Reference Class
 

Represents the <reference> element of an XML signature.

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

SystemObject
  System.Security.Cryptography.XmlReference

[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public class Reference
[HostProtectionAttribute(SecurityAction::LinkDemand, MayLeakOnAbort = true)]
public ref class Reference 
[<HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)>]
type Reference = class end
<HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort := True)>
Public Class Reference
NameDescription
System_CAPS_pubmethod Reference

Initializes a new instance of the Reference class with default properties.

System_CAPS_pubmethod Reference

Initializes a new instance of the Reference class with a hash value of the specified Stream.

System_CAPS_pubmethod Reference

Initializes a new instance of the Reference class with the specified Uri.

NameDescription
System_CAPS_pubproperty

Gets or sets the digest method Uniform Resource Identifier (URI) of the current Reference.

System_CAPS_pubproperty

Gets or sets the digest value of the current Reference.

System_CAPS_pubproperty

Gets or sets the ID of the current Reference.

System_CAPS_pubproperty

Gets the transform chain of the current Reference.

System_CAPS_pubproperty

Gets or sets the type of the object being signed.

System_CAPS_pubproperty

Gets or sets the Uri of the current Reference.

NameDescription
System_CAPS_pubmethod AddTransform

Adds a Transform object to the list of transforms to be performed on the data before passing it to the digest algorithm.

System_CAPS_pubmethod Equals

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethod Finalize

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethod GetHashCode

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethod GetType

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethod GetXml

Returns the XML representation of the Reference.

System_CAPS_pubmethod LoadXml

Loads a Reference state from an XML element.

System_CAPS_protmethod MemberwiseClone

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethod ToString

Returns a string that represents the current object.(Inherited from Object.)

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();
    }
}
'
' This example signs an XML file using an
' envelope signature. It then verifies the 
' signed XML.
'
Imports System
Imports System.Security.Cryptography
Imports System.Security.Cryptography.X509Certificates
Imports System.Security.Cryptography.Xml
Imports System.Text
Imports System.Xml



Public Class SignVerifyEnvelope

   Overloads Public Shared Sub Main(args() As [String])
      Try
         ' Generate a signing key.
         Dim Key As 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...")
         Dim result As Boolean = VerifyXmlFile("SignedExample.xml")

         ' Display the results of the signature verification to \
         ' the console.
         If result Then
            Console.WriteLine("The XML signature is valid.")
         Else
            Console.WriteLine("The XML signature is not valid.")
         End If
      Catch e As CryptographicException
         Console.WriteLine(e.Message)
      End Try
   End Sub 


   ' Sign an XML file and save the signature in a new file.
   Public Shared Sub SignXmlFile(FileName As String, SignedFileName As String, Key As RSA)
      ' Create a new XML document.
      Dim doc As 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.
      Dim signedXml As New SignedXml(doc)

      ' Add the key to the SignedXml document. 
      signedXml.SigningKey = Key

      ' Create a reference to be signed.
      Dim reference As New Reference()
      reference.Uri = ""

      ' Add an enveloped transformation to the reference.
      Dim env As 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).
      Dim keyInfo As New KeyInfo()
      keyInfo.AddClause(New RSAKeyValue(CType(Key, RSA)))
      signedXml.KeyInfo = keyInfo

      ' Compute the signature.
      signedXml.ComputeSignature()

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

      ' Append the element to the XML document.
      doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, True))


      If TypeOf doc.FirstChild Is XmlDeclaration Then
         doc.RemoveChild(doc.FirstChild)
      End If

      ' Save the signed XML document to a file specified
      ' using the passed string.
      Dim xmltw As New XmlTextWriter(SignedFileName, New UTF8Encoding(False))
      doc.WriteTo(xmltw)
      xmltw.Close()
   End Sub 
   ' Verify the signature of an XML file and return the result.
   Public Shared Function VerifyXmlFile(Name As [String]) As [Boolean]
      ' Create a new XML document.
      Dim xmlDocument As 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.
      Dim signedXml As New SignedXml(xmlDocument)

      ' Find the "Signature" node and create a new
      ' XmlNodeList object.
      Dim nodeList As XmlNodeList = xmlDocument.GetElementsByTagName("Signature")

      ' Load the signature node.
      signedXml.LoadXml(CType(nodeList(0), XmlElement))

      ' Check the signature and return the result.
      Return signedXml.CheckSignature()
   End Function 


   ' Create example data to sign.
   Public Shared Sub CreateSomeXml(FileName As String)
      ' Create a new XmlDocument object.
      Dim document As New XmlDocument()

      ' Create a new XmlNode object.
      Dim node As XmlNode = 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.
      Dim xmltw As New XmlTextWriter(FileName, New UTF8Encoding(False))
      document.WriteTo(xmltw)
      xmltw.Close()
   End Sub 
End Class
//
// This example signs an XML file using an
// envelope signature. It then verifies the 
// signed XML.
//
#using <System.Security.dll>
#using <System.Xml.dll>

using namespace System;
using namespace System::Security::Cryptography;
using namespace System::Security::Cryptography::X509Certificates;
using namespace System::Security::Cryptography::Xml;
using namespace System::Text;
using namespace System::Xml;

// Sign an XML file and save the signature in a new file.
void SignXmlFile( String^ FileName, String^ SignedFileName, RSA^ Key )
{

   // Create a new XML document.
   XmlDocument^ doc = gcnew XmlDocument;

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

   // Load the passed XML file using its name.
   doc->Load( gcnew XmlTextReader( FileName ) );

   // Create a SignedXml object.
   SignedXml^ signedXml = gcnew SignedXml( doc );

   // Add the key to the SignedXml document. 
   signedXml->SigningKey = Key;

   // Create a reference to be signed.
   Reference^ reference = gcnew Reference;
   reference->Uri = "";

   // Add an enveloped transformation to the reference.
   XmlDsigEnvelopedSignatureTransform^ env = gcnew 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 = gcnew KeyInfo;
   keyInfo->AddClause( gcnew RSAKeyValue( safe_cast<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)->GetType() == XmlDeclaration::typeid )
   {
      doc->RemoveChild( doc->FirstChild );
   }


   // Save the signed XML document to a file specified
   // using the passed string.
   XmlTextWriter^ xmltw = gcnew XmlTextWriter( SignedFileName,gcnew UTF8Encoding( false ) );
   doc->WriteTo( xmltw );
   xmltw->Close();
}


// Verify the signature of an XML file and return the result.
Boolean VerifyXmlFile( String^ Name )
{

   // Create a new XML document.
   XmlDocument^ xmlDocument = gcnew 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 = gcnew SignedXml( xmlDocument );

   // Find the "Signature" node and create a new
   // XmlNodeList object.
   XmlNodeList^ nodeList = xmlDocument->GetElementsByTagName( "Signature" );

   // Load the signature node.
   signedXml->LoadXml( safe_cast<XmlElement^>(nodeList->Item( 0 )) );

   // Check the signature and return the result.
   return signedXml->CheckSignature();
}


// Create example data to sign.
void CreateSomeXml( String^ FileName )
{

   // Create a new XmlDocument object.
   XmlDocument^ document = gcnew 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 = gcnew XmlTextWriter( FileName,gcnew UTF8Encoding( false ) );
   document->WriteTo( xmltw );
   xmltw->Close();
}

int main()
{
   try
   {

      // Generate a signing key.
      RSACryptoServiceProvider^ Key = gcnew 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 );
   }

}
.NET Framework
Available since 1.1

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

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