VB.NET

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. VB.NET

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 .key file:
success = privKey.LoadPemFile("privateKey.key")
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


' 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 sha256 hash algorithm.
' Other valid choices are "md2", "sha1", "sha384",
' "sha512", and "md5".
Dim hexSig As String = rsa.SignStringENC(strData,"sha256")

Debug.WriteLine(hexSig)

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

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


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

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

' Import the public key into the RSA object:
success = rsa2.UsePublicKey(pubKey)
If (success = False) 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,"sha256",hexSig)
If (success = False) Then
    Debug.WriteLine(rsa2.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Success.")