XmlDsigC14NWithCommentsTransform Class
Represents the C14N XML canonicalization transform for a digital signature as defined by the World Wide Web Consortium (W3C), with comments.
Assembly: System.Security (in System.Security.dll)
The XmlDsigC14NWithCommentsTransform class represents the C14N XML canonicalization transform that describes the canonical form of an XML document. This transform allows a signer to create a digest using the canonical form of an XML document. A recipient can then verify the digital signature using the same canonical form of the XML document with the same transform.
Use the XmlDsigC14NWithCommentsTransform class when you need to sign an XML document that contains comments.
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.
The URI that describes the XmlDsigC14NWithCommentsTransform class is defined by the XmlDsigC14NWithCommentsTransformUrl field and the XmlDsigCanonicalizationWithCommentsUrl field.
For more information about the C14N with comments transform, see Sections 6.5 and 6.6.1 of 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/TR/xml-c14n.
This section contains two code examples. The first example demonstrates how to sign an XML file using a detached signature. This example creates a signature of www.microsoft.com in an XML file and then verifies the file. The second example demonstrates how to sign an XML file using an envelope signature. This example creates a signature of an XML file and then saves the signature in new XML file.
Example #1
' This example signs a file specified by a URI ' using a detached signature. It then verifies ' the signed XML. Imports System Imports System.Security.Cryptography Imports System.Security.Cryptography.Xml Imports System.Text Imports System.Xml Class XMLDSIGDetached <STAThread()> _ Overloads Shared Sub Main(args() As String) ' The URI to sign. Dim resourceToSign As String = "http://www.microsoft.com" ' The name of the file to which to save the XML signature. Dim XmlFileName As String = "xmldsig.xml" Try ' Generate a signing key. Dim Key As New RSACryptoServiceProvider() Console.WriteLine("Signing: {0}", resourceToSign) ' Sign the detached resourceand save the signature in an XML file. SignDetachedResource(resourceToSign, XmlFileName, Key) Console.WriteLine("XML signature was succesfully computed and saved to {0}.", XmlFileName) ' Verify the signature of the signed XML. Console.WriteLine("Verifying signature...") 'Verify the XML signature in the XML file. Dim result As Boolean = VerifyDetachedSignature(XmlFileName) ' Display the results of the signature verification to ' the console. If result Then Console.WriteLine("The XML signature is valid.") Else Console.WriteLine("The XML signature is not valid.") End If Catch e As CryptographicException Console.WriteLine(e.Message) End Try End Sub ' Sign an XML file and save the signature in a new file. Public Shared Sub SignDetachedResource(URIString As String, XmlSigFileName As String, Key As RSA) ' Create a SignedXml object. Dim signedXml As New SignedXml() ' Assign the key to the SignedXml object. signedXml.SigningKey = Key ' Create a reference to be signed. Dim reference As New Reference() ' Add the passed URI to the reference object. reference.Uri = URIString ' Add the reference to the SignedXml object. signedXml.AddReference(reference) ' 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. signedXml.ComputeSignature() ' Get the XML representation of the signature and save ' it to an XmlElement object. Dim xmlDigitalSignature As XmlElement = signedXml.GetXml() ' Save the signed XML document to a file specified ' using the passed string. Dim xmltw As New XmlTextWriter(XmlSigFileName, New UTF8Encoding(False)) xmlDigitalSignature.WriteTo(xmltw) xmltw.Close() End Sub ' Verify the signature of an XML file and return the result. Public Shared Function VerifyDetachedSignature(XmlSigFileName As String) As [Boolean] ' Create a new XML document. Dim xmlDocument As New XmlDocument() ' Load the passed XML file into the document. xmlDocument.Load(XmlSigFileName) ' Create a new SignedXMl object. Dim signedXml As New SignedXml() ' 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 End Class
Example #2
' 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.Xml Imports System.Text Imports System.Xml Public Class SignVerifyEnvelope Overloads Public Shared Sub Main(args() As [String]) Try ' Generate a signing key. Dim Key As New RSACryptoServiceProvider() ' Create an XML file to sign. CreateSomeXml("Example.xml") 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.") Else Console.WriteLine("The XML signature is not valid.") End If Catch e As CryptographicException Console.WriteLine(e.Message) End Try End Sub ' Sign an XML file and save the signature in a new file. Public Shared Sub SignXmlFile(FileName As String, SignedFileName As String, 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 ' 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() reference.AddTransform(env) ' Add the reference to the SignedXml object. signedXml.AddReference(reference) ' 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. signedXml.ComputeSignature() ' 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 doc.RemoveChild(doc.FirstChild) End If ' Save the signed XML document to a file specified ' using the passed string. Dim xmltw As New XmlTextWriter(SignedFileName, New UTF8Encoding(False)) doc.WriteTo(xmltw) xmltw.Close() End Sub ' Verify the signature of an XML file and return the result. Public Shared Function VerifyXmlFile(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. xmlDocument.Load(Name) ' 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. Public Shared Sub CreateSomeXml(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, "", "MyElement", "samples") ' Add some text to the node. node.InnerText = "Example text to be signed." ' Append the node to the document. document.AppendChild(node) ' Save the XML document to the file name specified. Dim xmltw As New XmlTextWriter(FileName, New UTF8Encoding(False)) document.WriteTo(xmltw) xmltw.Close() End Sub End Class
System.Security.Cryptography.Xml.Transform
System.Security.Cryptography.Xml.XmlDsigC14NTransform
System.Security.Cryptography.Xml.XmlDsigC14NWithCommentsTransform
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.