如何保护聊天消息免受中间人的攻击(PHP、JavaScript）

我目前正在为我的网站开发聊天系统。我不知道如何保护信息的完整性。我目前正在通过进行此操作

chat.class.php

class Chat{
    private $config;
    private $randomJSONrpc;
    private $MySQL;
    function __construct($config = 'chat.config.json') {
        $this->config = $config;
        unset($config);
        if(file_exists($this->config)) {
            $config = json_decode(file_get_contents($this->config), false);
            $config->configfile = $this->config;
            $this->config = $config;
            unset($config);
        } else {
            $this->error('Configtest');
        }
        require_once 'jsonrpc.class.php';
        $jsonrpc = new JsonRpcClient('https://api.random.org/json-rpc/1/invoke');
        $this->randomJSONrpc = $jsonrpc;
        unset($jsonrpc);
        $this->MySQL = $this->database();
    }
    private function database() {
        if($this->config->salt == 'random') {
            $random = $this->random(8, 'string');
            $this->config->salt = $random;
            $file = $this->config->configfile;
            unset($this->config->configfile);
            file_put_contents($file, json_encode($this->config));
        } 
        $mysql_function = $this->config->drivers->mysql;
        if($mysql_function == 'mysqli') {
            $connection = new MySqLi($this->config->mysql->host, $this->config->mysql->user, $this->config->mysql->password, $this->config->mysql->database)or $this->error('MySQL connection', mysqli_error());
            return $connection;
        } else {
            error('MySQLi connection driver');
        }
    }
    public function hash($input, $algo = 'blowfish') {
        if($algo == 'blowfish') {
            $hash_algo = '$2a';
            $cost = '$10';
        } elseif($algo == 'md5') {
            $hash_algo = '$1';
            $cost = '';
        } else {
            $this->error('Algo availibility check', 'chat.class.php#class:Chat->hash('.$input.', '.$algo.')');
        }
        $salt = substr(sha1($this->config->salt),0,22);
        return crypt($input, $hash_algo.$cost.'$'.$salt);
    }
    public function random($length, $address = 'string') {
        $jsonrpc = $this->randomJSONrpc;
        if($address == 'string') {
            $params = new stdClass;
            $params->apiKey = $this->config->RANDOMapiKey;
            $params->n = 1;
            $params->length = $length;
            $params->characters = 'abcdefghijklmnopqrstuvwxyz1234567890';
            $params->replacement = true;
            $data = $jsonrpc->generateStrings($params);
            return $data->random->data[0];
        } else {
            $this->error('JSON-RPC address test');
        }
    }
    public function readNewMessages() {
        return 'dev.testing';
    }
    private function error($test, $extrainfo = false, $status = false) {
        if($status == false AND $extrainfo == false) {
            die($test.': <span style="color: red;">FAILED</span><br />'.PHP_EOL);
        } elseif($status != false AND $extrainfo == false) {
            echo $test.': <span style="color: green;">OK</span><br />'.PHP_EOL;
        } elseif($status == false AND $extrainfo != false) {
            die($test.': <span style="color: red;">FAILED('.$extrainfo.')</span><br />'.PHP_EOL);
        } elseif($status != false AND $extrainfo != false) {
            echo $test.': <span style="color: green;">OK('.$extrainfo.')</span><br />'.PHP_EOL;
        }
    }
}
?>

chat.php应该检索新的帖子

<?php
header('Content-Type: application/json');
include 'chat.class.php';
$chat = new Chat();
if(session_id()) {
    session_close();
}
$i = 1;
$message = null;
while(!$message) {
    sleep(1);
    $data = $chat->readNewMessages();
    $i++;
}
$response = array('data' => $data, 'itnegrity' => //here I wondered how to save the integrity. );
echo json_encode($message);
?>

我有三样东西，我可能会用到。

1. MD5哈希我的消息
2. 使用SSL
3. 通过客户端生成的密码对消息进行加密，该密码使用用户密码加密后发送到服务器，然后使用用户密码将消息加密后发送回

该应用程序仍在开发中，无法运行。我想使用长轮询从服务器检索消息或检测信号。