CipherReference Class

Definition

Namespace:

System.Security.Cryptography.Xml

Assembly:

System.Security.Cryptography.Xml.dll

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

public ref class CipherReference sealed : System::Security::Cryptography::Xml::EncryptedReference

public sealed class CipherReference : System.Security.Cryptography.Xml.EncryptedReference

type CipherReference = class
    inherit EncryptedReference

Public NotInheritable Class CipherReference
Inherits EncryptedReference

Inheritance

Object

EncryptedReference

CipherReference

Examples

The following code example creates a new instance of CipherReference.

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

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

/// This sample used the EncryptedData class to create an encrypted data element
/// and write it to an XML file. It demonstrates the use of CipherReference.

[STAThread]
int main()
{
   
   //Create a URI string.
   String^ uri = "http://www.woodgrovebank.com/document.xml";
   
   // Create a Base64 transform. The input content retrieved from the
   // URI should be Base64-decoded before other processing.
   Transform^ base64 = gcnew XmlDsigBase64Transform;
   
   //Create a transform chain and add the transform to it.
   TransformChain^ tc = gcnew TransformChain;
   tc->Add( base64 );
   
   //Create <CipherReference> information.
   CipherReference ^ reference = gcnew CipherReference( uri,tc );
   
   // Create a new CipherData object using the CipherReference information.
   // Note that you cannot assign both a CipherReference and a CipherValue
   // to a CipherData object.
   CipherData ^ cd = gcnew CipherData( reference );
   
   // Create a new EncryptedData object.
   EncryptedData^ ed = gcnew EncryptedData;
   
   //Add an encryption method to the object.
   ed->Id = "ED";
   ed->EncryptionMethod = gcnew EncryptionMethod( "http://www.w3.org/2001/04/xmlenc#aes128-cbc" );
   ed->CipherData = cd;
   
   //Add key information to the object.
   KeyInfo^ ki = gcnew KeyInfo;
   ki->AddClause( gcnew KeyInfoRetrievalMethod( "#EK","http://www.w3.org/2001/04/xmlenc#EncryptedKey" ) );
   ed->KeyInfo = ki;
   
   // Create new XML document and put encrypted data into it.
   XmlDocument^ doc = gcnew XmlDocument;
   XmlElement^ encryptionPropertyElement = dynamic_cast<XmlElement^>(doc->CreateElement( "EncryptionProperty", EncryptedXml::XmlEncNamespaceUrl ));
   EncryptionProperty ^ ep = gcnew EncryptionProperty( encryptionPropertyElement );
   ed->AddProperty( ep );
   
   // Output the resulting XML information into a file.
   try
   {
      String^ path = "c:\\test\\MyTest.xml";
      File::WriteAllText( path, ed->GetXml()->OuterXml );
   }
   catch ( IOException^ e ) 
   {
      Console::WriteLine( "File IO error. {0}", e );
   }

}

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

/// This sample used the EncryptedData class to create an encrypted data element
/// and write it to an XML file. It demonstrates the use of CipherReference.
namespace EncryptedDataSample
{
    class Example
    {
        [STAThread]
        static void Main(string[] args)
        {
            //Create a URI string.
            String uri = "http://www.woodgrovebank.com/document.xml";
            // Create a Base64 transform. The input content retrieved from the
            // URI should be Base64-decoded before other processing.
            Transform base64 = new XmlDsigBase64Transform();
            //Create a transform chain and add the transform to it.
            TransformChain tc = new TransformChain();
            tc.Add(base64);
            //Create <CipherReference> information.
            CipherReference reference = new CipherReference(uri, tc);

            // Create a new CipherData object using the CipherReference information.
            // Note that you cannot assign both a CipherReference and a CipherValue
            // to a CipherData object.
            CipherData cd = new CipherData(reference);

            // Create a new EncryptedData object.
            EncryptedData ed = new EncryptedData();

            //Add an encryption method to the object.
            ed.Id = "ED";
            ed.EncryptionMethod = new EncryptionMethod("http://www.w3.org/2001/04/xmlenc#aes128-cbc");
            ed.CipherData = cd;

            //Add key information to the object.
            KeyInfo ki = new KeyInfo();
            ki.AddClause(new KeyInfoRetrievalMethod("#EK", "http://www.w3.org/2001/04/xmlenc#EncryptedKey"));
            ed.KeyInfo = ki;

            // Create new XML document and put encrypted data into it.
            XmlDocument doc = new XmlDocument();
            XmlElement encryptionPropertyElement = (XmlElement)doc.CreateElement("EncryptionProperty", EncryptedXml.XmlEncNamespaceUrl);
            EncryptionProperty ep = new EncryptionProperty(encryptionPropertyElement);
            ed.AddProperty(ep);

            // Output the resulting XML information into a file.
            try
            {
                string path = @"c:\test\MyTest.xml";

                File.WriteAllText(path, ed.GetXml().OuterXml);
            }
            catch (IOException e)
            {
                Console.WriteLine("File IO error. {0}", e);
            }
        }
    }
}

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


'/ This sample used the EncryptedData class to create a EncryptedData element
'/ and write it to an XML file. It demonstrates the use of CipherReference.
Module Module1

    Sub Main()
        ' Create a URI string.
        Dim uri As String = "http://www.woodgrovebank.com/document.xml"
        ' Create a Base64 transform. The input content retrieved from the
        ' URI should be Base64-decoded before other processing.
        Dim base64 As Transform = New XmlDsigBase64Transform
        Dim tc As New TransformChain
        tc.Add(base64)
        ' Create <CipherReference> information.
        Dim reference As CipherReference = New CipherReference(uri, tc)

        ' Create a new CipherData object.
        ' Note that you cannot assign both a CipherReference and a CipherValue
        ' to a CipherData object.
        Dim cd As CipherData = New CipherData(Reference)

        ' Create a new EncryptedData object.
        Dim ed As New EncryptedData

        'Add an encryption method to the object.
        ed.Id = "ED"
        ed.EncryptionMethod = New EncryptionMethod("http://www.w3.org/2001/04/xmlenc#aes128-cbc")
        ed.CipherData = cd

        'Add key information to the object.
        Dim ki As New KeyInfo
        ki.AddClause(New KeyInfoRetrievalMethod("#EK", "http://www.w3.org/2001/04/xmlenc#EncryptedKey"))
        ed.KeyInfo = ki

        ' Create new XML document and put encrypted data into it.
        Dim doc As New XmlDocument
        Dim encryptionPropertyElement As XmlElement = CType(doc.CreateElement("EncryptionProperty", EncryptedXml.XmlEncNamespaceUrl), XmlElement)
        Dim ep As New EncryptionProperty(encryptionPropertyElement)
        ed.AddProperty(ep)

        ' Output the resulting XML information into a file.
        Dim path As String = "c:\test\MyTest.xml"
        File.WriteAllText(path, ed.GetXml().OuterXml)
    End Sub

End Module

Remarks

This class represents the <CipherReference> element in XML encryption. It identifies a source which, when processed, yields the encrypted data.

The actual encrypted data referenced by the <CipherReference> is obtained by the following process. The <CipherReference> URI property contains a Uniform Resource Identifier (URI) that is dereferenced. If the <CipherReference> element also contains a transform chain, the data resulting from dereferencing the URI is transformed as specified to produce the encrypted data. For example, if the encrypted data is base64-encoded within an XML document, the transforms would specify an XPath expression followed by a base64 decoding so the encrypted data can be extracted.

The syntax of the URI and transforms is similar to that of XML digital signatures. However, in XML digital signatures, both generation and validation processing start with the same source data and perform that transform in the same order. In XML encryption, the decrypting application has only the encrypted data and the specified transforms. The transforms are enumerated in the order necessary to obtain the encrypted data.

Note By default, you cannot dereference cipher references from documents with unknown sources, such as files from a Web site, because the DocumentEvidence property is null. For example, when you attempt to decrypt a file containing a <CipherReference> element that references a file on the Web, a SecurityException is thrown, even if the request is made by a fully trusted assembly.

If you are sure the documents you are decrypting can be trusted, you can change this behavior for fully trusted applications by using the following code:

Evidence ev = new Evidence();  
ev.AddHost (new Zone(SecurityZone.MyComputer));  
EncryptedXml exml = new EncryptedXml(doc, ev);  

Constructors

CipherReference()	Initializes a new instance of the CipherReference class.
CipherReference(String, TransformChain)	Initializes a new instance of the CipherReference class using the specified Uniform Resource Identifier (URI) and transform chain information.
CipherReference(String)	Initializes a new instance of the CipherReference class using the specified Uniform Resource Identifier (URI).

Properties

CacheValid	Gets a value that indicates whether the cache is valid. (Inherited from EncryptedReference)
ReferenceType	Gets or sets a reference type. (Inherited from EncryptedReference)
TransformChain	Gets or sets the transform chain of an EncryptedReference object. (Inherited from EncryptedReference)
Uri	Gets or sets the Uniform Resource Identifier (URI) of an EncryptedReference object. (Inherited from EncryptedReference)

Methods

AddTransform(Transform)	Adds a Transform object to the current transform chain of an EncryptedReference object. (Inherited from EncryptedReference)
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
GetXml()	Returns the XML representation of a CipherReference object.
LoadXml(XmlElement)	Loads XML information into the <CipherReference> element in XML encryption.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)