KeyInfoX509Data Constructors

Definition

Namespace:

System.Security.Cryptography.Xml

Assembly:

System.Security.Cryptography.Xml.dll

Initializes a new instance of the KeyInfoX509Data class.

Overloads

KeyInfoX509Data()	Initializes a new instance of the KeyInfoX509Data class.
KeyInfoX509Data(Byte[])	Initializes a new instance of the KeyInfoX509Data class from the specified ASN.1 DER encoding of an X.509v3 certificate.
KeyInfoX509Data(X509Certificate)	Initializes a new instance of the KeyInfoX509Data class from the specified X.509v3 certificate.
KeyInfoX509Data(X509Certificate, X509IncludeOption)	Initializes a new instance of the KeyInfoX509Data class from the specified X.509v3 certificate.

KeyInfoX509Data()

Source:

KeyInfoX509Data.cs

Initializes a new instance of the KeyInfoX509Data class.

public:
 KeyInfoX509Data();

public KeyInfoX509Data ();

Public Sub New ()

KeyInfoX509Data(Byte[])

Source:

KeyInfoX509Data.cs

Initializes a new instance of the KeyInfoX509Data class from the specified ASN.1 DER encoding of an X.509v3 certificate.

public:
 KeyInfoX509Data(cli::array <System::Byte> ^ rgbCert);

public KeyInfoX509Data (byte[] rgbCert);

new System.Security.Cryptography.Xml.KeyInfoX509Data : byte[] -> System.Security.Cryptography.Xml.KeyInfoX509Data

Public Sub New (rgbCert As Byte())

Parameters

rgbCert

Byte[]

The ASN.1 DER encoding of an X509Certificate object to initialize the new instance of KeyInfoX509Data from.

KeyInfoX509Data(X509Certificate)

Source:

KeyInfoX509Data.cs

Initializes a new instance of the KeyInfoX509Data class from the specified X.509v3 certificate.

public:
 KeyInfoX509Data(System::Security::Cryptography::X509Certificates::X509Certificate ^ cert);

public KeyInfoX509Data (System.Security.Cryptography.X509Certificates.X509Certificate cert);

new System.Security.Cryptography.Xml.KeyInfoX509Data : System.Security.Cryptography.X509Certificates.X509Certificate -> System.Security.Cryptography.Xml.KeyInfoX509Data

Public Sub New (cert As X509Certificate)

Parameters

cert

X509Certificate

The X509Certificate object to initialize the new instance of KeyInfoX509Data from.

Exceptions

ArgumentNullException

The cert parameter is null.

Examples

This section contains two code examples. The first example demonstrates how to sign an XML file using a detached signature. The second example demonstrates how to sign an XML file using an envelope signature.

Example #1

// Sign an XML file and save the signature in a new file.
void SignDetachedResource( String^ URIString, String^ XmlSigFileName, RSA^ Key, String^ Certificate )
{
   
   // Create a SignedXml object.
   SignedXml^ signedXml = gcnew SignedXml;
   
   // Assign the key to the SignedXml object.
   signedXml->SigningKey = Key;
   
   // Create a reference to be signed.
   Reference^ reference = gcnew Reference;
   
   // Add the passed URI to the reference object.
   reference->Uri = URIString;
   
   // Add the reference to the SignedXml object.
   signedXml->AddReference( reference );
   
   // Create a new KeyInfo object.
   KeyInfo^ keyInfo = gcnew KeyInfo;
   
   // Load the X509 certificate.
   X509Certificate^ MSCert = X509Certificate::CreateFromCertFile( Certificate );
   
   // Load the certificate into a KeyInfoX509Data object
   // and add it to the KeyInfo object.
   keyInfo->AddClause( gcnew KeyInfoX509Data( MSCert ) );
   
   // Add the KeyInfo object to the SignedXml object.
   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 = gcnew XmlTextWriter( XmlSigFileName,gcnew UTF8Encoding( false ) );
   xmlDigitalSignature->WriteTo( xmltw );
   xmltw->Close();
}

   // Sign an XML file and save the signature in a new file.
   public static void SignDetachedResource(string URIString, string XmlSigFileName, RSA Key, string Certificate)
   {
       // 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);

       // Create a new KeyInfo object.
       KeyInfo keyInfo = new KeyInfo();

       // Load the X509 certificate.
       X509Certificate MSCert = X509Certificate.CreateFromCertFile(Certificate);

       // Load the certificate into a KeyInfoX509Data object
       // and add it to the KeyInfo object.
       keyInfo.AddClause(new KeyInfoX509Data(MSCert));
 
       // Add the KeyInfo object to the SignedXml object.
       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();
   }

   ' Sign an XML file and save the signature in a new file.
   Public Shared Sub SignDetachedResource(URIString As String, XmlSigFileName As String, Key As RSA, Certificate As String)
      ' Create a SignedXml object.
      Dim signedXml As New SignedXml()
      
      ' Assign the key to the SignedXml object.
      signedXml.SigningKey = Key
      
      ' Create a reference to be signed.
      Dim reference As New Reference()
      
      ' Add the passed URI to the reference object.
      reference.Uri = URIString
      
      ' Add the reference to the SignedXml object.
      signedXml.AddReference(reference)
      
      ' Create a new KeyInfo object.
      Dim keyInfo As New KeyInfo()
      
      ' Load the X509 certificate.
      Dim MSCert As X509Certificate = X509Certificate.CreateFromCertFile(Certificate)
      
      ' Load the certificate into a KeyInfoX509Data object
      ' and add it to the KeyInfo object.
      keyInfo.AddClause(New KeyInfoX509Data(MSCert))
      
      ' Add the KeyInfo object to the SignedXml object.
      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()
      
      ' Save the signed XML document to a file specified
      ' using the passed string.
      Dim xmltw As New XmlTextWriter(XmlSigFileName, New UTF8Encoding(False))
      xmlDigitalSignature.WriteTo(xmltw)
      xmltw.Close()
   End Sub  
End Class

Example #2

// Sign an XML file and save the signature in a new file.
void SignXmlFile( String^ FileName, String^ SignedFileName, RSA^ Key, String^ Certificate )
{
   
   // 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 );
   
   // Create a new KeyInfo object.
   KeyInfo^ keyInfo = gcnew KeyInfo;
   
   // Load the X509 certificate.
   X509Certificate^ MSCert = X509Certificate::CreateFromCertFile( Certificate );
   
   // Load the certificate into a KeyInfoX509Data object
   // and add it to the KeyInfo object.
   keyInfo->AddClause( gcnew KeyInfoX509Data( MSCert ) );
   
   // Add the KeyInfo object to the SignedXml object.
   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();
}

   // Sign an XML file and save the signature in a new file.
   public static void SignXmlFile(string FileName, string SignedFileName, RSA Key, string Certificate)
   {
       // 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);

       // Create a new KeyInfo object.
       KeyInfo keyInfo = new KeyInfo();

       // Load the X509 certificate.
       X509Certificate MSCert = X509Certificate.CreateFromCertFile(Certificate);

       // Load the certificate into a KeyInfoX509Data object
       // and add it to the KeyInfo object.
       keyInfo.AddClause(new KeyInfoX509Data(MSCert));
 
       // Add the KeyInfo object to the SignedXml object.
       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();
   }

' 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, Certificate As String)
   ' 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)
   
   ' Create a new KeyInfo object.
   Dim keyInfo As New KeyInfo()
   
   ' Load the X509 certificate.
   Dim MSCert As X509Certificate = X509Certificate.CreateFromCertFile(Certificate)
   
   ' Load the certificate into a KeyInfoX509Data object
   ' and add it to the KeyInfo object.
   keyInfo.AddClause(New KeyInfoX509Data(MSCert))
   
   ' Add the KeyInfo object to the SignedXml object.
   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

KeyInfoX509Data(X509Certificate, X509IncludeOption)

Source:

KeyInfoX509Data.cs

Initializes a new instance of the KeyInfoX509Data class from the specified X.509v3 certificate.

public:
 KeyInfoX509Data(System::Security::Cryptography::X509Certificates::X509Certificate ^ cert, System::Security::Cryptography::X509Certificates::X509IncludeOption includeOption);

public KeyInfoX509Data (System.Security.Cryptography.X509Certificates.X509Certificate cert, System.Security.Cryptography.X509Certificates.X509IncludeOption includeOption);

new System.Security.Cryptography.Xml.KeyInfoX509Data : System.Security.Cryptography.X509Certificates.X509Certificate * System.Security.Cryptography.X509Certificates.X509IncludeOption -> System.Security.Cryptography.Xml.KeyInfoX509Data

Public Sub New (cert As X509Certificate, includeOption As X509IncludeOption)

Parameters

cert

X509Certificate

The X509Certificate object to initialize the new instance of KeyInfoX509Data from.

includeOption

X509IncludeOption

One of the X509IncludeOption values that specifies how much of the certificate chain to include.

Exceptions

ArgumentNullException

The cert parameter is null.

CryptographicException

The certificate has only a partial certificate chain.

Examples

The following code example demonstrates how to use the KeyInfoX509Data object while signing and verifying an XML document.

//
// This example signs an XML file using an
// envelope signature. It then verifies the 
// signed XML.
//
// You must have a certificate with a subject name
// of "CN=XMLDSIG_Test" in the "My" certificate store. 
//
// Run the following command to create a certificate
// and place it in the store.
// makecert -r -pe -n "CN=XMLDSIG_Test" -b 01/01/2005 -e 01/01/2010 -sky signing -ss my

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Xml;

public class SignVerifyEnvelope
{

    public static void Main(String[] args)
    {

        string Certificate = "CN=XMLDSIG_Test";

        try
        {

            // 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", Certificate);
            Console.WriteLine("XML file signed.");

            if (VerifyXmlFile("SignedExample.xml", Certificate))
            {
                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, string SubjectName)
    {
        if (null == FileName)
            throw new ArgumentNullException("FileName");
        if (null == SignedFileName)
            throw new ArgumentNullException("SignedFileName");
        if (null == SubjectName)
            throw new ArgumentNullException("SubjectName");

        // Load the certificate from the certificate store.
        X509Certificate2 cert = GetCertificateBySubject(SubjectName);

        // 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 = cert.GetRSAPrivateKey();

        // 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);

        // Create a new KeyInfo object.
        KeyInfo keyInfo = new KeyInfo();

        // Load the certificate into a KeyInfoX509Data object
        // and add it to the KeyInfo object.
        KeyInfoX509Data X509KeyInfo = new KeyInfoX509Data(cert, X509IncludeOption.WholeChain);

        keyInfo.AddClause(X509KeyInfo);

        // Add the KeyInfo object to the SignedXml object.
        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.
        using (XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false)))
        {
            doc.WriteTo(xmltw);
            xmltw.Close();
        }
    }

    // Verify the signature of an XML file against an asymmetric 
    // algorithm and return the result.
    public static Boolean VerifyXmlFile(String FileName, String CertificateSubject)
    {
        // Check the args.
        if (null == FileName)
            throw new ArgumentNullException("FileName");
        if (null == CertificateSubject)
            throw new ArgumentNullException("CertificateSubject");

        // Load the certificate from the store.
        X509Certificate2 cert = GetCertificateBySubject(CertificateSubject);

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

        // Load the passed XML file into the document. 
        xmlDocument.Load(FileName);

        // 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(cert, true);
    }

    public static X509Certificate2 GetCertificateBySubject(string CertificateSubject)
    {
        // Check the args.
        if (null == CertificateSubject)
            throw new ArgumentNullException("CertificateSubject");

        // Load the certificate from the certificate store.
        X509Certificate2 cert = null;

        X509Store store = new X509Store("My", StoreLocation.CurrentUser);

        try
        {
            // Open the store.
            store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);

            // Get the certs from the store.
            X509Certificate2Collection CertCol = store.Certificates;

            // Find the certificate with the specified subject.
            foreach (X509Certificate2 c in CertCol)
            {
                if (c.Subject == CertificateSubject)
                {
                    cert = c;
                    break;
                }
            }

            // Throw an exception of the certificate was not found.
            if (cert == null)
            {
                throw new CryptographicException("The certificate could not be found.");
            }
        }
        finally
        {
            // Close the store even if an exception was thrown.
            store.Close();
        }

        return cert;
    }

    // Create example data to sign.
    public static void CreateSomeXml(string FileName)
    {
        // Check the args.
        if (null == FileName)
            throw new ArgumentNullException("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.
        using (XmlTextWriter xmltw = new XmlTextWriter(FileName, new UTF8Encoding(false)))
        {
            document.WriteTo(xmltw);

            xmltw.Close();
        }
    }
}
// This code example displays the following to the console:
//
// New XML file created.
// XML file signed.
// The XML signature is valid.

'
' This example signs an XML file using an
' envelope signature. It then verifies the 
' signed XML.
'
' You must have a certificate with a subject name
' of "CN=XMLDSIG_Test" in the "My" certificate store. 
'
' Run the following command to create a certificate
' and place it in the store.
' makecert -r -pe -n "CN=XMLDSIG_Test" -b 01/01/2005 -e 01/01/2010 -sky signing -ss my
Imports System.Security.Cryptography
Imports System.Security.Cryptography.Xml
Imports System.Security.Cryptography.X509Certificates
Imports System.Text
Imports System.Xml



Module SignVerifyEnvelope


    Sub Main(ByVal args() As String)

        Dim Certificate As String = "CN=XMLDSIG_Test"

        Try

            ' 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", Certificate)
            Console.WriteLine("XML file signed.")

            If VerifyXmlFile("SignedExample.xml", Certificate) 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.
    Sub SignXmlFile(ByVal FileName As String, ByVal SignedFileName As String, ByVal SubjectName As String)
        If Nothing = FileName Then
            Throw New ArgumentNullException("FileName")
        End If
        If Nothing = SignedFileName Then
            Throw New ArgumentNullException("SignedFileName")
        End If
        If Nothing = SubjectName Then
            Throw New ArgumentNullException("SubjectName")
        End If
        ' Load the certificate from the certificate store.
        Dim cert As X509Certificate2 = GetCertificateBySubject(SubjectName)

        ' 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 = cert.GetRSAPrivateKey()

        ' 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)

        ' Create a new KeyInfo object.
        Dim keyInfo As New KeyInfo()

        ' Load the certificate into a KeyInfoX509Data object
        ' and add it to the KeyInfo object.
        Dim X509KeyInfo As New KeyInfoX509Data(cert, X509IncludeOption.WholeChain)

        keyInfo.AddClause(X509KeyInfo)

        ' Add the KeyInfo object to the SignedXml object.
        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))
        Try
            doc.WriteTo(xmltw)

        Finally
            xmltw.Close()
        End Try

    End Sub

    ' Verify the signature of an XML file against an asymmetric 
    ' algorithm and return the result.
    Function VerifyXmlFile(ByVal FileName As String, ByVal CertificateSubject As String) As [Boolean]
        ' Check the args.
        If Nothing = FileName Then
            Throw New ArgumentNullException("FileName")
        End If
        If Nothing = CertificateSubject Then
            Throw New ArgumentNullException("CertificateSubject")
        End If
        ' Load the certificate from the store.
        Dim cert As X509Certificate2 = GetCertificateBySubject(CertificateSubject)

        ' Create a new XML document.
        Dim xmlDocument As New XmlDocument()

        ' Load the passed XML file into the document. 
        xmlDocument.Load(FileName)

        ' 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(cert, True)

    End Function



    Function GetCertificateBySubject(ByVal CertificateSubject As String) As X509Certificate2
        ' Check the args.
        If Nothing = CertificateSubject Then
            Throw New ArgumentNullException("CertificateSubject")
        End If

        ' Load the certificate from the certificate store.
        Dim cert As X509Certificate2 = Nothing

        Dim store As New X509Store("My", StoreLocation.CurrentUser)

        Try
            ' Open the store.
            store.Open(OpenFlags.ReadOnly Or OpenFlags.OpenExistingOnly)

            ' Get the certs from the store.
            Dim CertCol As X509Certificate2Collection = store.Certificates

            ' Find the certificate with the specified subject.
            Dim c As X509Certificate2
            For Each c In CertCol
                If c.Subject = CertificateSubject Then
                    cert = c
                    Exit For
                End If
            Next c

            ' Throw an exception of the certificate was not found.
            If cert Is Nothing Then
                Throw New CryptographicException("The certificate could not be found.")
            End If
        Finally
            ' Close the store even if an exception was thrown.
            store.Close()
        End Try

        Return cert

    End Function


    ' Create example data to sign.
    Sub CreateSomeXml(ByVal FileName As String)
        ' Check the args.
        If Nothing = FileName Then
            Throw New ArgumentNullException("FileName")
        End If
        ' 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))
        Try
            document.WriteTo(xmltw)

        Finally
            xmltw.Close()
        End Try

    End Sub
End Module
' This code example displays the following to the console:
'
' New XML file created.
' XML file signed.
' The XML signature is valid.