TRADE Working Group                                        Kent Davidson
INTERNET-DRAFT                                              Differential
                                                       Yoshiai
                                                      Yoshiaki Kawatsura
                                                                 Hitachi
Expires: February March 2000                                       August                                       September 1999
draft-ietf-trade-iotp-v1.0-dsig-02.txt

 Digital Signatures for the v1.0 Internet Open Trading Protocol (IOTP)
 ------- ---------- --- --- ---- -------- ---- ------- -------- ------

Status of This Document

   This draft, file name draft-ietf-trade-iotp-v1.0-dsig-01.txt, draft-ietf-trade-iotp-v1.0-dsig-02.txt, is a
   part of the Internet Open Trading Protocol Specification version 1.0,
   and is intended to become an Informational RFC. Distribution of this
   document is unlimited. Comments should be sent to the TRADE working
   group mailing list <ietf-trade@elistx.com>.

   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.  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.''

   The

   To view the entire list of current Internet-Drafts, please check the
   "1id-abstracts.txt" listing contained in the Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow
   Directories can be accessed as listed at
   http://www.ietf.org/shadow.html. <http://www.ietf.org/shadow.html>.

Abstract

   A syntax and procedures are described for the computation and
   verification of digital signatures for use within Version 1.0 of the
   Internet Open Trading Protocol (IOTP).

Copyright

   Copyright (C) The Internet Society 1999.

Table of Contents

      Status of This Document....................................1
      Abstract...................................................1
      Copyright..................................................1

      Table of Contents..........................................2

      1. Introduction............................................3 Introduction............................................4

      2. Objective and Requirements..............................3 Requirements..............................5

      3. Signature Basics........................................4 Basics........................................6
      3.1 Signature Element......................................4 Element......................................6
      3.2 Digest Element.........................................4 Element.........................................6
      3.3 Originator and Recipient Information Elements..........5 Elements..........7
      3.4 Algorithm Element......................................6 Element......................................8
      4. Detailed Signature Syntax...............................6 Syntax...............................8
      4.1 Uniform Resource Names.................................6 Names.................................8
      4.2 IOTPSignatures.........................................6 IotpSignatures.........................................8
      4.3 Signature Component....................................7 Component....................................9
      4.3.1 Signature............................................7 Signature............................................9
      4.3.2 Manifest.............................................8 Manifest............................................10
      4.3.3 Algorithm............................................9 Algorithm...........................................11
      4.3.4 Digest...............................................9 Digest..............................................11
      4.3.5 Attribute...........................................10 Attribute...........................................12
      4.3.6 OriginatorInfo......................................11 OriginatorInfo......................................13
      4.3.7 RecipientInfo.......................................11 RecipientInfo.......................................13
      4.3.8 Parameter...........................................12 KeyIdentifier.......................................14
      4.3.9 Parameter...........................................15
      4.4 Certificate Component.................................13 Component.................................16
      4.4.1 Certificate.........................................13 Certificate.........................................16
      4.4.2 IssuerAndSerialNumber...............................14 IssuerAndSerialNumber...............................17
      4.5 Common Components.....................................14 Components.....................................17
      4.5.1 Value...............................................14 Value...............................................17
      4.5.2 Locator.............................................15 Locator.............................................18
      5. Supported Algorithms...................................15 Algorithms...................................18
      5.1 Digest Algorithms.....................................16 Algorithms.....................................18
      5.1.1 DOM-HASH............................................16 SHA1................................................19
      5.1.2 SHA1................................................16
      5.1.3 MD5.................................................17 DOM-HASH............................................19
      5.2 Signature Algorithms..................................17 Algorithms..................................20
      5.2.1 DSA.................................................17 DSA.................................................20
      5.2.2 HMAC................................................17 HMAC................................................21
      5.2.3 RSA.................................................17 RSA.................................................22
      5.2.4 ECDSA...............................................23
      6. Examples...............................................17 Examples...............................................24
      7. Signature DTD..........................................19 DTD..........................................25

      8. Security Considerations................................22
      9. References.............................................22

      9. Considerations................................28
      Full Copyright Statement..................................28
      References................................................29

      Author's Addresses.....................................23 Addresses........................................31
      Expiration and File Name..................................23 Name..................................31

1. Introduction

   The Internet Open Trading Protocol (IOTP) provides a payment system
   independent interoperable framework for Internet commerce as
   documented in [RFC xxx, xxxx, draft-ietf-trade-iotp-v1.0-protocol-*.txt].
   All IOTP messages are XML documents. XML, the Extensible Markup
   Language [XML], is a syntactical standard promulgated by the World
   Wide Web Consortium. XML is intended primarily for structuring data
   exchanged and served over the World Wide Web.

   Although IOTP assumes that any payment system used with it provides
   its own security, there are numerous cases where IOTP requires
   authentication and integrity services for portions of the XML
   messages it specifies.

2. Objective and Requirements

   This document covers how digital signatures may be used with XML
   documents to provide authentication and tamper-proof protocol
   messages specifically for Version 1.0 of the IOTP protocol. The
   reader should recognize that an effort towards general XML digital
   signatures exists but is unlikely to produce its final result in time
   for IOTP Version 1.0.  Future versions of IOTP will probably just adopt by
   reference the results of this general XML digital signature effort.

   The objective of this document is to propose syntax and procedures
   for the computation and verification of digital signatures applicable
   to Version 1.0 IOTP protocol messages, providing for:

   -- Authentication of IOTP transactions
   -- Provide a means by which an IOTP message may be made "tamper-
      proof", or detection of tampering is made evident
   -- Describe a set of available digest and signature algorithms at
      least one of which is mandatory to implement for interoperability
   -- Easily integrate within the IOTP 1.0 Specification
   -- Provide lightweight signatures with minimal redundancy
   -- Allow a signed portions of IOTP message to be "forwarded" to
      another trading roles with different signature algorithms than the
      original recipient

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 consists 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>
                   (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 references to, and a digests of, those pieces of information.

   The authentication is therefore "indirect".

3.2 Digest Element

   The Digest element consists of a unique and unambiguous reference to
   the XML resources being authenticated. It is constructed of a locator
   and the digest value data itself. The Digest algorithm is referred to
   indirectly via a DigestAlgorithmRef, so that Digest algorithms may be
   shared by multiple resources.

   <Digest DigestAlgorithmRef 'D.1'> DigestAlgorithmRef='D.1'>
       <Locator href 'resource href='resource locator'/>
       <Value>
            (Digest value)
       </Value>
   </Digest>
   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 Originator and Recipient Information Elements

   The purpose of the Originator and Recipient information elements is
   providing
   to provide 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
   [Schneier] Key Exchange algorithm.

3.4 Algorithm Element

   The Algorithm element is a generalised place to place any type of
   algorithm used within the signed IOTP message. The Algorithm may be a
   Signature algorithm or a Digest algorithm.  Each algorithm contains
   parameters specific to the algorithm used.

   <Algorithm type 'digest'" id='12'> type='digest' ID='12'>
       (algorithm information block)
   </Algorithm>

   Algorithms are required to contain an ID which allows for indirect
   reference to them from other places in the XML signature.

4. Detailed Signature Syntax

4.1 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].

4.2 IOTPSignatures IotpSignatures

   The IOTPSignatures IotpSignatures element is the top-level element in an IOTP
   signature block. It consists of a collection of Signature elements,
   and an optional set of Certificates.

   <!ELEMENT IOTPSignatures IotpSignatures (Signature+, Certificate*) >
   <!ATTLIST IOTPSignatures
           id IotpSignatures
           ID             ID            #IMPLIED >

   Content Description

   Signature: A collection of Signature elements.

   Certificate: Zero or more certificates used for signing

   Attributes Description

   ID: Element identifier that may be used to referencing reference the entire
   Signature element from a Resource element when implementing
   endorsement.

4.3 Signature Component

4.3.1 Signature

   The Signature element constitutes the majority 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 or values.

   The Value element contained within the Signature element is the
   encoded form of the signature of the Manifest element, and thus
   provides the verification of the Manifest.

   The process for generating the signed value is a multi-step process,
   involving a canonicalization algorithm, a digest algorithm, and a
   signature algorithm.

   First, the Manifest is canonicalized with an algorithm specified
   within the Algorithm element of the Manifest. The canonicalized form
   removes any inconsistencies in white space introduced by XML parsing
   engines.

   This canonicalized form is then converted into a digest form which
   uniquely identifies the canoicalized canonicalized document. Any slight
   modification in the original document will result in a very different
   digest value.

   Finally, the digest is then signed using a public-key public/symmetric key
   algorithm which digitally stamps the digest with (with the certificate of
   the signer. signer if available). The final signed digest is the value which
   is stored within the Signature's Value element.

   <!ELEMENT Signature (Manifest, Value+) >
   <!ATTLIST Signature
           ID              ID            #IMPLIED >

   Content Description

   Manifest: A set of attributes that actually constitutes the
   authenticated part of the document.

   Value:  One or more encodings of signature values. Multiple values
   allow for a multiple algorithms to be supported within a single
   signature block. component.

   Attributes Description
   ID: Element identifier that may be used to referencing reference the Signature
   element from a Resource element when implementing endorsement.

4.3.2 Manifest

   The Manifest element consists of a collection of attributes that
   specify such things as as references to the resources being
   authenticated and an indication of the keying material and algorithms
   to be used.

   <!ELEMENT Manifest
           (       Algorithm+,
                   Digest+,
                   Attribute*,
                   OriginatorInfo,
                   RecipientInfo+,
           )
   <!ATTLIST Manifest
           LocatorHRefBase          CDATA        #IMPLIED
   >

   Content Description

   Algorithm: A list of algorithms used for signing, digest computation,
   and canonicalization.

   Digest: A list of digests of resources to be authentication and
   signed.

   Attribute: 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.

   Attributes Description

   LocatorHrefBase: The LocatorHrefBase provides a similar construct to
   the HTML HREFBASE attribute and implicitly sets all relative URL
   references within the Manifest to be relative to the HrefBase. For
   example, the IOTP Manifest may contain:

   <Manifest
           LocatorHrefBase='iotp:globally-unique-tid#'> LocatorHrefBase='iotp:<globally-unique-tid>'>

   And subsequent Locators may be:

   <Locator href='C.9'>

   An implementation should concatenate the two locator references with
   "#" to create the entire URL. See definition of the Locator attribute
   on the Digest element for more detail.

4.3.3 Algorithm

   This specification uses an Algorithm data type which indicates many
   different types of algoirithms. The Algorithm element allows for
   specification of sub-algorithms as parameters of the primary
   algorithm. This is performed via a parameter within the algorithm
   that provides a reference to another Algorithm. An example of this is
   shown in the Parameter section.

   <!ELEMENT Algorithm (Parameter*) >
   <!ATTLIST Algorithm
           id
           ID             ID                #REQUIRED
           type     (digest|signature)      #IMPLIED
           name           NMTOKEN           #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:

   ID: The ID of the algorithm is used by the Digest and RecipientInfo
   to refer to the signing or digest algorithm used.

   type: The type of algorithm, either a digest or signature. This is
   implied by the element to which the algorithm is referred. That is,
   if the DigestAlgorithmRef refers to an algorithm, it is implicit by
   reference that the targetted algorithm is a digest.

   name:  The type of the algorithm expressed as a Uniform Resource
   Name.

4.3.4 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 Digest (Locator, Value) >
   <!ATTLIST Digest
           DigestAlgorithmRef       IDREF    #REQUIRED
   >

   Content Description

   Locator: Contains a "HREF" or URL locator Locator for the resource resources to be
   fingerprinted. References For use within IOTP a "scheme" with the value "iotp"
   may be used with the following structure:

      'iotp:<globally-unique-tid>#<id-value>'.

   This should be interpreted as referring to an element with an ID
   attribute that matches <id-value> in any IOTP Message that has a
   TransRefBlk Block with an IotpTransId that matches <globally-unique-
   tid>.

   If the LocatorHrefBase attribute is set on the Manifest element of
   which this Digest element is a child, then concatenate the value of
   the LocatorHrefBase attribute with the value of the Locator attribute
   before identifying the element that is being referred to.

   If the LocatorHrefBase attribute is omitted, <globally-unique-tid>
   should be interpreted as the currebt IotpTransId, which is included
   in the IOTP messages. message which contains the Manifest component.

   Value: Encoding of the fingerprint value.

   Attributes Description

   DigestAlgorithmRef: ID Reference of algorithm used for computation of
   the digest.

4.3.5 Attribute

   The Attribute element consists of a complementary piece of
   information, which shall be included in the authenticated part of the
   document. This element has been defined primarily for enabling some
   level of customization in the signature element. This is the area
   where a specific IOTP implementation may include custom attributes
   which must be authenticated directly. An Attribute element consists
   of a value, a type, and a criticality.

   At this time, no IOTP specific attributes are specified.

   <!ELEMENT Attribute ( ANY ) >
   <!ATTLIST Attribute
           type               NMTOKEN           #REQUIRED
           critical        ( true | false )     #REQUIRED
   >

   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 recognise. However, an
   unrecognised non-critical attribute may be ignored.

4.3.6 OriginatorInfo

   The OriginatorInfo element is used for providing identification and
   keying material information for the originator.

   <!ELEMENT OriginatorInfo ANY >
   <!ATTLIST OriginatorInfo
           OriginatorRef       NMTOKEN      #IMPLIED
   >

   Content Description

   ANY:  Identification and keying material information may consist of
   ANY construct.  Such a definition allows the adoption of
   application-specific schemes.

   Attributes Description

   OriginatorRef: A reference to the IOTP Org ID of the originating
   signer.

4.3.7 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.

   The RecipientInfo attributes provide a centralized location where
   signatures, algorithms, and certificates intended for a particular
   recipient are specified.

   The signature certificate reference ID MUST point to a certificate
   object.

   <!ELEMENT RecipientInfo ANY >
   <!ATTLIST RecipientInfo
           SignatureAlgorithmRef   IDREF        #REQUIRED
           SignatureValueRef       IDREF        #IMPLIED
           SignatureCertRef        IDREF        #IMPLIED
           RecipientRefs           NMTOKENS     #IMPLIED
   >

   Content Description

   ANY:  Identification and keying material information may consist of
   ANY construct.

   Attributes Description

   SignatureAlgorithmRef: A reference to the signature algorithm used to
   sign the SignatureValueRef intended for this recipient. The signature
   algorithm reference ID MUST point to a signature algorithm within the
   Manifest.

   SignatureValueRef: A reference to the signature value for this
   recipient. The signature value reference ID MUST point to a value
   structure directly included within a Manifest. This reference can be
   omitted if the application can specify the digest value.

   SignatureCertRef: A reference to the certificate used to sign the
   Value pointed to by the SignatureValueRef. This reference can be
   omitted if the application can identify the certificate.

   RecipientRefs: A list of references to the IOTP Org ID of the
   recipients this signature is intended for.

4.3.8 KeyIdentifier

   The key identifier element can identify the shared public/symmetric
   key identification between parties that benefit from a prior
   relationship. This element can be included in the ReceipientInfo
   Element.

   <!ELEMENT KeyIdentifier EMPTY>
   <!ATTLIST KeyIdentifier
     value             CDATA        #REQUIRED
   >

4.3.9 Parameter

   A Parameter element provides the value of a particular algorithm
   parameter, whose name and format have been specified for the
   algorithm considered.

   <!ELEMENT Parameter ANY >
   <!ATTLIST Parameter
           type       CDATA       #REQUIRED
   >

   For IOTP 1.0, the following parameter type is standardized:
   "AlgorithmRef".

   An AlgorithmRef contains an ID of a "sub-Algorithm" used when
   computing a sequence of algorithms. For example, a signature
   algorithm actually signs a digest algorithm. To specify a chain of
   algorithms used to compute a signature, AlgorithmRef parameter types
   are used in the following manner:

   <Algorithm ID A1 type 'digest' name 'urn:ibm:dom-hash'> ID='A1' type='digest' name='urn:ibm-com:dom-hash'>
           <Parameter type 'AlgorithmRef'>A2</Parameter> type='AlgorithmRef'>A2</Parameter>
   </Algorithm>
   <Algorithm ID A2 type 'digest' name 'urn:fips:sha1'> ID='A2' type='digest' name='urn:nist-gov:sha1'>
   </Algorithm>
   <Algorithm ID A3 type 'signature' name 'urn:ibm:hmac'> ID='A3' type='signature' name='urn:rsasdi-com:rsa-encryption'>
           <Parameter type 'AlgorithmRef'>A1</Parameter> type='AlgorithmRef'>A1</Parameter>
   </Algorithm>

   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.

4.4 Certificate Component

4.4.1 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 Certificate
   (       IssuerAndSerialNumber,
           ( Value | Locator ) )
   >
   <!ATTLIST Certificate
           id
           ID           ID           #IMPLIED
           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 security protocol being used.

   Attributes Description

   ID: Element identifier that may be used to reference the Cerfiticate
   element from a RecipientInfo element.

   type: Type of the digital certificate. This attribute is specified as
   a Universal Resource Name, as indicated Name. Support for the X.509 version 3
   certificate [X.509] is mandatory in this sepecification if the "Supported
   Algorithms" section.
   Certificate element is used.  The URN for such certificates is
   "urn:X500:X509v3".

4.4.2 IssuerAndSerialNumber

   The IssuerAndSerialNumber element identifies a certificate, and
   thereby an entity and a public key, by the name of the certificate
   issuer and an issuer-specific certificate identification.

   <!ELEMENT IssuerAndSerialNumber EMPTY >
   <!ATTLIST IssuerAndSerialNumber
           issuer        CDATA         #REQUIRED
           number        CDATA         #REQUIRED >

   Attributes Description

   issuer: Name of the issuing certification authority.

   number: Issuer-specific certificate identification.

4.5 Common Components

4.5.1 Value

   A value contains the "raw" data of a signature or digest algorithm,
   usually in a base-64 encoded form. See [RFC 2045] for algorithm used
   to base-64 encode data.

   <!ELEMENT Value ( #PCDATA ) >
   <!ATTLIST Value
           id
           ID                 ID            #IMPLIED
           encoding      (base64|none)     #IMPLIED     'base64'
   >

   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. This document recognises 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.

4.5.2 Locator

   The Locator element consists of simple XML link [XLink].  This
   element allows unambiguous reference to a resource or fragment of a
   resource.

   <!ELEMENT Locator EMPTY>
   <!ATTLIST Locator
           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. Supported Algorithms

   The IOTP specification 1.0 requires the implementation of the DOM-
   HASH, SHA1, MD5, DSA, and
   DOM-HASH, SHA1, HMAC algorithms to provide a compliant
   implementation of IOTP 1.0. algorithms. Implementation of RSA is also
   recommended.

5.1 Digest Algorithms

   This specification contemplates two types of digest algorithms, both
   of which provide a digest string as a result:

   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 Any
   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. produced unless they affect
   the core semantic.

5.1.1 DOM-HASH

   XML canonical 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 is documented in NIST FIPS Publication
   180-1 [SHA1].

   This algorithm does not require any parameter.

   The SHA1 URN used for this specification is "urn:nist-gov:sha1".

5.1.2 DOM-HASH

   XML canonical digest algorithm proposed by IBM Tokyo Research
   Laboratory. 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
   include a surface string digest algorithm such as SHA1.

   The DOM-HASH URN used for this specification is "urn:ibm:dom-hash".

   Example
   <Algorithm name='urn:ibm:dom-hash' type='digest'>
   </Algorithm>

5.1.2 SHA1

   Surface string "urn:ibm-com:dom-
   hash".

   The DOM-HASH uses a surface-string digest algorithm designed by the US government for use
   with the Digital Signature Standard. This algorithm produces computation
   of a 160-
   bit hash value.

   This algorithm does not require any parameter. fingerprint. The SHA1 URN used for this specification is "urn:fips:sha1".

5.1.3 MD5

   The MD5 Algorithm was invented by RSA Data Securities and is similar
   to its predecessors, MD2 and MD4, but faster and simpler than MD2
   while stronger than MD4. [RFC 1321]

   The MD5 Algorithm takes no parameters.

   The MD5 URN used for recommended in this specification is "urn:rsa:md5". specification.

   Example
   <Algorithm name='urn:fips:sha1' type='digest' ID='P.3'>
   </Algorithm>
   <Algorithm name='urn:ibm:dom-hash' type='digest' ID='P.5'>
   <Parameter type='AlgorithmRef'>P.3</Parameter>
   </Algorithm>

5.2 Signature Algorithms

   This specification 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 ECDSA and message
   authentication codes such as HMAC [RFC 2104].

5.2.1 DSA

   Public-key signature algorithm proposed by NIST for use with the
   Digital Signature Standard. This standard is documented in NIST FIPS
   Publication 186 [DSS] and ANSI X9.30 [X9.30].

   The DSA algorithm requires a single parameter, which includes the
   canonical digest algorithm to be used for computing the fingerprint
   of the signature Manifest.

   The DSA URN used in this specification is "urn:fips:dsa".

5.2.2 HMAC

   See [RFC 2104] "urn:nist-gov:dsa".

   The DSA uses a canonical or surfce-string digest algorithm for
   computation of the Manifest fingerprint. The DOM-HASH is recommended
   in this specification.

   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 [PKCS#1] specification
   with a k parameter equals to 20.

   Example
   <Algorithm name='urn:nist-gov:dsa' type='signature' ID='P.3'>
     <Parameter type="AlgorithmRef">P.4</Parameter>
   </Algorithm>
   <Algorithm name='urn:ibm-com:dom-hash' type='digest' ID='P.4'>
     <Parameter type='AlgorithmRef'>P.5</Parameter>
   </Algorithm>
   <Algorithm name='urn:nist-gov:sha1' type='digest' ID='P.5'>
   </Algorithm>

5.2.2 HMAC

   Message Authentication Code proposed by H. Krawczyk and al. and
   documented in [RFC 2104].

   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( SecretKey, H(Manifest))

   This specification also considered HMAC output truncation such as
   proposed by Preneel and van Oorschot. In their paper [PV] 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.

   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.

   The HMAC URN used in this specification is "urn:ietf-org:hmac".

   Canonical digest algorithm: Canonical or surface-string digest
   algorithm is to be used for computation of the Manifest fingerprint.
   The type of this parameter is set to "AlgorithmRef".  The recommended
   value of this Parameter should be the ID reference for the Algorithm
   element DOM-HASH.

   Hash-function: Hash function is to be used to compute the MAC value
   from the secret key and the fingerprint of the signature Manifest.
   The type of this parameter is set to "HashAlgorithmRef" and the value
   of this parameter should be set to the ID reference for the Algorithm
   element of SHA1.

   Output-length: Length in bits of the truncated MAC value. The type of
   this parameter is set to "KeyLength" and the value of this parameter
   is set the length in bits of the truncated MAC value.

   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 [PKCS#1] specification with a k parameter equals to  ((Hlen
   +7) mod8), Mlen being the length in bits of the MAC value.

   Example
   <Algorithm name='urn:ietf-org:hmac' type='signature' ID='P.3'>
     <Parameter type="AlgorithmRef">P.4</Parameter>
     <Parameter type="HashAlgorithmRef">P.5</Parameter>
     <Parameter type="KeyLength">128</Parameter>
   </Algorithm>
   <Algorithm name='urn:ibm-com:dom-hash' type='digest' ID='P.4'>
     <Parameter type='AlgorithmRef'>P.5</Parameter>
   </Algorithm>
   <Algorithm name='urn:nist-gov:sha1' type='digest' ID='P.5'>
   </Algorithm>

5.2.3 RSA

   Public-key signature algorithm proposed by RSA Laboratories and
   documented in PKCS#1 [PKCS#1].

   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

   The RSA URN used in this specification is "urn:rsasdi-com:rsa-
   encription".

   The RSA uses a canonical or surfce-string digest algorithm for
   computation of the Manifest fingerprint. The DOM-HASH is recommended
   in this specification.

   Signature Value Encoding:

   The output of this algorithm consists of single octet-stream. No
   further encoding is required.

   Example
   <Algorithm name='urn:rsasdi-com:rsa-encription'
                                       type='signature' ID='P.3'>
     <Parameter type="AlgorithmRef">P.4</Parameter>
   </Algorithm>
   <Algorithm name='urn:ibm-com:dom-hash' type='digest' ID='P.4'>
     <Parameter type='AlgorithmRef'>P.5</Parameter>
   </Algorithm>
   <Algorithm name='urn:nist-gov:sha1' type='digest' ID='P.5'>
   </Algorithm>

5.2.4 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 [X9.62]
   and IEEE/P1363 standard draft proposal [IEEE P1363].

   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

   The ECDSA URN used in this specification is "urn:ansi-org:ecdsa".

   The ECDSA uses a canonical or surfce-string digest algorithm for
   computation of the Manifest fingerprint. The HMAC URN used DOM-HASH is recommended
   in this specification is is "urn:ibm:hmac".

5.2.3 RSA specification.

   Signature Value Encoding:

   The RSA URN used in 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 [PKCS#1] specification is "urn:rsa:rsa".
   with a k parameter equals to 20.

   Example
   <Algorithm name='urn:ansi-org:ecdsa' type='signature' ID='P.3'>
     <Parameter type="AlgorithmRef">P.4</Parameter>
   </Algorithm>
   <Algorithm name='urn:ibm-com:dom-hash' type='digest' ID='P.4'>
     <Parameter type='AlgorithmRef'>P.5</Parameter>
   </Algorithm>
   <Algorithm name='urn:nist-gov:sha1' type='digest' ID='P.5'>
   </Algorithm>

6. Examples

   The following is an example signed IOTP message:

   <IotpMessage>
      <TransRefBlk ID='M.1'>
          <TransId
              ID='M.2'
              version='1.0'
              IOtpTransID='19990809215923@www.iotp.org'
              IOtpTransType='BaselinePurchase'
              IotpTransID='19990809215923@www.iotp.org'
              IotpTransType='BaselinePurchase'
              TransTimeStamp='1999-08-09T12:58:40.000Z+9'>
          </TransId>
          <MsgId xml:lang='en' SoftwareID='Iotp wallet version 1.0'>
          </MsgId>
      </TransRefBlk>
      <IOTPSignatures>
      <IotpSignatures>
          <Signature>
              <Manifest LocatorHrefBase='iotp:'>
              <Manifest>
                  <Algorithm name='urn:sha1' name='urn:nist-gov:sha1'
                                              type='digest' id='P.3'> ID='P.3'>
                  </Algorithm>
                  <Algorithm name='urn:rsa' name='urn:nist-gov:dsa'
                                              type='signature' ID='P.4'>
                      <Parameter type AlgorithmRef>P.5</Parameter> type="AlgorithmRef">P.5</Parameter>
                  </Algorithm>
                  <Algorithm name='urn:dom-hash' name='urn:ibm-com:dom-hash'
                                              type='digest' id='P.5'> ID='P.5'>
                      <Parameter type='AlgorithmRef'>P.3</Parameter>
                  </Algorithm>
                  <Digest DigestAlgorithmRef='P.6'>
                      <Locator href='P.1'/>
                      <Value>
                       xsqsfasDys2h44u4ehJDe54he5j4dJYTJ
                      </Value>
                  </Digest>
                  <OriginatorInfo
                      <IssuerAndSerialNumber
                       issuer='o=Iotp Ltd., c=US'
                       number='12345678987654'/>
                  </OriginatorInfo>
                  <RecipientInfo
                      SignatureAlgorithmRef='P.4'
                  </RecipientInfo>
              </Manifest>
              <Value>
                   9dj28fjakA9sked0Ks01k2d7a0kgmf9dk19lf63kkDSs0
              </Value>
          </Signature>
          <Certificate type='urn:X500:X509v3'>
              <IssuerAndSerialNumber
                   issuer='o=GlobeSet Inc., c=US'
                   number='123456789102356'/>
              <Value>
               xsqsfasDys2h44u4ehJDe54he5j4dJYTJ=
              </Value>
         </Certificate>
      </IOTPSignatures>
      </IotpSignatures>
      <PayExchBlk ID='P.1'>
          <PaySchemeData
              ID='P.2'
              PaymentRef='M.5'
              ContentSoftwareId='abcdefg'>
                  <PackagedContent Name='FirstPiece'>
                       snroasdfnas934k
                  </PackagedContent>
         </PaySchemeData>
      </PayExchBlk>
   </IotpMessage>

7. Signature DTD

   <!--
   ******************************************************
   * IOTP SIGNATURES BLOCK DEFINITION                   *
   ******************************************************
   -->

   <!ELEMENT IOTPSignatures IotpSignatures (Signature+ ,Certificate*) >
   <!ATTLIST IOTPSignatures IotpSignatures
           ID        ID        #IMPLIED
   >

   <!--
   ******************************************************
   * IOTP SIGNATURE COMPONENT DEFINITION                *
   ******************************************************
   -->

   <!ELEMENT Signature (Manifest, Value+) >
   <!ATTLIST Signature
           ID         ID        #IMPLIED
   >

   <!ELEMENT Manifest
           (       Algorithm+,
                   Digest+,
                   Attribute*,
                   OriginatorInfo,
                   RecipientInfo+
           )
   >

   <!ATTLIST Manifest
           LocatorHRefBase       CDATA             #IMPLIED
   >

   <!ELEMENT Algorithm (Parameter*) >
   <!ATTLIST Algorithm
           id
           ID                     ID                #REQUIRED
           type            (digest|signature)      #IMPLIED
           name                  NMTOKEN           #REQUIRED
   >

   <!ELEMENT Digest (Locator, Value) >
   <!ATTLIST Digest
           DigestAlgorithmRef    IDREF             #REQUIRED
   >

   <!ELEMENT Attribute ( ANY ) >
   <!ATTLIST Attribute
           type                   NMTOKEN           #REQUIRED
           critical            ( true | false )     #REQUIRED
   >

   <!ELEMENT OriginatorInfo ANY >
   <!ATTLIST OriginatorInfo
           OriginatorRef           NMTOKEN          #IMPLIED
   >

   <!ELEMENT RecipientInfo ANY >
   <!ATTLIST RecipientInfo
           SignatureAlgorithmRef   IDREF            #REQUIRED
           SignatureValueRef       IDREF            #IMPLIED
           SignatureCertRef        IDREF            #IMPLIED
           RecipientRefs           NMTOKENS         #IMPLIED
   >

   <!ELEMENT KeyIdentifier EMPTY>
   <!ATTLIST KeyIdentifier
           value                    CDATA           #REQUIRED
   >

   <!ELEMENT Parameter ANY >
   <!ATTLIST Parameter
           type                     CDATA           #REQUIRED
   >
   <!--
   ******************************************************
   * IOTP CERTIFICATE COMPONENT DEFINITION              *
   ******************************************************
   -->

   <!ELEMENT Certificate
     (  IssuerAndSerialNumber,  ( Value | Locator ) )
   >

   <!ATTLIST Certificate
           ID                        ID                #IMPLIED
           type                      NMTOKEN           #REQUIRED
   >

   <!ELEMENT IssuerAndSerialNumber EMPTY >
   <!ATTLIST IssuerAndSerialNumber
           issuer                     CDATA            #REQUIRED
           number                     CDATA            #REQUIRED
   >

   <!--
   ******************************************************
   * IOTP SHARED COMPONENT DEFINITION                   *
   ******************************************************
   -->
   <!ELEMENT Value ( #PCDATA ) >
   <!ATTLIST Value
           id
           ID               ID           #IMPLIED
           encoding    (base64|none)    #IMPLIED      'base64'
   >

   <!ELEMENT Locator EMPTY>
   <!ATTLIST Locator
           xml:link        CDATA         #FIXED        'simple'
           href            CDATA         #REQUIRED
   >

8. Security Considerations

   This entire document concerns the IOTP v1 protocol signature element
   which is used for authentication.  See the Security Considerations
   section of [RFC xxxx] "Interenet "Internet Open Trading Protocol - IOTP, Version
   1.0".

9.

Full Copyright Statement

   Copyright (C) The Internet Society 1999.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

References

   [DSA] - Federal Information Processing Standards Plublication FIPS
   PUB 186, "Digital Signature Standard(DSS)", 1994,
   <http://csrc.nist.gov>

   [IEEE P1363] - IEEE P1363, "Standard Specifications for Public-Key
   Cryptography", draft, 1997, <http://stdsbbs.ieee.org/>

   [PKCS#1] - RSA Laboratories, "PKCS #1: RSA Encription Standard.
   Version 1.5", November 1993.

   [PV] - B. Preneel and P. van Oorschot, "Building fast MACs from hash
   functions", Advances in Cryptology -- CRYPTO'95 Proceedings, Lecture
   Notes in Computer Science, Springer-Verlag Vol.963, 1995, pp. 1-14.

   [RFC 1321] - R. Rivest, "The MD5 Message-Digest Algorithm", April
   1992.

   [RFC 2045]- N. Freed & N. Borenstein, "Multipurpose Internet Mail
   Extensions (MIME) Part One: Format of Internet Message Bodies",
   November 1996.

   [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.

   [RFC xxxx] - D. Burdett, "Interenet Open Trading Protocol - IOTP,
   Version 1.0", August 1999. (currently draft-ietf-trade-iotp-v1.0-
   protcool-*.txt)

   [Schneier] - Bruce Schneier, "Applied Cryptography: Protocols,
   Algorithms, and Source Code in C", 1996, John Wiley and Sons

   [SHA1] - NIST FIPS PUB 180-1, "Secure Hash Standard," National
   Institute of Standards and Technology, U.S. Department of Commerce,
   April 1995.

   [X.509] - ITU-T Recommendation X.509 (1997 E), "Information
   Technology - Open Systems Interconnection - The Directory:
   Authentication Framework", June 1997.

   [X9.30] - ASC X9 Secretariat: American Bankers Association, "American
   National Standard for Financial Services - Public Key Cryptography
   Using Irreversible Algorithms for the Financial Services Industry -
   Part 1: The Digital Signature Algorithm(DSA)", 1995.

   [X9.62] - ASC X9 Secretariat: American Bankers Association,"American
   National Standard for Financial Services - Public Key Cryptography
   Using Irreversible Algorithms for the Financial Services Industry -
   The Elliptic Curve Digital Signature Algorithm (ECDSA)", draft, 1997.

   [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>

9.

Author's Addresses

   This document is based on work originally done on general XML digital
   signatures by Richard Brown at GlobeSet, Inc. <rdbrown@GlobeSet.com>
   but has been narrowed and changed.

   The authors of this document are:

        Kent M. Davidson
        Differential, Inc.
        440 Clyde Ave.
        Mountain View, CA 94043 USA
        email: kent@differential.com

        Yoshiaki Kawatsura
        Hitachi, Ltd.
        890
        890-12 Kashimada Saiwai Kawasaki,
        Kanagawa 2118567 Japan
        email: kawatura@bisd.hitachi.co.jp

   Contributors to the design of the IOTP DTD include, in alphabetic
   order:

   David Burdett, Mondex Commerce One

   Andrew Drapp, Hitachi

   Donald Eastlake 3rd, IBM

Expiration and File Name

   This draft expires February March 2000.

   Its file name is draft-ietf-trade-iotp-v1.0-dsig-01.txt. draft-ietf-trade-iotp-v1.0-dsig-02.txt.