Can I set the BaseURI to empty?

[ralph-xmlsecurity]

Hi,

I create and sign a Document that does not have a URI: I intend to send it 
over the net as a Java-serialised object (because I use a P2P net for 
sending). So the XML does not really exist as a file anywhere and I would 
like to set the BaseURI to "" (empty). Signing with this works, but the 
verification gives me: WARNING: Verification failed for URI "".

If I create a file and use that as a BaseURI, it works, but I never write to 
that file or read from it, so what's the point?

As I understand http://www.w3.org/TR/xmldsig-core/#sec-URI, the Reference URI 
is allowed be empty:

"If the URI attribute is omitted altogether, the receiving application is 
expected to know the identity of the object."

Obviously, I do know the identity, but how do I enable the verification with 
empty BaseURI? I have attached the source.

Source: 
BaseURI = file.toURL().toString();
XMLSignature sig = new XMLSignature(document, BaseURI,
XMLSignature.ALGO_ID_SIGNATURE_RSA_SHA1);
Transforms transforms = new Transforms(document);
String filter[][] = { { XPath2FilterContainer.INTERSECT,
                                                "//Body/message" } };
transforms.addTransform(Transforms.TRANSFORM_XPATH2FILTER,
        XPath2FilterContainer.newInstances(document, filter));
transforms.addTransform(Transforms.TRANSFORM_C14N_WITH_COMMENTS);
sig.addDocument(BaseURI, transforms, Constants.ALGO_ID_DIGEST_SHA1);
sig.addKeyInfo(publicKey);
sig.sign(privateKey);


Element sigElement = ParserHelper.uniqueElementExctractorNS(
        document.getDocumentElement(), "ds",
        "http://www.w3.org/2000/09/xmldsig#";, "Signature");
XMLSignature signature = new XMLSignature(sigElement, BaseURI);
PublicKey pkembed = signature.getKeyInfo().getPublicKey();

if (signature.checkSignatureValue(pk))
        System.out.println("hooray");
else System.out.println("dump");

Thanks,
Ralph

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For contact details, please see www.ralphholz.de.

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