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POBase64 HMAC SHA1 String in VBA
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copied!<p>I'm trying to convert an ASP/VBScript OAuth library to VBA. One of the challenges is this line of code:</p> <pre><code>Get_Signature = b64_hmac_sha1(strSecret, strBaseSignature) </code></pre> <p>This function, b64_hmac_sha1 is actually a function contained in a JavaScript library. It appears to me that calling a JavaScript function from VBA is fairly impractical.</p> <p>Because I know so little about encryption, it's not even clear to me what this b64_hmac_sha1 function does. Is HMAC SHA1 different from SHA1?</p> <p>I half suspect I might be able to find some VBA code online to do what I need to do if I just understood what this function is actually doing. If I do not find an existing function, I could possibly write one that would use the .NET Cryptography library (you can actually call the .NET cryptography libraries from VBA if you know how).</p> <p>I'm not looking for someone to convert this JavaScript to VBA. I'm only trying to understand what it is that this b64_hmac_sha1 function is outputting so I can try to find ways to achieve the same output in VBA if possible.</p> <p>A copy of this JavaScript library is visible on this website. You'll have to scroll down past the VBScript to the JavaScript section. <a href="http://solstice.washington.edu/solstice/ASP_Signing_REST_Example" rel="nofollow">http://solstice.washington.edu/solstice/ASP_Signing_REST_Example</a></p> <p><strong>Edit1:</strong><br> OK, so here's the functions I ended up writing and using: </p> <pre><code>Public Function Base64_HMACSHA1(ByVal sTextToHash As String, ByVal sSharedSecretKey As String) Dim asc As Object, enc As Object Dim TextToHash() As Byte Dim SharedSecretKey() As Byte Set asc = CreateObject("System.Text.UTF8Encoding") Set enc = CreateObject("System.Security.Cryptography.HMACSHA1") TextToHash = asc.Getbytes_4(sTextToHash) SharedSecretKey = asc.Getbytes_4(sSharedSecretKey) enc.Key = SharedSecretKey Dim bytes() As Byte bytes = enc.ComputeHash_2((TextToHash)) Base64_HMACSHA1 = EncodeBase64(bytes) Set asc = Nothing Set enc = Nothing End Function Private Function EncodeBase64(ByRef arrData() As Byte) As String Dim objXML As MSXML2.DOMDocument Dim objNode As MSXML2.IXMLDOMElement Set objXML = New MSXML2.DOMDocument ' byte array to base64 Set objNode = objXML.createElement("b64") objNode.DataType = "bin.base64" objNode.nodeTypedValue = arrData EncodeBase64 = objNode.Text Set objNode = Nothing Set objXML = Nothing End Function </code></pre> <p>Using this function:</p> <pre><code>Debug.Print Base64_HMACSHA1("abc", "123") VAsMU9SSWDe9krP3Gr56nXC2dsQ= </code></pre>

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