// Sign an XML file.
// This document cannot be verified unless the verifying
// code has the key with which it was signed.
public static void SignXml(XmlDocument xmlDoc, RSA Key)
{
// Check arguments.
if (xmlDoc == null)
throw new ArgumentException("xmlDoc");
if (Key == null)
throw new ArgumentException("Key");
// Create a SignedXml object.
SignedXml signedXml = new SignedXml(xmlDoc);
// Add the key to the SignedXml document.
signedXml.SigningKey = Key;
// Create a reference to be signed.
Reference reference = new Reference();
reference.Uri = "";
// Add an enveloped transformation to the reference.
XmlDsigEnvelopedSignatureTransform env = new XmlDsigEnvelopedSignatureTransform();
reference.AddTransform(env);
// Add the reference to the SignedXml object.
signedXml.AddReference(reference);
// Compute the signature.
signedXml.ComputeSignature();
// Get the XML representation of the signature and save
// it to an XmlElement object.
XmlElement xmlDigitalSignature = signedXml.GetXml();
// Append the element to the XML document.
xmlDoc.DocumentElement.AppendChild(xmlDoc.ImportNode(xmlDigitalSignature, true));
}