//

// This example signs an XML file using an

// envelope signature. It then verifies the 

// signed XML.

//

using System;

using System.Security.Cryptography;

using System.Security.Cryptography.X509Certificates;

using System.Security.Cryptography.Xml;

using System.Text;

using System.Xml;

​

public class SignVerifyEnvelope

{

​

    public static void Main(String[] args)

    {

        try

        {

           // Generate a signing key.

           RSACryptoServiceProvider Key = new RSACryptoServiceProvider();

​

           // Create an XML file to sign.

           CreateSomeXml("Example.xml");

           Console.WriteLine("New XML file created."); 

​

           // Sign the XML that was just created and save it in a 

           // new file.

           SignXmlFile("Example.xml", "signedExample.xml", Key);

           Console.WriteLine("XML file signed."); 

​

           // Verify the signature of the signed XML.

           Console.WriteLine("Verifying signature...");

           bool result = VerifyXmlFile("SignedExample.xml", Key);

​

           // Display the results of the signature verification to 

           // the console.

           if(result)

           {

               Console.WriteLine("The XML signature is valid.");

           }

           else

           {

            Console.WriteLine("The XML signature is not valid.");

           }

        }

        catch(CryptographicException e)

        {

            Console.WriteLine(e.Message);

        }

    }

​

​

    // Sign an XML file and save the signature in a new file. This method does not  

    // save the public key within the XML file.  This file cannot be verified unless  

    // the verifying code has the key with which it was signed.

    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key)

    {

        // Create a new XML document.

        XmlDocument doc = new XmlDocument();

​

        // Load the passed XML file using its name.

        doc.Load(new XmlTextReader(FileName));

​

        // Create a SignedXml object.

        SignedXml signedXml = new SignedXml(doc);

​

        // 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.

        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, true));

​

        if (doc.FirstChild is XmlDeclaration)  

        {

            doc.RemoveChild(doc.FirstChild);

        }

​

        // Save the signed XML document to a file specified

        // using the passed string.

        XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false));

        doc.WriteTo(xmltw);

        xmltw.Close();

    }

​

    // Verify the signature of an XML file against an asymetric 

    // algorithm and return the result.

    public static Boolean VerifyXmlFile(String Name, RSA Key)

    {

        // Create a new XML document.

        XmlDocument xmlDocument = new XmlDocument();

​

        // Load the passed XML file into the document. 

        xmlDocument.Load(Name);

​

        // Create a new SignedXml object and pass it

        // the XML document class.

        SignedXml signedXml = new SignedXml(xmlDocument);

​

        // Find the "Signature" node and create a new

        // XmlNodeList object.

        XmlNodeList nodeList = xmlDocument.GetElementsByTagName("Signature");

​

        // Load the signature node.

        signedXml.LoadXml((XmlElement)nodeList[0]);

​

        // Check the signature and return the result.

        return signedXml.CheckSignature(Key);

    }

​

​

    // Create example data to sign.

    public static void CreateSomeXml(string FileName)

    {

        // Create a new XmlDocument object.

        XmlDocument document = new XmlDocument();

​

        // Create a new XmlNode object.

        XmlNode  node = document.CreateNode(XmlNodeType.Element, "", "MyElement", "samples");

​

        // Add some text to the node.

        node.InnerText = "Example text to be signed.";

​

        // Append the node to the document.

        document.AppendChild(node);

​

        // Save the XML document to the file name specified.

        XmlTextWriter xmltw = new XmlTextWriter(FileName, new UTF8Encoding(false));

        document.WriteTo(xmltw);

        xmltw.Close();

    }

}