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DSAKeyValue Class

Represents the DSA private key of the <KeyInfo> element.

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

'Declaration
Public Class DSAKeyValue _
	Inherits KeyInfoClause
'Usage
Dim instance As DSAKeyValue

The KeyInfo class represents the <KeyInfo> element, which contains a DSA public key.

Use DSAKeyValue to identify the public key that corresponds to the DSA private key that was used to create the digital signature.

If a key is not explicitly supplied to the constructor, a new DSA key pair is randomly generated.

The DSAKeyValue class is used with XML signatures. For more information about the W3C specification, see http://www.w3.org/TR/xmldsig-core/.

The following code example demonstrates how to use the DSAKeyValue class in XML encryption to create a detached signature.


' 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 DSA signing key. 
         Dim DSAKey As New DSACryptoServiceProvider()

         Console.WriteLine("Signing: {0}", resourceToSign)

         ' Sign the detached resourceand save the signature in an XML file.
         SignDetachedResource(resourceToSign, XmlFileName, DSAKey)

         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, DSAKey As DSA)
      ' Create a SignedXml object. 
      Dim signedXml As New SignedXml()

      ' Assign the DSA key to the SignedXml object.
      signedXml.SigningKey = DSAKey

      ' 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 a DSAKeyValue to the KeyInfo (optional; helps recipient find key to validate). 
      Dim keyInfo As New KeyInfo()
      keyInfo.AddClause(New DSAKeyValue(CType(DSAKey, DSA)))
      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

The following code example demonstrates how to use the DSAKeyValue class in XML encryption to create 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.Xml
Imports System.Text
Imports System.Xml



Public Class SignVerifyEnvelope


   Overloads Public Shared Sub Main(args() As [String])
      Try 
         ' Generate a DSA signing key. 
         Dim DSAKey As New DSACryptoServiceProvider()

         ' 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", DSAKey)
         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, DSAKey As DSA)
      ' 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 DSA key to the SignedXml document. 
      signedXml.SigningKey = DSAKey

      ' Create a reference to be signed. 
      Dim reference As New Reference()
      reference.Uri = "" 

      ' Add a transformation to the reference. 
      Dim trns = New XmlDsigC14NTransform()
      reference.AddTransform(trns)

      ' 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 a DSAKeyValue to the KeyInfo (optional; helps recipient find key to validate). 
      Dim keyInfo As New KeyInfo()
      keyInfo.AddClause(New DSAKeyValue(CType(DSAKey, DSA)))
      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.Object
  System.Security.Cryptography.Xml.KeyInfoClause
    System.Security.Cryptography.Xml.DSAKeyValue

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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