Visual Basic 6.0

Verfies an RSA Signature

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Verifies an RSA signature against the original data. Visual Basic 6.0

Dim success As Long
success = 0

' 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 ChilkatBinData
Dim i As Long
For i = 0 To 100
    success = bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex")
Next

' Load the signature
Dim bdSig As New ChilkatBinData
success = bdSig.LoadFile("rsaSignatures/test1.sig")
If (success = 0) Then
    Debug.Print "Failed to load the RSA signature"
    Exit Sub
End If

' Get the public key to be used for signature verification.
Dim pubKey As New PublicKey
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
If (success = 0) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Dim rsa As New ChilkatRsa
success = rsa.UsePublicKey(pubKey)
If (success = 0) Then
    Debug.Print 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 = 0) Then
    Debug.Print rsa.LastErrorText
    Debug.Print "Signature invalid."
Else
    Debug.Print "Signature valid."
End If