SignedXml generates invalid signatures

I've been trying to get the XMLDSIG support in .NET to behave properly, more specifically the SignedXml class. I'm implementing a third party service and they've just recently started requiring that all messages have to be digitally signed... My problem is that, I can't seem to generate valid signatures. Both the third party service, and an online signature verifier I found, report the signature as invalid. The verification service (http://www.aleksey.com/xmlsec/xmldsig-verifier.html) reports that there's a mismatch between the digest and the data, and I've so far been unable to figure out what I'm doing wrong. Here's the relevant code - hopefully someone will be able to spot my mistake; ``` public static XDocument SignDocument(XDocument originalDocument, X509Certificate2 certificate) { var document = new XmlDocument(); document.LoadXml(originalDocument.ToString(SaveOptions.DisableFormatting)); if (document.DocumentElement == null) throw new InvalidOperationException("Invalid XML document; no root element found."); var signedDocument = new SignedXml(document); Reference signatureReference = GetSignatureReference(); KeyInfo certificateKeyInfo = GetCertificateKeyInfo(certificate); var dataObject = new DataObject("", "text/xml", "utf-8", document.DocumentElement); signedDocument.AddReference(signatureReference); signedDocument.AddObject(dataObject); signedDocument.SigningKey = certificate.PrivateKey; signedDocument.KeyInfo = certificateKeyInfo; signedDocument.ComputeSignature(); return XDocument.Parse(signedDocument.GetXml().OuterXml, LoadOptions.PreserveWhitespace); } private static Reference GetSignatureReference() { var signatureReference = new Reference(""); signatureReference.AddTransform(new XmlDsigEnvelopedSignatureTransform()); return signatureReference; } private static KeyInfo GetCertificateKeyInfo(X509Certificate certificate) { var certificateKeyInfo = new KeyInfo(); certificateKeyInfo.AddClause(new KeyInfoX509Data(certificate)); return certificateKeyInfo; } ```