XMLDSIG Working Group Richard D. Brown
GlobeSet, Inc.
Expires December 1999 June 1999
Digital Signatures for XML
------- ---------- --- ---
Richard D. Brown
GlobeSet, Inc.
Document Status
This document, file name <draft-ietf-xmldsig-signature-00.txt> is
intended to become a Proposed Standard RFC. Distribution of this
document is unlimited. Comments should be sent to the XMLDSIG
mailing list or to the author. Additional information can be found
on the web sites maintained by the working group.
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
Abstract
This specification defines syntax and procedures for the computation,
verification, and encoding of digital signatures using XML. In
addition, it proposes a solution to authenticating Web resources by
means of XML.
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Revision History
18-June-99:
Remove Comments and Suggestions chapter,
Change Mailing List Reference
Add Contacts Section
04-April-99:
Fix numerous typos,
Complete the algorithm chapters,
Add a Comments and Suggestions chapter,
Insert the DTD definition,
Add a Resources element -- CS #99122601
13-October-98:
Revision to reflect 1998-09-16 XML Namespaces proposal
16-June-98:
Initial Draft
Contacts
Chair(s):
Donald Eastlake 3rd <dee3@torque.pothole.com>
Joseph Reagle Jr. <reagle@w3.org>
Author:
Richard D. Brown <rdbrown@globeset.com>
Mailing List:
Discussion: w3c-ietf-xmldsig@w3.org
Archive: http://lists.w3.org/Archives/Public/w3c-ietf-xmldsig
Subscription: w3c-ietf-xmldsig-request@w3.org
specify (un)subscribe in SUBJECT line with an empty body.
Web Sites:
IETF: http://www.ietf.org/html.charters/xmldsig-charter.html
W3C: http://www.w3.org/Signature
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Table of Contents
Document Status............................................1
Abstract .................................................1
Revision History ..........................................2
Contacts...................................................2
Table of Contents..........................................3
1. Introduction............................................5
2. Objective and Requirements..............................5
3. Signature Basics........................................6
3.1 Signature Element......................................6
3.2 Resources Element......................................7
3.3 Other Attributes Element...............................7
3.4 Originator and Recipient Information Elements..........8
3.5 Key Agreement Algorithm Element........................9
3.6 Signature Algorithm Element............................9
4. Signature Principles....................................9
4.1 Enabling Signature in XML Applications.................9
4.2 Encapsulating Arbitrary Contents......................10
4.3 Implementing Endorsement..............................11
4.4 Supporting Composite Documents........................11
4.5 Facilitating One-pass Processing......................13
5. Syntax Comments........................................14
5.1 Namespace Attributes..................................14
5.2 dsig:eval Global Attribute............................14
5.3 Uniform Resource Names................................15
5.4 Basic Data Types......................................16
5.5 Algorithm Definitions.................................16
6. Detailed Signature Syntax..............................17
6.1 Algorithm.............................................17
6.2 Attribute.............................................18
6.3 Attributes............................................18
6.4 Certificate...........................................19
6.5 Certificates..........................................20
6.6 ContentInfo...........................................20
6.7 Date..................................................21
6.8 Digest................................................21
6.9 DigestAlgorithms......................................22
6.10 Identifier...........................................22
6.11 Integer..............................................23
6.12 IssuerAndSerialNumber................................23
6.13 KeyAgreementAlgorithm................................24
6.14 Keyword..............................................24
6.15 Locator..............................................25
6.16 Manifest.............................................25
6.17 OriginatorInfo.......................................26
6.18 Package..............................................27
6.19 Parameter............................................27
6.20 Real.................................................28
6.21 RecipientInfo........................................29
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6.22 Resource.............................................29
6.23 Resources............................................30
6.24 Signature............................................30
6.25 SignatureAlgorithm...................................31
6.26 Signatures...........................................31
6.27 Value................................................32
7. Default Document Element...............................32
8. Standard Attributes....................................34
8.1 Signing-time Attribute................................34
9. Digest Algorithms......................................34
9.1 SHA1..................................................35
9.2 DOM-HASH..............................................35
9.3 XHASH.................................................36
10. Key Agreement Algorithms..............................37
10.1 PKCS12-PBE...........................................38
11. Key Exchange Algorithms...............................39
11.2 Diffie Hellman.......................................39
12. Signature Algorithms..................................39
12.1 HMAC.................................................39
12.2 DSA..................................................41
12.3 RSA-Encryption.......................................42
12.4 ECDSA................................................43
13. References............................................43
14. Signature DTD.........................................44
15. Embedded Content Example..............................49
16. Detached Signature Example............................51
17. Domain-specific Example...............................52
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1. Introduction
XML, the Extensible Markup Language [x], is a syntactical standard
elaborated by the World Wide Web Consortium. Subset of an
international text-processing standard known as SGML (Standard
Generalized Markup Language), XML is intended primarily for
structuring data exchanged and served over the World Wide Web.
Structuring information permits data to be easily read, exchanged,
and acted upon by software agents. It is a first step toward the
production of a Web of machine-readable semantics. But, the
usefulness of such structured information is limited if its
authenticity and trustworthiness cannot be verified. The Web cannot
suffice with XML - it needs Signed-XML.
2. Objective and Requirements
The objective of this specification is to define syntax and
procedures for the computation, verification, and encoding of digital
signatures using XML. It proposes a solution to authenticating Web
resources by means of XML.
This specification has been established in light of the requirements
that have been gathered while reviewing diverse projects and
alternative proposals such as IOTP [x], BIPS [x], SDML [x], FSML [x]
and XMLDSIG [x]. Previous experiences with binary cryptographic
syntaxes such as PKCS#7 [x] and CMS [x] have also played an
important role in this specification.
The redaction of this specification has been driven by the following
requirements:
- The solution shall provide a means for building authentication
into XML applications, but shall also propose an XML
alternative to binary signature syntax for signing arbitrary
contents.
- The solution shall provide for digital signature and message
authentication codes, considering symmetric and asymmetric
authentication schemes as well as dynamic establishment of
keying material.
- The solution shall provide for certificate-based and account-based
authentication schemes.
- The solution shall provide a mechanism that eases the production
of composite documents that consist of the combination by addition
or deletion of authenticated blocks of information, while
preserving verifiability of the origin and authenticity of
these blocks of information.
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- The solution shall enable authentication of part or totality of a
Web document.
- The solution shall enable authentication of internal and external
resources.
- The solution shall provide for extended signature functionality
such as co-signature, endorsement, plurality of recipients, etc.
3. Signature Basics
3.1 Signature Element
This specification consists primarily of the definition of an XML
element known as the Signature element. This element is comprised of
two sub elements. The first one is a set of authenticated attributes,
known as the signature Manifest, which comprises such things as a
unique reference to the resources being authenticated and an
indication of the keying material and algorithms being used. The
second sub-element consists of the digital signature value.
<Signature>
<Manifest>
(resources information block)
(other attributes)
(originator information block)
(recipient information block)
(key agreement algorithm information block)
(signature algorithm information block)
</Manifest>
<Value encoding='encoding scheme'>
(encoded signature value)
</Value>
</Signature>
The digital signature is not computed directly from the pieces of
information to be authenticated. Instead, the digital signature is
computed from a set of authenticated attributes (the Manifest), which
includes a reference to, and a digest of, these pieces of
information. The authentication is therefore 'indirect'.
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3.2 Resources Element
The Resources element consists of a collection of Resource elements
that, in turn, consist of a unique and unambiguous reference to a
resource being authenticated. Each Resource element is constructed of
a locator, a fingerprint, and optionally a content-type qualifier.
<Resources>
<Resource>
<Locator href='resource locator'/>
<ContentInfo type='type qualifier'/>
<Digest>
(digest information block)
</Digest>
</Resource>
<Resource>
...
</Resource>
</Resources>
The resource locator is implemented as a simple XML Link [x]. This
not only provides a unique addressing scheme for internal and
external resources, but also facilitates authentication of composite
documents.
3.3 Other Attributes Element
The Attributes element consists of a collection of Attribute elements
that enable attachment and authentication of specific pieces of
information that relate to a given signature. An Attribute element is
constructed of a type, a criticality, and a value.
<Attributes>
<Attribute type='signing-time' critical='true'>
<Date value='1998-10-28T08:15-0500' />
</Attribute>
<Attribute type='private-type' critical='false'>
(ANY attribute value)
</Attribute>
</Attributes>
The attribute value consists of ANY content that is defined in the
application DTD. Nevertheless, to facilitate the adoption of
'standard' attributes, the Signature DTD provides for common types
such as 'signing time.'
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3.4 Originator and Recipient Information Elements
The purpose of the Originator and Recipient information elements
consists of providing identification and keying material for these
respective parties.
<OriginatorInfo>
(identification information block)
(keying material information block)
</OriginatorInfo>
<RecipientInfo>
(identification information block)
(keying material information block)
</RecipientInfo>
The actual content of these two elements depends on the
authentication scheme being used and the existence or non-existence
of a prior relationship between the parties. In some circumstances,
it may be quite difficult to distinguish between identification and
keying material information. A unique reference to a digital
certificate provides for both. This may also stand true for an
account number when a prior relationship exists between the parties.
The Originator information element is mandatory. Depending on the
existence or non-existence of a prior relationship with the
recipient, this block either refers to a public credential such as a
digital certificate or displays a unique identifier known by the
recipient.
The Recipient information element may be used when a document
contains multiple signature information blocks, each being intended
for a particular recipient. A unique reference in the Recipient
information block helps the recipients identify their respective
Signature information block.
The Recipient information element may also be used when determination
of the authentication key consists of a combination of keying
material provided by both parties. This would be the case, for
example, when establishing a key by means of Diffie Hellman [x ] Key
Exchange algorithm.
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3.5 Key Agreement Algorithm Element
The Key Agreement Algorithm element is an optional element that could
be used to indicate the algorithm to be used for deriving a one-time
session key from a master key. Usage of one-time session key prevents
some kinds of attack that require a large volume of cipher-text to be
produced by a given key.
<KeyAgreementAlgorithm>
(algorithm information block)
</KeyAgreementAlgorithm>
3.6 Signature Algorithm Element
The Signature Algorithm element indicates the algorithm to be used
for computation of the signature value.
<SignatureAlgorithm>
(algorithm information block)
</SignatureAlgorithm>
In consideration of the requirements stated previously, this document
uses the terminology of 'signature' for qualifying indifferently
signature and authentication schemes. Therefore, the signature
algorithm mentioned above might refer to a signature algorithm such
as DSS or to a message authentication code (MAC) such as HMAC.
4. Signature Principles
4.1 Enabling Signature in XML Applications
As mentioned previously, this specification provides among others a
means for building authentication into XML applications. The
mechanism adopted herein considers the 'XML Namespaces' specification
[x], which defines the requirements for combining multiple DTDs or
parts of individual DTD into a single document
According to this specification, an XML application can build digital
signature support by referring explicitly to the elements defined in
the Signature DTD. This is accomplished by associating a namespace
prefix to the Signature DTD and qualifying Signature element names by
means of this prefix.
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Association of a namespace prefix to a DTD shall be done by means of
a xmlns attribute, which could appear in any element that either
refers to or contains sub-elements that refer to elements of the DTD
considered. A qualified name consists of a namespace prefix, a colon,
and a name.
<MyDocument xmlns:dsig='Signature-DTD-URI'>
<MyElement id='authenticated-infos'>
...
</MyElement>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='authenticated-infos'/>
</dsig:Resource>
</dsig:Resources>
...
</dsig:Manifest>
<dsig:Value>
...
</dsig:Value>
</dsig:Signature>
</MyDocument>
4.2 Encapsulating Arbitrary Contents
To facilitate encapsulation of arbitrary contents into an XML
document, the Signature DTD defines a Package element. Quite similar
to a MIME wrapper, this element provides for such things as content
type and content encoding.
<dsig:Package>
<dsig:ContentInfo type='type qualifier'/>
<dsig:Value encoding='encoding scheme'>
(safe content)
</dsig:Value>
</dsig:Package>
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4.3 Implementing Endorsement
Endorsement consists of signing another signature. To facilitate
endorsement, the definition of the Signature element provides for an
element identifier attribute, which can be used to target a Signature
element from a Resource element.
<dsig:Signature id='signature'>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='resource locator'/>
...
</dsig:Resource>
</dsig:Resources>
...
</dsig:Manifest>
...
</dsig:Signature>
<dsig:Signature id='counter-signature'>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='signature'/>
...
</dsig:Resource>
</dsig:Resources>
...
</dsig:Manifest>
...
</dsig:Signature>
4.4 Supporting Composite Documents
Some protocols consist of the exchange of documents that result from
the combination by addition or deletion of common information blocks.
The current proposal shall preserve verifiability of the origin and
authenticity of these blocks of information as they are exchanged
between parties
To facilitate authentication of such composite documents, this
specification has adopted an 'indirect' authentication scheme - the
signature is applied to unambiguous references to the resources being
authenticated instead of their contents. Signature verification does
not require the actual contents of the resources.
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This indirect scheme can be further extended when multiple signatures
must be produced for a large number of resources -- repeating the
resource elements in multiple signature Manifests might not be
optimal. In such circumstances, the application DTD can leverage the
Resources element to share the resource definitions between multiple
signature elements.
<dsig:Resources id='shared=resources'>
<dsig:Resource>
...
</dsig:Resource>
<dsig:Resource>
...
</dsig:Resource>
...
</dsig:Resources>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='shared-resources'>
...
</dsig:Resource>
</dsig:Resources>
...
</dsig:Manifest>
...
</dsig:Signature>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='shared-resources'>
...
</dsig:Resource>
</dsig:Resources>
...
</dsig:Manifest>
...
</dsig:Signature>
The adoption of simple XML links as resource locators makes possible
the authentication of composite documents. If IDREFs were used
instead, it would have been impossible to ensure validity of partial
documents - some IDREFs could have been left referencing non-
embedded IDs.
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4.5 Facilitating One-pass Processing
Without further definitions, it would be impossible to determine
which blocks of information require authentication and which
algorithms need to be employed before interpretation of the Resource
elements. These elements being generally located at the end of the
document, this restriction would prevent computation of the digests
during acquisition of the blocks of information.
To facilitate one-pass processing, the current specification uses
another functionality offered by the namespaces proposal. This
functionality provides for the definition of global attributes that
may be used and recognized across multiple elements. This document
specifies the dsig:eval global attribute, which could be used for
identifying the blocks of information to be authenticated
The dsig:eval attribute shall refer to an Algorithm element or list
of Algorithm elements that identify the algorithms and parameters to
be used for computation of the digest of the element being
authenticated. To comply with the requirements of one-pass
processing, the Algorithm element should be declared before making
use of the dsig:eval attribute.
<dsig:DigestAlgorithms id='digest-algorithm'>
<Algorithm id='SHA1' type='urn:nist-gov:sha1'\>
<Algorithm id='MD5' type='urn:rsasdi-com:MD5'\>
</dsig:DigestAlgorithms>
<MyElement id='authenticated-infos'
dsig:eval='SHA1 MD5'>
...
</MyElement>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='authenticated-infos'>
<Digest>
<Algorithm id='SHA1' type='urn:nist-gov:sha1'\>
<Value encoding='base64'>
ANBbdshh456wh5==
</Value>
</dsig:Resource>
</dsig:Resources>
...
</dsig:Manifest>
...
</dsig:Signature>
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When encountering the dsig:eval global attribute on an element, the
XML parser is immediately aware of the requirement of computing the
digest or digests of this element. All the pieces of information
necessary for such computation are provided by the Algorithm element
or elements referenced by the attribute.
The dsig:eval attribute is purely declarative. Discrepancies between
the dsig:eval attribute and the digest algorithm definition in the
Resource element shall not invalidate the signature. At the most,
such discrepancies will result in a verification failure if the
signature-agent cannot memorize nor rewind its input stream.
5. Syntax Comments
5.1 Namespace Attributes
All the elements defined by the Signature DTD are explicitly bound to
the XMLDSIG namespace by means of a dsig prefix. In order to make
sure that every element could be individually imported by other XML
applications, the element definitions given hereinafter
systematically declare a fixed xmlns:dsig attribute.
<!ELEMENT dsig:element definition...>
<!ATTLIST dsig:element
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
...
>
Recall that many XML applications, presumably including namespaces
sensitive ones, fail to require validating processors. For correct
operations with such applications, namespaces declarations must be
also provided either directly or via default attributes declared in
the internal subset of the DTD.
5.2 dsig:eval Global Attribute
As mentioned previously, this specification defines a dsig:eval
global attribute that could be used for identifying a block of
information to be authenticated. This attribute shall refer to an
Algorithm element or elements, which should be declared before making
use of the attribute.
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The XML Namespaces specifications do not explicitly provide for
declaration of global attributes. Distinguishing between global
attributes and element attributes exists only in the prose
description of such attributes. An essential property of global
attributes consists nonetheless of the uniqueness of their name that
is independent of the elements where they are defined.
The definition of elements that could be subject to authentication
may define the dsig:eval attribute as follows:
<!ELEMENT element definition...>
<!ATTLIST element
dsig:eval IDREFS #IMPLIED
>
Recall that the namespace prefix that is bound to the XMLDSIG
namespace shall be defined before being employed. However, such
definition may occur in the element that defines the dsig:eval
attribute.
The reader shall notice that the terminology 'dsig:eval' is
inappropriate and used solely for illustrative purposes. This simply
means that the name of this attribute is eval and it belongs to the
XMLDSIG namespace (whatever prefix is used).
5.3 Uniform Resource Names
To prevent potential name conflicts in the definition of the numerous
type qualifiers considered herein, this specification uses Uniform
Resource Names [RFC 2141]. Nonetheless, this specification leverages
established standards such as MIME types by providing unambiguous
mapping conventions.
A complete list of proposed URNs is given in appendix. This list is
temporary and will be submitted for approval to the authors or
promoters of the algorithms and data types referenced by these URNs.
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5.4 Basic Data Types
To facilitate the adoption of common procedures for the encoding of
attribute and parameter values, this specification defines a series
of elements not directly mandated by the Signature DTD. These
definitions propose a common approach to encoding basic data types
such as Integer, Float, Date, etc... It is expected that these
definitions will be reconsidered, as the results of other W3C
Activities in this area (i.e. XML-Data) will be adopted.
5.5 Algorithm Definitions
This specification adopts a unique Algorithm data type. Though
noticeably different from its ASN1 counterpart, this data type serves
a similar purpose and provides for the definition of algorithm
specific parameters.
The most noticeable difference with ASN1 consists of the assimilation
of sub algorithms as parameters of the primary algorithm. In other
words, where ASN1 recognizes an algorithm of the type AlgxWithAlgy
(i.e. DsaWithSha1) the current specifications recognize Algx with an
Algy parameter.
This recursive construct is expected to be more versatile and shall
provide a solution applicable to the definition of algorithms in
general. However, this definition does not preclude the adoption of
shortcuts such as the ones proposed by ASN1. It does not preclude
either the adoption of default parameter values.
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6. Detailed Signature Syntax
6.1 Algorithm
The Algorithm element consists of a basic data type that uniquely
identifies a given algorithm and indicates the parameter values to be
used during computation. The construct is recursive and allows a
parameter value to refer to another Algorithm element.
<!ELEMENT dsig:Algorithm ( dsig:Parameter* )>
<!ATTLIST dsig:Algorithm
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
id ID #IMPLIED
type CDATA #REQUIRED
>
Content Description
Parameter: The contents of an Algorithm element consists of an
optional collection of Parameter elements, which are specified
on a per algorithm basis.
Attributes Description
id: Element identifier that could be used for referencing this
element (from a dsig:eval global attribute for example).
type: The type of the algorithm expressed as a Uniform Resource
name.
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6.2 Attribute
The Attribute element consists of a complementary piece of
information, which shall be included in the authenticated part of the
document. Though this specification defines standard attributes, this
element has been defined primarily for enabling some level of
customization in the signature element. An Attribute element consists
of a value, a type, and a criticality.
<!ELEMENT dsig:Attribute ANY>
<!ATTLIST dsig:Attribute
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type NMTOKEN #REQUIRED
critical ( true | false ) #IMPLIED 'false'
>
Content Description
ANY: The actual value of an attribute depends solely upon its
type.
Attributes Description
type: Type of the attribute expressed as a Uniform Resource Name.
critical: Boolean value that indicates if the attribute is
critical (true) or not (false). A recipient shall reject a
signature that contains a critical attribute that he does not
recognize. However, an unrecognized non-critical attribute may
be ignored.
6.3 Attributes
The Attributes element consists of a collection of complementary
attributes, which shall be included in the authenticated part of the
document.
<!ELEMENT dsig:Attributes ( dsig:Attribute+ )>
<!ATTLIST dsig:Attributes
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
Attribute: Collection of Attribute elements.
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6.4 Certificate
The Certificate element may be used for either providing the value of
a digital certificate or specifying a location from where it may be
retrieved.
<!ELEMENT dsig:Certificate (
dsig:IssuerAndSerialNumber,
( dsig:Value | dsig:Locator )
)>
<!ATTLIST dsig:Certificate
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type NMTOKEN #REQUIRED
>
Content Description
IssuerAndSerialNumber: Unique identifier of this certificate.This
element has been made mandatory is order to prevent unnecessary
decoding during validation of a certificate chain. This
feature also helps certificates caching, especially when the
value is not directly provided.
Value: Encoding of the certificate value. The actual value to be
encoded depends upon the type of the certificate
Locator: XML link element that could be used for retrieving a copy
of the digital certificate. The actual value being returned by
means of this locator depends upon the protocol being used.
Attributes Description
type: Type of the digital certificate expressed as a Uniform
Resource Name.
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6.5 Certificates
The Certificates element consists of a collection of Certificate
elements. The Certificate elements contained in this element are
intended to be sufficient to make chains from the originator
credential(s) to a recognized 'certification authority' for all the
recipients. However, this element may contain more Certificate
elements than necessary or, alternatively, less than necessary if it
is known that recipients have an alternate means of obtaining
necessary certificates.
<!ELEMENT dsig:Certificates ( dsig:Certificate+ )>
<!ATTLIST dsig:Certificates
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
Certificate: A collection of Certificate elements.
6.6 ContentInfo
The purpose of the ContentInfo element is to describe a given content
such that a receiving user agent can deal with the data in an
appropriate manner.
<!ELEMENT dsig:ContentInfo EMPTY>
<!ATTLIST dsig:ContentInfo
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type CDATA #REQUIRED
subtype CDATA #IMPLIED
>
Attributes Description
type: Type of the content expressed as a Uniform Resource Name.
subtype: Optional sub-classing of the content type.
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6.7 Date
The Date element consists of a constrained ISO 8601:1998 date and
time value.
<!ELEMENT dsig:Date EMPTY>
<!ATTLIST dsig:Date
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: The date value expressed according to the format defined
below.
Date Format
This specification requires date values to be expressed according
to the following pattern:
YYYY '-' MM '-' DD 'T' hh ':' mm [':' ss ['.' f+]]('+' | '-') zzzz
YYYY: four-digit year
MM: two-digit month (01=January, etc.)
DD: two-digit day of the month (01-31)
hh: two digits of hour (00-23)
mm: two digits of minute (00-59)
ss: two digits of second (00-59) optional
f: digit(s) of fractions of second - optional
zzzz: four digits of amount of offset from UTC expressed in
hour (00-11) and minute (00-59)
For example, '1994-11-05T16:15:02.031-0500' denotes November 5,
1994, 4:15:02 pm and 31 milliseconds, US Eastern Standard Time.
6.8 Digest
The Digest element consists of the fingerprint of a given resource.
This element is constructed of two sub-elements. This first one
indicates the algorithm to be used for computation of the
fingerprint. The second element consists of the fingerprint value.
<!ELEMENT dsig:Digest ( dsig:Algorithm, dsig:Value )>
<!ATTLIST dsig:Digest
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
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Content Description
Algorithm: Algorithm to be used for computation of the digest
value.
Value: Digest value after proper encoding.
6.9 DigestAlgorithms
The DigestAlgorithms element consists of a collection of Algorithm
elements that define the algorithms and parameter values to be
employed in the computation of digest values. It is primarily used
along with the dsig:eval global attribute for enabling one-pass
processing.
<!ELEMENT dsig:DigestAlgorithms ( dsig:Algorithm+ )>
<!ATTLIST dsig:DigestAlgorithms
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
Algorithm: A collection of digest algorithm definitions.
6.10 Identifier
The Identifier element enables identification between parties that
benefit from a prior relationship. The actual meaning and content of
this element is left to the parties.
<!ELEMENT dsig:Identifier EMPTY>
<!ATTLIST dsig:Identifier
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Identification data value.
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6.11 Integer
The Integer element is a primary data type that is used in the
definition of algorithm parameters.
<!ELEMENT dsig:Integer EMPTY>
<!ATTLIST dsig:Integer
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Value of the element given according to the format given
below.
Integer Format
This specification requires integer values to be expressed
according to the following pattern:
['+'|'-'] n+
For example, +128, -35635, and 64535 are valid integer values.
6.12 IssuerAndSerialNumber
The IssuerAndSerialNumber element identifies a certificate, and
thereby an entity and a public key, by the distinguished name of the
certificate issuer and an issuer-specific certificate serial number.
<!ELEMENT dsig:IssuerAndSerialNumber EMPTY>
<!ATTLIST dsig:IssuerAndSerialNumber
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
issuer CDATA #REQUIRED
number CDATA #REQUIRED
>
Attributes Description
issuer: Distinguished name of the issuing certification authority.
number: Issuer-specific certificate serial number.
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6.13 KeyAgreementAlgorithm
The KeyAgreementAlgorithm element specifies the algorithm to be
employed for establishment of a one-time session key.
<!ELEMENT dsig:KeyAgreementAlgorithm ( dsig:Algorithm )>
<!ATTLIST dsig: KeyAgreementAlgorithm
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
Algorithm: Algorithm and parameters to be used for establishment
of the session key.
6.14 Keyword
The Keyword element is a primary data type that is used in the
definition of algorithm parameters.
<!ELEMENT dsig:Keyword EMPTY>
<!ATTLIST dsig:Keyword
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Value of the element given as a free form string.
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6.15 Locator
The Locator element consists of simple XML link [XLink]. This
element allows unambiguous reference to a resource or fragment of a
resource.
<!ELEMENT dsig:Locator EMPTY>
<!ATTLIST dsig:Locator
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
xml:link CDATA #FIXED 'simple'
href CDATA #REQUIRED
>
Attributes Description
xml:link: Required XML link attribute that specifies the nature of
the link (simple in this case).
href: Locator value that may contains either a URI [RFC 2396], a
fragment identifier, or both.
6.16 Manifest
The Manifest element consists of a collection of attributes that
specify such things as a unique reference to the resource being
authenticated and an indication of the keying material and algorithms
to be used. The signature value is actually computed from the
Manifest.
<!ELEMENT dsig:Manifest (
dsig:Resources, dsig:Attributes?,
dsig:OriginatorInfo, dsig:RecipientInfo?,
dsig:KeyAgreementAlgorithm?, dsig:SignatureAlgorithm
)>
<!ATTLIST dsig:Manifest
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
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Content Description
Resources: A collection of Resource elements that consist of a
unique and unambiguous reference to the resources being
authenticated.
Attributes: Optional element that consists of a collection of
complementary attributes to be authenticated.
OriginatorInfo: Element that provides identification and keying
material information related to the originator.
RecipientInfo: Optional element that provides identification and
keying material information related to the recipient.
KeyAgreementAlgorithm: Optional element that indicates the
algorithm to be used for establishment of a one-time session
key.
SignatureAlgorithm: Algorithm to be used for computation of the
signature value.
6.17 OriginatorInfo
The OriginatorInfo element is used for providing identification and
keying material information for the originator.
<!ELEMENT dsig:OriginatorInfo ANY>
<!ATTLIST dsig:OriginatorInfo
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
ANY: Identification and keying material information may consist of
ANY construct. Such a definition allows the adoption of
application-specific schemes. However, implementations that
comply with the current DTD MUST be able to recognize and
process the elements Identifier and IssuerAndSerialNumber
defined below.
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6.18 Package
The Package element enables encapsulation of an arbitrary content
into an XML document. Behaving like a MIME wrapper, the Package
element provides for such things as content type identification and
content encoding.
<!ELEMENT dsig:Package (
dsig:ContentInfo?, dsig:Value
)>
<!ATTLIST dsig:Package
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
dsig:eval IDREF #IMPLIED
id ID #IMPLIED
>
Content Description
ContentInfo: Element that provides type information regarding the
content of the Package.
Value: Element that displays the content value of the Package and
provides information regarding possible encoding.
Attributes Description
id: Element identifier that could be used for referencing this
element from a Resource element.
6.19 Parameter
A Parameter element provides the value of a particular algorithm
parameter, whose name and format have been specified for the
algorithm considered.
<!ELEMENT dsig:Parameter ANY>
<!ATTLIST dsig:Parameter
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type CDATA #REQUIRED
>
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Content Description
ANY: The contents of a Parameter element consists of ANY valid
construct, which is specified on a per algorithm per parameter
basis.
Attributes Description
type: The type of the parameter expressed as a free form string,
whose value is specified on a per algorithm basis.
6.20 Real
The Real element is a primary data type that is used in the
definition of algorithm parameters.
<!ELEMENT dsig:Real EMPTY>
<!ATTLIST dsig:Real
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Value of the element given according to the format given
below.
Real Format
This specification requires real values to be expressed according
to the following pattern:
['+'|'-'] n+ ['.' f+] ['E' ('+'|'-') ee]
For example, 12, -12.34, +12.34E-01, and +0.5 are valid real
values.
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6.21 RecipientInfo
The RecipientInfo element is used for providing identification and
keying material information for the recipient. This element is used
either for enabling recognition of a Signature element by a given
recipient or when determination of the authentication key consists of
the combination of keying material provided by both the recipient and
the originator.
Content Description
The content of this element is similar to the one defined for the
originator (cf. OriginatorInfo element description).
6.22 Resource
The Resource element consists of a unique and unambiguous reference
to a resource being authenticated. It is comprised of a resource
locator, a fingerprint, and optionally a content-type qualifier.
<!ELEMENT dsig:Resource (
dsig:Locator, dsig:ContentInfo?, dsig:Digest
)>
<!ATTLIST dsig:Resource
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
ContentInfo: Optional element that provides type information
regarding the resource.
Locator: Locator value that contains a URI [RFC 2396], a fragment
identifier, or both. Notice that making use of a fragment
identifier for a document content other than XML is out of the
scope of this specification and may lead to inconsistent
results.
Digest: Fingerprint of the resource.
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6.23 Resources
The Resources element consists of a collection of Resource elements.
Though inaccessible from the Document element of the Signature DTD,
this element is available to more sophisticated constructs that make
use of composite documents.
<!ELEMENT dsig:Resources ( dsig:Resource+ )>
<!ATTLIST Resources
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
dsig:eval IDREF #IMPLIED
id ID #IMPLIED
>
Content Description
Resource: A collection of Resource elements.
Attributes Description
id: Element identifier that could be used for referencing this
element from a Resource element.
6.24 Signature
The Signature element constitutes the core of this specification. It
is comprised of two sub-elements. The first one is a set of
attributes, known as the Manifest, which actually constitutes the
authenticated part of the document. The second sub-element consists
of the signature value.
<!ELEMENT dsig:Signature ( dsig:Manifest, dsig:Value )>
<!ATTLIST dsig:Signature
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
dsig:eval IDREF #IMPLIED
id ID #IMPLIED
>
Content Description
Manifest: Element constructed from the set of attributes that
constitute the authenticated part of the document.
Value: The signature value after proper encoding.
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Attributes Description
id: Element identifier that could be used for referencing the
Signature element from a Resource element when implementing
endorsement.
6.25 SignatureAlgorithm
The SignatureAlgorithm element specifies the algorithm to be employed
for computation of a signature value.
<!ELEMENT dsig:SignatureAlgorithm ( dsig:Algorithm )>
<!ATTLIST dsig:SignatureAlgorithm
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
Algorithm: Algorithm and parameters to be used for computation of
the signature value.
6.26 Signatures
The Signatures element consists of a collection of Signature
elements. As mentioned in a previous paragraph, this element has been
defined for the purpose of facilitating DOM manipulations.
<!ELEMENT dsig:Signatures ( dsig:Signature+ )>
<!ATTLIST dsig:Signatures
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
Signature: A collection of Signature elements.
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6.27 Value
The Value element consists of a primary data type that is used
throughout this proposal for inlining and encoding of arbitrary
values.
<!ELEMENT dsig:Value ( #PCDATA )>
<!ATTLIST dsig:Value
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
encoding ( base64 | none ) #IMPLIED 'none'
>
Content Description
PCDATA: Content value after adequate encoding.
Attributes Description
encoding: This attribute specifies the scheme to be employed for
recovering the original byte stream from the content of the
element. This specification recognizes the following two
schemes:
none: the content has not been subject to any particular
encoding. This does not preclude however the use of native
XML encoding such as CDATA section or XML escaping.
base64: The content has been encoded by means of the base64
encoding scheme.
7. Default Document Element
Though it is primarily intended for enabling authentication in other
XML applications, the XML Signature DTD specifies a default document
element. This definition has been intentionally kept simple and is
intended to provide an XML alternative to the ASN1 data types
Authenticated Data and Signed Data defined by CMS [x] and PKCS#7 [x]
binary syntax standards.
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The definition given below addresses the following requirements:
- Authentication of arbitrary contents: This may be done by adequate
encapsulation and encoding of the arbitrary contents into the
Package element, which shall be further authenticated by means of
a Signature element.
- Detached signature: This may be done by means of a Signature
element that refers to a resource external to the document.
- Authentication versus signature: The distinction between
authentication and signature only depends upon the algorithms
being employed for computation of the 'signature' value.
- Plurality of recipients: This consists of the insertion of a
plurality of Signature elements, each making use of recipient
dependent keying material.
- Plurality of signers: This consists of the insertion of a
plurality of Signature elements, each making use of originator
dependent keying material.
<!ELEMENT dsig:Document (
( dsig:DigestAlgorithms, dsig:Package+ )?,
dsig:Signatures, dsig:Certificates?
)>
<!ATTLIST dsig:Document
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
DigestAlgorithms: This element has been made mandatory whenever
the document embeds the contents to be authenticated. This
element specifies the algorithm to be used for computation of
the digest of the Package elements, thus enabling one-pass
processing.
Package: This element is used for enveloping and encoding of the
contents to be authenticated. Whenever employed, this element
shall make use of the dsig:eval global attribute
Signatures: This element consists of a collection of Signature
elements.
Certificates: This element consists of a collection of Certificate
elements, which may be required by a given key management
infrastructure.
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8. Standard Attributes
This specification recognizes the following standard attributes.
8.1 Signing-time Attribute
Standard attribute that could be used for specifying the time at
which the originator purportedly performed the signature process.
This attribute content shall be given as a Date element.
Specification:
URN: urn:ietf-org:xmldsig-signing-time
Type: dsig:Date
Example:
<dsig:Attribute type='urn:xml-dsig-ietf-org:signing-time'>
<dsig:Date value='1994-11-05T16:15:02.031-0500'\>
</dsig:Attribute>
9. Digest Algorithms
This specification contemplates two types of digest algorithms:
- Surface string digest algorithms: These algorithms do not have any
particular knowledge about the content being digested and operate
on the raw content value. Changes in the surface string of a given
content affect directly the value of the digest being produced.
- Canonical digest algorithms: These algorithms have been tailored
for a particular content type and produce a digest value that
depends upon the core semantics of such content. Changes limited
to the surface string of a given content do not affect the value
of the digest being produced.
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9.1 SHA1
Surface string digest algorithm designed by NIST and NSA for use with
the Digital Signature Standard. This algorithm is documented in NIST
FIPS Publication 180-1.
Specifications:
URN: urn:nist-gov:sha1
Parameters:
This algorithm does not require any parameter.
9.2 DOM-HASH
XML canonical digest algorithm proposed by IBM Tokyo Research
Laboratory and documented in the DOMHASH proposal [x]. This algorithm
operates on the DOM representation of the document and provides an
unambiguous means for recursive computation of the hash value of the
nodes that constitute the DOM tree. This algorithm has many
applications such as computation of digital signature and
synchronization of DOM trees. However, because the hash value of an
element is computed from the hash values of the inner elements, this
algorithm is better adapted to small documents that do not require
one-pass processing.
As of today, this algorithm is limited to the contents of an XML
document and, therefore, does not provide for authentication of the
internal or external subset of the DTD.
The DOM-HASH algorithm requires a single parameter, which shall
consist of a surface string digest algorithm such as SHA1.
Specifications:
URN: urn:ibm-com:dom-hash
Parameters:
digest-algorithm Surface string digest algorithm to be used for
computation of the digest value.
type: dsig:Algorithm
default: urn:nist-gov:sha1
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Example:
<dsig:Algorithm type='urn:ibm-com:dom-hash'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:nist-gov:sha1'/>
</dsig:Parameter>
</dsig:Algorithm>
9.3 XHASH
XML canonical digest algorithm proposed by GlobeSet and documented in
the XHASH proposal [x]. This algorithm has been inspired by the DOM
HASH proposal, but operates closer to the surface string of the
document. Elements and attributes are subject to formalization in a
way quite similar to the one proposed by DOM-HASH - XML delimiters
are represented by binary values and entities are replaced by their
actual values. However, formalization happens as elements are
acquired. Furthermore, this algorithm takes into account some
specifics of this specification (e.g. dsig:eval attribute).
The XHASH algorithm makes use of two parameters. The first one
consists of a surface string digest algorithm such as SHA1. The
second one, optional, may be used for specifying how non-significant
SPACE characters shall be handled by default. Actually, the XML
Specifications define the xml:space attribute that could be used for
specifying if non-significant SPACE characters are to be preserved.
However, possible values for this attribute are limited to 'default'
and 'preserve'. Thus, there is no known way to explicitly specify
that non-significant SPACE characters should be discarded
Specifications:
URN: urn:globeset-com:xhash
Parameters:
digest-algorithm Surface string digest algorithm to be used
for computation of the digest value.
type: dsig:Algorithm
default: urn:nist-gov:sha1
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white-spaces Default processing of non-significant SPACE
characters.
type: dsig:Keyword
value: preserve: Non-significant SPACE characters are to be
preserved in a way similar to what should be done in
presence of an xml:space preserve attribute.
ignore: Unless overridden by means of an xml:space preserve
attribute, non-significant SPACE characters shall be ignored
during computation of the canonical form of the contents.
default: ignore
Example
<dsig:Algorithm type='urn:globeset-com:xhash'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:nist-gov:sha1'/>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
10. Key Agreement Algorithms
A key-agreement algorithm consists of a function that is used for
deriving a one-time session key from a given master key. Usage of
one-time session keys prevents some kinds of attacks that require a
large volume of cipher-text to be produced with a given key.
Usage of a key-agreement algorithm is recommended when authentication
is based upon a shared secret. This shared secret could have been
exchanged either by offline means (e.g. mail) or computed dynamically
by means of a key-exchange algorithm such as Diffie Hellman [x].
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10.1 PKCS12-PBE
Key-agreement algorithm proposed by RSA Laboratories and documented
in PKCS12 [x]. This algorithm is a generalization of the PBE
algorithm defined in PKCS5 [x] and provides for the generation of
symmetric keys and other cryptographic parameters from an established
password.
This algorithm requires three parameters. The first one consists of a
one-way hash function (i.e. SHA1), the second one of a random string
(salt), and the last one of an iteration count
Specifications
URN: urn:rsasdi-com:pkcs12-pbe
Parameters:
digest-algorithm One-way hash function used as the pseudo-
random number generator.
type: dsig:Algorithm
default: urn:nist-gov:sha1
random-string Random string value used to seed the PRNG.
type: dsig:Value
default: no default.
iteration-count
type: dsig:Integer
default: 256
Example
<dsig:Algorithm type='urn:rsasdi-com:pkcs12-pbe'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:nist-gov:sha1'/>
</dsig:Parameter>
<dsig:Parameter type='random-string'>
<dsig:Value encoding='base64'>
Abkirjegks123qwgtawd456g47
</dsig:Value>
</dsig:Parameter>
<dsig:Parameter type='iteration-count'>
<dsig:Integer value='128'/>
</dsig:Parameter>
</dsig:Algorithm>
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11. Key Exchange Algorithms
A key-exchange algorithm enables dynamic establishment of a master
secret key that results from the combination of keying material
provided by the parties involved in an exchange. The parties may
further establish a one-time session key from such a master secret
key by means of a key-agreement algorithm.
Key-exchange algorithms shall not be defined in the body of a signed
document. Their usage is implicit and depends solely upon the keying
material being used for authentication.
11.1 Diffie Hellman
Key-exchange algorithm named from its authors and documented in
X9.42.
12. Signature Algorithms
This specification abusively uses the terminology of 'digital
signature' for qualifying indifferently digital signature and message
authentication codes. Thus, the signature algorithms contemplated
herein include public-key digital signature algorithms such as DSA
and message authentication codes such as HMAC.
12.1 HMAC
Message Authentication Code proposed by H. Krawczyk and al. and
documented in RFC2104
This specification adopts a scheme that differs a bit from the common
usage of this algorithm -- computation of the MAC is performed on the
hash of the contents being authenticated instead of the actual
contents. Thence, the actual signature value output by the algorithm
might be depicted as follows:
SignatureValue = HMAC( SecretKet, H(dsig:Manifest))
This specification also considered HMAC output truncation such as
proposed by Preneel and van Oorschot. In their paper [x] these two
researchers have shown some analytical advantages of truncating the
output of hash-based MAC functions. Such output truncation is also
considered in the RFC document.
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HMAC requires three parameters. The first one consists of a canonical
digest algorithm. The second one consists of a hash function. The
last one is optional and specifies the length in bit of the truncated
output. If this last parameter is absent, no truncation shall occur.
Specifications
URN: urn:ietf-org:hmac
Parameters:
digest-algorithm Canonical or surface-string digest algorithm
to be is used for computation of the Manifest fingerprint.
type: dsig:Algorithm
default: urn:nist-gov:sha1
hash-function Hash function that is used to compute the MAC
value from the secret key and the fingerprint of the signature
Manifest.
type: dsig:Algorithm
default: urn:nist-gov:sha1
output-length Length in bits of the truncated MAC value.
type: dsig:Integer
default: no default.
Signature Value Encoding:
The output of this algorithm can be assumed as a large integer value.
The signature value shall consist of the octet-encoded value of this
integer. Integer to octet-stream conversion shall be done according
to PKCS#1 [x] specification with a k parameter equals to ((Hlen +7)
mod8), Mlen being the length in bits of the MAC value.
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Example
<dsig:Algorithm type='urn:ietf-org:hmac'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:globeset-com:xhash'/>
</dsig:Parameter>
<dsig:Parameter type='hash-function'>
<dsig:Algorithm type='urn:nist-gov:sha1'/>
</dsig:Parameter>
<dsig:Parameter type=output-length'>
<dsig:Integer value='128'/>
</dsig:Parameter>
</dsig:Algorithm>
12.2 DSA
Public-key signature algorithm proposed by NIST for use with the
Digital Signature Standard. This standard is documented in NIST FIPS
Publication 186 [x] and ANSI X9.30 [x].
The DSA algorithm requires a single parameter, which consists of the
canonical digest algorithm to be used for computing the fingerprint
of the signature Manifest.
Specifications
URN: urn:nist-gov:dsa
Parameters:
digest-algorithm Canonical or surface-string digest algorithm
to be is used for computation of the Manifest fingerprint.
type: dsig:Algorithm
default: urn:nist-gov:sha1
Signature Value Encoding:
The output of this algorithm consists of a pair of integers usually
referred by the pair (r, s). The signature value shall consist 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 PKCS#1 [x] specification with a
k parameter equals to 20.
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Example
<dsig:Algorithm type='urn:nist-gov:dsa'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:globeset-com:xhash'/>
</dsig:Parameter>
</dsig:Algorithm>
12.3 RSA-Encryption
Public-key signature algorithm proposed by RSA Laboratories and
documented in PKCS#1 [x].
This specification adopts the RSA encryption algorithm with padding
block type 01. For computing the signature value, the signer shall
first digest the signature Manifest and then encrypt the resulting
digest with his private key.
This signature algorithm requires a single parameter, which consists
of the canonical digest algorithm to be used for computing the
fingerprint of the signature Manifest.
Specifications
URN: urn:rsasdi-com:rsa-encryption
Parameters:
digest-algorithm Canonical or surface-string digest algorithm
to be is used for computation of the Manifest fingerprint.
type: dsig:Algorithm
default: urn:nist-gov:sha1
Signature Value Encoding:
The output of this algorithm consists of single octet-stream. No
further encoding is required.
Example
<dsig:Algorithm type='urn:rsasdi-com:rsa-encryption'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:globeset-com:xhash'/>
</dsig:Parameter>
</dsig:Algorithm>
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12.4 ECDSA
Public-key signature algorithm proposed independently by Neil Koblitz
and Victor Miller. This algorithm is being proposed as an ANSI
standard and is documented in ANSI X9.62 standard proposal [x] and
IEEE/P1363 standard draft proposal [x].
The ECDSA algorithm requires a single parameter, which consists of
the canonical digest algorithm to be used for computing the
fingerprint of the signature Manifest.
Specifications
URN: urn:ansi-org:ecdsa
Parameters:
digest-algorithm Canonical or surface-string digest algorithm
to be is used for computation of the Manifest fingerprint.
type: dsig:Algorithm
default: urn:nist-gov:sha1
Signature Value Encoding:
The output of this algorithm consists of a pair of integers usually
referred by the pair (r, s). The signature value shall consist 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 PKCS#1 [x] specification with a
k parameter equals to 20.
Example
<dsig:Algorithm type='urn:ansi-org:ecdsa'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:globeset-com:xhash'/>
</dsig:Parameter>
</dsig:Algorithm>
13. References
[...more to come...]
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14. Signature DTD
<-- XML Signature DTD - 990404 - Revision 0 --->
<!ENTITY % xmldsig.dtd 'http://www.dtd.reg.int/xmldsig'>
<!ELEMENT dsig:Document (
( dsig:DigestAlgorithms, dsig:Package+ )?,
dsig:Signatures, dsig:Certificates?
)>
<!ATTLIST dsig:Document
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Algorithm ( dsig:Parameter* )>
<!ATTLIST dsig:Algorithm
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
id ID #IMPLIED
type CDATA #REQUIRED
>
<!ELEMENT dsig:Attribute ANY>
<!ATTLIST dsig:Attribute
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type NMTOKEN #REQUIRED
critical ( true | false ) #IMPLIED 'false'
>
<!ELEMENT dsig:Attributes ( dsig:Attribute+ )>
<!ATTLIST dsig:Attributes
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Certificate (
dsig:IssuerAndSerialNumber,
( dsig:Value | dsig:Locator )
)>
<!ATTLIST dsig:Certificate
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type NMTOKEN #REQUIRED
>
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<!ELEMENT dsig:Certificates ( dsig:Certificate+ )>
<!ATTLIST dsig:Certificates
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:ContentInfo EMPTY>
<!ATTLIST dsig:ContentInfo
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type CDATA #REQUIRED
subtype CDATA #IMPLIED
>
<!ELEMENT dsig:Date EMPTY>
<!ATTLIST dsig:Date
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
<!ELEMENT dsig:Digest ( dsig:Algorithm, dsig:Value )>
<!ATTLIST dsig:Digest
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:DigestAlgorithms ( dsig:Algorithm+ )>
<!ATTLIST dsig:DigestAlgorithms
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Identifier EMPTY>
<!ATTLIST dsig:Identifier
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
<!ELEMENT dsig:Integer EMPTY>
<!ATTLIST dsig:Integer
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
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<!ELEMENT dsig:IssuerAndSerialNumber EMPTY>
<!ATTLIST dsig:IssuerAndSerialNumber
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
issuer CDATA #REQUIRED
number CDATA #REQUIRED
>
<!ELEMENT dsig:KeyAgreementAlgorithm ( dsig:Algorithm )>
<!ATTLIST dsig: KeyAgreementAlgorithm
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Keyword EMPTY>
<!ATTLIST dsig:Keyword
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
<!ELEMENT dsig:Locator EMPTY>
<!ATTLIST dsig:Locator
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
xml:link CDATA #FIXED 'simple'
href CDATA #REQUIRED
>
<!ELEMENT dsig:Manifest (
dsig:Resources, dsig:Attributes?,
dsig:OriginatorInfo, dsig:RecipientInfo?,
dsig:KeyAgreementAlgorithm?, dsig:SignatureAlgorithm
)>
<!ATTLIST dsig:Manifest
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:OriginatorInfo ANY>
<!ATTLIST dsig:OriginatorInfo
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
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<!ELEMENT dsig:RecipientInfo ANY>
<!ATTLIST dsig: RecipientInfo
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Package (
dsig:ContentInfo?, dsig:Value
)>
<!ATTLIST dsig:Package
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
dsig:eval IDREF #IMPLIED
id ID #IMPLIED
>
<!ELEMENT dsig:Parameter ANY>
<!ATTLIST dsig:Parameter
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
type CDATA #REQUIRED
>
<!ELEMENT dsig:Real EMPTY>
<!ATTLIST dsig:Real
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
<!ELEMENT dsig:Resource (
dsig:Locator, dsig:ContentInfo?, dsig:Digest
)>
<!ATTLIST dsig:Resource
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Resources ( dsig:Resource+ )>
<!ATTLIST Resources
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
dsig:eval IDREF #IMPLIED
id ID #IMPLIED
>
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<!ELEMENT dsig:Signature ( dsig:Manifest, dsig:Value )>
<!ATTLIST dsig:Signature
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
dsig:eval IDREF #IMPLIED
id ID #IMPLIED
>
<!ELEMENT dsig:SignatureAlgorithm ( dsig:Algorithm )>
<!ATTLIST dsig:SignatureAlgorithm
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Signatures ( dsig:Signature+ )>
<!ATTLIST dsig:Signatures
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
<!ELEMENT dsig:Value ( #PCDATA )>
<!ATTLIST dsig:Value
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
encoding ( base64 | none ) #IMPLIED 'none'
>
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15. Embedded Content Example
This example illustrates use of the default document element for
attachment and authentication of an arbitrary piece of information.
<?xml version='1.0'?>
<!DOCTYPE dsig:Document PUBLIC 'urn:ietf-org:xmldsig.dtd'
SYSTEM 'http://www.dtd.reg.int/dtd/xmldsig.dtd'>
<dsig:Document>
<dsig:DigestAlgorithms>
<dsig:Algorithm id='xhash' type='urn:com-
globeset:xhash'/>
</dsig:DigestAlgorithms>
<dsig:Package id='data' dsig:eval='xhash'>
<dsig:ContentInfo
type='urn:mime:application%2fmsword'/>
<dsig:Value>
abncjflf311257gghn6mj2k134h64AANHdd12==
</dsig:Value>
</dsig:Package>
<dsig:Signatures>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='data'/>
<dsig:Digest>
<dsig:Algorithm type='urn:com-globeset:xhash'/>
<dsig:Value encoding='base64'>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
</dsig:Resources>
<dsig:Attributes>
<dsig:Attribute
type='urn:ietf-org:xmldsig-signing-time'>
<dsig:Date value='1998-10-29T13:26-0500'/>
</dsig:Attribute>
</dsig:Attributes>
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<dsig:OriginatorInfo>
<dsig:IssuerAndSerialNumber
issuer='o=GlobeSet Inc., c=US'
number='123456789102356'/>
</dsig:OriginatorInfo>
<dsig:SignatureAlgorithm>
<dsig:Algorithm type='urn:rsasdi-com:rsa-
encryption'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:globeset-com:xhash'/>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:SignatureAlgorithm>
</dsig:Manifest>
<dsig:Value>
xsqsfasDys2h44u4ehJDe54he5j4dJYTJ=
</dsig:Value>
</dsig:Signature>
</dsig:Signatures>
<dsig:Certificates>
<dsig:Certificate type='urn:X500:X509v3'>
<dsig:IssuerAndSerialNumber
issuer='o=GlobeSet Inc., c=US'
number='123456789102356'/>
<dsig:Locator
href='http://certs.globeset.com/smith.der'/>
</dsig:Certificate>
<dsig:Certificate type='urn:X500:X509v3'>
<dsig:IssuerAndSerialNumber
issuer='o=GlobeSet Inc., c=US'
number='123456789102356'/>
<dsig:Value>
xsqsfasDys2h44u4ehJDe54he5j4dJYTJ=
</dsig:Value>
</dsig:Certificate>
</dsig:Certificates>
</dsig:Document>
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16. Detached Signature Example
This example illustrates use of the default document element for
production of a detached-signature. This example assumes that
recipient and originator benefit from a prior relationship.
<?xml version='1.0'?>
<!DOCTYPE dsig:Document PUBLIC 'urn:ietf-org:xmldsig.dtd'
SYSTEM 'http://www.dtd.reg.int/dtd/xmldsig.dtd'>
<dsig:Document>
<dsig:Signatures>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator
ref='http://www.globeset.com/xml.doc'/>
<dsig:ContentInfo
type='urn:mime:application%2fmsword'/>
<dsig:Digest>
<dsig:Algorithm type='urn:nist-gov:sha1'/>
<dsig:Value>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
</dsig:Resources>
<dsig:OriginatorInfo>
<dsig:Identifier value="0695123"/>
</dsig:OriginatorInfo>
<dsig:SignatureAlgorithm>
<dsig:Algorithm type='urn:ietf-org:hmac'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:globeset-com:xhash'/>
</dsig:Parameter>
<dsig:Parameter type='output-length'>
<dsig:Integer value='128'/>
</dsig:Parameter>
</dsig:SignatureAlgorithm>
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</dsig:Manifest>
<dsig:Value>
xsqsfasDys2h44u4ehJDe54he5j4dJYTJ=
</dsig:Value>
</dsig:Signature>
</dsig:Signatures>
</dsig:Document>
17. Domain-specific Example
This example illustrates how to leverage the XML Signature DTD to
enable authentication in another XML application.
This application contemplates the production of authenticated Ticket
documents that conform to the following DTD
<!-- Include XML DSIG Definitions -->
<!ENTITY % XmlDsigDtd SYSTEM
'http://www.dtd.reg.int/dtd/xmldsig.dtd'>
%XmlDsigDtd;
<!-- Application Specific Definitions -->
<!ELEMENT Ticket (
Body, dsig:Signature, dsig:Certificate
)>
<!ELEMENT Body (Event, Beneficiary)>
<!ATTLIST Body
number ID #REQUIRED
>
<!ELEMENT Event EMPTY>
<!ATTLIST Event
desc CDATA #REQUIRED
date CDATA #REQUIRED
>
<!ELEMENT Beneficiary EMPTY>
<!ATTLIST Beneficiary
name CDATA #REQUIRED
uid CDATA #REQUIRED
>
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The following consists of a Ticket document that conforms to the
previous DTD. The system makes use of a public-key signature
algorithm (RSA) and relies upon X509v3 credentials.
<?xml version='1.0'?>
<!DOCTYPE Ticket>
<Ticket>
<Body number='120456789'>
<Event
desc='concert in Austin'
date='1999-04-12T20:30-0500'/>
<Beneficiary
name='John smith'
ssno='435-56-4023'/>
</Body>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resources>
<dsig:Resource>
<dsig:Locator href='120456789'/>
<dsig:Digest>
<dsig:Algorithm type='urn:com-globeset:xhash'/>
<dsig:Value encoding='base64'>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
</dsig:Resources>
<dsig:OriginatorInfo>
<dsig:IssuerAndSerialNumber
issuer='o=GlobeSet Inc., c=US'
number='123456789102356'/>
</dsig:OriginatorInfo>
<dsig:SignatureAlgorithm>
<dsig:Algorithm type='urn:rsasdi-com:rsa-encryption'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:globeset-com:xhash'/>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:SignatureAlgorithm>
</dsig:Manifest>
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<dsig:Value>
xsqsfasDys2h44u4ehJDe54he5j4dJYTJ=
</dsig:Value>
</dsig:Signature>
<dsig:Certificate type='urn:X500:X509v3'>
<dsig:IssuerAndSerialNumber
issuer='o=GlobeSet Inc., c=US'
number='123456789102356'/>
<dsig:Value>
xsqsfasDys2h44u4ehJDe54he5j4dJYTJ=
</dsig:Value>
</dsig:Certificate>
</dsig:Ticket>
File Name: draft-ietf-xmldsig-signature-00.txt
Expires: Deember 1999
Richard D. Brown [Page 54]
