>
The normative specification of Canonical XML is [XML-c14n].
6.6 Transform Algorithms
A Transform algorithm has three implicit parameters. The first is a
byte stream from the Reference or as the output of an earlier
Transform. The second and third are the optional MimeType and Charset
attributes that can be specified on the Transform element.
Application developers are strongly encouraged to support all
transforms listed in this section as RECOMMENDED unless the
application environment has resource constraints that would make such
support impractical. The Working Group goal is to maximize application
interoperability on XML signatures, and the working group expects
ubiquitous availability of software to support these transforms that
can be incorporated into applications without extensive development.
6.6.1 Canonicalization
Any canonicalization algorithm that can be used for
CanonicalizationMethod can be used as a Transform.
6.6.2 Base-64 and Quoted-Printable Decoding
Identifiers:
http://www.w3.org/2000/01/xmldsig#base-64
http://www.w3.org/2000/01/xmldsig#qp
Eastlke, Reagle, Solo [Page 27]
Internet Draft XML-Signature Syntax February 2000
The normative specification for base 64 and quoted-printable decoding
transforms is [MIME]. The base-64 Transform element has no content.
The input is base-64 decoded by this algorithm. This transform is
useful if an application needs to sign the raw data associated with
base-64 encoded content of an element.
6.6.3 XPath Filtering
Identifier:
http://www.w3.org/TR/1999/REC-xpath-19991116
The Transform element content MUST conform to the XML Path Language
[XPath] syntax. XPath is a language for addressing parts of an XML
document. Hence, an XPath expression MUST be applied to an entire
well-formed XML document.
Note: The current output of a Reference's IDREF cannot be used as
input to an XPath transform. The XPath transform could be defined to
provide an XML declaration when one is found not to exist since the
encoding attribute could be set equal to the XPath transform's Charset
attribute. However, there is currently no way to communicate the
correct byte order mark to the transform. For security reasons, a
default cannot be selected.
The XPath transform applies the W3C XML canonicalization [XML-C14N] to
the input resource. This ensures all entity reference substitutions
and attribute normalizations are performed in a manner consistent with
a validating XML processor. Linefeeds are normalized, and CDATA
sections are eliminated. The types of quotes around attributes are
normalized, and the order of attributes is defined. Namespace
attributes are created in descendant elements that use namespace
definitions. All of these modifications are necessary to achieve a
consistent interpretation of the XPath expression and a consistent
output of the XPath transform.
Finally, the XPath expression is evaluated assuming that the entity
references created by canonicalization have been replaced by the
corresponding entity values and that each block of consecutive text
characters has been replaced by a single text node.
The result of the XPath is a string, boolean, number, or node-set. If
the result of the XPath expression is a string, then the string is the
output of the XPath transform. If the XPath result is a boolean or
number, then the result is converted to a string using the XPath
string() function. If the result of the XPath expression is a
node-set, then the output of the transform is a string containing the
text rendering of the nodes in the node-set. The nodes are selected
for rendering based on the document order (as defined in [XPath]) of
the canonicalized input resource. The text rendering is performed in
accordance with [XML-C14N].
It is RECOMMENDED that the XPath be constructed such that the result
of this operation is a well-formed XML document. This should be the
Eastlke, Reagle, Solo [Page 28]
Internet Draft XML-Signature Syntax February 2000
case if root element of the input resource is included by the XPath
(even if a number of its descendant elements and attributes are
omitted by the XPath).
6.6.4 XSLT Transform
Identifier:
http://www.w3.org/TR/1999/REC-xslt-19991116
The Transform element content MUST conform to the XSL Transforms
[XSLT] language syntax. The processing rules for the XSLT transform
are stated in the XSLT specification [XSLT].
7.0 XML Canonicalization and Syntax Constraint Considerations
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 data object 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 three categories. There are those related to the basic
Eastlke, Reagle, Solo [Page 29]
Internet Draft XML-Signature Syntax February 2000
[XML], as described in 7.1 below. There are those related to [DOM],
[SAX], or similar processing as described in 7.2 below. And, third,
there is the possibility of character set conversion, such as between
UTF-8 and UTF-16, both of which all XML standards compliant processors
are required to support. Any canonicalization algorithm should yield
output in a specific fixed character set. For both the minimal
canonicalization defined in this specification and the W3C Canonical
XML [XML-c14n], that character set is UTF-8.
7.1 XML 1.0, Syntax Constraints, and Canonicalization
XML 1.0 [XML] defines an interface where a conformant application
reading XML is given certain information from that XML and not other
information. In particular,
1. line endings are normalized to the single character #xA by
dropping #xD characters if they are immediately followed by a #xA
and replacing them with #xA in all other cases,
2. missing attributes declared to have default values are provided to
the application as if present with the default value,
3. character references are replaced with the corresponding
character,
4. entity references are replaced with the corresponding declared
entity,
5. attribute values are normalized by
A. replacing character and entity references as above,
B. replacing occurrences of #x9, #xA, and #xD with #x20 (space)
except that the sequence #xD#xA is replaced by a single
space, and
C. if the attribute is not declared to be CDATA, stripping all
leading and trailing spaces and replacing all interior runs
of spaces with a single space, and
6. for elements declared to have element content, eliminate white
space that appears within their content but not within the content
of any enclosed element.
Note that items (2), (4), (5C), and (6) depend on specific Schema,
DTD, or similar declarations. In the general case, such declarations
will not be available to or used by the signature verifier. Thus, to
interoperate between different XML implementations, the following
syntax contraints MUST be observed when generating any signed material
to be processed as XML, including the SignedInfo element:
1. attributes having default values be explicitly present,
2. all entity references (except "amp", "lt", "gt", "apos", and
"quot" which are pre-defined) be expanded,
3. attribute value white space be normalized, and
4. insignificant white space not be generated within elements having
element content.
7.2 DOM/SAX Processing and Canonicalization
In addition to the canonicalization and syntax constraints discussed
above, many XML applications use the Document Object Model [DOM] or
The Simple API for XML [SAX]. DOM maps XML into a tree structure of
Eastlke, Reagle, Solo [Page 30]
Internet Draft XML-Signature Syntax February 2000
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 the 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
syntax constraints given in section 7.1 be followed but an appropriate
XML canonicalization MUST be specified so that the verifier can
re-serialize DOM/SAX mediated input into the same byte sequence that
was signed.
8.0 Security Considerations
The XML Signature specification provides a very flexible digital
signature mechanism. Implementors must give consideration to their
application threat models and to the following factors.
8.1 Only What is Signed is Secure
A requirement of this specification is to permit signatures to "apply
to a part or totality of a XML document." [3.1.3 XML-Signature-RD] 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 the form itself might
use XPath [XPath] to exclude those portions the user needs to change.
Transforms may be arbitrarily specified and may include
canonicalization instructions or even XSLT transformations. Of course,
signatures over such a dervied document do not secure any information
discarded by the Transforms.
Furthermore, 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 application may
be satisfied with verifying an XML signature over a cached copy of
already transformed data. Other application might require that content
be freshly dereferenced and transformed.
8.2 Only What is "Seen" Should be Signed
If signing is intended to convey the judgment or consent of an
automated mechanism or person concerning some information, then it is
Eastlke, Reagle, Solo [Page 31]
Internet Draft XML-Signature Syntax February 2000
normally necessary to secure as exactly as practical the information
that was presented to that mechanism or person. Note that this can be
accomplished by literally signing what was presented, for example the
screen images shown a user. However, this may result in data which it
is difficult for subsequent software to manipulate. It can be
effective instead to secure the full data along with whatever filters,
style sheets, or the like were used to control the part of the
information that was presented.
Also 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 explitly represents the namespace that an element would
otherwise inhereit. Those application that do not canonicalize XML
content (especially the SignedInfo element) SHOULD NOT use internal
entities and SHOULD represent the name space explicitly within the
content being signed since they can not rely upon canonicalization to
do this for them.
8.3 Check the Security Model
This standard specifies public key signatures and keyed hash
authentication codes. These have substantially different security
models. Furthermore, it permits user specified additions 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 standard permits user provided signature algorithms and keying
information designators. Such user provided algorithms may have
further 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.
8.4 Key Lengths, Algorithms, Certificates, Etc.
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
Eastlke, Reagle, Solo [Page 32]
Internet Draft XML-Signature Syntax February 2000
distribution mechanisms, certificate chain valiation policy,
protection of cryptographic processing from hostile observation and
tampering, etc. The security of an overall system would also depend on
the security and integrity of its operating procedures, its personnel,
and on the administrative enforcement of those procedures. The factors
listed in this paragraph, while critical to the overall security of a
system, are mostly beyond the scope of this specification.
9.0 Schema, DTD, and Data Model
XML Signature Schema Instance
xmldsig-core-schema.xsd
XML schema instance validates to 19991207 Schema DTD
[XML-Schema].
XML Signature DTD
xmldsig-core-schema.dtd
XML DTD that could still use improvement.
RDF Data Model
xmldsig-datamodel-20000112.gif
10.0 Example syntax
XML Signature Example
signature-example.xml
Well formed XML that validates under the schema and DTD. The
non-normative cryptographic values were generated by Ed Simon
and Tamura Kent. The text below was edited for readability.
<Signature xmlns="http://www.w3.org/2000/01/xmldsig">
<SignedInfo Id="mypage">
<CanonicalizationMethod
Algorithm="http://www.w3.org/1999/07/WD-xml-c14n-19990729">
</CanonicalizationMethod>
<SignatureMethod Algorithm="http://www.w3.org/2000/01/xmldsig/dsa">
</SignatureMethod>
<Reference URI="http://www.w3.org/TR/xml-stylesheet/">
<Transforms>
<Transform Algorithm="http://www.w3.org/2000/01/xmldsig/base64"/>
<Transform Algorithm="http://www.w3.org/2000/01/xmldsig/null"/>
</Transforms>
<DigestMethod Algorithm="http://www.w3.org/2000/01/xmldsig/sha1">
</DigestMethod>
<DigestValue>j6lwx3rvEPO0vKtMup4NbeVu8nk=</DigestValue>
</Reference>
<Reference URI="http://www.w3.org/TR/REC-xml-names/">
<Transforms>
<Transform Algorithm="http://www.w3.org/2000/01/xmldsig/base64"/>
</Transforms>
<DigestMethod Algorithm="http://www.w3.org/2000/01/xmldsig/sha1">
</DigestMethod>
<DigestValue>UrXLDLBIta6skoV5/A8Q38GEw44=</DigestValue>
Eastlke, Reagle, Solo [Page 33]
Internet Draft XML-Signature Syntax February 2000
</Reference>
</SignedInfo>
<SignatureValue>MC0CFFrVLtRlkMc3Daon4BqqnkhCOlEaAhUAk8pH1iRNK+q1I
+sisDTz2TFEALE=</SignatureValue>
<KeyInfo>
<KeyValue xmlns:java="http://xsl.lotus.com/java"
xmlns:dsig="http://www.w3.org/2000/01/xmldsig">
MIIBtzCCASwGByqGSM44BAEwggEfAoGBAP1/U4EddRIpUt9KnC7s5Of2E
bdSPO9EAMMeP4C2USZpRV1AIlH7WT2NWPq/xfW6MPbLm1Vs14E7gB00b/
JmYLdrmVClpJ+f6AR7ECLCT7up1/63xhv4O1fnxqimFQ8E+4P208UewwI1
VBNaFpEy9nXzrith1yrv8iIDGZ3RSAHHAhUAl2BQjxUjC8yykrmCouuEC/
BYHPUCgYEA9+GghdabPd7LvKtcNrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeO
utRZT+ZxBxCBgLRJFnEj6EwoFhO3zwkyjMim4TwWeotUfI0o4KOuHiuzpn
WRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImog9/hWuWfBpKLZl6Ae1UlZAFM
O/7PSSoDgYQAAoGAQFL0+RhXZbDxdt17o05PlMzQGqDnAq2NM1eun+ie21
4okrmIp4r0CGKvHM1HbFgwXMlBpkXyStYg64RTMnL9dtShw5rCkEv145TV
0EYVoxBQ5X0gmrQ2NftRHH8imBhx9glz//y6NE4JhfIVPu3o+55VYUwdFP
0cbBvWkKOngo0=
</KeyValue>
</KeyInfo>
</Signature>
11.0 Definitions
Authentication, Message
"A signature should identify what is signed, making it
impracticable to falsify or alter either the signed matter or
the signature without detection." [Digital Signature
Guidelines, ABA]
Authentication, Signer
"A signature should indicate who signed a document, message or
record, and should be difficult for another person to produce
without authorization." [Digital Signature Guidelines, ABA] See
non-repudiation.
Core
The syntax and processing defined by this specification,
including core validation. We use this term to distinguish
other markup, processing, and applications semantics from our
own.
Data Object (Content/Document)
The actual binary/octet data being operated on (transformed,
digested, or signed) by an application -- frequently an HTTP
entity [HTTP]. Note that the proper noun Object 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
[XML]. The term XML document is used to describe data objects
which conform to the XML specification [XML].
Integrity
Eastlke, Reagle, Solo [Page 34]
Internet Draft XML-Signature Syntax February 2000
The inability to change a message without also changing the
signature value. See message authentication.
Non-repudiation
The inability of a key holder to assert that their key was not
associated with a message given a strong signature algorithm.
(This definition speaks nothing of the number of key holders,
the key length, whether the key is comprised, whether the
signature was coerced, etc.) See signer authentication.
Object
An XML Signature element wherein arbitrary (non-core) data may
be placed. An Object element is merely one type of digital data
(or document) that can be signed via a Reference.
Resource
"A resource can be anything that has identity. Familiar
examples include an electronic document, an image, a service
(e.g., 'today's weather report for Los Angeles'), and a
collection of other resources.... The resource is the
conceptual mapping to an entity or set of entities, not
necessarily the entity which corresponds to that mapping at any
particular instance in time. Thus, a resource can remain
constant even when its content---the entities to which it
currently corresponds---changes over time, provided that the
conceptual mapping is not changed in the process." [URI] In
order to avoid a collision of the term entity within the URI
and XML specifications, we use the term data object, content or
document to refer to the actual bits being operated upon.
Signature
A value generated from the application of a key to a message
via a cryptographic algorithm such that it has the properties
of signer authentication, integrity, and non-repudiation. A
signature may be (non-exclusively) described as detached,
enveloping, or enveloped.
Signature, Detached
The signature is over content external to the Signature
element, and can be identified via a URI, IDREF, 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.
Signature, Enveloping
The signature is over content found within the Object element
of the signature itself. The Object(or its content) is
identified via a Reference (via IDREF or transform). The
enveloping Signature element is used to provide the root
document element.
Eastlke, Reagle, Solo [Page 35]
Internet Draft XML-Signature Syntax February 2000
Signature, Enveloped
The signature is over the XML content that contains the
signature as an element. The content provides the root XML
document element. Obviously, enveloped signatures must take
care not to include their own value in the calculation of the
SignatureValue.
Transform
The processing of a byte stream from source content to derived
content. Typical transforms include XML Canonicalization,
XPath, and XSLT.
Validation, Core
The core processing requirements of this specification
requiring signature validation and SignedInfo reference
validation.
Validation, Reference
The hash value of the identified and transformed content,
specified by Reference, matches its specified DigestValue.
Validation, Signature
The SignatureValue matches the result of processing SignedInfo
with CanonicalizationMethod and SignatureMethod as specified
in section 6.2.
Validation, Trust/Application
The application determines that the semantics associated with a
signature are valid. For example, an application may validate
the time stamps or the integrity of the signer key -- though
this behavior is external to this core specification.
12.0 References
ABA
Digital Signature Guidelines.
http://www.abanet.org/scitech/ec/isc/dsgfree.html
Bourret
Ron Bourret. Declaring Elements and Attributes in an XML DTD.
http://www.informatik.tu-darmstadt.de/DVS1/staff/bourret/xml/xm
ldtd.html
DOM
Document Object Model (DOM) Level 1 Specification.
http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001/
DOMHASH
Internet Draft. Digest Values for DOM (DOMHASH)
http://search.ietf.org/internet-drafts/draft-hiroshi-dom-hash-0
1.txt .
DSS
Eastlke, Reagle, Solo [Page 36]
Internet Draft XML-Signature Syntax February 2000
FIPS PUB 186-1. Digital Signature Standard (DSS). U.S.
Department of Commerce/National Institute of Standards and
Technology.
HMAC
RFC 2104. HMAC: Keyed-Hashing for Message Authentication. H.
Krawczyk, M. Bellare, R. Canetti. INFORMATIONAL.
HTTP
RFC 2616.Hypertext Transfer Protocol -- HTTP/1.1. J. Gettys, J.
Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee.
http://www.ietf.org/rfc/rfc2616.txt
KEYWORDS
RFC2119 -- Key words for use in RFCs to Indicate Requirement
Levels.
http://www.ietf.org/rfc/rfc2119.txt
MD5
RFC 1321. The MD5 Message-Digest Algorithm. R. Rivest.
INFORMATIONAL.
http://www.ietf.org/rfc/rfc1321.txt
MIME
RFC 2045. Multipurpose Internet Mail Extensions (MIME) Part
One: Format of Internet Message Bodies. N. Freed & N.
Borenstein. DRAFT STANDARD.
http://www.ietf.org/rfc/rfc2045.txt
RANDOM
RFC1750 -- Randomness Recommendations for Security.
http://www.ietf.org/rfc/rfc1750.txt
RDF
RDF Schema
http://www.w3.org/TR/1999/PR-rdf-schema-19990303/
RDF Model and Syntax
http://www.w3.org/TR/1999/REC-rdf-syntax-19990222
RSA
RFC 2437. PKCS #1: RSA Cryptography Specifications Version 2.0.
B. Kaliski, J. Staddon. INFORMATIONAL.
http://www.ietf.org/rfc/rfc2432.txt
SAX
David Megginson et. al. SAX: The Simple API for XML May 1998.
http://www.megginson.com/SAX/index.html
SHA-1
FIPS PUB 180-1. Secure Hash Standard. U.S. Department of
Commerce/National Institute of Standards and Technology.
http://csrc.nist.gov/fips/fip180-1.pdf
Eastlke, Reagle, Solo [Page 37]
Internet Draft XML-Signature Syntax February 2000
URI
RFC2396 - Uniform Resource Identifiers (URI): Generic Syntax
http://www.ietf.org/rfc/rfc2396.txt
URL
RFC1738. Uniform Resource Locators (URL). Berners-Lee, T.,
Masinter, L., and M. McCahill . December 1994.
http://www.ietf.org/rfc/rfc1738.txt
URN
RFC 2141. URN Syntax. R. Moats. PROPOSED STANDARD.
ftp://ftp.isi.edu/in-notes/rfc2141.txt
RFC 2611. URN Namespace Definition Mechanisms. L. Daigle, D.
van Gulik, R. Iannella, P. Falstrom. BEST CURRENT PRACTICE.
ftp://ftp.isi.edu/in-notes/rfc2611.txt
XLink
XML Linking Language
http://www.w3.org/1999/07/WD-xlink-19990726
XML
Extensible Markup Language (XML) Recommendation.
http://www.w3.org/TR/1998/REC-xml-19980210
XML-c14n
Canonical XML. W3C Working Draft
http://www.w3.org/TR/1999/WD-xml-c14n-19991115
XML-ns
Namespaces in XML
http://www.w3.org/TR/1999/REC-xml-names-19990114
XPath
XML Path Language (XPath)Version 1.0. W3C Proposed
Recommendation
http://www.w3.org/TR/1999/PR-xpath-19991008
XPointer
XML Pointer Language (XPointer). W3C Working Draft.
http://www.w3.org/1999/07/WD-xptr-19990709
XML-schema
XML Schema Part 1: Structures
http://www.w3.org/TR/1999/WD-xmlschema-1-19991217/
XML Schema Part 2: Datatypes
http://www.w3.org/TR/1999/WD-xmlschema-2-19991217/
XML-Signature-RD
XML-Signature Requirements
http://www.w3.org/1999/08/WD-xmldsig-requirements-990820
XSL
Extensible Stylesheet Language (XSL) W3C Working Draft
Eastlke, Reagle, Solo [Page 38]
Internet Draft XML-Signature Syntax February 2000
http://www.w3.org/TR/2000/WD-xsl-20000112/
XSLT
XSL Transforms (XSLT) Version 1.0. W3C Proposed Recommendation
http://www.w3.org/TR/1999/PR-xslt-19991008
WebData
Web Architecture: Describing and Exchanging Data.
http://www.w3.org/1999/04/WebData
12. Author's Address
[other authors - TBD]
Donald E. Eastlake 3rd
Motorola
65 Shindegan Hill Road
Carmel, NY 10512 USA
Phone: 1-508-261-5434
Email: dee3@torque.pothole.com
Joseph M. Reagle Jr., W3C
Massachusetts Institute of Technology
Laboratory for Computer Science
NE43-350, 545 Technology Square
Cambridge, MA 02139
Phone: 1.617.258.7621
Email: reagle@w3.org
David Solo
Citigroup
666 Fifth Ave, 3rd Floor
NY, NY 10103 USA
Phone: +1-212-830-8118
Email: dsolo@alum.mit.edu
Eastlke, Reagle, Solo [Page 39]
| PAFTECH AB 2003-2026 | 2026-04-24 04:44:32 |