Example Transformations

• Canonicalization: Making the XML textual representation unambigous
• Base64: Used if the document is in binary format
• XSLT: A full XSLT transform is used on the XML source
• XPath: A set of XPath expressions to filter parts of the XML document

For example, an enveloped signature on the rest of the document:

  <Document>
    ...
    <Signature xmlns:dsig="...">
      <SignedInfo>
        <Reference Id="">
          <Transform Algorithm="..">
            <XPath>
              not(ancestor-or-self::dsig:Signature)
            </XPath>
          </Transform>
        </Reference>
        ...
    </Signature>
    ...
  </Document>