在(3)中我们会一块块的读取
那么,如果说我们在每块内加点东西,那么程序就不能运行,再减去你加的那些,程序又能以运行
由此你可以想到对自己的程序(加密),这里不是真正加密

我做的程序是在向文件写入时写入两次,这种方法你的程序会加大一倍,如果你有时间,那就用char类型加密,(别有数组4096)加密部分代码,其它不变就可以

代码如下
unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    OpenDialog1: TOpenDialog;
    SaveDialog1: TSaveDialog;
    Edit1: TEdit;
    Edit2: TEdit;
    SpeedButton1: TSpeedButton;
    SpeedButton2: TSpeedButton;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure SpeedButton1Click(Sender: TObject);
    procedure SpeedButton2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
Var SouFile,DescFile:TFileStream;
    Buf:Array [1..4096] of Char;
    iLen:integer;
begin
if (edit1.Text='') or (edit2.Text='') then
begin
application.messagebox('请填写正确路径','提示',mb_ok);
exit;
end;
SouFile:=TfileStream.Create(edit1.Text,fmOpenRead or fmShareDenyWrite);
DescFile:=TFileStream.Create(edit2.Text,fmCreate);
SouFile.Position:=0;
  While SouFile.Position <=SouFile.Size do
  begin
If (SouFile.Size-SouFile.Position)>4096 Then
    Begin
    SouFile.ReadBuffer(Buf,sizeof(buf));
    DescFile.WriteBuffer(Buf,sizeof(buf));
     DescFile.WriteBuffer(Buf,sizeof(buf));
   end
else
  begin
  iLen:=SouFile.Size-SouFile.Position;
    SouFile.ReadBuffer(Buf,iLen);
    DescFile.WriteBuffer(Buf,iLen);
    Break;
    End;
end;
 SouFile.Free();
  DescFile.Free();
  application.messagebox('加密成功','good',mb_ok);

end;

procedure TForm1.Button2Click(Sender: TObject);
Var SouFile,DescFile:TFileStream;
   buf1, Buf:Array [1..4096] of Char;
    iLen:integer;
begin
if (edit1.Text='') or (edit2.Text='') then
begin
application.messagebox('请填写正确路径','提示',mb_ok);
exit;
end;
SouFile:=TfileStream.Create(edit1.Text,fmOpenRead or fmShareDenyWrite);
SouFile.Position:=0;
SouFile.ReadBuffer(Buf,sizeof(buf));
SouFile.ReadBuffer(Buf1,sizeof(buf));
if buf<>buf1 then
begin
application.messagebox('些程序未加密','提示',mb_ok);
 SouFile.Free();
exit;
end;
DescFile:=TFileStream.Create(edit2.Text,fmCreate);
SouFile.Position:=0;
  While SouFile.Position <=SouFile.Size do
  begin
If (SouFile.Size-SouFile.Position)>4096 Then
    Begin
    SouFile.ReadBuffer(Buf,sizeof(buf));
    DescFile.WriteBuffer(Buf,sizeof(buf));
    SouFile.Position:=SouFile.Position+4096;
   end
else
  begin
  iLen:=SouFile.Size-SouFile.Position;
    SouFile.ReadBuffer(Buf,iLen);
    DescFile.WriteBuffer(Buf,iLen);

    Break;
    End;
end;
 SouFile.Free();
  DescFile.Free();
 application.messagebox('复原成功','good',mb_ok);

end;

procedure TForm1.SpeedButton1Click(Sender: TObject);
begin
if opendialog1.Execute then
edit1.Text:=opendialog1.FileName;
end;

procedure TForm1.SpeedButton2Click(Sender: TObject);
begin
if savedialog1.Execute then
edit2.Text:=savedialog1.FileName;
end;

end.

如果自己做不好可以下载我的源码试着学
下载地址
http://www.cnitblog.com/Files/shuyezi122/加解.rar