(Visual Basic 6.0) RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

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

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim privKey As New PrivateKey

' Load the private key from an RSA .key file:
Dim success As Long
success = privKey.LoadPemFile("privateKey.key")
If (success <> 1) Then
    Debug.Print privKey.LastErrorText
    Exit Sub
End If

Dim privKeyXml As String
' Get the private key in XML format:
privKeyXml = privKey.GetXml()

Dim rsa As New ChilkatRsa

' Import the private key into the RSA component:
success = rsa.ImportPrivateKey(privKeyXml)
If (success <> 1) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Create the signature as a hex string:
rsa.EncodingMode = "hex"

Dim strData As String
strData = "This is the string to be signed."

' Sign the string using the sha-1 hash algorithm.
' Other valid choices are "md2", "sha256", "sha384",
' "sha512", and "md5".
Dim hexSig As String
hexSig = rsa.SignStringENC(strData,"sha-1")

Debug.Print hexSig

' Load a digital certificate from a .cer file:
Dim cert As New ChilkatCert

success = cert.LoadFromFile("myCert.cer")
If (success <> 1) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

Dim pubKey As PublicKey

Set pubKey = cert.ExportPublicKey()

' Now verify using a separate instance of the RSA object:
Dim rsa2 As New ChilkatRsa

' Import the public key into the RSA object:
success = rsa2.ImportPublicKey(pubKey.GetXml())
If (success <> 1) Then
    Debug.Print rsa2.LastErrorText
    Exit Sub
End If

' The signature is a hex string, so make sure the EncodingMode is correct:
rsa2.EncodingMode = "hex"

' Verify the signature:
success = rsa2.VerifyStringENC(strData,"sha-1",hexSig)
If (success <> 1) Then
    Debug.Print rsa2.LastErrorText
    Exit Sub
End If

Debug.Print "Success."