Internet Draft Richard D. Brown
GlobeSet, Inc.
Expires July 1999 January 1999
Digital Signatures for XML
------- ---------- --- ---
Richard D. Brown
GlobeSet, Inc.
Status of This Document
This draft, file name draft-brown-xml-dsig-00.txt, is intended to be
become a Proposed Standard RFC. Distribution of this document is
unlimited. Comments should be sent to the DSIG mailing list <xml-
dsig@socratic.org> or to the author.
This document is an Internet-Draft. 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. Internet-Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet-
Drafts as reference material or to cite them other than as a
``working draft'' or ``work in progress.''
To view the entire list of current Internet-Drafts, please check the
"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern
Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific
Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).
Abstract
A syntax and procedures for the computation and verification of XML
digital signatures is specified.
Richard D. Brown [Page 1]
INTERNET-DRAFT January 1999 Digital Signatures for XML
Table of Contents
Status of This Document....................................1
Abstract...................................................1
Table of Contents..........................................2
1. Introduction............................................4
2. Objective and Requirements..............................4
3. Signature Basics........................................5
3.1 Signature Element......................................5
3.2 Resource Element.......................................5
3.3 Other Attributes Element...............................6
3.4 Originator and Recipient Information Elements..........6
3.5 Key Agreement Algorithm Element........................7
3.6 Signature Algorithm Element............................8
4. Signature Principles....................................8
4.1 Enabling Signature in XML Applications.................8
4.2 Encapsulating Arbitrary Contents.......................9
4.3 Implementing Endorsement..............................10
4.4 Supporting Composite Documents........................10
4.5 Facilitating One-pass Processing......................11
5. Detailed Signature Syntax..............................12
5.1 Namespace Attributes..................................12
5.2 dsig:eval Global Attribute............................13
5.3 Uniform Resource Names................................14
5.4 Document..............................................14
5.5 DigestAlgorithm.......................................15
5.6 Algorithm.............................................16
5.7 Parameter.............................................16
5.8 Package...............................................17
5.9 ContentInfo...........................................18
5.10 Value................................................18
5.11 Signatures...........................................19
5.12 Signature............................................19
5.13 Manifest.............................................20
5.14 Resource.............................................20
5.15 Locator..............................................21
5.16 Digest...............................................21
5.17 Attributes...........................................22
5.18 Attribute............................................22
5.19 Date.................................................23
5.20 OriginatorInfo.......................................24
5.21 RecipientInfo........................................24
5.22 Identifier...........................................25
5.23 IssuerAndSerialNumber................................25
5.24 SignatureAlgorithm...................................26
5.25 Certificates.........................................26
5.26 Certificate..........................................26
5.27 Integer..............................................27
Richard D. Brown [Page 2]
INTERNET-DRAFT January 1999 Digital Signatures for XML
5.28 Real.................................................28
5.29 Keyword..............................................28
5.30 Resources............................................29
6. Supported Algorithms...................................29
6.1 Digest Algorithms.....................................30
6.2 Key Agreement Algorithms..............................30
6.3 Key Exchange Aglorithms...............................30
6.4 Signature Algorithms..................................31
6.5 SHA1..................................................31
6.6 DOM-HASH..............................................31
6.7 XHASH.................................................32
6.8 PKCS12-PBE............................................32
6.9 HMAC..................................................33
6.10 DSA..................................................33
6.11 RSA..................................................33
6.12 ECDSA................................................34
7. Uniform Resource Names.................................34
8. Certificate Supplement.................................34
9. Conformance Requirements...............................35
10. Examples..............................................35
10.1 Signature DTD - Embedded Content.....................35
10.2 Signature DTD - Detached Signature...................37
10.3 Extended DTD - Domain-specific Attribute.............38
11. Signature DTD.........................................40
12. Security Considerations...............................41
References................................................42
Author's Address..........................................42
Expiration and File Name..................................42
Richard D. Brown [Page 3]
INTERNET-DRAFT January 1999 Digital Signatures for XML
1. Introduction
XML, the Extensible Markup Language [XML], is a syntactical standard
elaborated by the World Wide Web Consortium. XML is a subset of an
existing and widely used 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.
As it is anticipated that XML will be widely used in the exchange of
business and commercial data, and it has been already established
that digital signatures will play an important role in enabling
electronic commerce, the necessity to promote a digital signature
standard for general XML documents becomes evident.
Drafted with IOTP (Internet Open Trading Protocol) requirements in
mind, this document has been further enhanced as comments were
received and alternative proposals disclosed. It is now expected that
it provides a more general solution to signing XML documents.
2. Objective and Requirements
The objective of this document is to propose syntax and procedures
for the computation and verification of digital signatures applicable
to general XML documents.
This proposal has been established in light of the requirements that
have been gathered while reviewing diverse projects and alternative
approaches such as IOTP [draft-ietf-trade-iotp-v1.0-protocol-*.txt],
eCheck [x], BIPS [x], SDML [x], and XMLDSIG [x]. The following
requirements have been identified:
-- 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 indifferently for digital signature and
message authentication codes, considering symmetric and asymmetric
authentication schemes as well as dynamic negotiation of keying
material.
-- 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.
Richard D. Brown [Page 4]
INTERNET-DRAFT January 1999 Digital Signatures for XML
-- The solution shall enable authentication of part or totality of an
XML 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 resource 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>
(resource information block)
(originator information block)
(recipient information block)
(other attributes)
(signature algorithms 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
include a reference to, and a digest of, these pieces of information.
The authentication is therefore "indirect".
3.2 Resource Element
The Resource element consists of a unique and unambiguous reference
to the resource being authenticated. It is constructed of a locator,
Richard D. Brown [Page 5]
INTERNET-DRAFT January 1999 Digital Signatures for XML
a fingerprint, and optionally a content-type qualifier.
<Resource>
<Locator href= "resource locator"/>
<ContentType type= "type qualifier"/>
<Digest>
(digest information block)
</Digest>
</Resource>
The resource locator is implemented as a simple XML Link [XLink].
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 could be used for inserting specific pieces of information
directly into the Signature element. 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 such as
'signing-time.'
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.
Richard D. Brown [Page 6]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<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
[Schneier] Key Exchange algorithm.
3.5 Key Agreement Algorithm Element
The Key Agreement Algorithm element indicates 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>
Richard D. Brown [Page 7]
INTERNET-DRAFT January 1999 Digital Signatures for XML
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 a means for
building authentication into general XML applications. The mechanism
adopted herein considers the "XML Namespaces" specifications[x],
which define the requirements for combining multiple DTDs or parts of
individual DTD into a single document.
According to these specifications, 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.
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.
Richard D. Brown [Page 8]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<Document xmlns:dsig="Signature-DTD-URI">
<MyElement id="authenticated-infos" ...>
...
</MyElement>
<dsig:Signature>
<Manifest>
<Resource>
<Locator href=" #authenticated-infos"/>
...
</Resource>
...
</Manifest>
<Value>
...
</Value>
</dsig:Signature>
</Document>
[The XML Namespaces specifications are still work in progress at W3C.
A final draft should be available soon, as the specifications entered
"last call" September 16, 1998.
There are still a few unknowns regarding combination of DTD and use
of qualified names in an application DTD that inherits definitions
from another DTD. The current paragraph will be developed, as
clarifications will be obtained.]
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.
<Package>
<ContentType type= "type qualifier"/>
<Value encoding= "encoding scheme">
(safe content)
</Value>
</Package>
Though it addresses a similar purpose, the Package element specified
by this draft proposal is radically different from the one given in
the " XML Package" proposal[x]. Such decision has been driven by the
possibility to leverage other element definitions of this DTD.
However, the current definition might be amended in time if the
Richard D. Brown [Page 9]
INTERNET-DRAFT January 1999 Digital Signatures for XML
Package proposal were to be adopted.
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.
<Signature id=" Signature">
<Manifest>
<Resource>
<Locator href=" resource locator"/>
...
</Resource>
...
</Manifest>
...
</Signature>
<Signature id=" CounterSignature">
<Manifest>
<Resource
<Locator href="# Signature"/>
...
</Resource>
...
</Manifest>
...
</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.
This proposal preserves verifiability of the origin and authenticity
of these blocks of information as they are exchanged between parties.
To facilitate creation and verifiability of composite documents, the
current draft proposal has adopted an element, known as the Resources
element, which consist of a collection of Resource elements. The
authentication of the Resources element is sufficient for ensuring
proper authentication of the blocks of information that it
references, and verifiability is preserved when individual blocks of
information are missing.
Richard D. Brown [Page 10]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<Block id=" Block01">
...
</Block>
<Block id=" Block02">
...
</Block>
<Resources id=" Resources">
<Resource>
<Locator href="# Block01"/>
...
</Resource>
<Resource>
<Locator href="# Block02">
...
</Resource>
</Resources>
<Signature>
<Manifest>
<Resource>
<Locator href="# Resources">
...
</Resource>
...
</Manifest
...
</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.
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, this specification uses another
functionality offered by the namespaces proposal. This functionality
provides for the definition of global attributes that may be used and
Richard D. Brown [Page 11]
INTERNET-DRAFT January 1999 Digital Signatures for XML
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. This attribute shall
reference a Digest Algorithms element, which should be declared
before making use of the attribute.
<dsig:DigestAlgorithm id="digest-algorithm">
...
</dsig:DigestAlgorithm>
<MyElement id="authenticated-infos"
dsig:eval="digest-algorith">
...
</MyElement>
<dsig:Signature>
<Manifest>
<Resource>
<Locator href="#authenticated-infos">
...
</Resource>
...
</Manifest>
...
</dsig:Signature>
When encountering the dsig:eval global attribute on the Authenticated
Block element, the XML parser is immediately aware of the requirement
of computing the digest of this element. All the pieces of
information necessary for such computation are provided by the Digest
Algorithm element referenced by the attribute.
5. Detailed Signature Syntax
Though it is expected that Signature support will be primarily built
into general XML applications by incorporating definitions of the
Signature DTD into other XML applications, the Signature DTD defines
the elements necessary to providing an XML alternative to binary
signature syntaxes.
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
Richard D. Brown [Page 12]
INTERNET-DRAFT January 1999 Digital Signatures for XML
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
operation 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 draft proposal specifies a dsig:eval
global attribute that could be used for identifying a block of
information to be authenticated. This attribute shall refer to a
Digest Algorithms element, which should be declared before making use
of the attribute.
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 IDREF #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 hash and it belongs to the
XMLDSIG namespace (whatever prefix is used).
Richard D. Brown [Page 13]
INTERNET-DRAFT January 1999 Digital Signatures for XML
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, the current draft proposal
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.
5.4 Document
The Document element constitutes the outermost envelope of an XML
document that conforms to the Signature DTD. The definition of this
element 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 PKCS7[x] binary syntax standards.
It is expected that this simple, though complete, definition will
help the adoption of this proposal and facilitate the production of
conformant implementations by a plurality of providers. This
definition does not preclude however the definition of more
sophisticated constructions to be adopted by particular XML
applications. Such applications may either redefine the Document
element or promote their own DTD, which shall be partially
constructed of elements defined by the Signature DTD.
<!ELEMENT dsig:Document (
( dsig:DigestAlgorithms, dsig:Package )?,
dsig:Signatures, dsig:Certificates?
)>
<!ATTLIST dsig:Document
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
The definition given above has been deemed sufficient for
implementing the following functionality provided by CMS or PKCS7:
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
Richard D. Brown [Page 14]
INTERNET-DRAFT January 1999 Digital Signatures for XML
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.
Content Description
DigestAlgorithms: This element has been made mandatory whenever
the document embeds the contents to be authenticated. This
element specifies the algorithms to be used for computation
of the digest of the Package element, 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 to
refer to the Digest Algorithms element described above.
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.
The definition of collection elements (i.e. Certificates and
Signatures) for the sole purpose of grouping similar sub-elements has
been adopted for facilitat- ing DOM manipulations.
5.5 DigestAlgorithm
The purpose of the DigestAlgorithm element consists of specifying the
algorithm to be employed in the computation of a message digest. This
element is used either as a standalone element for enabling one-pass
processing or as a sub-element of the Digest element.
<!ELEMENT dsig:DigestAlgorithm (dsig:Algorithm)>
<!ATTLIST dsig:DigestAlgorithms
xmlns CDATA #FIXED %xmldsig.dtd;
id ID #IMPLIED
>
Content Description
Richard D. Brown [Page 15]
INTERNET-DRAFT January 1999 Digital Signatures for XML
Algorithm: Algorithm and parameters to be used for Computation of
the digest value.
Attributes Description
id: Element identifier that is used on standalone element for
enabling reference by the dsig:eval global attribute.
5.6 Algorithm
The current draft proposal has adopted 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.
<!ELEMENT dsig:Algorithm ( dsig:Parameter* )>
<!ATTRLIST dsig:Algorithm
xmlns:dsig PCDATA #FIXED %xmldsig.dtd;
type PCDATA #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
type: The type of the algorithm expressed as a Uniform Resource
Name.
5.7 Parameter
A Parameter element provides the value of a particular algorithm
parameter, Whose name and format have been specified fo rthe
algorithm considered.
Richard D. Brown [Page 16]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<!ELEMENT dsig:Parameter ANY>
<!ATTLIST dsig:Parameter
xmlns:dsig PCDATA #FIXED %xmldsig.dtd;
type PCDATA #REQUIRED
>
Content Description
ANY: The contents of a Parameter element consists of ANY valid
Construct, which is specified on a per algoritm 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.
5.8 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: Type qualifier for the content.
Value: Content value.
Attributes Description
id: Element identifier that could be used for referencing this
element from a Resource element.
Richard D. Brown [Page 17]
INTERNET-DRAFT January 1999 Digital Signatures for XML
5.9 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:ContentType EMPTY>
<!ATTLIST dsig:ContentType
xmlns:dsig PCDATA #FIXED %xmldsig.dtd;
type PCDATA #REQUIRED
subtype PCDATA #IMPLIED
>
Attributes Description
type: Type of the content expressed as a Universal Resource Name.
subtype: Optional sub-classing of the content type.
5.10 Value
<!ELEMENT dsig:Value ( #PCDATA )>
<!ATTLIST dsig:Value
xmlns:disg CDATA #FIXED %xmldsig.dtd;
encoding ( base64 | none ) #REQUIRED 'none'
>
Content Description
PCDATA: Content value after adequate encoding.
Attributes Description
encoding: This attribute specifies the decoding scheme to be
employed for recovering the original byte stream from the
content of the element. The current draft proposal 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.
Richard D. Brown [Page 18]
INTERNET-DRAFT January 1999 Digital Signatures for XML
5.11 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.
5.12 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: A set of attributes that actually constitutes the
authenticated part of the document.
Value: Encoding of the signature value.
Attributes Description
id: Element identifier that could be used for referencing the
Signature element from a Resource element when implementing
endorsement.
Richard D. Brown [Page 19]
INTERNET-DRAFT January 1999 Digital Signatures for XML
5.13 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.
<!ELEMENT dsig:Manifest (
dsig:Resource, dsig:Attributes?,
dsig:OriginatorInfo, dsig:RecipientInfo?,
dsig:KeyAgreementAlgorithm?, dsig:SignatureAlgorithm
)>
<!ATTLIST dsig:Manifest
xmlns:dsig PCDATA #FIXED %xmldsig.dtd;
>
Content Description
Resource: Unique and unambiguous reference to the resource being
authenticated.
Attributes: Optional element that consists of a collection of
complementary attributes to be authenticated.
OriginatorInfo: Element that provides dentification 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.
5.14 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.
Richard D. Brown [Page 20]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<!ELEMENT dsig:Resource (
dsig:ContentInfo?, dsig:Locator, dsig:Digest
)>
<!ATTLIST dsig:Resource
xmlns:dsig CDATA #FIXED %xmldsig.dtd;
>
Content Description
ContentInfo: Content type qualifier.
Locator: Locator value that contains either 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 draft proposal and may lead to
inconsistent results.
Digest: Fingerprint of the resource.
5.15 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:disg 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.
5.16 Digest
The Digest element consists of the fingerprint of a given resource.
This element is constructed of two sub-elements. This first one
Richard D. Brown [Page 21]
INTERNET-DRAFT January 1999 Digital Signatures for XML
indicates the algorithm to be used for computation of the
fingerprint. The second element consists of the fingerprint value.
<!ELEMENT dsig:Digest ( dsig:DigestAlgorithm, dsig:Value )>
<!ATTLIST dsig:Digest
xmlns:disg CDATA #FIXED %xmldsig.dtd;
>
Content Description
DigestAlgorithm: Algorithm to be used for computation of the
fingerprint.
Value: Encoding of the fingerprint value.
5.17 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:disg PCDATA #FIXED %xmldsig.dtd;
>
Content Description
Attribute: Collection of Attribute elements.
5.18 Attribute
The Attribute element consists of a complementary piece of
information, which shall be included in the authenticated part of the
document. Though the current draft proposal defines well-known
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.
Richard D. Brown [Page 22]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<!ELEMENT dsig:Attribute ANY>
<!ATTLIST dsig:Attribute
xmlns:disg CDATA #FIXED %xmldsig.dtd;
type NMTOKEN #REQUIRED
critical ( true | false ) #REQUIRED 'false'
>
Content Description
ANY: The actual value of an attribute depends solely upon its
type.
Attributes Description
type: Type of the attribute.
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.
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 (cf.
element description). The type identifier of this attribute is
given in the URN appendix.
5.19 Date
The Date element consists of a constrained ISO 8601:1998 date and
time value.
<!ELEMENT dsig:Date EMPTY>
<!ATTLIST dsig:Date
xmlns:disg CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Identification data value.
Date Format
Richard D. Brown [Page 23]
INTERNET-DRAFT January 1999 Digital Signatures for XML
The current draft proposal requires date values to be expressed
according to the following pattern: YYYY '-' MM '-' DD 'T' hh
':' mm [':' ss ['.' f+]]('+' | '-') hhmm
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.
5.20 OriginatorInfo
The OriginatorInfo element is used for providing identification and
keying material information for the originator.
<!ELEMENT dsig:OriginatorInfo ANY>
<!ATTLIST dsig:OriginatorInfo
xmlns:disg PCDATA #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.
5.21 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.
Richard D. Brown [Page 24]
INTERNET-DRAFT January 1999 Digital Signatures for XML
Content Description
The content of this element is similar to the one defined for the
Originator (cf. OriginatorInfo element descrition).
5.22 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:disg CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Identification data value.
5.23 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:disg 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.
Richard D. Brown [Page 25]
INTERNET-DRAFT January 1999 Digital Signatures for XML
5.24 SignatureAlgorithm
The SignatureAlgorithms element is used for specifying the algorithms
to be used for computation of the signature value.
<!ELEMENT dsig:SignatureAlgorithm ( dsig:Algorithm )>
<!ATTLIST dsig:SignatureAlgorithm
xmlns:dsig PCDATA #FIXED %xmldsig.dtd;
>
Content Description
Algorithm: Algorithm and parameters to be used for computation of
the signature value.
5.25 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.
5.26 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.
Richard D. Brown [Page 26]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<!ELEMENT dsig:Certificate (
dsig:IssuerAndSerialNumber,
( dsig:Value | dsig:Locator )
)>
<!ATTLIST dsig:Certificate
xmlns:disg 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. This attribute is
specified as a Universal Resource Name (cf. Certificate
Supplement).
5.27 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:disg CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Value of the element given according to the format given
below.
Richard D. Brown [Page 27]
INTERNET-DRAFT January 1999 Digital Signatures for XML
Integer Format
The current specification requires integer values to be expressed
According to the following pattern:
['+'|'-'] n+
For example, +128, -35635, and 64535 are valid integer
values.
5.28 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:disg CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Value of the element given according to the format given
below.
Real Format
The current 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
numbers.
5.29 Keyword
The Keyword element is a primary data type that is used in the
definition of algorithm parameters.
Richard D. Brown [Page 28]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<!ELEMENT dsig:Keyword EMPTY>
<!ATTLIST dsig:Keyword
xmlns:disg CDATA #FIXED %xmldsig.dtd;
value CDATA #REQUIRED
>
Attributes Description
value: Value of the element given as a free form string.
5.30 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:disg 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. Supported Algorithms
This specification uses 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
Richard D. Brown [Page 29]
INTERNET-DRAFT January 1999 Digital Signatures for XML
Algy parameter. Such a recursive construct is expected to facilitate
integration with cryptographic toolkits.
6.1 Digest Algorithms
This specificaiton contemplates two kinds 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.
6.2 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.
Key-agreement algorithms shall not be mistaken with key-exchange
algorithms, which may be implicitly employed for computation of a
master key that results from the combination of keying material
provided by the parties involved in an exchange. In other words,
parties provided with credentials such as Diffie-Hellmann-based
certificates shall establish the value of the master key by means of
the key exchange algorithm and may further derive a one-time session
key from this master key by means of a key-agreement algorithm. A
similar procedure is recommended when making use of a message
authentication code and a shared secret.
6.3 Key Exchange Aglorithms
A key-exchange algorithm consists of a function that is used for
deriving a one-time session key from a given master key. (TBD)
Richard D. Brown [Page 30]
INTERNET-DRAFT January 1999 Digital Signatures for XML
6.4 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 [RFC 2104].
6.5 SHA1
Surface string digest algorithm designed by NIST and NSA for use with
the Digital Signature Standard. This algorithm produces a 160-bit
hash value.
This algorithm does not require any parameter.
6.6 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. Also, there is no explicit
support for XML Namespaces.
The DOM-HASH algorithm requires a single parameter, which shall
consist of a surface string digest algorithm such as SHA1.
Example
<dsig:Algorithm type='dom-hash urn'>
<dsig:Parameter type='digst-algorithm'>
<dsig:Algorithm type='sha1 urn'/>
</dsig:Parameter>
</dsig:Algorithm>
Richard D. Brown [Page 31]
INTERNET-DRAFT January 1999 Digital Signatures for XML
6.7 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 has been tailored for explicit
support of the XML Namespaces and it 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.
Example
<dsig:Algorithm type='xhash urn'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='sha1 urn'/>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'>
<dsig:Algorithm type='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
6.8 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.
Richard D. Brown [Page 32]
INTERNET-DRAFT January 1999 Digital Signatures for XML
Example
<dsig:Algorithm type='pkcs12-pbe urn'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='sha1 urn'/>
</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>
6.9 HMAC
Generalities [RFC 2104]
Example
<dsig:Algorithm type='hmac urn'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='xhash urn'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='sha1 urn'/>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'>
<dsig:Keyword value='ignore'>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:Parameter>
</dsig:Algorithm>
6.10 DSA
6.11 RSA
Richard D. Brown [Page 33]
INTERNET-DRAFT January 1999 Digital Signatures for XML
6.12 ECDSA
<dsig:Algorithm type='eccdsa urn'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='xhash urn'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='sha1 urn'/>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'>
<dsig:Keyword value='ignore'>
</dsig:Parameter>
</dsig:Parameter>
<dsig:Parameter type='curve-factor-a'>
<dsig:Integer value='3'>
</dsig:Parameter>
<dsig:Parameter type='curve-factor-b'>
<dsig:Integer value='5'>
</dsig:Parameter>
<dsig:Parameter type='point'>
<dsig:Integer value='7'>
</dsig:Parameter>
</dsig:Algorithm>
7. Uniform Resource Names
Generalities [RFC 2141]
Content-type URNs
Leveraging MIME [RFC 2046] types.
Other content-types
Algorithm URNs
Certificate Type URNs
8. Certificate Supplement
Locator Protocols (HTTP, LDAP)
Expected Formats
Richard D. Brown [Page 34]
INTERNET-DRAFT January 1999 Digital Signatures for XML
9. Conformance Requirements
TBD
10. Examples
The URN given in the following examples are purely illustrative and,
therefore, shall not be used as reference material.
10.1 Signature DTD - Embedded Content
<?xml version='1.0'?>
<!DOCTYPE dsig:Document PUBLIC 'urn:ietf:xmldsig.dtd'
SYSTEM 'http://www.dtd.reg.int/dtd/xmldsig.dtd'
>
<dsig:Document>
<dsig:DigestAlgorithm id='digest-algorithm'>
<dsig:Algorithm type='urn:com-globeset:xhash'>>
<dsig:Parameter type='digest-algorithm'/>
<dsign:Algorithm type='urn:fips:sha1'>>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'/>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:DigestAlgorithm>
<dsig:Package id='data'
dsig:eval='#digest-algorithms'>
<dsig:ContentInfo type='urn:mime:application-msword'/>
<dsig:Value encoding='base64'>
abncjflf311257gghn6mj2k134h64AANHdd12==
</dsig:Value>
</dsig:Package>
<dsig:Signatures>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resource>
<dsig:Locator href='#data'/>
<dsig:ContentInfo type='urn:mime:application-msword'/>
<dsig:Digest>
<dsig:Algorithm type='urn:com-globeset:xhash'>>
<dsig:Parameter type='digest-algorithm'/>
Richard D. Brown [Page 35]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<dsign:Algorithm type='urn:fips:sha1'>>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'/>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
<dsig:Value encoding='base64'>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
<dsig:OriginatorInfo>
<dsig:IssuerAndSerialNumber
issuer='o=GlobeSet Inc., c=US'
number='123456789102356'/>
</dsig:OriginatorInfo>
<dsig:Attributes>
<dsig:Attribute
type='urn:ietf:xmldsig.signing-time'>
<dsig:Date value='1998-10-29T13:26-0500'/>
</dsig:Attribute>
</dsig:Attributes>
<dsig:SignatureAlgorithm>
<dsig:Algorithm type='urn:com-rsa:rsa-pks1'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:com-globeset:xhash'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:fips:sha1'/>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:SignatureAlgorithm>
</dsig:Manifest>
<dsig:Value encoding='base64'>
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'/>
Richard D. Brown [Page 36]
INTERNET-DRAFT January 1999 Digital Signatures for XML
<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 encoding='base64'>
xsqsfasDys2h44u4ehJDe54he5j4dJYTJ
</dsig:Value>
</dsig:Certificate>
</dsig:Certificates>
</dsig:Document>
10.2 Signature DTD - Detached Signature
<?xml version='1.0'?>
<!DOCTYPE dsig:Document PUBLIC 'urn:ietf:xmldsig.dtd'
SYSTEM 'http://www.dtd.reg.int/dtd/xmldsig.dtd'
>
<dsig:Document>
<dsig:Signatures>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resource>
<dsig:ContentInfo type='urn:mime:application-msword'/>
<dsig:Locator href='http://www.globeset.com/xml.doc'/>
<dsig:Digest>
<dsig:Algorithm type='urn:fips:sha1'/>
<dsig:Value encoding='base64'>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
<dsig:OriginatorInfo>
<dsig:IssuerAndSerialNumber
issuer='o=GlobeSet Inc., c=US'
number='123456789102356'/>
</dsig:OriginatorInfo>
<dsig:Attributes>
<dsig:Attribute
type='urn:ietf:xmldsig.signing-time'>
<dsig:Date value='1998-10-29T13:26-0500'/>
</dsig:Attribute>
Richard D. Brown [Page 37]
INTERNET-DRAFT January 1999 Digital Signatures for XML
</dsig:Attributes>
<dsig:SignatureAlgorithm>
<dsig:Algorithm type='urn:com-rsa:rsa-pks1'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:com-globeset:xhash'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:fips:sha1'/>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:SignatureAlgorithm>
</dsig:Manifest>
<dsig:Value encoding='base64'>
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:Certificates>
</dsig:Document>
10.3 Extended DTD - Domain-specific Attribute
<?xml version='1.0'?>
<!DOCTYPE Document PUBLIC 'urn:ietf:xmldsig.dtd'
SYSTEM 'http://www.dtd.reg.int/dtd/xmldsig.dtd' [
<!ELEMENT MyDocument (
dsig:Resources, dsig:Signature
)>
<!ELEMENT AssetCategory EMPTY>
<!ATTLIST AssetCategory
type PCDATA #REQUIRED
>
Richard D. Brown [Page 38]
INTERNET-DRAFT January 1999 Digital Signatures for XML
]>
<MyDocument>
<dsig:Resources id='data'>
<dsig:Resource>
<dsig:ContentType type='urn:com-globeset:demo-invoice'/>
<dsig:Locator href='http://www.globeset.com/invoice.xml'/>
<dsig:Digest>
<dsig:Algorithm type='urn:com-globeset:xhash'>>
<dsig:Parameter type='digest-algorithm'/>
<dsign:Algorithm type='urn:fips:sha1'>>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'/>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
<dsig:Value encoding='base64'>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
<dsig:Resource>
<dsig:ContentType type='urn:com-globeset:demo-receipt'/>
<dsig:Locator href='http://www.globeset.com/receipt.xml'/>
<dsig:Digest>
<dsig:Algorithm type='urn:com-globeset:xhash'>>
<dsig:Parameter type='digest-algorithm'/>
<dsign:Algorithm type='urn:fips:sha1'>>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'/>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
<dsig:Value encoding='base64'>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
</dsig:Resources>
<dsig:Signature>
<dsig:Manifest>
<dsig:Resource>
<dsig:Locator href='#data'/>
<dsig:Digest>
<dsig:Algorithm type='urn:com-globeset:xhash'>>
<dsig:Parameter type='digest-algorithm'/>
<dsign:Algorithm type='urn:fips:sha1'>>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'/>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
Richard D. Brown [Page 39]
INTERNET-DRAFT January 1999 Digital Signatures for XML
</dsig:Algorithm>
<dsig:Value encoding='base64'>
bndWGryrt245u6t1dgURTIrr4ir5=
</dsig:Value>
</dsig:Digest>
</dsig:Resource>
<dsig:OriginatorInfo>
<dsig:Identifier value='smith'/>
</dsig:OriginatorInfo>
<dsig:Attributes>
<dsig:Attribute
type='urn:com-globeset:asset-category'
critical='true'
>
<AssetCategory type='HDW325DPT7896'/>
</dsig:Attribute>
</dsig:Attributes>
<dsig:SignatureAlgorithm>
<dsig:Algorithm type='urn:com-rsa:rsa-pks1'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:com-globeset:xhash'>
<dsig:Parameter type='digest-algorithm'>
<dsig:Algorithm type='urn:fips:sha1'/>
</dsig:Parameter>
<dsig:Parameter type='white-spaces'>
<dsig:Keyword value='ignore'/>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:Parameter>
</dsig:Algorithm>
</dsig:SignatureAlgorithm>
</dsig:Manifest>
<dsig:Value encoding='base64'>
xsqsfasDys2h44u4ehJDe54he5j4dJYTJ=
</dsig:Value>
</dsig:Signature>
</MyDocument>
11. Signature DTD
(Insert here)
Richard D. Brown [Page 40]
INTERNET-DRAFT January 1999 Digital Signatures for XML
12. Security Considerations
The entirety of this document is concerned with a signature standard
for XML.
Richard D. Brown [Page 41]
INTERNET-DRAFT January 1999 Digital Signatures for XML
References
[RFC 2046] - N. Freed & N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", November 1996.
[RFC 2104] - H. Krawczyk, M. Bellare, R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", February 1997.
[RFC 2141] - R. Moats, "URN Syntax", May 1997.
[RFC 2396] - T. Berners-Lee, R. Fielding, L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", August 1998.
[Schneier] - Bruce Schneier, "Applied Cryptography: Protocols,
Algorithms, and Source Code in C", 1996, John Wiley and Sons
[XLink] - Eve Maler, Steve DeRose, "XML Linking Language (XLink)",
<http://www.w3.org/TR/1998/WD-xlink-19980303>
[XML] - Tim Bray, Jean Paoli, C. M. Sperber-McQueen, "Extensible
Markup Language (XML) 1.0", <http://www.w3.org/TR/1998/REC-xml-
19980210>
[...more to come]
draft-ietf-trade-iotp-v1.0-protocol-*.txt - David Burdett
Author's Address
Richard D. Brown
GlobeSet, Inc.
1250 Capital of TX Hwy. So.
Building One, Suite 300
Austin, TX 78746 USA
EMail: richard_dbrown@globeset.com
Expiration and File Name
This draft expires July 1999.
Its file name is draft-brown-xml-dsig-00.doc.
Richard D. Brown [Page 42]
