VB.NET

Verfies an RSA Signature

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Verifies an RSA signature against the original data. VB.NET

Dim success As Boolean = False

' The following data was signed by the following example:
' RSA Sign using a Private Key on a USB Token or Smartcard
Dim bd As New Chilkat.BinData
Dim i As Integer
For i = 0 To 100
    bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex")
Next

' Load the signature
Dim bdSig As New Chilkat.BinData
success = bdSig.LoadFile("rsaSignatures/test1.sig")
If (success = False) Then
    Debug.WriteLine("Failed to load the RSA signature")
    Exit Sub
End If


' Get the public key to be used for signature verification.
Dim pubKey As New Chilkat.PublicKey
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
If (success = False) Then
    Debug.WriteLine(pubKey.LastErrorText)
    Exit Sub
End If


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


' Verify the hash of the data against the signature.
' We pass in the original data.  Internally, the hash is generated
' and used to validate the signature.
' Validating the RSA signature means two things:  
' (1) the original data is exactly what was signed, and 
' (2) it was signed by the owner of the RSA private key.
success = rsa.VerifyBd(bd,"sha256",bdSig)

If (success = False) Then
    Debug.WriteLine(rsa.LastErrorText)
    Debug.WriteLine("Signature invalid.")
Else
    Debug.WriteLine("Signature valid.")
End If