(VB.NET) Verify HMAC XML Digital Signature

Demonstrates how to validate an XML digital signature signed with an HMAC key.

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' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' The XML containing the Signature to be verified contains the following:

' <?xml version="1.0" encoding="UTF-8" standalone="no"?>
' <collection Id="root">
' 	<album>
' 		<title>Questions, unanswered</title>
' 		<artist>Steve and the flubberblubs</artist>
' 		<year>1989</year>
' 		<t:tracks xmlns:t="http://test.xades4j/tracks">
' 			<t:song length="4:05" tracknumber="1">
' 				<t:title>What do you know?</t:title>
' 				<t:artist>Steve and the flubberblubs</t:artist>
' 				<t:lastplayed>2006-10-17-08:31</t:lastplayed>
' 			</t:song>
' 			<t:song length="3:45" tracknumber="2">
' 				<t:title>Who do you know?</t:title>
' 				<t:artist>Steve and the flubberblubs</t:artist>
' 				<t:lastplayed>2006-10-17-08:35</t:lastplayed>
' 			</t:song>
' 			<t:song length="5:14" tracknumber="3">
' 				<t:title>When do you know?</t:title>
' 				<t:artist>Steve and the flubberblubs</t:artist>
' 				<t:lastplayed>2006-10-17-08:39</t:lastplayed>
' 			</t:song>
' 			<t:song length="4:19" tracknumber="4">
' 				<t:title>Do you know?</t:title>
' 				<t:artist>Steve and the flubberblubs</t:artist>
' 				<t:lastplayed>2006-10-17-08:44</t:lastplayed>
' 			</t:song>
' 		</t:tracks>
' 	</album>
' <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#hmac-sha256"/><ds:Reference URI="#root"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>rD/g8soqKz8EiPUBhEWfcQacS0ta4ULHX3dKMEH6ZoQ=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>R8dXP95VRYJBfL6d0Peogybdk27+R+JIfX8jnVu0NOI=</ds:SignatureValue></ds:Signature></collection>


' The above XML is available at https://www.chilkatsoft.com/exampleData/hmacSigned.xml
' First fetch the XML..

Dim url As String = "https://www.chilkatsoft.com/exampleData/hmacSigned.xml"
Dim http As New Chilkat.Http
Dim sbXml As New Chilkat.StringBuilder
Dim success As Boolean = http.QuickGetSb(url,sbXml)
If (success <> True) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If


Dim verifier As New Chilkat.XmlDSig

' Load the XML containing the signature to be verified.
success = verifier.LoadSignatureSb(sbXml)
If (success <> True) Then
    Debug.WriteLine(verifier.LastErrorText)
    Exit Sub
End If


' Provide the HMAC key
' The HMAC key for this signature is the us-ascii bytes of the string "secret",
' It can be set in any of the following ways (and also more ways not shown here..)
verifier.SetHmacKey("secret","ascii")
' or
verifier.SetHmacKey("c2VjcmV0","base64")
' or
verifier.SetHmacKey("736563726574","hex")


' Verify the signature
Dim bVerified As Boolean = verifier.VerifySignature(True)
Debug.WriteLine("Signature verified = " & bVerified)