(Excel) Get a Certificate's Key Size

Demonstrates how to get the RSA key size of a certificate (for example, 1024-bit, 2048-bit, etc.)

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'  For this example, I have a certificate in raw base64 format (not PEM),
'  that looks like this:  "MIIGkDCCBHigAwIBAgIUMDA ... s/iqLsLA=="
Dim sbCertBase64 As Chilkat.StringBuilder
Set sbCertBase64 = Chilkat.NewStringBuilder

success = sbCertBase64.LoadFile("qa_data/certs/base64Cert.txt","utf-8")

Dim cert As Chilkat.Cert
Set cert = Chilkat.NewCert
success = cert.LoadFromBase64(sbCertBase64.GetAsString())
If (success <> True) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

'  Get the public key.

Set pubKey = cert.ExportPublicKey()
If (cert.LastMethodSuccess <> True) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

'  In Chilkat version v9.5.0.67, the KeySize property was added.

numBits = pubKey.KeySize
Debug.Print "Number of bits = "; numBits

'  If using an older version of Chilkat, the key size can be obtained like this:
Dim xml As Chilkat.Xml
Set xml = Chilkat.NewXml
success = xml.LoadXml(pubKey.GetXml())

Dim binDat As Chilkat.BinData
Set binDat = Chilkat.NewBinData
success = binDat.AppendEncoded(xml.GetChildContent("Modulus"),"base64")

numBits = 8 * binDat.NumBytes
Debug.Print "Number of bits = "; numBits