Login Method

<?php
$enc_user = md5(sha1($_SERVER['REMOTE_ADDR']));

function login_admin($enc_user){
    /*basic method
    If the user has a time stamp, check if the timestamps mathch, if they do, update the timestamp and login the user as admin.
    If they don't match attempt to login the user using their IP address. If they are successful, issue them with a timestamp and update the local timestamp
    as well as allowing them to login.
    */
    //check if the user has a timestamp
    $admin = false; //assume that the user is not the admin.
    if($_COOKIE['timestamp']){
        $usr_timestamp = $_COOKIE['timestamp'];
        if(file_exists("users/admin_timestamp.txt")){
            $fh[1] = fopen("users/admin_timestamp.txt", 'r');
            $admin_timestamp = trim(fgets($fh[1]));
            fclose($fh[1]);
            if(sha1(md5(crypt($usr_timestamp, $usr_timestamp))) == $admin_timestamp){
                //user is admin, log them in and update the timestamp file
                //updating the timestamp file is also an increased measure of security
                $fh[2] = fopen("users/admin_timestamp.txt", 'w');
                if(file_exists("users/admin_timestamp.txt")){
                    $current_time = microtime()*rand(1, 100000000); //time in milliseconds*random value between 1 and 100 000 000 (one hundred million)
                    //this will increase the amount of entropy involved in attempting to crack this system. (How does one crack random?)
                    $usr_enc_timestamp = sha1(md5($current_time));
                    $server_enc_timestamp = sha1(md5(crypt($usr_enc_timestamp, $usr_enc_timestamp)));
                    //update the user and server timestamp files, as well as updating the admin.txt hash of the users IP
                    setcookie("timestamp", $usr_enc_timestamp); //update user
                    fwrite($fh[2], $server_enc_timestamp); //update server
                    if(file_exists("users/admin.txt")){
                        $fh[3] = fopen("users/admin.txt", 'w');
                        fwrite($fh[3], $enc_user); //update the admin IP file
                        fclose($fh[3]);
                    }
                    fclose($fh[2]);
                }
                $admin = true;
            }
        }
    }
    //Secondarily test if the IP addresses match if the login is still unsuccesful
    if(!$admin){
        //open the users file
        $fh[4] = fopen("users/admin.txt", 'r');
        $enc_admin = trim(fgets($fh[4]));
        fclose($fh[4]);
        if($enc_user == $enc_admin){
            $fh[5] = fopen("users/admin_timestamp.txt", 'w');
            if(file_exists("users/admin_timestamp.txt")){
                $current_time = microtime(); //time in milliseconds
                $usr_enc_timestamp = sha1(md5($current_time));
                $server_enc_timestamp = sha1(md5(crypt($usr_enc_timestamp, $usr_enc_timestamp)));
                //update the user and server timestamp files, as well as updating the admin.txt hash of the users IP
                setcookie("timestamp", $usr_enc_timestamp); //update user
                fwrite($fh[5], $server_enc_timestamp); //update server
                if(file_exists("users/admin.txt")){
                    $fh[3] = fopen("users/admin.txt", 'w');
                    fwrite($fh[3], $enc_user); //update the admin IP file
                    fclose($fh[3]);
                }
                fclose($fh[5]);
            }
            $admin = true;
        }
    }
    return $admin;
}
?>