<Signature>
  <SignedInfo>
    <Reference URI=""> <!--what is signed ?-->
      <DigestValue>.....</DigestValue> <!--base64 SHA1 digest -->
    </Reference>
  </SignedInfo>
  <SignatureValue>
    <!--base64 of r,s of DSA signature -->
  </SignatureValue>
  <KeyInfo>
    <!-- info abnout the key used -->
    <X509Data>
      <X509Certificate>
        <!-- base64 cert of the public test key for the signature -->
      </X509Certificate>
    </X509Data>
  </KeyInfo>
</Signature>