(Visual Basic 6.0) Get a Certificate's Key Size

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

' For this example, I have a certificate in raw base64 format (not PEM),
' that looks like this:  "MIIGkDCCBHigAwIBAgIUMDA ... s/iqLsLA=="
Dim sbCertBase64 As New ChilkatStringBuilder
Dim success As Long
success = sbCertBase64.LoadFile("qa_data/certs/base64Cert.txt","utf-8")

Dim cert As New ChilkatCert
success = cert.LoadFromBase64(sbCertBase64.GetAsString())
If (success <> 1) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

' Get the public key.
Dim pubKey As PublicKey
Set pubKey = cert.ExportPublicKey()
If (cert.LastMethodSuccess <> 1) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

' In Chilkat version v9.5.0.67, the KeySize property was added.
Dim numBits As Long
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 New ChilkatXml
success = xml.LoadXml(pubKey.GetXml())

Dim binDat As New ChilkatBinData
success = binDat.AppendEncoded(xml.GetChildContent("Modulus"),"base64")

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