Securing trough files

' specify the path to a file and this routine will calculate your hash
    Public Function MD5CalcFile(ByVal filepath As String) As String

        ' open file (as read-only)
        Using reader As New System.IO.FileStream(filepath, IO.FileMode.Open, IO.FileAccess.Read)
            Using md5 As New System.Security.Cryptography.MD5CryptoServiceProvider
                ' hash contents of this stream
                Dim hash() As Byte = md5.ComputeHash(reader)
                ' return formatted hash
                Return ByteArrayToString(hash)
            End Using
        End Using
    End Function


    ' utility function to convert a byte array into a hex string
    Private Function ByteArrayToString(ByVal arrInput() As Byte) As String
        Dim sb As New System.Text.StringBuilder(arrInput.Length * 2)
        For i As Integer = 0 To arrInput.Length - 1
            sb.Append(arrInput(i).ToString("X2"))
        Next
        Return sb.ToString().ToLower
    End Function

if MD5CalcFile(filepath) = "md5 of the check file" = true then
'logon script
else
msgbox("Key not found, please contact creator")
end if