(VB.NET) RSA Signature/Verify with .key and .cer

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

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

Dim privKey As New Chilkat.PrivateKey

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


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

Dim rsa As New Chilkat.Rsa

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


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

Dim strData As String = "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 = rsa.SignStringENC(strData,"sha-1")

Debug.WriteLine(hexSig)

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

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


Dim pubKey As Chilkat.PublicKey

pubKey = cert.ExportPublicKey()


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

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


Debug.WriteLine("Success.")