XmlDsigExcC14NWithCommentsTransform Class


Represents the exclusive C14N XML canonicalization transform for a digital signature as defined by the World Wide Web Consortium (W3C), with comments.

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


<HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort := True)>
Public Class XmlDsigExcC14NWithCommentsTransform
	Inherits XmlDsigExcC14NTransform


Initializes a new instance of the XmlDsigExcC14NWithCommentsTransform class.


Initializes a new instance of the XmlDsigExcC14NWithCommentsTransform class specifying a list of namespace prefixes to canonicalize using the standard canonicalization algorithm.


Gets or sets the Uniform Resource Identifier (URI) that identifies the algorithm performed by the current transform.(Inherited from Transform.)


Gets or sets an XmlElement object that represents the document context under which the current Transform object is running. (Inherited from Transform.)


Gets or sets a string that contains namespace prefixes to canonicalize using the standard canonicalization algorithm. (Inherited from XmlDsigExcC14NTransform.)


Gets an array of types that are valid inputs to the LoadInput method of the current XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)


Gets an array of types that are possible outputs from the GetOutput methods of the current XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)


Gets or sets a Hashtable object that contains the namespaces that are propagated into the signature. (Inherited from Transform.)


Sets the current XmlResolver object.(Inherited from Transform.)


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


Returns the digest associated with a XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)


Serves as the default hash function. (Inherited from Object.)


Returns an XML representation of the parameters of a XmlDsigExcC14NTransform object that are suitable to be included as subelements of an XMLDSIG <Transform> element.(Inherited from XmlDsigExcC14NTransform.)


Returns the output of the current XmlDsigExcC14NTransform object(Inherited from XmlDsigExcC14NTransform.)


Returns the output of the current XmlDsigExcC14NTransform object as an object of the specified type.(Inherited from XmlDsigExcC14NTransform.)


Gets the Type of the current instance.(Inherited from Object.)


Returns the XML representation of the current Transform object.(Inherited from Transform.)


Parses the specified XmlNodeList object as transform-specific content of a <Transform> element and configures the internal state of the current XmlDsigExcC14NTransform object to match the <Transform> element.(Inherited from XmlDsigExcC14NTransform.)


When overridden in a derived class, loads the specified input into the current XmlDsigExcC14NTransform object.(Inherited from XmlDsigExcC14NTransform.)


Creates a shallow copy of the current Object.(Inherited from Object.)


Returns a string that represents the current object.(Inherited from Object.)

The XmlDsigExcC14NWithCommentsTransform class represents the exclusive C14N XML canonicalization transform with comments. This class is similar to the XmlDsigExcC14NTransform class, which allows a signer to create a digest using the canonical form of an XML document. However, the XmlDsigExcC14NWithCommentsTransform class excludes ancestor context from a canonicalized subdocument.

Use the XmlDsigExcC14NWithCommentsTransform class when you need to canonicalize an XML subdocument so that it is independent from its XML context. For example, applications such as Web services that use signed XML within complex communication protocols often need to canonicalize XML in this manner. Such applications often envelop XML within various dynamically constructed elements, which can substantially change the document and cause XML signature verification to fail. The XmlDsigExcC14NWithCommentsTransform class solves this problem by excluding such ancestor context from the canonical subdocument.

Note that you cannot directly create a new instance of a canonicalization transform class. To specify a canonicalization transform, pass the Uniform Resource Identifier (URI) that describes the transform to the CanonicalizationMethod property, which is accessible from the SignedInfo property. To acquire a reference to the canonicalization transform, use the CanonicalizationMethodObject property, which is accessible from the SignedInfo property.

The URI that describes the XmlDsigExcC14NWithCommentsTransform class is defined by the XmlDsigExcC14NWithCommentsTransformUrl field.

For more information about the exclusive C14N transform, see the XMLDSIG specification, which is available from the World Wide Web Consortium (W3C) at www.w3.org/TR/xmldsig-core/. The canonicalization algorithm is defined in the W3C Canonical XML specification, which is available at www.w3.org/2001/10/xml-exc-c14n.

The following code example shows how to sign and verify an XML document using the XmlDsigExcC14NWithCommentsTransform class. This example creates an envelope signature.

' This example signs an XML file using an
' envelope signature. It then verifies the 
' signed XML.
Imports System
Imports System.Security.Cryptography
Imports System.Security.Cryptography.X509Certificates
Imports System.Security.Cryptography.Xml
Imports System.Text
Imports System.Xml

Module SignVerifyEnvelope

    Sub Main(ByVal args() As String)
            ' Generate a signing key.
            Dim Key As New RSACryptoServiceProvider()

            ' Create an XML file to sign.
            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", Key);
            Console.WriteLine("XML file signed.")

            ' Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...")
            Dim result As Boolean = VerifyXmlFile("SignedExample.xml")

            ' Display the results of the signature verification to 
            ' the console.
            If result Then
                Console.WriteLine("The XML signature is valid.")
                Console.WriteLine("The XML signature is not valid.")
            End If
        Catch e As CryptographicException
        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 Key As RSA)
        ' 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

        ' Specify a canonicalization method.
        signedXml.SignedInfo.CanonicalizationMethod = signedXml.XmlDsigExcC14NWithCommentsTransformUrl

        ' Set the InclusiveNamespacesPrefixList property.
        Dim canMethod As XmlDsigExcC14NWithCommentsTransform = CType(signedXml.SignedInfo.CanonicalizationMethodObject, XmlDsigExcC14NWithCommentsTransform)
        canMethod.InclusiveNamespacesPrefixList = "Sign"

        ' 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()

        ' Add the reference to the SignedXml object.

        ' Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        Dim keyInfo As New KeyInfo()
        keyInfo.AddClause(New RSAKeyValue(CType(Key, RSA)))
        signedXml.KeyInfo = keyInfo

        ' Compute the signature.

        ' 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
        End If

        ' Save the signed XML document to a file specified
        ' using the passed string.
        Dim xmltw As New XmlTextWriter(SignedFileName, New UTF8Encoding(False))

    End Sub

    ' Verify the signature of an XML file and return the result.
    Function VerifyXmlFile(ByVal Name As String) As [Boolean]
        ' Create a new XML document.
        Dim xmlDocument As New XmlDocument()

        ' Format using white spaces.
        xmlDocument.PreserveWhitespace = True

        ' Load the passed XML file into the document. 

        ' 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()

    End Function

    ' Create example data to sign.
    Sub CreateSomeXml(ByVal FileName As String)
        ' Create a new XmlDocument object.
        Dim document As New XmlDocument()

        ' Create a new XmlNode object.
        Dim node As XmlNode = document.CreateNode(XmlNodeType.Element, "", "MyXML", "Don't_Sign")

        ' Append the node to the document.

        ' Create a new XmlNode object.
        Dim subnode As XmlNode = document.CreateNode(XmlNodeType.Element, "", "TempElement", "Sign")

        ' Add some text to the node.
        subnode.InnerText = "Here is some data to sign."

        ' Append the node to the document.

        ' Save the XML document to the file name specified.
        Dim xmltw As New XmlTextWriter(FileName, New UTF8Encoding(False))

    End Sub
End Module

.NET Framework
Available since 2.0

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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