Verify an enveloped signature using a RSA key

IMPORT xml

MAIN
  DEFINE doc xml.DomDocument
  DEFINE node xml.DomNode
  DEFINE sig xml.Signature
  DEFINE key xml.CryptoKey
  DEFINE list xml.DomNodeList
  # Create DomDocument object
  LET doc = xml.DomDocument.Create()
  # Notice that whitespaces are significants in crytography, 
  # therefore it is recommended to remove unnecessary ones 
  CALL doc.setFeature("whitespace-in-element-content",FALSE)
  TRY
    # Load original document with enveloped signature into a DomDocument object
    CALL doc.load("MyDocumentEnvelopedSignature.xml")
    # Because the signature can be anywhere in the original document, 
    # we must first retrieve it
    LET list = signature.getElementsByTagNameNS("Signature",
      "http://www.w3.org/2000/09/xmldsig#")
    IF list.getCount() != 1 THEN
      DISPLAY "Unable to find one Signature node"
      EXIT PROGRAM (-1)
    ELSE
      LET node = list.getItem(1)
    END IF
    # Create RSA key
    LET key = xml.CryptoKey.Create(
      "http://www.w3.org/2000/09/xmldsig#rsa-sha1")
    CALL key.loadPEM("RSAKey.pem")
    # Create signature object from DomNode object and set RSA key to use
    LET sig = xml.Signature.CreateFromNode(node)
    CALL sig.setKey(key)
    # Verify enveloped signature validity of original document
    LET isVerified = sig.verify(doc)
    # Notice that if something has been modified in the node with 
    # attribute 'xml:id="code"' of the original XML document with the 
    # enveloped signature, the program will display "FAILED".
    IF isVerified THEN
      DISPLAY "Signature OK"
    ELSE
      DISPLAY "Signature FAILED"
    END IF
  CATCH
    DISPLAY "Unable to verify the enveloped signature :",STATUS
  END TRY
END MAIN