I need some help with using Rijndael encryption algorithm

[vfclists]

I am using the Rijndael algorithm to encrypt some application settings, but it does not generate the type of variation in the encrypted output I expect.
I am not quite sure if that is a flaw, just normal behaviour, or I am failing to set some additional parameters properly.

Here is my current implementation. I expect a whole lot more variation in the output when I add more characters, but the earlier characters of the output don't change much.

Code: [Select]

    unit testform;

    {$mode objfpc}{$H+}

    interface

    uses
      Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
      StdCtrls, DCPrijndael, DCPsha1;

    type

      { TForm1 }

      TForm1 = class(TForm)
        edtKeyString: TEdit;
        edtInputText: TEdit;
        edtEncryptedText: TEdit;
        Label1: TLabel;
        Label2: TLabel;
        Label3: TLabel;
        procedure edtInputTextChange(Sender: TObject);
      private
        { private declarations }
      public
        { public declarations }
      end;

    var
      Form1: TForm1;

    implementation

    { TForm1 }

    procedure TForm1.edtInputTextChange(Sender: TObject);
    var
      Cipher: TDCP_rijndael;
    begin
      Cipher:= TDCP_rijndael.Create(Self);
      Cipher.InitStr(edtKeyString.Text,TDCP_sha1);
      edtEncryptedText.Text := Cipher.EncryptString(edtInputText.Text);
      Cipher.Burn;
      Cipher.Free;
    end;

    initialization
      {$I testform.lrs}

end.
regards

/vfclists