(VB.NET) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Note: This example requires Chilkat v11.0.0 or greater.

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Dim success As Boolean = False

' 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 PEM file:
success = privKey.LoadAnyFormatFile("raul_privateKey.key","a0123456789")
If (success = False) Then
    Debug.WriteLine(privKey.LastErrorText)
    Exit Sub
End If


Dim rsa As New Chilkat.Rsa

' Import the private key into the RSA component:
success = rsa.UsePrivateKey(privKey)
If (success = False) Then
    Debug.WriteLine(rsa.LastErrorText)
    Exit Sub
End If


' This example will sign a string, and receive the signature
' in a hex-encoded string.  Therefore, set the encoding mode
' to "hex":
rsa.EncodingMode = "hex"

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

' Sign the string using the sha256 hash algorithm.
' Other valid choices are sha1, sha384, sha512 and others.
Dim hexSig As String = rsa.SignStringENC(strData,"sha256")
If (rsa.LastMethodSuccess = False) Then
    Debug.WriteLine(rsa.LastErrorText)
    Exit Sub
End If


Debug.WriteLine(hexSig)

' Now verify with the public key.
' This example shows how to use the public key from 
' a digital certificate (.cer file)
Dim cert As New Chilkat.Cert
success = cert.LoadFromFile("raul_publicKey.cer")
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


Dim pubKey As New Chilkat.PublicKey
cert.GetPublicKey(pubKey)

Dim rsa2 As New Chilkat.Rsa
success = rsa2.UsePublicKey(pubKey)
If (success = False) Then
    Debug.WriteLine(rsa2.LastErrorText)
    Exit Sub
End If


' Verify the signature against the original data:
rsa2.EncodingMode = "hex"
success = rsa2.VerifyStringENC(strData,"sha256",hexSig)
If (success = False) Then
    Debug.WriteLine(rsa2.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Signature verified!")

' Verify with incorrect data:
success = rsa2.VerifyStringENC("something else","sha256",hexSig)
If (success <> True) Then
    Debug.WriteLine("Signature not verified! (which was expected in this case)")
Else
    Debug.WriteLine("Hmmm... that's not right...")
End If