More on signatures

• It is possible to sign part of the document only!
• eg, get a signature on the persons with a mobile phone:

  <Reference URI="file:addresses.xml">

    <Transforms>

      <Transform Algorithm="http://.../REC-xpath-19991116">

        <XPath>//Addresses/Person[Tel/@where = 'mobile']</XPath>

      </Transform>

    </Transforms>

    ...

  </Reference>

• make the syntax differences disappear
  • use XML canonicalization
  • for example: original vs. canonical