About RSA Public/Private Keys

Download Chilkat RSA ActiveX

Dim cert As New ChilkatCert

Dim success As Long

'  Load a digital certificate.
success = cert.LoadFromFile("digitalCert.cer")
If (success <> 1) Then
    MsgBox cert.LastErrorText
    Exit Sub
End If

Dim pubKey As PublicKey

'  A .cer file does not contain the private key.  It should contain
'  the public key...
Set pubKey = cert.ExportPublicKey()

'  Let's have a look at it (in XML format).
Text1.Text = Text1.Text & "Public Key from Certificate:" & vbCrLf
Text1.Text = Text1.Text & pubKey.GetXml() & vbCrLf

'  An RSA public key consists of a modulus and exponent.

'  An RSA private key includes both the modulus and exponent,
'  as well as other "big" numbers: P, Q, D, etc.

'  Let's load an RSA private key from a DER-encoded file:
Dim privKey As New PrivateKey

success = privKey.LoadRsaDerFile("PrivateKey.key")
If (success <> 1) Then
    MsgBox privKey.LastErrorText
    Exit Sub
End If

'  If this private key is the matching half to the public key from
'  the certificate, then the modulus and exponent should
'  be identical.  (Thus, a "private key" really contains both the public part as well as the private parts...).
Text1.Text = Text1.Text & "Private Key from DER:" & vbCrLf
Text1.Text = Text1.Text & privKey.GetXml() & vbCrLf

Dim rsa As New ChilkatRsa
success = rsa.UnlockComponent("Anything for 30-day trial.")
If (success <> 1) Then
    MsgBox rsa.LastErrorText
    Exit Sub
End If

'  You now realize that the private key really contains both
'  private and public parts.  Therefore, we may import the private
'  key and the choose to use either the public or private in our
'  encrypt/decrypt operations:
Dim privKeyXml As String
privKeyXml = privKey.GetXml()
success = rsa.ImportPrivateKey(privKeyXml)
If (success <> 1) Then
    MsgBox rsa.LastErrorText
    Exit Sub
End If