(Visual Basic 6.0) Convert RSA Private Key to Public Key

Demonstrates how to get a public RSA key from a private RSA key.

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

Dim key As New PrivateKey

' Step 1: Load the private key from a source.
' (Chilkat can load private keys from all types of formats, and from in-memory bytes or encoded strings.
' see the online reference documentation for more options.)
Dim success As Long
success = key.LoadPemFile("qa_data/pem/VP_Private.pem")
If (success <> 1) Then
    Debug.Print key.LastErrorText
    Exit Sub
End If

' Step 2: Get the public key object from the private key object.
Dim pubKey As PublicKey
Set pubKey = key.GetPublicKey()
If (key.LastMethodSuccess <> 1) Then
    Debug.Print key.LastErrorText
    Exit Sub
End If

' Step 3: Save the public key in a desired format. 
' (Chilkat can load or save public and private keys in many different formats.  See
' the online reference documentation for more options.)

' Saves to a PKCS8 PEM file.
Dim bPreferPkcs1 As Long
bPreferPkcs1 = 0
success = pubKey.SavePemFile(bPreferPkcs1,"qa_data/pem/VP_Public.pem")
If (pubKey.LastMethodSuccess <> 1) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Debug.Print "Extracted and saved public key from private key."