Visual Basic Source: KeyFromHMACSecret.frm

[This sample code uses features that were implemented in MSXML 5.0 for Microsoft Office Applications. XML digital signatures are not supported in MXSML 6.0 and later.]

Dim xmldoc As New DOMDocument50
Dim xmldsig As New MXDigitalSignature50
Dim dsigKey As IXMLDSigKey
Dim DSIGNS, sigOut, sigTmp As String
Const KEYVALUE = 1

Private Function LoadXML(ByVal file As String)
    ' Read the input xml file and display the content in the text3.
    Path = App.Path + "\" + file
    xmldoc.async = False
    xmldoc.preserveWhiteSpace = True
    xmldoc.validateOnParse = False
    If xmldoc.Load(Path) = False Then
        Text1.Text = Text1.Text + "can't load " + Path + vbNewLine _
                   + xmldoc.parseError.reason + vbNewLine
        LoadXML = False
        Exit Function
    End If
    xmldoc.setProperty "SelectionNamespaces", DSIGNS
    Set xmldsig.signature = xmldoc.selectSingleNode(".//ds:Signature")
    
    LoadXML = True
End Function
Private Function SignXML(ByVal secret As String, ByVal length As Long)
    If xmldsig.signature Is Nothing Then
        Text1.Text = Text1.Text + "Invalid signature template."
        SignXML = False
        Exit Function
    End If
    
    Set oKey = xmldsig.createKeyFromHMACSecret(secret, length)
    If oKey Is Nothing Then
        Text1.Text = Text1.Text + _
            "Failed to create key from HMAC secret value\n"
        SignXML = False
        Exit Function
    End If
    
    Set oSignedKey = xmldsig.sign(oKey, KEYVALUE)
    If oSignedKey Is Nothing Then
        Text1.Text = Text1.Text + "sign failed." + vbNewLine
        SignXML = False
        Exit Function
    End If

    xmldoc.save sigOut

    Text1.Text = Text1.Text _
            + "The data referenced in the signature template " _
            + "was signed successfully." + vbNewLine _
            + "Resultant signature:" + vbNewLine + vbNewLine _
            + xmldoc.xml + vbNewLine
    SignXML = True
End Function

Private Function VerifyXML(ByVal secret As String, ByVal length As Long)
    If xmldsig.signature Is Nothing Then
        Text1.Text = Text1.Text + "Invalid signature object."
        VerifyXML = False
        Exit Function
    End If
    
    Set oKey = xmldsig.createKeyFromHMACSecret(secret, length)
    If oKey Is Nothing Then
        Text1.Text = Text1.Text + _
               "Failed to create key from HMAC secret value\n"
        VerifyXML = False
        Exit Function
    End If
    
    Set oVerifyKey = xmldsig.verify(oKey)
    If oVerifyKey Is Nothing Then
        Text1.Text = Text1.Text + "verify failed." + vbNewLine
        VerifyXML = False
        Exit Function
    End If
    
    Text1.Text = Text1.Text _
            + "The data referenced in the signature object " _
            + "was verified successfully." + vbNewLine + vbNewLine
    
    VerifyXML = True
End Function

Private Sub Form_Load()

    ' Resize the text box control to the size of the form
    Text1.Top = 100
    Text1.Left = 100
    Text1.Width = Form1.Width - 350
    Text1.Height = Form1.Height - 750

    DSIGNS = "xmlns:ds='http://www.w3.org/2000/09/xmldsig#'"
    sigTmp = "signature-template-enveloping-hmac-sha1.xml"
    sigOut = "signature-enveloping-hmac-sha1.xml"
    hmacSecret = "c2VjcmV0"
    hmacLength = -1
    Text1.Text = ""
    
    If LoadXML(sigTmp) = False Then
       Exit Sub
    End If
    
    If SignXML(hmacSecret, hmacLength) = False Then
       Exit Sub
    End If
    
    If VerifyXML(hmacSecret, hmacLength) = False Then
       Exit Sub
    End If
End Sub

Private Sub Form_Resize()
    ' Resize the text box control to the size of the form
    Text1.Width = Form1.Width - 350
    Text1.Height = Form1.Height - 750
End Sub

Try It!

1. Ensure that you have completed all the procedures in Getting Started with XML Digital Signatures.

2. Copy the signature template resource file, and paste it into a text editor. Save the file as signature-template-enveloping-hmac-sha1.xml.

3. Create a Standard EXE project in Visual Basic. Save the empty project as KeyFromHMACSecret.vbp to the same directory where you saved signature-template-enveloping-hmac-sha1.xml. Name the form file KeyFromHMACSecret.frm.

4. Create a reference to MSXML 5.0 for Microsoft Office Applications. To do this, select References... from the Project menu, and then check the box for Microsoft XML, v5.0.

5. Copy the Visual Basic code listing above, and paste it into the code editor to replace whatever code is already there.

6. Place a TextBox control onto the form. It should be named as Text1 (the default name). Click it to select it in the Properties window, and then modify the following properties for Text1: set the ScrollBars property to "2 – Vertical" and the MultiLine Property to True.

7. Execute the code by selecting Start from the Run menu.

8. Verify that the output is similar to that listed in the Output topic. You can resize the form to more easily view the output.