6d

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Memo2: TMemo;
    Button1: TButton;
    Memo3: TMemo;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function cEcezar(s:string;key:byte):string;
var i:integer; c,d:char;
begin
  for i:=1 to length(s) do
  begin
    c:=s[i];
    if not (c in [#10, #13]) then
      d:=chr((ord(c)+ key)mod 255)
    else d := c;
    Result:=Result+d;
  end;
end;


function CaesarDecipher(toDecode: string;n:integer): string;
var i, T: integer;
begin
  for i := 1 to length(toDecode) do begin
    T := (Ord(toDecode[ i ]) - n);
    if T < 0 then Inc(T, 256);
    toDecode[ i ] := Chr(T);
  end;
  CaesarDecipher := toDecode;
end;


procedure TForm1.Button1Click(Sender: TObject);
begin
Memo2.Text := cEcezar(Memo1.Text, 3);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
Memo3.Text := CaesarDecipher(memo2.text,3);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin

end;

end.