procedure TForm1.Button1Click(Sender: TObject);
 var
 s: String[255];
 c: array[0..255] of Byte absolute s;
 i: Integer;
 begin
 {encode}

 s := 'SwissDelphiCenter.ch';
 for i := 1 to Ord(s[0]) do c[i] := 23 xor c[i];
 Label1.Caption := s;

 {Decode}

 s := Label1.Caption;
 for i := 1 to Length(s) do s[i] := Char(23 xor Ord(c[i]));
 Label2.Caption := s;
 end;