EncryptionMethod Constructors

Definition

Namespace:

System.Security.Cryptography.Xml

Assembly:

System.Security.Cryptography.Xml.dll

Initializes a new instance of the EncryptionMethod class.

Overloads

EncryptionMethod()	Initializes a new instance of the EncryptionMethod class.
EncryptionMethod(String)	Initializes a new instance of the EncryptionMethod class specifying an algorithm Uniform Resource Identifier (URI).

EncryptionMethod()

Source:

EncryptionMethod.cs

Initializes a new instance of the EncryptionMethod class.

public:
 EncryptionMethod();

public EncryptionMethod ();

Public Sub New ()

Remarks

This constructor initializes a new instance of the EncryptionMethod class without specifying the Uniform Resource Identifier (URI) of an encryption algorithm.

EncryptionMethod(String)

Source:

EncryptionMethod.cs

Initializes a new instance of the EncryptionMethod class specifying an algorithm Uniform Resource Identifier (URI).

public:
 EncryptionMethod(System::String ^ algorithm);

public EncryptionMethod (string? algorithm);

new System.Security.Cryptography.Xml.EncryptionMethod : string -> System.Security.Cryptography.Xml.EncryptionMethod

Public Sub New (algorithm As String)

Parameters

algorithm

String

The Uniform Resource Identifier (URI) that describes the algorithm represented by an instance of the EncryptionMethod class.

Examples

The following code example demonstrates how to create a simple utility class that uses the TripleDES algorithm to encrypt an XML document.

#using <System.Security.dll>
#using <System.dll>
#using <System.Xml.dll>

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

ref class TrippleDESDocumentEncryption
{
protected:
   XmlDocument^ docValue;
   TripleDES^ algValue;

public:
   TrippleDESDocumentEncryption( XmlDocument^ Doc, TripleDES^ Key )
   {
      if ( Doc != nullptr )
      {
         docValue = Doc;
      }
      else
      {
         throw gcnew ArgumentNullException( L"Doc" );
      }

      if ( Key != nullptr )
      {
         algValue = Key;
      }
      else
      {
         throw gcnew ArgumentNullException( L"Key" );
      }
   }


   property XmlDocument^ Doc
   {
      XmlDocument^ get()
      {
         return docValue;
      }

      void set( XmlDocument^ value )
      {
         docValue = value;
      }

   }

   property TripleDES^ Alg
   {
      TripleDES^ get()
      {
         return algValue;
      }

      void set( TripleDES^ value )
      {
         algValue = value;
      }

   }
   void Clear()
   {
      if ( algValue != nullptr )
      {
         algValue->Clear();
      }
      else
      {
         throw gcnew Exception( L"No TripleDES key was found to clear." );
      }
   }

   void Encrypt( String^ Element )
   {

      // Find the element by name and create a new
      // XmlElement object.
      XmlElement^ inputElement = dynamic_cast<XmlElement^>(docValue->GetElementsByTagName( Element )->Item( 0 ));

      // If the element was not found, throw an exception.
      if ( inputElement == nullptr )
      {
         throw gcnew Exception( L"The element was not found." );
      }


      // Create a new EncryptedXml object.
      EncryptedXml^ exml = gcnew EncryptedXml( docValue );

      // Encrypt the element using the symmetric key.
      array<Byte>^rgbOutput = exml->EncryptData( inputElement, algValue, false );

      // Create an EncryptedData object and populate it.
      EncryptedData^ ed = gcnew EncryptedData;

      // Specify the namespace URI for XML encryption elements.
      ed->Type = EncryptedXml::XmlEncElementUrl;

      // Specify the namespace URI for the TrippleDES algorithm.
      ed->EncryptionMethod = gcnew EncryptionMethod( EncryptedXml::XmlEncTripleDESUrl );

      // Create a CipherData element.
      ed->CipherData = gcnew CipherData;

      // Set the CipherData element to the value of the encrypted XML element.
      ed->CipherData->CipherValue = rgbOutput;

      // Replace the plaintext XML elemnt with an EncryptedData element.
      EncryptedXml::ReplaceElement( inputElement, ed, false );
   }

   void Decrypt()
   {

      // XmlElement object.
      XmlElement^ encryptedElement = dynamic_cast<XmlElement^>(docValue->GetElementsByTagName( L"EncryptedData" )->Item( 0 ));

      // If the EncryptedData element was not found, throw an exception.
      if ( encryptedElement == nullptr )
      {
         throw gcnew Exception( L"The EncryptedData element was not found." );
      }


      // Create an EncryptedData object and populate it.
      EncryptedData^ ed = gcnew EncryptedData;
      ed->LoadXml( encryptedElement );

      // Create a new EncryptedXml object.
      EncryptedXml^ exml = gcnew EncryptedXml;

      // Decrypt the element using the symmetric key.
      array<Byte>^rgbOutput = exml->DecryptData( ed, algValue );

      // Replace the encryptedData element with the plaintext XML elemnt.
      exml->ReplaceData( encryptedElement, rgbOutput );
   }

};

int main()
{

   // Create an XmlDocument object.
   XmlDocument^ xmlDoc = gcnew XmlDocument;

   // Load an XML file into the XmlDocument object.
   try
   {
      xmlDoc->PreserveWhitespace = true;
      xmlDoc->Load( L"test.xml" );
   }
   catch ( Exception^ e )
   {
      Console::WriteLine( e->Message );
      return 0;
   }


   // Create a new TripleDES key.
   TripleDESCryptoServiceProvider^ tDESkey = gcnew TripleDESCryptoServiceProvider;

   // Create a new instance of the TrippleDESDocumentEncryption object
   // defined in this sample.
   TrippleDESDocumentEncryption^ xmlTDES = gcnew TrippleDESDocumentEncryption( xmlDoc,tDESkey );
   try
   {

      // Encrypt the "creditcard" element.
      xmlTDES->Encrypt( L"creditcard" );

      // Display the encrypted XML to the console.
      Console::WriteLine( L"Encrypted XML:" );
      Console::WriteLine();
      Console::WriteLine( xmlTDES->Doc->OuterXml );

      // Decrypt the "creditcard" element.
      xmlTDES->Decrypt();

      // Display the encrypted XML to the console.
      Console::WriteLine();
      Console::WriteLine( L"Decrypted XML:" );
      Console::WriteLine();
      Console::WriteLine( xmlTDES->Doc->OuterXml );
   }
   catch ( Exception^ e )
   {
      Console::WriteLine( e->Message );
   }
   finally
   {

      // Clear the TripleDES key.
      xmlTDES->Clear();
   }

   return 1;
}

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

    class Program
    {
        static void Main(string[] args)
        {

            // Create an XmlDocument object.
            XmlDocument xmlDoc = new XmlDocument();

            // Load an XML file into the XmlDocument object.
            try
            {
                xmlDoc.PreserveWhitespace = true;
                xmlDoc.Load("test.xml");
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                return;
            }

            // Create a new TripleDES key.
            TripleDESCryptoServiceProvider tDESkey = new TripleDESCryptoServiceProvider();

            // Create a new instance of the TrippleDESDocumentEncryption object
            // defined in this sample.
            TrippleDESDocumentEncryption xmlTDES = new TrippleDESDocumentEncryption(xmlDoc, tDESkey);
            
            try
            {
                // Encrypt the "creditcard" element.
                xmlTDES.Encrypt("creditcard");

                // Display the encrypted XML to the console.
                Console.WriteLine("Encrypted XML:");
                Console.WriteLine();
                Console.WriteLine(xmlTDES.Doc.OuterXml);

                // Decrypt the "creditcard" element.
                xmlTDES.Decrypt();

                // Display the encrypted XML to the console.
                Console.WriteLine();
                Console.WriteLine("Decrypted XML:");
                Console.WriteLine();
                Console.WriteLine(xmlTDES.Doc.OuterXml);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            finally
            {
                // Clear the TripleDES key.
                xmlTDES.Clear();
            }
        }
    }

class TrippleDESDocumentEncryption
{
    protected XmlDocument docValue;
    protected TripleDES algValue;

    public TrippleDESDocumentEncryption(XmlDocument Doc, TripleDES Key)
    {
        if (Doc != null)
        {
            docValue = Doc;
        }
        else
        {
            throw new ArgumentNullException("Doc");
        }

        if (Key != null)
        {

            algValue = Key;
        }
        else
        {
            throw new ArgumentNullException("Key");
        }
    }

    public XmlDocument Doc { set { docValue = value; } get { return docValue; } }
    public TripleDES Alg { set { algValue = value; } get { return algValue; } }

    public void Clear()
    {
        if (algValue != null)
        {
            algValue.Clear();
        }
        else
        {
            throw new Exception("No TripleDES key was found to clear.");
        }
    }

    public void Encrypt(string Element)
    {
        // Find the element by name and create a new
        // XmlElement object.
        XmlElement inputElement = docValue.GetElementsByTagName(Element)[0] as XmlElement;

        // If the element was not found, throw an exception.
        if (inputElement == null)
        {
            throw new Exception("The element was not found.");
        }

        // Create a new EncryptedXml object.
        EncryptedXml exml = new EncryptedXml(docValue);

        // Encrypt the element using the symmetric key.
        byte[] rgbOutput = exml.EncryptData(inputElement, algValue, false);

        // Create an EncryptedData object and populate it.
        EncryptedData ed = new EncryptedData();

        // Specify the namespace URI for XML encryption elements.
        ed.Type = EncryptedXml.XmlEncElementUrl;

        // Specify the namespace URI for the TrippleDES algorithm.
        ed.EncryptionMethod = new EncryptionMethod(EncryptedXml.XmlEncTripleDESUrl);

        // Create a CipherData element.
        ed.CipherData = new CipherData();

        // Set the CipherData element to the value of the encrypted XML element.
        ed.CipherData.CipherValue = rgbOutput;

        // Replace the plaintext XML elemnt with an EncryptedData element.
        EncryptedXml.ReplaceElement(inputElement, ed, false);
    }

    public void Decrypt()
    {

        // XmlElement object.
        XmlElement encryptedElement = docValue.GetElementsByTagName("EncryptedData")[0] as XmlElement;

        // If the EncryptedData element was not found, throw an exception.
        if (encryptedElement == null)
        {
            throw new Exception("The EncryptedData element was not found.");
        }

        // Create an EncryptedData object and populate it.
        EncryptedData ed = new EncryptedData();
        ed.LoadXml(encryptedElement);

        // Create a new EncryptedXml object.
        EncryptedXml exml = new EncryptedXml();

        // Decrypt the element using the symmetric key.
        byte[] rgbOutput = exml.DecryptData(ed, algValue);

        // Replace the encryptedData element with the plaintext XML elemnt.
        exml.ReplaceData(encryptedElement, rgbOutput);
    }
}

Imports System.Xml
Imports System.Security.Cryptography
Imports System.Security.Cryptography.Xml



Module Program

    Sub Main(ByVal args() As String)

        ' Create an XmlDocument object.
        Dim xmlDoc As New XmlDocument()

        ' Load an XML file into the XmlDocument object.
        xmlDoc.PreserveWhitespace = True
        xmlDoc.Load("test.xml")


        ' Create a new TripleDES key. 
        Dim tDESkey As New TripleDESCryptoServiceProvider()

        ' Create a new instance of the TrippleDESDocumentEncryption object
        ' defined in this sample.
        Dim xmlTDES As New TrippleDESDocumentEncryption(xmlDoc, tDESkey)

        Try
            ' Encrypt the "creditcard" element.
            xmlTDES.Encrypt("creditcard")

            ' Display the encrypted XML to the console.
            Console.WriteLine("Encrypted XML:")
            Console.WriteLine()
            Console.WriteLine(xmlTDES.Doc.OuterXml)

            ' Decrypt the "creditcard" element.
            xmlTDES.Decrypt()

            ' Display the encrypted XML to the console.
            Console.WriteLine()
            Console.WriteLine("Decrypted XML:")
            Console.WriteLine()
            Console.WriteLine(xmlTDES.Doc.OuterXml)
        Catch e As Exception
            Console.WriteLine(e.Message)
        Finally
            ' Clear the TripleDES key.
            xmlTDES.Clear()
        End Try

    End Sub
End Module 'Program



Class TrippleDESDocumentEncryption
    Protected docValue As XmlDocument
    Protected algValue As TripleDES


    Public Sub New(ByVal Doc As XmlDocument, ByVal Key As TripleDES)
        If Not (Doc Is Nothing) Then
            docValue = Doc
        Else
            Throw New ArgumentNullException("Doc")
        End If

        If Not (Key Is Nothing) Then

            algValue = Key
        Else
            Throw New ArgumentNullException("Key")
        End If

    End Sub


    Public Property Doc() As XmlDocument
        Get
            Return docValue
        End Get
        Set(ByVal value As XmlDocument)
            docValue = value
        End Set
    End Property

    Public Property Alg() As TripleDES
        Get
            Return algValue
        End Get
        Set(ByVal value As TripleDES)
            algValue = value
        End Set
    End Property

    Public Sub Clear()
        If Not (algValue Is Nothing) Then
            algValue.Clear()
        Else
            Throw New Exception("No TripleDES key was found to clear.")
        End If

    End Sub


    Public Sub Encrypt(ByVal Element As String)
        ' Find the element by name and create a new
        ' XmlElement object.
        Dim inputElement As XmlElement = docValue.GetElementsByTagName(Element)(0)

        ' If the element was not found, throw an exception.
        If inputElement Is Nothing Then
            Throw New Exception("The element was not found.")
        End If

        ' Create a new EncryptedXml object.
        Dim exml As New EncryptedXml(docValue)

        ' Encrypt the element using the symmetric key.
        Dim rgbOutput As Byte() = exml.EncryptData(inputElement, algValue, False)

        ' Create an EncryptedData object and populate it.
        Dim ed As New EncryptedData()

        ' Specify the namespace URI for XML encryption elements.
        ed.Type = EncryptedXml.XmlEncElementUrl

        ' Specify the namespace URI for the TrippleDES algorithm.
        ed.EncryptionMethod = New EncryptionMethod(EncryptedXml.XmlEncTripleDESUrl)

        ' Create a CipherData element.
        ed.CipherData = New CipherData()

        ' Set the CipherData element to the value of the encrypted XML element.
        ed.CipherData.CipherValue = rgbOutput

        ' Replace the plaintext XML elemnt with an EncryptedData element.
        EncryptedXml.ReplaceElement(inputElement, ed, False)

    End Sub


    Public Sub Decrypt()

        ' XmlElement object.
        Dim encryptedElement As XmlElement = docValue.GetElementsByTagName("EncryptedData")(0)

        ' If the EncryptedData element was not found, throw an exception.
        If encryptedElement Is Nothing Then
            Throw New Exception("The EncryptedData element was not found.")
        End If

        ' Create an EncryptedData object and populate it.
        Dim ed As New EncryptedData()
        ed.LoadXml(encryptedElement)

        ' Create a new EncryptedXml object.
        Dim exml As New EncryptedXml()

        ' Decrypt the element using the symmetric key.
        Dim rgbOutput As Byte() = exml.DecryptData(ed, algValue)

        ' Replace the encryptedData element with the plaintext XML elemnt.
        exml.ReplaceData(encryptedElement, rgbOutput)

    End Sub
End Class

The following code example demonstrates how to encrypt an XML document using a symmetric key. This example does not include any key information in the encrypted XML document.

#using <System.Security.dll>
#using <System.dll>
#using <System.Xml.dll>

using namespace System;
using namespace System::Xml;
using namespace System::Security::Cryptography;
using namespace System::Security::Cryptography::Xml;
static void Encrypt( XmlDocument^ Doc, String^ ElementToEncrypt, SymmetricAlgorithm^ Alg )
{

   // Check the arguments.
   if ( Doc == nullptr )
      throw gcnew ArgumentNullException( L"Doc" );

   if ( ElementToEncrypt == nullptr )
      throw gcnew ArgumentNullException( L"ElementToEncrypt" );

   if ( Alg == nullptr )
      throw gcnew ArgumentNullException( L"Alg" );


   ////////////////////////////////////////////////
   // Find the specified element in the XmlDocument
   // object and create a new XmlElemnt object.
   ////////////////////////////////////////////////
   XmlElement^ elementToEncrypt = dynamic_cast<XmlElement^>(Doc->GetElementsByTagName( ElementToEncrypt )->Item( 0 ));

   // Throw an XmlException if the element was not found.
   if ( elementToEncrypt == nullptr )
   {
      throw gcnew XmlException( L"The specified element was not found" );
   }


   //////////////////////////////////////////////////
   // Create a new instance of the EncryptedXml class
   // and use it to encrypt the XmlElement with the
   // symmetric key.
   //////////////////////////////////////////////////
   EncryptedXml^ eXml = gcnew EncryptedXml;
   array<Byte>^encryptedElement = eXml->EncryptData( elementToEncrypt, Alg, false );

   ////////////////////////////////////////////////
   // Construct an EncryptedData object and populate
   // it with the desired encryption information.
   ////////////////////////////////////////////////
   EncryptedData^ edElement = gcnew EncryptedData;
   edElement->Type = EncryptedXml::XmlEncElementUrl;

   // Create an EncryptionMethod element so that the
   // receiver knows which algorithm to use for decryption.
   // Determine what kind of algorithm is being used and
   // supply the appropriate URL to the EncryptionMethod element.
   String^ encryptionMethod = nullptr;
   if ( dynamic_cast<TripleDES^>(Alg) )
   {
      encryptionMethod = EncryptedXml::XmlEncTripleDESUrl;
   }
   else
   if ( dynamic_cast<DES^>(Alg) )
   {
      encryptionMethod = EncryptedXml::XmlEncDESUrl;
   }
   else
   if ( dynamic_cast<Aes^>(Alg) )
   {
      switch ( Alg->KeySize )
      {
         case 128:
            encryptionMethod = EncryptedXml::XmlEncAES128Url;
            break;

         case 192:
            encryptionMethod = EncryptedXml::XmlEncAES192Url;
            break;

         case 256:
            encryptionMethod = EncryptedXml::XmlEncAES256Url;
            break;
      }
   }
   else
   {

      // Throw an exception if the transform is not in the previous categories
      throw gcnew CryptographicException( L"The specified algorithm is not supported for XML Encryption." );
   }



   edElement->EncryptionMethod = gcnew EncryptionMethod( encryptionMethod );

   // Add the encrypted element data to the
   // EncryptedData object.
   edElement->CipherData->CipherValue = encryptedElement;

   ////////////////////////////////////////////////////
   // Replace the element from the original XmlDocument
   // object with the EncryptedData element.
   ////////////////////////////////////////////////////
   EncryptedXml::ReplaceElement( elementToEncrypt, edElement, false );
}

static void Decrypt( XmlDocument^ Doc, SymmetricAlgorithm^ Alg )
{

   // Check the arguments.
   if ( Doc == nullptr )
      throw gcnew ArgumentNullException( L"Doc" );

   if ( Alg == nullptr )
      throw gcnew ArgumentNullException( L"Alg" );


   // Find the EncryptedData element in the XmlDocument.
   XmlElement^ encryptedElement = dynamic_cast<XmlElement^>(Doc->GetElementsByTagName( L"EncryptedData" )->Item( 0 ));

   // If the EncryptedData element was not found, throw an exception.
   if ( encryptedElement == nullptr )
   {
      throw gcnew XmlException( L"The EncryptedData element was not found." );
   }


   // Create an EncryptedData object and populate it.
   EncryptedData^ edElement = gcnew EncryptedData;
   edElement->LoadXml( encryptedElement );

   // Create a new EncryptedXml object.
   EncryptedXml^ exml = gcnew EncryptedXml;

   // Decrypt the element using the symmetric key.
   array<Byte>^rgbOutput = exml->DecryptData( edElement, Alg );

   // Replace the encryptedData element with the plaintext XML element.
   exml->ReplaceData( encryptedElement, rgbOutput );
}

int main()
{

   // Create an XmlDocument object.
   XmlDocument^ xmlDoc = gcnew XmlDocument;

   // Load an XML file into the XmlDocument object.
   try
   {
      xmlDoc->PreserveWhitespace = true;
      xmlDoc->Load( L"test.xml" );
   }
   catch ( Exception^ e )
   {
      Console::WriteLine( e->Message );
      return 0;
   }


   // Create a new TripleDES key.
   TripleDESCryptoServiceProvider^ tDESkey = gcnew TripleDESCryptoServiceProvider;
   try
   {

      // Encrypt the "creditcard" element.
      Encrypt( xmlDoc, L"creditcard", tDESkey );

      // Display the encrypted XML to the console.
      Console::WriteLine( L"Encrypted XML:" );
      Console::WriteLine();
      Console::WriteLine( xmlDoc->OuterXml );

      // Decrypt the "creditcard" element.
      Decrypt( xmlDoc, tDESkey );

      // Display the encrypted XML to the console.
      Console::WriteLine();
      Console::WriteLine( L"Decrypted XML:" );
      Console::WriteLine();
      Console::WriteLine( xmlDoc->OuterXml );
   }
   catch ( Exception^ e )
   {
      Console::WriteLine( e->Message );
   }
   finally
   {

      // Clear the TripleDES key.
      tDESkey->Clear();
   }

}

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

class Program
{
    static void Main(string[] args)
    {

        // Create an XmlDocument object.
        XmlDocument xmlDoc = new XmlDocument();

        // Load an XML file into the XmlDocument object.
        try
        {
            xmlDoc.PreserveWhitespace = true;
            xmlDoc.Load("test.xml");
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
            return;
        }

        // Create a new TripleDES key.
        TripleDESCryptoServiceProvider tDESkey = new TripleDESCryptoServiceProvider();

        try
        {
            // Encrypt the "creditcard" element.
            Encrypt(xmlDoc, "creditcard", tDESkey);

            // Display the encrypted XML to the console.
            Console.WriteLine("Encrypted XML:");
            Console.WriteLine();
            Console.WriteLine(xmlDoc.OuterXml);

            // Decrypt the "creditcard" element.
            Decrypt(xmlDoc, tDESkey);

            // Display the encrypted XML to the console.
            Console.WriteLine();
            Console.WriteLine("Decrypted XML:");
            Console.WriteLine();
            Console.WriteLine(xmlDoc.OuterXml);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            // Clear the TripleDES key.
            tDESkey.Clear();
        }
    }

    public static void Encrypt(XmlDocument Doc, string ElementToEncrypt, SymmetricAlgorithm Alg)
    {
        // Check the arguments.
        if (Doc == null)
            throw new ArgumentNullException("Doc");
        if (ElementToEncrypt == null)
            throw new ArgumentNullException("ElementToEncrypt");
        if (Alg == null)
            throw new ArgumentNullException("Alg");

        ////////////////////////////////////////////////
        // Find the specified element in the XmlDocument
        // object and create a new XmlElemnt object.
        ////////////////////////////////////////////////

        XmlElement elementToEncrypt = Doc.GetElementsByTagName(ElementToEncrypt)[0] as XmlElement;

        // Throw an XmlException if the element was not found.
        if (elementToEncrypt == null)
        {
            throw new XmlException("The specified element was not found");
        }

        //////////////////////////////////////////////////
        // Create a new instance of the EncryptedXml class
        // and use it to encrypt the XmlElement with the
        // symmetric key.
        //////////////////////////////////////////////////

        EncryptedXml eXml = new EncryptedXml();

        byte[] encryptedElement = eXml.EncryptData(elementToEncrypt, Alg, false);

        ////////////////////////////////////////////////
        // Construct an EncryptedData object and populate
        // it with the desired encryption information.
        ////////////////////////////////////////////////

        EncryptedData edElement = new EncryptedData();
        edElement.Type = EncryptedXml.XmlEncElementUrl;

        // Create an EncryptionMethod element so that the
        // receiver knows which algorithm to use for decryption.
        // Determine what kind of algorithm is being used and
        // supply the appropriate URL to the EncryptionMethod element.

        string encryptionMethod = null;

        if (Alg is TripleDES)
        {
            encryptionMethod = EncryptedXml.XmlEncTripleDESUrl;
        }
        else if (Alg is DES)
        {
            encryptionMethod = EncryptedXml.XmlEncDESUrl;
        }
        else if (Alg is Aes)
        {
            switch (Alg.KeySize)
            {
                case 128:
                    encryptionMethod = EncryptedXml.XmlEncAES128Url;
                    break;
                case 192:
                    encryptionMethod = EncryptedXml.XmlEncAES192Url;
                    break;
                case 256:
                    encryptionMethod = EncryptedXml.XmlEncAES256Url;
                    break;
            }
        }
        else
        {
            // Throw an exception if the transform is not in the previous categories
            throw new CryptographicException("The specified algorithm is not supported for XML Encryption.");
        }

        edElement.EncryptionMethod = new EncryptionMethod(encryptionMethod);

        // Add the encrypted element data to the
        // EncryptedData object.
        edElement.CipherData.CipherValue = encryptedElement;

        ////////////////////////////////////////////////////
        // Replace the element from the original XmlDocument
        // object with the EncryptedData element.
        ////////////////////////////////////////////////////

        EncryptedXml.ReplaceElement(elementToEncrypt, edElement, false);
    }

    public static void Decrypt(XmlDocument Doc, SymmetricAlgorithm Alg)
    {
        // Check the arguments.
        if (Doc == null)
            throw new ArgumentNullException("Doc");
        if (Alg == null)
            throw new ArgumentNullException("Alg");

        // Find the EncryptedData element in the XmlDocument.
        XmlElement encryptedElement = Doc.GetElementsByTagName("EncryptedData")[0] as XmlElement;

        // If the EncryptedData element was not found, throw an exception.
        if (encryptedElement == null)
        {
            throw new XmlException("The EncryptedData element was not found.");
        }

        // Create an EncryptedData object and populate it.
        EncryptedData edElement = new EncryptedData();
        edElement.LoadXml(encryptedElement);

        // Create a new EncryptedXml object.
        EncryptedXml exml = new EncryptedXml();

        // Decrypt the element using the symmetric key.
        byte[] rgbOutput = exml.DecryptData(edElement, Alg);

        // Replace the encryptedData element with the plaintext XML element.
        exml.ReplaceData(encryptedElement, rgbOutput);
    }
}

Imports System.Xml
Imports System.Security.Cryptography
Imports System.Security.Cryptography.Xml



Module Program

    Sub Main(ByVal args() As String)

        ' Create an XmlDocument object.
        Dim xmlDoc As New XmlDocument()

        ' Load an XML file into the XmlDocument object.
        Try
            xmlDoc.PreserveWhitespace = True
            xmlDoc.Load("test.xml")
        Catch e As Exception
            Console.WriteLine(e.Message)
            Return
        End Try

        ' Create a new TripleDES key. 
        Dim tDESkey As New TripleDESCryptoServiceProvider()


        Try
            ' Encrypt the "creditcard" element.
            Encrypt(xmlDoc, "creditcard", tDESkey)

            ' Display the encrypted XML to the console.
            Console.WriteLine("Encrypted XML:")
            Console.WriteLine()
            Console.WriteLine(xmlDoc.OuterXml)

            ' Decrypt the "creditcard" element.
            Decrypt(xmlDoc, tDESkey)

            ' Display the encrypted XML to the console.
            Console.WriteLine()
            Console.WriteLine("Decrypted XML:")
            Console.WriteLine()
            Console.WriteLine(xmlDoc.OuterXml)
        Catch e As Exception
            Console.WriteLine(e.Message)
        Finally
            ' Clear the TripleDES key.
            tDESkey.Clear()
        End Try

    End Sub


    Sub Encrypt(ByVal Doc As XmlDocument, ByVal ElementToEncrypt As String, ByVal Alg As SymmetricAlgorithm)
        ' Check the arguments.  
        If Doc Is Nothing Then
            Throw New ArgumentNullException("Doc")
        End If
        If ElementToEncrypt Is Nothing Then
            Throw New ArgumentNullException("ElementToEncrypt")
        End If
        If Alg Is Nothing Then
            Throw New ArgumentNullException("Alg")
        End If
        '''''''''''''''''''''''''''''''''''''''''''''''''''
        ' Find the specified element in the XmlDocument
        ' object and create a new XmlElemnt object.
        '''''''''''''''''''''''''''''''''''''''''''''''''''
        Dim elementEncrypt As XmlElement = Doc.GetElementsByTagName(ElementToEncrypt)(0)


        ' Throw an XmlException if the element was not found.
        If ElementToEncrypt Is Nothing Then
            Throw New XmlException("The specified element was not found")
        End If

        '''''''''''''''''''''''''''''''''''''''''''''''''''
        ' Create a new instance of the EncryptedXml class 
        ' and use it to encrypt the XmlElement with the 
        ' symmetric key.
        '''''''''''''''''''''''''''''''''''''''''''''''''''
        Dim eXml As New EncryptedXml()

        Dim encryptedElement As Byte() = eXml.EncryptData(elementEncrypt, Alg, False)

        '''''''''''''''''''''''''''''''''''''''''''''''''''
        ' Construct an EncryptedData object and populate
        ' it with the desired encryption information.
        '''''''''''''''''''''''''''''''''''''''''''''''''''

        Dim edElement As New EncryptedData()
        edElement.Type = EncryptedXml.XmlEncElementUrl

        ' Create an EncryptionMethod element so that the 
        ' receiver knows which algorithm to use for decryption.
        ' Determine what kind of algorithm is being used and
        ' supply the appropriate URL to the EncryptionMethod element.
        Dim encryptionMethod As String = Nothing

        If TypeOf Alg Is TripleDES Then
            encryptionMethod = EncryptedXml.XmlEncTripleDESUrl
        ElseIf TypeOf Alg Is DES Then
            encryptionMethod = EncryptedXml.XmlEncDESUrl
        ElseIf TypeOf Alg Is Aes Then
            Select Case Alg.KeySize
                Case 128
                    encryptionMethod = EncryptedXml.XmlEncAES128Url
                Case 192
                    encryptionMethod = EncryptedXml.XmlEncAES192Url
                Case 256
                    encryptionMethod = EncryptedXml.XmlEncAES256Url
            End Select
        Else
            ' Throw an exception if the transform is not in the previous categories
            Throw New CryptographicException("The specified algorithm is not supported for XML Encryption.")
        End If

        edElement.EncryptionMethod = New EncryptionMethod(encryptionMethod)

        ' Add the encrypted element data to the 
        ' EncryptedData object.
        edElement.CipherData.CipherValue = encryptedElement

        '''''''''''''''''''''''''''''''''''''''''''''''''''
        ' Replace the element from the original XmlDocument
        ' object with the EncryptedData element.
        '''''''''''''''''''''''''''''''''''''''''''''''''''
        EncryptedXml.ReplaceElement(elementEncrypt, edElement, False)

    End Sub


    Sub Decrypt(ByVal Doc As XmlDocument, ByVal Alg As SymmetricAlgorithm)
        ' Check the arguments.  
        If Doc Is Nothing Then
            Throw New ArgumentNullException("Doc")
        End If
        If Alg Is Nothing Then
            Throw New ArgumentNullException("Alg")
        End If
        ' Find the EncryptedData element in the XmlDocument.
        Dim encryptedElement As XmlElement = Doc.GetElementsByTagName("EncryptedData")(0)

        ' If the EncryptedData element was not found, throw an exception.
        If encryptedElement Is Nothing Then
            Throw New XmlException("The EncryptedData element was not found.")
        End If

        ' Create an EncryptedData object and populate it.
        Dim edElement As New EncryptedData()
        edElement.LoadXml(encryptedElement)

        ' Create a new EncryptedXml object.
        Dim exml As New EncryptedXml()

        ' Decrypt the element using the symmetric key.
        Dim rgbOutput As Byte() = exml.DecryptData(edElement, Alg)

        ' Replace the encryptedData element with the plaintext XML element.
        exml.ReplaceData(encryptedElement, rgbOutput)

    End Sub
End Module

Remarks

This constructor initializes a new instance of the EncryptionMethod class using the URI of an encryption algorithm.

Use one of the URI identifiers defined by the World Wide Web Consortium XML Encryption Syntax and Processing specification. All URI identifiers are accessible as static fields of the EncryptedXml class.