[PHP]AJAX logowanie, pomoc w zabezpieczeniu kodu Opcje

[casperii]

Witam.
postanowiłem napisać logowanie opartym o jquery i teraz się zastanawiam czy to będzie dobry pomysł pod względem bezpieczeństwa.

php:

[PHP] pobierz, plaintext 
/*Funkcja zapisująca ciasteczka */
function docookie($setuid, $setusername) {
	$info = base64_encode("$setuid:$setusername");
	setcookie("user","$info",time()+3600);
	return $info;
}
 
 
	$user = $_GET['Username'];
	$password = trim($_GET['Password']);
 
	$query = $pdo->prepare("SELECT `user`, `password`, `pass_pass`, `id_user` FROM `users` WHERE `user` = :user AND `password` = :password LIMIT 1");
	$query->bindValue(':user', $user, PDO::PARAM_STR);
	$query->bindValue(':password',  SafePassword($password), PDO::PARAM_STR);
 
	$query->execute();
	$fetch = $query->fetch();
 
	if(empty($user)){
		$status = "error";
		$message = "".LANG_AJAX_LOGIN_NIEPODANO.".";
	}elseif(!is_array($fetch)){
		$status = "error";
		$message = ''.LANG_AJAX_LOGIN_NIEMA.'.';
	}elseif(empty($password)){
		$status = "error";
		$message = "".LANG_AJAX_HASLO_NIEPODANO.".";
	}else{
 
		mt_srand ((double)microtime()*1000000);
		$maxran = 1000000;
		$random_num = mt_rand(0, $maxran);
 
 
		$datekey = date("F j");
		$rcode = hexdec(md5($_SERVER['HTTP_USER_AGENT'] . $random_num . $datekey));
		$code = substr($rcode, 2, 6);
 
		docookie($fetch['id_user'], $user);
 
		$status = "success";
		$message = 'Zalogowano poprawnie.'.$code;
       }
[PHP] pobierz, plaintext 

JS:

[HTML] pobierz, plaintext 
	var SignIn = function() {
		$('#LoginButton,#LoginButtonTop').on('click', function (){
			var form = $('#login').serialize(),
			responseMsg = $('#messageLogin,#messageLoginTop');
			responseMsg.hide().addClass('response-waiting').text('czekaj...').fadeIn(200);
 
			$.ajax({
				type: 'GET',
                url: "/ajax.php?p=login",
                data: form,
                processData: false,
                contentType: false, 
                success: function(data){
					var responseData = jQuery.parseJSON(data), 
                    klass = '';
					switch(responseData.status){
						case 'error':
						klass = 'response-error';
						break;
 
						case 'success':
						klass = 'response-success';
						break; 
					}            
 
					responseMsg.fadeOut(200,function(){
						$(this).removeClass('response-waiting').addClass(klass).html(responseData.message).fadeIn(200,function(){
 
							if(responseData.status == 'error'){
							setTimeout(function(){
								responseMsg.fadeOut(200,function(){
									$(this).removeClass(klass);
								});
							},3000);
 
							}else { setTimeout('go_to_private_page()', 3000); } 
 
 
						});
					});	             
				}
			});
			return false;
		});
	}
[HTML] pobierz, plaintext