lazarus：用DCPCrypt对文本文件加密

需要uses两个单元：DCPrc4, DCPsha1。

加密过程：

procedure TForm1.ButtonEnCryptClick(Sender: TObject);
var
  Cipher: TDCP_rc4;
  Source, Target: TFileStream;
begin

  if not FileExists(EditSource.Text) then begin
  ShowMessage('出错了: 源文件不存在！');
  Exit;
  end;

  if FileExists(EditTarget.Text) then
    RenameFile(EditTarget.Text, EditTarget.Text+'.bak');

  try
    Source:= TFileStream.Create(EditSource.Text,fmOpenRead);
    Target:= TFileStream.Create(EditTarget.Text,fmCreate);
    Cipher:= TDCP_rc4.Create(Self);
    Cipher.InitStr(KeyStr,TDCP_sha1);
    Cipher.EncryptStream(Source,Target,Source.Size);
    Cipher.Burn;
    Cipher.Free;
    Target.Free;
    Source.Free;
    ShowMessage('搞定！');
  except
    ShowMessage('错误: 读写文件错误！');
  end;
end;   

解密过程：

procedure TForm1.ButtonDeCryptClick(Sender: TObject);
var
  Cipher: TDCP_rc4;
  Source, Target: TFileStream;
  begin

  if not FileExists(EditTarget.Text) then begin
    ShowMessage('出错了: 源文件不存在！');
    Exit;
  end;

   if FileExists(EditSource.Text) then
    RenameFile(EditSource.Text, EditSource.Text+'.bak');

   try
     Source:= TFileStream.Create(EditTarget.Text,fmOpenRead);
     Target:= TFileStream.Create(EditSource.Text,fmCreate);
     Cipher:= TDCP_rc4.Create(Self);
     Cipher.InitStr(KeyStr,TDCP_sha1);
     Cipher.DecryptStream(Source,Target,Source.Size);
     Cipher.Burn;
     Cipher.Free;
     Target.Free;
     Source.Free;
     ShowMessage('加密完成！');
   except
     ShowMessage('错误: 读写文件错误！');
   end;
  end; 

源文本文件：

加密后：