DataReference Class

Represents the <DataReference> element used in XML encryption. This class cannot be inherited.

System.Object
  System.Security.Cryptography.Xml.EncryptedReference
    System.Security.Cryptography.Xml.DataReference

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

[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public sealed class DataReference : EncryptedReference

The DataReference type exposes the following members.

  NameDescription
Public methodDataReference()Initializes a new instance of the DataReference class.
Public methodDataReference(String)Initializes a new instance of the DataReference class using the specified Uniform Resource Identifier (URI).
Public methodDataReference(String, TransformChain)Initializes a new instance of the DataReference class using the specified Uniform Resource Identifier (URI) and a TransformChain object.
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  NameDescription
Protected propertyCacheValidGets a value that indicates whether the cache is valid. (Inherited from EncryptedReference.)
Public propertyTransformChainGets or sets the transform chain of an EncryptedReference object. (Inherited from EncryptedReference.)
Public propertyUriGets or sets the Uniform Resource Identifier (URI) of an EncryptedReference object. (Inherited from EncryptedReference.)
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  NameDescription
Public methodAddTransformAdds a Transform object to the current transform chain of an EncryptedReference object. (Inherited from EncryptedReference.)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (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 the XML representation of an EncryptedReference object. (Inherited from EncryptedReference.)
Public methodLoadXmlLoads an XML element into an EncryptedReference object. (Inherited from EncryptedReference.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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The DataReference class represents the <DataReference> element that contains the location of encrypted data used with XML encryption.

<DataReference> elements are used to refer to <EncryptedData> elements that were encrypted using the key defined in the enclosing <EncryptedKey> element. Multiple <DataReference> elements can occur if multiple <EncryptedData> elements exist that are encrypted using the same key.

For more information about XML encryption standards, see http://www.w3.org/TR/xmlenc-core/.

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 use the DataReference class to encrypt and decrypt multiple XML elements using different session keys.


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);
        }

        // Create a new RSA key.  This key will encrypt a symmetric key, 
        // which will then be imbedded in the XML document.  
        RSA rsaKey = new RSACryptoServiceProvider();


        try
        {
            // Encrypt the "creditcard" element.
            Encrypt(xmlDoc, "creditcard", "EncryptedElement1", rsaKey, "rsaKey");

            // Encrypt the "creditcard2" element.
            Encrypt(xmlDoc, "creditcard2", "EncryptedElement2", rsaKey, "rsaKey");

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

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

            // 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 RSA key.
            rsaKey.Clear();
        }

        Console.ReadLine();


    }

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

        //////////////////////////////////////////////// 
        // 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  
        // a new random symmetric key. 
        ////////////////////////////////////////////////// 

        // Create a 256 bit Rijndael key.
        RijndaelManaged sessionKey = new RijndaelManaged();
        sessionKey.KeySize = 256;

        EncryptedXml eXml = new EncryptedXml();

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

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


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

        // Create an EncryptionMethod element so that the  
        // receiver knows which algorithm to use for decryption.

        edElement.EncryptionMethod = new EncryptionMethod(EncryptedXml.XmlEncAES256Url);

        // Encrypt the session key and add it to an EncryptedKey element.
        EncryptedKey ek = new EncryptedKey();

        byte[] encryptedKey = EncryptedXml.EncryptKey(sessionKey.Key, Alg, false);

        ek.CipherData = new CipherData(encryptedKey);

        ek.EncryptionMethod = new EncryptionMethod(EncryptedXml.XmlEncRSA15Url);

        // Set the KeyInfo element to specify the 
        // name of the RSA key. 

        // Create a new KeyInfo element.
        edElement.KeyInfo = new KeyInfo();

        // Create a new KeyInfoName element.
        KeyInfoName kin = new KeyInfoName();

        // Specify a name for the key.
        kin.Value = KeyName;

        // Add the KeyInfoName element to the  
        // EncryptedKey object.
        ek.KeyInfo.AddClause(kin);

        // Create a new DataReference element 
        // for the KeyInfo element.  This optional 
        // element specifies which EncryptedData  
        // uses this key.  An XML document can have 
        // multiple EncryptedData elements that use 
        // different keys.
        DataReference dRef = new DataReference();

        // Specify the EncryptedData URI. 
        dRef.Uri = "#" + EncryptionElementID;

        // Add the DataReference to the EncryptedKey.
        ek.AddReference(dRef);

        // Add the encrypted key to the  
        // EncryptedData object.

        edElement.KeyInfo.AddClause(new KeyInfoEncryptedKey(ek));

        // 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, RSA Alg, string KeyName)
    {
        // Check the arguments.   
        if (Doc == null)
            throw new ArgumentNullException("Doc");
        if (Alg == null)
            throw new ArgumentNullException("Alg");
        if (KeyName == null)
            throw new ArgumentNullException("KeyName");

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

        // Add a key-name mapping. 
        // This method can only decrypt documents 
        // that present the specified key name.
        exml.AddKeyNameMapping(KeyName, Alg);

        // Decrypt the element.
        exml.DecryptDocument();

    }

}

// To run this sample, place the following XML 
// in a file called test.xml.  Put test.xml 
// in the same directory as your compiled program. 
//  
//  <root> 
//     <creditcard xmlns="myNamespace" Id="tag1">
//         <number>19834209</number> 
//         <expiry>02/02/2002</expiry> 
//     </creditcard> 
//     <creditcard2 xmlns="myNamespace" Id="tag2">
//         <number>19834208</number> 
//         <expiry>02/02/2002</expiry> 
//     </creditcard2> 
// </root>

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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