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EncryptionMethod Class

Encapsulates the encryption algorithm used for XML encryption.

System.Object
  System.Security.Cryptography.Xml.EncryptionMethod

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

[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public class EncryptionMethod

The EncryptionMethod type exposes the following members.

  NameDescription
Public methodEncryptionMethod()Initializes a new instance of the EncryptionMethod class.
Public methodEncryptionMethod(String)Initializes a new instance of the EncryptionMethod class specifying an algorithm Uniform Resource Identifier (URI).
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  NameDescription
Public propertyKeyAlgorithmGets or sets a Uniform Resource Identifier (URI) that describes the algorithm to use for XML encryption.
Public propertyKeySizeGets or sets the algorithm key size used for XML encryption.
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  NameDescription
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodGetXmlReturns an XmlElement object that encapsulates an instance of the EncryptionMethod class.
Public methodLoadXmlParses the specified XmlElement object and configures the internal state of the EncryptionMethod object to match.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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The <EncryptionMethod> tag uses a Uniform Resource Identifier (URI) to identify the encryption algorithm that must be used to decrypt XML data. The EncryptionMethod class encapsulates the <EncryptionMethod> tag defined by the World Wide Web Consortium XML Encryption specification located at http://www.w3.org/TR/xmlenc-core/.

Use the EncryptionMethod class to identify the encryption algorithm associated with the EncryptedData element or the EncryptedKey element.

Use one of the URI identifiers defined by the World Wide Web Consortium XML Encryption specification located at http://www.w3.org/TR/xmlenc-core/. All URI identifiers are accessible as static fields of the EncryptedXml class.

NoteNote

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

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

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);

	}

}

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;
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 Rijndael)
        {
            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);

    }


}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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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