Cryptography Ontology (Crypto) 1.0

Working Draft 24 December 2003

Editor: Garret Wilson (GlobalMentor, Inc.) mailto:garret@globalmentor.com

Latest Version: http://www.globalmentor.com/reference/specifications/crypto/specification/

Abstract

The Cryptography Ontology (Crypto) specifies a consistent set of RDF classes and properties to use to specify encryption-related information in an RDF instance. Crypto is derived in part from the W3C "XML Encryption Syntax and Processing" and "XML-Signature Syntax and Processing" specifications. (TODO cite)

Status of This Document

This is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use this draft as reference material or to cite it as other than "work in progress".

Overview

This section is informative.

[XMLENC] (TODO: cite) provides several short examples of encoding character data within an XML info set. Two of these have been combined below into a single non-normative example of XML encryption:


<?xml version='1.0'?>
<PaymentInfo xmlns='http://example.org/paymentv2'>
  <Name>John Smith</Name>
  <CreditCard Limit='5,000' Currency='USD'>
    <Number>
      <EncryptedData xmlns='http://www.w3.org/2001/04/xmlenc#' Type='http://www.w3.org/2001/04/xmlenc#Content'>
        <EncryptionMethod Algorithm='http://www.w3.org/2001/04/xmlenc#tripledes-cbc'/>
        <ds:KeyInfo xmlns:ds='http://www.w3.org/2000/09/xmldsig#'>
          <ds:KeyName>John Smith</ds:KeyName>
        </ds:KeyInfo>
        <CipherData>
          <CipherValue>A23B45C56</CipherValue>
        </CipherData>
      </EncryptedData>
    </Number>
    <Issuer>Example Bank</Issuer>
    <Expiration>04/02</Expiration>
  </CreditCard>
</PaymentInfo>

An RDF instance containing the same information might be constructed as in the following non-normative example, which encodes the same information as an RDF plain literal:


<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:crypto="http://globalmentor.com/namespaces/2003/crypto#"
>
  <PaymentInfo xmlns='http://example.org/paymentv2'>
    <name>John Smith</name>
    <method>
      <CreditCard>
        <limit>
          <rdf:value>5,000</rdf:value>
          <currency>USD</currency>
          <number rdf:parseType="Resource">
            <crypto:algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc"/>
            <crypto:key>
              <crypto:Key>
                <crypto:keyName>John Smith</crypto:keyName>
              </crypto:Key>>
            </crypto:key>
            <crypto:cipherData>A23B45C56</crypto:cipherData>
          </number>
        </limit>
        <issuer>Example Bank</issuer>
        <expiration>04/02</expiration>
      </CreditCard>
    </method>
  </PaymentInfo>
</rdf:RDF>

Several points can be made about the differences between [XMLENC] (TODO: cite) and Crypto:

Crypto properties apply to the RDF resource with which they are defined. There is therefore no need for the XML Encryption Type attribute in the above example: the Crypto properties apply to the object resource of the example number property.
The Crypto namespace contains information that parallels both [XMLENC] and [XMLSIG] (TODO: cite).
Crypto retains the use of algorithms defined in [XMLENC], such as "http://www.w3.org/2001/04/xmlenc#tripledes-cbc".

Crypto can also be used to specify encoding information for resources with content outside the RDF instance, such as in the following non-normative example:


<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:crypto="http://globalmentor.com/namespaces/2003/crypto#"
  xmlns:xpackage="http://xpackage.org/namespaces/2003/xpackage#"
  xmlns:mime="http://xpackage.org/namespaces/2003/mime#"
  xmlns:xlink="http://www.w3.org/1999/xlink">
>
  <rdf:Description>
    <xpackage:location xlink:type="simple" xlink:href="image.png">
    <mime:contentType>image/png</mime:contentType>
    <crypto:algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc"/>
    <crypto:key>
      <crypto:Key>
        <crypto:keyName>Secret Key</crypto:keyName>
        <crypto:keyValue>
          <crypto:RSAKeyValue>
            <crypto:modulus>xA7SEU+e0yQH5rm9kbCDN9o3aPIo7HbP7tX6WOocLZAtNfyxSZDU16ksL6W
              jubafOqNEpcwR3RdFsT7bCqnXPBe5ELh5u4VEy19MzxkXRgrMvavzyBpVRgBUwUlV
              5foK5hhmbktQhyNdy/6LpQRhDUDsTvK+g9Ucj47es9AQJ3U=</crypto:modulus>
          <crypto:exponent>AQAB</crypto:exponent>
        </crypto:RSAKeyValue>
      </crypto:Key>>
    </crypto:key>
  <rdf:Description>
</rdf:RDF>

This example uses the XPackage ontology [XPackage] (TODO: cite) to indicate the resource's external physical location and specify its MIME type—here, a PNG image.
As the resource contents are stored externally, the crypto:cipherData property is not necessary.
Similarly, as the RDF instance is likely stored separately from the encrypted content, it includes the key value—here, an RSA key value taken from [XMLSIG] (TODO: cite).

OWL Definitions

TODO