<?php
/**
 * Created by PhpStorm.
 * User: cly
 * Date: 2016-07-16
 * Time: 16:11
 */

class AES {
    protected $password = "";

    function __construct($password=Null) {
        if (!$this->is_openssl()) {
            throw new Exception("Open-ssl not present.");
        }
        if ($password) {
            $this->$password = $password;
        } else {
            $this->$password = openssl_random_pseudo_bytes(128);
        }
    }

    function encrypt($data) {
        $method = $this->get_encryption_mode();
        $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($method));
        $encrypted = openssl_encrypt($data, $method, $this->password, true, $iv);
        $string = "%s%s";
        $data = sprintf($string, $encrypted, $iv);
        return $data;
    }
    function decrypt ($data) {
        $method = "aes-256-cbc";
        $iv_len = openssl_cipher_iv_length($method);
        $iv = substr($data, -$iv_len);
        $data = substr($data, 0, strlen($data)-$iv_len);
        $decrypted = openssl_decrypt($data, $method, $this->password, true, $iv);
        return $decrypted;
    }

    function is_openssl() {
        $methods = ["openssl_get_cipher_methods",
            "openssl_random_pseudo_bytes",
            "openssl_encrypt",
            "openssl_get_cipher_methods"
        ];
        $exists = True;
        foreach ($methods as $m) {
            $exists = $exists && $m;
        }
        return $exists;
    }

    function get_encryption_mode () {
        $preferred = ["aes-256-cbc", "aes-256-ofb", "aes-256-cfb", "aes-256-ecb"];
        $method = "";
        $methods = openssl_get_cipher_methods();
        foreach ($preferred as $m) {

            if (in_array($m, $methods)) {
                $method = $m;
                break;
            }
        }
        return $method;

    }
}

$data = "I am a cow from mars that yells";

$test = new AES("kel");
$d = $test->encrypt($data);
echo $test->decrypt($d), "\n";