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Reference Class

Represents the <reference> element of an XML signature.

Namespace:  System.Security.Cryptography.Xml
Assembly:  System.Security (in System.Security.dll)

public class Reference

The Reference object represents the <reference> element of an XML digital signature defined by the XML digital signature specification.

Use the Reference object to specify the following information:

  • The digest algorithm used to sign of the data object. This value is required.

  • The Uniform Resource Identifier (URI) of the data object to sign. The URI can specify a file path or specific elements within an XML document. This value is required.

  • A chain of transforms to apply before generating the digest. This value is optional.

  • The type of object to sign. This value is optional.

  • A unique identifier used to reference the current <reference> element. This value is optional.

For more information about the <reference> element, see the W3C specification at www.w3.org/TR/xmldsig-core/.

The following code example demonstrates how to generate and verify an enveloped XML signature using the Reference object.

// 
// 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");

            // 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. 
    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key)
    {
        // Create a new XML document.
        XmlDocument doc = new XmlDocument();

        // Format the document to ignore white spaces.
        doc.PreserveWhitespace = false;

        // Load the passed XML file using it's 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);

		
        // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        KeyInfo keyInfo = new KeyInfo();
        keyInfo.AddClause(new RSAKeyValue((RSA)Key));
        signedXml.KeyInfo = keyInfo;

        // 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 and return the result. 
    public static Boolean VerifyXmlFile(String Name)
    {
        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Format using white spaces.
        xmlDocument.PreserveWhitespace = true;

        // 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();
    }

    // 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();
    }
}

The following code example demonstrates how to generate and verify a detached XML signature using the Reference object.

// 
// This example signs a file specified by a URI  
// using a detached signature. It then verifies   
// the signed XML. 
// 

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;



class XMLDSIGDetached
{
	
    [STAThread]
    static void Main(string[] args)
    {
    // The URI to sign.
        string resourceToSign = "http://www.microsoft.com";
		
        // The name of the file to which to save the XML signature.
        string XmlFileName = "xmldsig.xml";

        try
        {

            // Generate a signing key.
            RSACryptoServiceProvider Key = new RSACryptoServiceProvider();

            Console.WriteLine("Signing: {0}", resourceToSign);

            // Sign the detached resourceand save the signature in an XML file.
            SignDetachedResource(resourceToSign, XmlFileName, Key);

            Console.WriteLine("XML signature was succesfully computed and saved to {0}.", XmlFileName);

            // Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...");

            //Verify the XML signature in the XML file. 
            bool result = VerifyDetachedSignature(XmlFileName);

            // 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. 
    public static void SignDetachedResource(string URIString, string XmlSigFileName, RSA Key)
    {
        // Create a SignedXml object.
        SignedXml signedXml = new SignedXml();

        // Assign the key to the SignedXml object.
        signedXml.SigningKey = Key;

        // Create a reference to be signed.
        Reference reference = new Reference();

        // Add the passed URI to the reference object.
        reference.Uri = URIString;
		
        // Add the reference to the SignedXml object.
        signedXml.AddReference(reference);

        // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        KeyInfo keyInfo = new KeyInfo();
        keyInfo.AddClause(new RSAKeyValue((RSA)Key));	
        signedXml.KeyInfo = keyInfo;

        // Compute the signature.
        signedXml.ComputeSignature();

        // Get the XML representation of the signature and save 
        // it to an XmlElement object.
        XmlElement xmlDigitalSignature = signedXml.GetXml();

        // Save the signed XML document to a file specified 
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(XmlSigFileName, new UTF8Encoding(false));
        xmlDigitalSignature.WriteTo(xmltw);
        xmltw.Close();
    }
    // Verify the signature of an XML file and return the result. 
    public static Boolean VerifyDetachedSignature(string XmlSigFileName)
    {	
        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Load the passed XML file into the document.
        xmlDocument.Load(XmlSigFileName);
	
        // Create a new SignedXMl object.
        SignedXml signedXml = new SignedXml();

        // 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();
    }
}

System.Object
  System.Security.Cryptography.Xml.Reference

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

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