One document matched: draft-ietf-xmldsig-core-02.txt
Differences from draft-ietf-xmldsig-core-01.txt
XML Digital Signatures Working Group D. Eastlake,
INTERNET-DRAFT IBM
draft-ietf-xmldsig-core-02 J. Reagle,
Expires May 19, 1999 W3C/MIT
D. Solo,
Citigroup
XML-Signature Core Syntax
Copyright Notice
Copyright (c) 1999 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/1999/WD-xmldsig-core-19991119/
The latest version of this draft series may be found at:
http://www.w3.org/TR/xmldsig-core
This is a public WG Draft that follows the November IETF meeting.
Consequently it includes a editoral changes and recrafting though no
major design changes. This version includes the experimental use of
XML Schema and XML entity references. The XML schema declarations
within the specification may contain errors, though the complete WG
schema definition does validate to the Schema DTD. We expect the final
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draft will include a DTD and schema.
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 the syntax and processing rules for the
encoding of digital signatures using XML. Such signatures can provide
integrity, message authentication, and/or signer authentication
services for data of any type, whether located within the XML that
includes the signature or locatable elsewhere.
Table of Contents
1. Introduction
1.1 Editorial Conventions
1.2 Design Philosophy
1.3 Namespaces and Identifiers
1.4 Versions
2. Signature Overview
2.1 The Signature Element
2.2 The SignedInfo Element
2.3 The ObjectReference Element
2.4 The Manifest and Package Elements
2.5 The SignatureProperties Element
3. Core Signature Syntax
3.1 The Signature element
3.2 The SignatureValue Element
3.3 The SignedInfo Element
3.4 The KeyInfo Element
3.5 The Object Element
4. Additional Signature Syntax
4.1 The Manifest and Package Elements
4.2 The SignatureProperties Element
4.3 Processing Instructions
4.4 Comments in dsig Elements
5. Algorithms
5.1 Algorithm Identifiers, Parameters, and Implementation
Requirements
5.2 Message Digests
5.3 Message Authentication Codes
5.4 Signature Algorithms
5.5 Canonicalization Algorithms
5.6 Transform Algorithms
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6.0 Processing rules
6.1 Generation
6.2 Signature Validation
7.0 Security Considerations
7.1 Only What is Signed is Secure
7.2 Only What is "Seen" Should be Signed
7.3 Check the Security Model
7.4 Algorithms, Key Lengths, Etc.
8.0 Example syntax
9.0 Schema
10 Definitions
11.0 Other Useful Types (normative)
12.0 References
13.0 Acknowledgements (non-normative)
14.0 Open Issues (non-normative)
1.0 Introduction
This document describes the proposed syntax and processing rules for
the XML Digital Signature specification. This specification provides a
mechanism for applying digital signatures to XML documents and other
Internet resources and encoding those signatures as XML.
The structure allows for both embedded and detached signatures. An
embedded signature can include the signature within the signed object
or embed the signed object within the signature. A detached signature
allows the signature to be independent of the object. The processing
structure allows for switching between embedded and detached
signatures without necessarily invalidating the signature.
This document also defines other useful types including methods of
referencing collections of resources, and key management and algorithm
definitions.
1.1 Editorial Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This document includes a list of open issues which are still being
addressed by the working group and may include editorial comments
within the text.
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 Namespaces and Identifiers
The XML namespace [XML-namespace] URI that MUST be used by
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experimental implementations of this dated specification is:
xmlns="http://www.w3.org/1999/11/xmldsig-core"
While applications MUST support XML and XML-namespaces, the use of
internal entities 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 the 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 specifications
namespace
http://www.w3.org/1999/11/dsig-core/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/1999/11/dsig-core/SHA1
FIPS PUB 180-1. Secure Hash Standard. U.S. Department of
Commerce/National Institute of Standards and Technology.
Finally, in order to provide for terse namespace declarations we use
XML internal entities as macros within URIs. For instance:
<?xml version="1.0" ?>
<!DOCTYPE Signature SYSTEM "xmldsig.dtd" [
<!ENTITY dsig 'http://www.w3.org/1999/10/signature-core'>]>
...
<SignedInfo>
<SignatureMethod Algorithm="&dsig;/dsaWithSHA-1"/>
...
</SignedInfo>
Security Comment: XML processors will automatically expand entity
declarations prior to signature generation. Consequently, this feature
does not permit a substitution attack whereby an attacker replaces the
entity declaration with another so as to change the meaning of the
signature. Furthemore, we define this entity as part of the Signature
XML Schema such that one does not have to rely upon an internal subset
declaration. However, since this specification presently permits a
CanonicalizationMethod of null over SignedInfo, entity declarations
will not be expanded in those instances (or where the schema is not
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present) and we have not completely assessed the security risk.
1.4 Versions
No provision is made for an explicit version number in this syntax. If
a future version is needed, it is expected to use a different
Namespace.
2.0 Signature Overview
This section provides an overview of XML digital signature syntax and
processing. The formal specification is provided in º3. The editors
assume the reader is familiar with basic digital signature and XML
concepts.
2.1 The Signature Element
XML digital signatures are very flexible and may be used to apply
signatures to any type of resource. The resource(s) being signed may
be included within the signature, outside the signature in the same
document, or completely outside of the document.
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 digest calculated over each of the data
objects being signed. The core signature verification includes the
verification of these digests. The algorithms used in calculating the
SignatureValue are also included in the signed information. The
signature can not cover itself so the SignatureValue element is
outside SignedInfo.
KeyInfo indicates what key was used to create the signature, such as
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. However, if the signer wishes to bind the keying
information to the signature, an ObjectReference can easily identify
and include the KeyInfo as part of the signature.
Object is an optional element for including data within a signature.
The data can be optionally typed and/or encoded.
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Signature properties, such as time of signing, can be included in the
SignatureProperties element. (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)
(ObjectReference)+
</SignedInfo>
(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.
The ObjectReference element identifies a resource, specifies any
transformations, specifies the digest algorithm, and includes the
resulting digest value. A resource is signed by computing the contents
digest value and the signature over that value. The signature is later
checked via resource (defn) and signature validation (defn).
2.3 The ObjectReference Element
The ObjectReference element has the structure indicated below.
...
<SignedInfo>
(CanonicalizationMethod)?
(SignatureMethod)
<ObjectReference (URI=? | IDREF=?) Type=?>
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(Transforms)?
(DigestMethod)
(DigestValue)
</ObjectReference>+
</SignedInfo>
...
The optional URI/IDREF attribute of ObjectReference idenitifies the
signed resource.
Several mechanisms are provided for maintaining signature validity
over resources which can not be persistently identified via a URL.
First, no pointer to the signed object need be given at all for one
ObjectReference in a Signature. Second, objects within ObjectReference
need not be identified via URLs, instead location independent URIs
(such as a URN or other URI schemes) are permitted -- by definition.
Note, if a URL is used to identify an ojbect, this acts as an
assertion by the signer that they are signing the content of the
dereferenced URL. Third, the ObjectReference may reference a Manifest
or the like which references instructions for dereferencing the
appropriate content.
The optional Type attribute provides information about the content of
the resource identified by URI/IDREF. In particular, it can indicate
that an Object contains a SignatureProperties, Manifest, or Package
elements.
Transforms is an optional ordered list of processing steps that are
applied to the resource's content before it is digested. Transforms
can include arbitrary specifications such as canonicalization,
encoding/decoding (including compression/inflation), XSLT and XPath.
XSLT/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
we address 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 identified by the URI/IDREF is digested directly.
Arbritrary user specified transforms are permitted. To promote
interoperability, we specify mandatory to implement canonicalization
and decoding algorithms. Additional canonicalization, coding, XSLT,
and XPath based transform algorithms are specified as recommended or
optional;
DigestMethod is the algorithm applied to the object after Transforms
is applied 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 and Package Elements
There are cases where it is efficient to have one signature cover many
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items. One approach is to include multiple ObjectReferences within
SignedInfo. Since the core verification behavior includes verifying
the digests of objects referenced within SignedInfo, some applications
may need an alternative approach which allows pushing the validation
decision to the application. This allows more complex processing to be
defined on an application specific basis. For example, it may be
sufficient if the signature's validity for n out of m of the items can
be verified or there may be a large number of items that it is desired
to sign with multiple signature algorithms and / or keys where listing
all of the items within the SignedInfo element of each Signature is
too verbose.
To answer these requirements, additional object types have been
defined which may be referenced by SignedInfo. The Manifest element is
provided which similarly contains a collection of references and
objects (like SignedInfo), but leaves it entirely up to the
application which digest or digests it will verify. Multiple
signatures over the possibly large number of items in a Manifest need
only point to the Manifest from one ObjectReference in each
signature's SignedInfo.
The structure of Manifest, which reuses the ObjectReference and Object
elements described above, is as follows:
<Manifest>
(ObjectReference)+
(Object)*
</Manifest>
A Package is syntactically identical to a Manifest but asserts the
identity of each of its ObjectReference elements after Transforms
application.
Manifest and Package may appear as the content of an Object.
2.5 The SignatureProperties Element
Statements or assertions concerning data blocks should be included in
those data blocks or in other data blocks signed in parallel with
them. Statements about the signature process itself, however, such as
time of signing or serial number or hardware used in calculation of
the signature, can be included in a SignatureProperties block. Such
blocks can be signed, via an ObjectReference, or not, as appropriate.
<SignatureProperties>
<SignatureProperty Target= >
(ObjectReference)+
(Object)*
</SignatureProperty>*
</Manifest>
The structure of SignatureProperties is shown above. It reuses the
ObjectReference and Object elements. The mandatory Target attribute
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references the element to which the property applies.
3.0 Core Signature Syntax
The general structure of an XML signature is described in section 2
above. This section provides detailed syntax of the core signature
features and actual exampes. The syntax is defined via [XML-Schema]
with the following XML preamble, declaration, and internal entity:
<?xml version='1.0'?>
<!DOCTYPE schema
SYSTEM
'http://www.w3.org/TR/1999/WD-xmlschema-1-19991105/structures.dtd'
[
<!ENTITY dsig 'http://www.w3.org/1999/10/signature-core'>
]>
<schema targetNS='http://www.w3.org/1999/10/signature-core'
version='0.1'
xmlns='http://www.w3.org/1999/XMLSchema'>
<textEntity
name="dsig">http://www.w3.org/1999/10/signature-core</textEntity>
3.1 The Signature element
The Signature element is the root element of a XML Signature. A simple
example of a complete signature follows:
<!DOCTYPE Signature [
<!ENTITY dsig 'http://www.w3.org/1999/10/signature-core'>]>
<Signature xmlns="http://www.w3.org/1999/11/xmldsig-core">
<SignedInfo>
<!ENTITY dsig "http://www.w3.org/1999/11/xmldsig-core">
<CanonicalizationMethod
Algorithm="http://www.w3.org/1999/07/WD-xml-c14n-19990729"/>
<SignatureMethod Algorithm="&dsig;/dsaWithSHA-1"/>
<ObjectReference Location="http://www.mypage.com">
<DigestMethod Algorithm="&dsig;/sha1"/>
<DigestValue encoding="&dsig;/base64">a23bcd43</DigestValue>
</ObjectReference>
</SignedInfo>
<SignatureValue >dd2323dd</SignatureValue>
<KeyInfo>
<keyname>Solo</keyname>
</KeyInfo>
</Signature>
Note: this example will be revised to include generated hash/signature
values that validate.
<element name='Signature'>
<archetype order='seq' content='elemOnly'>
<element ref='SignedInfo'/>
<element ref='SignatureValue'/>
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<element ref='KeyInfo' minOccurs='0' maxOccurs='1' />
<element ref='Object' minOccurs='0' maxOccurs='*'/>
</archetype'>
</element>
3.2 The SignatureValue Element
The SignatureValue element contains the actual value of the digital
signature. The encoding of this value is determined by the
SignatureMethod used. For all SignatureMethods specified herein, that
encoding is Base 64 [RFC2045]. The ability to define a SignatureMethod
and SignatureValue pair which includes multiple distinct signatures is
explicitly permitted (e.g. "rsawithsha-1 and ecdsawithsha-1").
<element name='SignatureValue' type='string'/>
3.3 The SignedInfo Element
The structure of SignedInfo includes a canonicalization algorithm, a
signature algorithm, and one or more references to objects. The
SignedInfo element may contain an optional ID attribute that will
allow it to be referenced by other signatures and objects.
<element name='SignedInfo'>
<archetype order='seq' content='elemOnly'>
<element ref='CanonicalizationMethod' minOccurs='0'
maxOccurs='1'/>
<element ref='SignatureMethod'/>
<element ref='ObjectReference' minOccurs='1' maxOccurs='*'/>
<attribute name='Id' type='ID' />
</archtype>
</element>
SignedInfo does not include explicit signature properties. If an
application needs to associate properties (such as signing time,
signing device, etc.) with the signature, it may add an additional
Object that includes that data and reference that Object via an
ObjectReference. See the SignatureProperties element below.
3.3.1 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 in which a URI is used to identify the
algorithm and the contents of the element contain any parameter needed
by the algorithm. Possible options may include a minimal algorithm
(CRLF and charset normalization), or more extensive operations such as
[XML-C14N]. An expected default for this value will be defined once
the specification of XML aware canonicalization algorithms are
finalized. If the CanonicalizationMethod is omitted, no change is made
to SignedInfo.
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<element name='CanonicalizationMethod'>
<archetype>
<attribute name='Algorithm' type='uri' />
</archetype>
</element>
3.3.2 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, etc.). This
element uses the general structure here for algorithms in which a URI
is included as an attribute naming the algorithm and contents of the
element contain any parameter needed by the algorithm. While there is
a single identifier, that identifier may specify a format containing
multiple distinct signature values.
<element name='SignatureMethod'>
<archetype>
<attribute name='Algorithm' type='uri' />
</archetype>
</element>
3.3.3 The ObjectReference Element
ObjectReference is an element that may occur one or more times. It
identifies the object being signed, the type of the object, an
optional list of transforms to be applied prior to digesting, a digest
algorithm and digest value. An optional ID attribute permits an
ObjectReference to be easily referenced from elsewhere.
<element name='ObjectReference' minOccurs='1' maxOccurs='*'>
<archetype order='seq'>
<element ref='Transforms' minOccurs='0' maxOccurs='*'/>
<element ref='DigestMethod'/>
<element ref='DigestValue'/>
<attribute name='Id' type='ID' />
<attribute name='URI' type='uri' />
<attribute name='IDREF' type='IDREF' />
<attribute name='Type' type='string' />
</archetype>
</element>
The URI/IDREF attribute identifies the Object using a URI [URI] or
IDREF [XML]. We distinguish between URIs and IDREFs so as to provide
expositional clarity and ease signature processing in the face of
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.
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This choice permits ObjectReferences to identify a fragment of a
document that is encoded: the ObjectReference identifies the resource,
the first Transform specifies decoding, the second Transform specifies
the fragement.
Note that a null URI (URI="") is permitted and identifies the parent
document.
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 ommit this attribute given
the identity of the object is part of the application context. This
attribute may be omitted from at most one ObjectReference in any
particular SignedInfo, Manifest, or Package.
The digest algorithm is applied to the content yielded after the URI
is dereferenced, decoded, and transformed. If the URI indicates an XML
document, the document is assumed to be unparsed prior to the
application of Transforms. If there are no Transforms, then the
indicated resource is passed to the digest algorithm unmodified.
The optional Type attribute contains information about the type of
object being signed (e.g. manifest, package, signature properties,
document). This is represented as a URI. For example:
Type="&dsig;/Manifest"
Type="&dsig;/SignatureProperty"
3.3.3.1 The Transforms Element
Transforms is an optional element that contains one or more operations
to be performed on an indicated resource prior to digest calculation.
(These operations are different from the CanonicalizationMethod
specified in the Signature that id applied over SignedInfo.) If the
Transforms element is omitted, the exact data referenced is digested
byte for byte.
The Transforms element contains an ordered list of Transform elements.
The output of each Transform serves as input to the next Transform.
The input to the first Transform is the raw data yielded by
dereferencing the resource identifier. The output from the last
Transform is the input for the DigestMethod algorithm.
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
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processing.
<element name='Transforms' minOccurs='0' maxOccurs='1'>
<archetype>
<element ref='Transform'/>
<attribute name='Algorithm' type='string' />
</archetype>
</element>
<element name='Transform' minOccurs='1' maxOccurs='*'>
<archetype>
<attribute name='Algorithm' type='uri' />
<attribute name='Encoding' type='uri' />
<attribute name='Type' type='uri' />
</archetype>
</element>
Examples of resource transforms include but are not limited to base-64
decoding [RFC2045], 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 the Java
Transform algorithm. However, applications should refrain from using
application-specific transforms whenever possible since the resulting
signature will not necessarily be verifiable outside of the
application domain. The section Transform Algorithms defines the list
of standard transformations.
Implementation Comment: When transformations are applied the signer is
not signing the native (original) document but the resulting
(transformed) document.
3.3.3.2 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 in which a URI is included as an
attribute naming the algorithm and optional contents of the element
contain any parameter needed by the algorithm.
<element name='DigestMethod'>
<archetype>
<element name='Parameter' minOccurs='0' maxOccurs='*'/>
<attribute name='Algorithm' type='uri' />
</archetype>
</element>
3.3.3.3 The DigestValue Element
DigestValue is an element which contains the encoded value of the
digest. The optional Encoding attribute gives the encoding method
which defaults to Base 64 [RFC2045].
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<element name='DigestValue' type='string'>
<archetype>
<attribute name='Encoding' type='uri' default="&dsig;/Base64"/ />
</archetype>
</element>
3.4 The KeyInfo Element
KeyInfo may contain keys, names, certificates and other public key
management information (such as inband key distribution or agreement
data or data supporting any other method.) This specification defines
a few simple types but applications may place (embed) their own key
identification and exchange semantics within this element through the
XML-namespace facility. [XML-namespace]
<element name='KeyInfo' minOccurs='0' maxOccurs='1'>
<archetype order='seq' content='any'>
<element name='KeyName' type='string' />
<element name='KeyValue' type='string' />
<element name='SubjectName' type='string' />
<element name='RetrievalMethod' type='string' />
<element ref='X509Data' type='string'>
<element ref='PGPData' type='string'>
<element name='MgmtData' type='string' minOccurs='0'
maxOccurs='1'/>
</archetype>
</element>
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. This element contains one KeyInfo
data element providing information for the recipient(s). 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 name, index, 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).
* SubjectName contains one or more names for the sender. Forms to be
supported include a simple name string, encoded DN, email address,
etc.
* 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
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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.
<element name='X509Data' type='string'>
<archetype order='seq' content='any'>
<element name='X509IssuerSerial' type='string'>
<archetype order='seq' content='elemOnly'>
<element name='X509Name' type='string' />
<element name='X509SerialNumber' type='string' />
</archetype>
</element>
<element name='X509SKI' type='string' />
<element name='X509Name' type='string' />
<element name='X509Certificate' type='string' />
<element name='X509CRL' type='string' />
</archetype>
</element>
<element name='PGPData' type='string'>
<archetype order='seq' content='elemOnly'>
<element name='PGPKeyID' type='string' />
<element name='PGPKeyPacket' type='string' />
</archetype>
</element>
<element name='MgmtData' type='string' minOccurs='0' maxOccurs='1'/>
</archetype>
</element>
Note: This section is preliminary. A more detailed version will be
included in a subsequent version of this specification.
3.5 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 type, ID, and encoding attributes.
The Object's ID is referenced from the ObjectReference in SignedInfo.
This element is used for embedded 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. If the application wishes to exclude the <Object> tags from the
digest calculation a transform must be used. (Exclusion of the object
tags may be desired for cases where the signature is intended to
survive a change between embedded and detached objects 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.)
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<element name='Object' minOccurs='0' maxOccurs='*'>
<archetype content='any'>
<attribute name='Id' type='ID' />
<attribute name='Type' type='uri' />
<attribute name='Encoding' type='uri' />
</archetype>
</element>
4.0 Additional Signature Syntax
This section describes the optional to implement Manifest and Package
elements and describes the handling of XML Processing Instructions and
Comments.
4.1 The Manifest and Package Elements
The Manifest element provides a list of ObjectReferences. 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
verification 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.
A Package has the same syntax as a Manifest but also asserts the
equality of each of its referenced objects, after any transforms. The
testing of this equality and action if it fails is also entirely at
the discretion of the applicaiton.
<element name='Manifest'>
<archetype>
<element ref='ObjectReference' minOccurs='1' maxOccurs='*'/>
<element ref='Object' minOccurs='0' maxOccurs='*'/>
<attribute name='Id' type='id' />
</archetype>
</element>
<element name='Package'>
<archetype>
<element ref='ObjectReference' minOccurs='1' maxOccurs='*'/>
<element ref='Object' minOccurs='0' maxOccurs='*'/>
<attribute name='Id' type='id' />
</archetype>
</element>
4.2 4.2 The SignatureProperties Element
Additional information items concerning the signature or particular
ObjectReferences can be placed in SignatureProperty elements within a
SignatureProperties element within an Object. This should be such
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information as signing time or the serial number of crypto hardware
used. An additional information concerning data being signed should be
with that data.
<element name='SignatureProperties' >
<archetype >
<element ref='SignatureProperty' minOccurs='1' maxOccurs='*'>
<attribute name='Target' type='idref' />
</archetype>
</element>
4.3 Processing Instructions
TDB - will specify the use, if any, of XML processing instructions by
this specification and the handling of PIs appearing within elements
specified in this document.
4.4 4.4 Comments in dsig Elements
TDB - will specify the use, if any, and handling of XML comments
appearing within elements specified in this document.
5.0 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.
5.1 Algorithm Identifiers, Parameters, 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 they 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 description
element name, which is frequently algorithm specific, and MUST be in
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 &dsig;/sha1
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Encoding
Base64 REQUIRED &dsig;/base64
QuotedPrintable RECOMMENDED &dsig;/qp
MAC
HMAC-SHA1 REQUIRED &dsig;/hmac-sha1
Signature
DSAwithSHA1 (DSS) REQUIRED &dsig;/dsa
RSAwithSHA1 RECOMMENDED &dsig;/rsa-sha1
ECDSAwithSHA1 OPTIONAL &dsig;/ecdsa
Canonicalization
minimal REQUIRED &dsig;/minimal
XML-Canonicalization RECOMMENDED
http://www.w3.org/1999/07/WD-xml-c14n-19990729
Transform
XSLT RECOMMENDED http://www.w3.org/TR/1999/PR-xslt-19991008
XPath RECOMMENDED http://www.w3.org/TR/1999/PR-xpath-19991008
XPointer RECOMMENDED http://www.w3.org/1999/07/WD-xptr-19990709
Java OPTIONAL urn:ECMA-org:java
5.2 Message Digests
Only one digest algorithm is defined herein. However, it is expected
that one or more additional strong digest algorithms will come out of
the US Advanced Encryption Standard effort. Use of MD5 [RFC xxxx] is
NOT RECOMMENDED because recent advances in cryptography have cast
doubt on its strength.
Digest algorithms take as an implicit parameter a byte string to be
digested.
5.2.1 SHA-1
The SHA-1 algorithm [SHA-1] identifier is &dsig;/sha1. The SHA-1
algorithm takes no explicit parameters. An example of an SHA-1
DigestAlg element is
<DigestMethod Algorithm="&dsig;/sha1"/>
An 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. 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>
5.3 Message Authentication Codes
MAC algorithms take two implicit parameters, their keying material
determined from KeyInfo and the byte stream output by
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CanonicalizationMethod or SignedInfo directly if there is no
CanonicalizationMethod. MACs and signature algorithms are
syntactically identical but a MAC implies a shared secret key.
5.3.1 HMAC
The HMAC algorithm [HMAC] identifiers are &dsig;/hmac-sha1. The HMAC
algorithm takes the truncation length in bits as a parameter
(parameter identifier urn:ietf-org:hmac-outputlength). An example of
an HMAC SignatureMethod element:
<SignatureMethod Algorithm="&dsig;/hmac-sha1">
<hmac-outputlength xmlns="&dsig;/hmac-sha1">
128
</hmac-outputlength>
</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-MD5 digest
9294727A 3638BB1C 13F48EF8 158BFC9D
from the test vectors in [RFC 2104] would be
<SignatureValue>kpRyejY4uxwT9I74FYv8nQ==</SignatureValue>
5.4 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
CanonicalizationMethod. Signature and MAC algorithms are syntactically
identical but a signature implies public key cryptography.
5.4.1 DSA
The DSA algorithm [DSA] identifier is &dsig;/dsa. The DSA algorithm
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 PKCS #1 specification with a k
parameter equal to 20. Example: the SignatureValue element for a DSA
signature (r, s) with values specified in hexadecimal
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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.
<!ELEMENT DssKeyValue (P, Q, G, Y, J?, (seed, pgenCounter)?) >
<!-- Each of these fields consists a CDATA where the data is base64
encoded -->
5.4.2 RSA
The expression "RSA algorithm" as used in this document refers to the
RSASSA-PKCS1-v1_5 algorithm described in RFC 2437 [RSA].
The RSA algorithm identifiers are &dsig;/rsa-sha1 and
urn:rsasdi-com:rsa-md5. 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.
<!ELEMENT RSAKeyValue ( Modulus, Exponent ) > <!-- Each field contains
a CDATA which is the value for that item base64 encoded -->
5.4.3 ECDSA
The expression ECDSA [ECDSA] as used in this document refers to the
signature algorithms specified in ANSI X9.62. Additional details are
to be provided.
5.5 5.5 Canonicalization Algorithms
5.5.1 Null Canonicalization
Null canonicalization, i.e., no modification whatsoever, can be
achieved for signed data by simply not putting any canonicalization in
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the Transforms element (omitting it entirely if no other tranforms are
needed) for a data object or omitting CanonicalizationMethod for
SignedInfo.
5.5.2 Minimal Canonicalization
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
This algorithm is only applicable to XML resources.
5.5.3 Canonical XML
The algorithm identifier for XML canonicalization is
http://www.w3.org/1999/07/WD-xml-c14n-19990729. An example of an XML
canonicalization element is
<CanonicalizationMethod
Algorithm="http://www.w3.org/1999/07/WD-xml-c14n-19990729"/>
See the Canonical XML specification.
5.6 Transform Algorithms
A Transform algorithm has three implicit parameters. The first is the
byte stream from the ObjectReference URI/IDREF 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 severe 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.
5.6.1 Canonicalization
Any canonicalization algorithm that can be used for
CanonicalizationMethod can be used as a Transform.
5.6.2 Base-64 and Quoted-Printable Decoding
The Algorithm values for the base 64 and quoted-printable decoding
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transforms [RFC2045] are &dsig;/base64 and &dsig;/qp.
The base-64 Transform element has no content. The input (from the
URI/IDREF or from the previous Transform) 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.
5.6.3 XPath Filtering
The Algorithm value for the XPath filtering transform is
"http://www.w3.org/TR/1999/PR-xpath-19991008"
The Transform element content MUST conform to the XML Path Language
(XPath) syntax.
XPath assumes that an XML processor has processed the input resource.
So, for example, entity reference expansion, normalization of
linefeeds and attribute values are normalized, and CDATA section
replacement are expected. As well, XPath joins all consecutive text
characters into a single text nodes.
The input resource MUST be a well-formed XML document. The result of
applying the XPath to the input resource MUST be a node-set (as
defined in XPath). The output of this transform is a new XML document
with the following characteristics:
1. The output document has the XML declaration of the input resource
(see rule 23 XMLDecl in XML specification). If the encoding is
UTF-16, the output document has the same byte order mark as the
input resource.
2. The output document contains the nodes in the node-set identified
by the XPath, and excludes the nodes of the input resource that
are not not in the node-set identified by the XPath.
3. The nodes in the output document appear in the document order (as
defined in XPath) of the input resource.
4. The output document has all of the input resource's entity
references expanded, except that characters corresponding to
illegal XML are reencoded as character references (XML rule 66)
except the ampersand and less than symbol, which are encoded using
& and <, respectively.
5. Attribute values are normalized in accordance with the rules for a
validating XML processor (even if the implementation did not use a
validating XML processor to parse the input resource).
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
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).
5.6.4 XPointer Filtering
The Algorithm value for the XPointer filtering transform is
"http://www.w3.org/1999/07/WD-xptr-19990709".
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The Transform element content MUST conform to the XML Pointer Language
(XPointer) syntax.
The processing rules for XPointer filtering are identical to those for
XPath filtering (stated above), except that the additional
functionality offered by XPointer can be utilized in constructing the
output node-set.
The XPointer filter is particularly important if the input resource is
processed by a validating XML processor since the XPointer barename
shortcut could then be used to implement the well-known fragment
identification by ID attribute.
NOTE: In application environments with severe resource limitations,
applications MAY constrain XPointer support to barename processing and
also to determination of the ID attribute by means other than a
validating XML processor. In fact, the use of an XML processor for
barename resolution is OPTIONAL. However, the output expectations of
this transform MUST be supported by the application.
5.6.5 XSLT Transform
The Algorithm value for the XSLT transform is
"http://www.w3.org/TR/1999/PR-xslt-19991008"
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.
5.6.6 Java Transform
The Algorithm value for the Java transform is urn:ECMA-org:java.
Details to be determined.
Although the Algorithm attribute of a Transform can take
application-specific values, having a Java transform seems to be the
most reasonable way to allow application-specific transforms that can
be processed outside of the application domain.
6.0 Processing rules
These sections describe the operations to be performed as part of
signature generation and validation. The description is of a logical
behavior and does not specify an order of execution, nor specify
discrete steps.
6.1 Generation
1. apply Transforms determined by application to each object being
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signed.
2. calculate digest over each transformed object (including start and
end tags)
3. create ObjectReference element(s) including location of object,
digest, digest algorithm, and transform elements, if required.
4. create SignedInfo element with SignatureMethod,
CanonicalizationMethod if required, and ObjectReference(s).
5. canonicalize and calculate signature over SignedInfo based on
algorithms in step 4.
6. construct signature document with SignedInfo, Object (s) (if
desired, encoding may be different than that used for signing),
KeyInfo (if required), and SignatureValue.
6.2 Signature Validation
1. locate object and apply Transforms to the specified resource based
on each ObjectReference(s) in the SignedInfo element. Each
transform is applied in order from left to right to the object
with the output of each transform being the input to the next.
2. calculate digest over each transformed signed object(s) (including
start and end tags) based on the algorithm in ObjectReference(s).
3. compare value against DigestValue in SignedInfo for each reference
(if any mismatch, validation fails).
4. canonicalize the SignedInfo element based on the
CanonicalizationMethod, if any, in SignedInfo.
5. obtain the validation keying info from KeyInfo or externally.
6. validate the SignatureValue based on the SignatureMethod in the
SignedInfo element, the key obtained in step 5, and the results of
step 4. - Digest calculation is performed over the SignedInfo
element including start and end tags.
Any processing beyond cryptographic validation (e.g. certificate
validation, applicability decisions, time related processing) is
outside the scope of this specification.
7.0 Security Considerations
The XML digital signature standard provides a very flexible mechanism.
In designing a system to make use of it, due consideration should be
given to the threat model being defended against and to the factors
covered in the subsections below.
7.1 Only What is Signed is Secure
The flexible Transforms mechanism, including canonicalization and
explicit filtering and extraction, permit securing only a subset of
data in an object. This is good for many applications where a limited
portion of an object must change after the signature or different
signatures secure different parts or the application modifies aspects
of the object that are not significant and can be omitted from
signature coverage or the like. Keep in mind that whenever this is
done, those aspects that are not signed can be arbitrarily modified
and the signature will still validate.
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7.2 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
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.
7.3 Check the Security Model
This standard specifies public key signatures and secret key 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 secret key
can create signatures. The number of holders of the secret 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 secret key is an
important issue, usually addressed by certificate or on line 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 "key" which is a physical
characteristic of the user and thus can not be changed the way public
or secret keys can be and may have other security model differences.
7.4 Algorithms, Key Lengths, 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 [RFC 1750] and the size of
the key, the security of key and certificate authentication and
distribution mechanisms, protection of all 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,
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while critical to the overall security of a system, are mostly beyond
the scope of this document.
8.0 Example syntax
<Signature xmlns="http://www.w3.org/1999/11/xmldsig-core">
<SignedInfo ID="5">
<CanonicalizationMethod
Algorithm="http://www.w3.org/1999/07/WD-xml-c14n-19990729"/>
<SignatureMethod Algorithm="&dsig;/dsa"/>
<ObjectReference URI="http://www.mypage.com">
<Transforms>
<Transform Algorithm="&dsig;/null">
<Encoding Algorithm="&dsig;/base64"/>
</Transforms>
<DigestMethod Algorithm="&dsig;/sha1"/>
<DigestValue>a23bcd43</DigestValue>
</ObjectReference>
<ObjectReference IDREF="timestamp"
Type="&dsig;/signatureattributes">
<Transforms>
<CanonicalizationMethod name="http://..."/>
</Transforms>
<DigestMethod Algorithm="&dsig;/sha1"/>
<DigestValue>a53uud43</DigestValue>
</ObjectReference>
</SignedInfo>
<SignatureValue>dd2323dd</SignatureValue>
<Object ID="timestamp"
type="&dsig;/SignatureAttributes" >
<timestamp about="5"
xmlns="http://www.ietf.org/rfcXXXX.txt">
<date>19990908</date>
<time>14:34:34:34</time>
</timestamp>
</Object>
<KeyInfo>
<keyname>Solo</keyname>
</KeyInfo>
</Signature>
9.0 Schema
[TBD: xmldsig-core-schema-19991117.xml]
10 Definitions
[needs work]
Authentication, Message
?
Authentication, Signer
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?
Data
?
Object
An XML element defined by this specification for embedding
resources within a signature.
Resource
"A resource can be anything that has identity." [URI]
Validation, Resource
When the value of hash over the transformed content yielded
from the dereferenced URI matches the DigetsValue in
SignedInfo.
Validation, Signature
When the SignatureValue matches the result of processing
SignedInfo with CanonicalizationMethod and SignatureMethod as
specified in º6.2, including the resource validation of
SignedInfo ObjectReferences.
Validation, Trust
When the application determines that the semantics associated
with the signature are valid. For example, the validation of
time stamps or confirming the integrity of the signer key.
11 Other Useful Types (normative)
We define the following types for use in identifying XML resources
that include Signture semantics.
http://www.w3.org/1999/11/xmldsig-core/SignatureProperties
designates that the referenced resource is a statement about
the referring signature.
http://www.w3.org/1999/11/xmldsig-core/Manifest
designates that the referenced resource is a collection of
other resources.
http://www.w3.org/1999/11/xmldsig-core/Package
designates that the referenced resources is a collection of
other resources and the creator of that collection asserts that
the specified resources, when transformed as specified, yield
the same exact content.
12 References
DOMHASH
Internet Draft. Digest Values for DOM (DOMHASH)
http://search.ietf.org/internet-drafts/draft-hiroshi-dom-hash-0
1.txt .
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DSS
FIPS PUB 186-1. Digital Signature Standard (DSS). U.S.
Department of Commerce/National Institute of Standards and
Technology.
http://www.ietf.org/rfc/rfc2104.txt
ECSDA
?ANSI X9.62
HMAC
RFC 2104. HMAC: Keyed-Hashing for Message Authentication. H.
Krawczyk, M. Bellare, R. Canetti. INFORMATIONAL.
MD5
RFC 1321. The MD5 Message-Digest Algorithm. R. Rivest.
INFORMATIONAL.
http://www.ietf.org/rfc/rfc1321.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
RFC1750
RFC1750 -- Randomness Recommendations for Security.
http://www.ietf.org/rfc/rfc1750.txt
RFC2045
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
RFC2119
RFC2119 -- Key words for use in RFCs to Indicate Requirement
Levels.
http://www.ietf.org/rfc/rfc2119.txt
RSA
RFC 2437. PKCS #1: RSA Cryptography Specifications Version 2.0.
B. Kaliski, J. Staddon. INFORMATIONAL.
http://www.ietf.org/rfc/rfc2432.txt
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
URI
RFC2396 - Uniform Resource Identifiers (URI): Generic Syntax
http://www.ietf.org/rfc/rfc2396.txt
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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-Canonicalization
Canonical XML. W3C Working Draft
http://www.w3.org/1999/07/WD-xml-c14n-19990729
XML-namespace
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-1-19991105/
XML Schema Part 2: Datatypes
http://www.w3.org/TR/1999/WD-xmlschema-2-19991105/
XML-Signature-RD
XML-Signature Requirements
http://www.w3.org/1999/08/WD-xmldsig-requirements-990820
XSL
Extensible Stylesheet Language (XSL) W3C Working Draft
http://www.w3.org/TR/1999/WD-xsl-19990421
XSLT
Eastlake, Reagle, Solo [Page 29]
Internet Draft XML-Signature Core Syntax November 1999
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
13.0 Acknowledgements (non-normative)
* Milton Anderson, FSTC
* Mark Bartel, JetForm Corporation (Author)
* John Boyer, UWI.com (Author)
* Richard Brown, Globeset
* Donald Eastlake 3rd, IBM (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.
* Chris Smithies, PenOp
* David Solo, Citigroup (Editor)
* Winchel Todd Vincent III, GSU
* Greg Whitehead, Signio Inc.
14.0 Open Issues (non-normative)
1. More detail for KeyInfo types, based on IETF'46, we need proposals
for the actual XML'ized algorithm parameters.
2. Make sure we are consistent with respect to types, algorithm IDs,
URIs, etc.
3. The signature data structures specified in this document are not
yet associated with a data model.
Eastlake, Reagle, Solo [Page 30]
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