About RSA Public/Private Keys

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Dim cert As New Chilkat.Cert()

Dim success As Boolean

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


Dim pubKey As Chilkat.PublicKey

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

'  Let's have a look at it (in XML format).
TextBox1.Text = TextBox1.Text & "Public Key from Certificate:" & vbCrLf
TextBox1.Text = TextBox1.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 Chilkat.PrivateKey()

success = privKey.LoadRsaDerFile("PrivateKey.key")
If (success <> true) 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...).
TextBox1.Text = TextBox1.Text & "Private Key from DER:" & vbCrLf
TextBox1.Text = TextBox1.Text & privKey.GetXml() & vbCrLf


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