W3C home > Mailing lists > Public > w3c-ietf-xmldsig@w3.org > April to June 2000

Revised core section

From: Donald Eastlake 3rd <dee3@torque.pothole.com>
Date: Mon, 01 May 2000 17:17:26 -0400
Message-Id: <200005012117.RAA06508@noah.dma.isg.mot.com>
To: w3c-ietf-xmldsig@w3.org
cc: lde008@dma.isg.mot.com
Here is the revised section to eliminate the MimeType and
Charset attributes and provide for them as parameters.  It claims
that none of the Transforms specified in the doc need them but 
is this true form canonicalization?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<h4> The <a name="sec-Transforms"><code>Transforms</code></a> Element </h4>

<p>The optional <code>Transforms</code> element contains an ordered
list of <code>Transform</code> elements; these describe how the
signer obtained the data object that was digested. The output of each
<code>Transform</code> (octets) serves as input to the next
<code>Transform</code>.  The input to the first <code>Transform</code>
is the source data. The output from the last <code>Transform</code> is
the input for the <code>DigestMethod</code> algorithm. When transforms
are applied the signer is not signing the native (original) document
but the resulting (transformed) document (See section 8.2: <a
href="#sec-Seen">Only What is &quot;Seen&quot; Should be Signed</a>.)

<p>Each <code>Transform</code> consists of an <code>Algorithm</code>
attribute and content parameters, if any, appropriate for the given
algorithm. The <code>Algorithm</code> attribute value specifies the
name of the algorithm to be performed, and the <code>Transform</code>
content provides additional data to govern the algorithm's processing
of the input resource (see section 6.1: <a href="#sec-AlgID">Algorithm
Identifiers and Implementation Requirements</a>).</p>

<p>Some <code>Transform</code> may require explicit
<code>MimeType</code>, <code>Charset</code> (IANA
registered character set), or other such information
concerning the data they are receiving from an earlier <code>Transform</code>
or the source data, although no 
<code>Transform</code> algorithm specified in this document needs 
such information.  Such data characteristics are provided as
parameters to the <code>Transform</code> algorithm and should be
described in the specification for the algorithm. </p>

<pre class="xml-dtd">   Schema Definition:

   &lt;element name='Transforms' &gt; 
     &lt;complexType content='elementOnly'&gt; 
       &lt;element ref='ds:Transform' minOccurs='1' maxOccurs='*'/&gt;  

   &lt;element name='Transform'&gt; 
     &lt;complexType content='mixed'&gt;
       &lt;any minOccurs='0' maxOccurs='*'/&gt;
       &lt;attribute name='Algorithm' type='string' minOccurs='1' maxOccurs='1'/&gt; 

<pre class="xml-dtd">   DTD:

   &lt;!ELEMENT Transforms (Transform+)&gt;

   &lt;!ELEMENT Transform (#PCDATA)&gt;
   &lt;!ATTLIST Transform 
             Algorithm    CDATA     #REQUIRED &gt;

<p>Examples of transforms include but are not limited to base64
decoding [<a href="#ref-MIME">MIME</a>], canonicalization [<a
href="#ref-XML-c14n">XML-c14n</a>], XPath filtering [<a
href="#ref-XPath">XPath</a>], and XSLT [<a
href="#ref-XSLT">XSLT</a>]. The generic definition of the
<code>Transform</code> element also allows application-specific
transform algorithms. For example, the transform could be a
decompression routine given by a Java class appearing as a base64
encoded parameter to a Java <code>Transform</code> algorithm. However,
applications should refrain from using application-specific transforms
if they wish their signatures to be verifiable outside of their
application domain.  Section 6.6: <a HREF="#sec-Transforms">Transform
Algorithms</a> defines the list of standard transformations. </p>


 Donald Eastlake 3rd  +1 978-562-2827(h)  dee3@torque.pothole.com
 140 Forest Avenue     +1 508-261-5434(w)  lde008@dma.isg.mot.com
 Hudson, MA 01749 USA
Received on Monday, 1 May 2000 17:32:00 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:21:33 UTC